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Hewitt, David A. "Natural mortality of blue crab : estimation and influence on population dynamics /." W&M ScholarWorks, 2008. http://www.vims.edu/library/Theses/Hewitt08.pdf.
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Schulman, Jessica L. "Habitat Complexity as a Determinant of Juvenile Blue Crab Survival." W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539617703.
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Hovel, Kevin. "The effect of seagrass habitat fragmentation on juvenile blue crab survival." W&M ScholarWorks, 1999. https://scholarworks.wm.edu/etd/1539616700.
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Habitat fragmentation leads to small, isolated habitat patches in which ecological processes may differ substantially from those in larger, continuous habitats. Seagrass is a structurally complex but fragmented subtidal habitat that serves as a refuge from predation for juveniles of the blue crab, Callinectes sapidus Rathbun. I compared the effects of eelgrass ( Zostera marina L.) patch size and shoot density on juvenile blue crab survival both before (June) and after (September) shoot defoliation and cownose ray disturbance changed eelgrass habitat, and used artificial seagrass to determine the influence of eelgrass patch size on juvenile blue crab survival in the absence of covarying shoot density. Under natural conditions, eelgrass patch size, eelgrass shoot density and density-dependent cannibalism all influenced juvenile blue crab survival, but crab survival varied temporally. Crab survival was inversely correlated with eelgrass patch size in the absence of covarying shoot density, in contrast to patterns typically observed in fragmented terrestrial landscapes; this was likely due to low predator abundance in small patches. I tested the hypothesis that crab survival is maximized at an intermediate level of seagrass fragmentation due to the inverse relationship between crab survival and patch size by modeling the joint effects of patch size and proportional cover on juvenile blue crab survival. When I assumed predation on crabs to be independent of crab density, maximal crab survival (ca. 34%) occurred at intermediate values of seagrass fragmentation. Approximately 18% of crabs survived irrespective of the proportion of the landscape covered by seagrass when crab survival was assumed to be density-dependent. My findings indicate that (i) effects of habitat fragmentation on survival may differ between seagrass and terrestrial landscapes, (ii) seagrass habitat fragmentation has a significant but not overriding influence on faunal survival, and (iii) seagrass patch size, seagrass complexity, and blue crab density all influence juvenile blue crab survival, but their effects vary temporally. Habitat fragmentation studies should incorporate multiple scales of space and time, as well as potentially confounding environmental variables.
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Wood, Megan. "Juvenile Blue Crab (Callinectes Sapidus) Response to Altered Nursery Habitat." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1499449868.
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Habitats of Chesapeake Bay have been altered due to anthropogenic impacts and climate change. Due to these human disturbances, seagrasses have been extirpated from many areas in lower Chesapeake Bay and persisting beds face future losses as water temperatures continue to rise. Further loss of seagrass habitat will negatively impact juvenile blue crabs (Callinectes sapidus) that use seagrass beds as nursery grounds. Habitat degradation allows for more successful introductions of exotic species, and the communities formed from the mixing of native and exotic species are known as emerging ecosystems. Gracilaria vermiculophylla, an exotic macroalga, may be an emerging nursery habitat for juvenile blue crabs in Chesapeake Bay; however the extent to which the alga is present and used as a nursery by juvenile blue crabs are largely unknown. I investigated algal distribution in the shallow littoral areas of the York River, a subestuary of Chesapeake Bay, over two years (2013 – 2014) and found that G. vermiculophylla presence correlated with salinity and that algal presence and biomass increased with seagrass presence, although biomass was generally low. The alga was present in areas where seagrasses have been lost, and is therefore likely providing nursery habitat in these areas of high megalopal recruitment. Benthic epifaunal communities had lower species richness and were less abundant in G. vermiculophylla relative to seagrass, while benthic infaunal communities had lower species richness but similar abundance in the alga relative to seagrass. Juvenile blue crab densities were similar in the alga and seagrass, although seagrass supported about 3 times as many first and second instar crabs than G. vermiculophylla. Young juvenile blue crabs preferred seagrass, which may be due to epifaunal prey preference, and G. vermiculophylla likely represents a secondary nursery habitat. Juvenile blue crab growth rates of crabs 15 – 50 mm carapace width were similar in the alga, native seagrass, and unvegetated habitat, indicating that growth does not drive ontogenetic shifts in habitat use by larger (20 – 30 mm carapace width) juveniles. Similar growth rates also suggest that G. vermiculophylla performs similarly to seagrass as a nursery habitat in terms of providing resources for growth. Simulations of density-dependent migration of young juvenile blue crabs between habitat types suggest that G. vermiculophylla may mediate continued seagrass loss, at least in part. Together, these results increase our understanding of an emerging Chesapeake Bay ecosystem and the impacts that changes to nursery habitats have on the juvenile component of the blue crab population.
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Brylawski, Bryce J. "Cultural eutrophication and the clam Macoma balthica: Evidence for trophic disruption and effects on blue crabs." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539616585.
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Cultural eutrophication (CE) is the allochthonous input introduction of a quantity of matter, such as sediments, organic material, or nutrients, into a water body over the pre-anthropogenic (natural) levels. In most coastal estuaries CE has come to refer primarily to an increase in the concentration of phyto-nutrients. CE has been identified as the cause of very graphic phenomena such as hypoxia and fish kills. In this work I examine the potential for CE to alter the composition of the primary producer community and potentially alter or disrupt the benthic food web, using Macoma balthica as an indicator species. A series of surveys and experiments identified that clams in areas with greater than average nutrient concentrations had lower health, slower growth, and greater non-predatory mortality than clams in less eutrophic areas. Primary production, as estimated from chlorophyll a concentration, was greater at higher nutrient locations while the health and growth of clams was lower. The phytoplankton community in the more eutrophic areas had a lower proportion of diatoms relative to dinoflagellates. A biochemical analysis of clam tissue indicated that the clams from the less nutrient rich sites had a greater proportion of Eicosapentaenoic acid (EPA) relative to other fatty acids. Diatoms are rich in EPA compared to dinoflagellates. Thus, we hypothesize that CE induced shifts from diatom based production toward dinoflagellates may be limiting trophic transfer due to a lack of EPA. Using a series of models we were able to predict that trophic disruption could significantly reduce the scope for growth of the blue crab, Callenecties sapidus . Thus it is possible that the CE induced changes to primary producer community could disrupt the food web creating a trophic bottleneck.
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Eggleston, David B. "Predator-Prey Dynamics between the Blue Crab: Callineates sapidus Rathbun, and Juvenile Oysters Crassostrea virginica (Gmelin)." W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539617593.
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Davis, John Howell. "Implications of a Decrease in the Mature Size of Female Blue Crab, Callinectes sapidus." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-01032006-152433/.
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The size-at-maturity of female blue crabs is declining and the proportion of very small mature females (<100mm carapace width (CW)) is increasing North Carolina. Decreasing mature size of the female may have an effect on the mating success and mortality of size-disparate mating pairs. To test the effect of body size on mating behavior, I used controlled mating experiments comparing size-disparate mating pairs with similarly-sized mating pairs. Small males handled large females longer than any other mating pair combination; however, no increase in injury or mortality was found. Neither large nor small males transferred significantly different numbers of sperm to large and small females. Size-disparity appears to have no effect on mating success in blue crabs, suggesting that diversity of size-related genotypic traits can be preserved in the population. I also designed a mathematical model to estimate the lifetime spawning potential of different size-cohorts of female blue crabs subject to different mortality pressures. Cohorts of very small females (<100mm CW) that are not subject to fishery mortality produce 5.1 ? 58.1% more eggs over two spawning seasons than larger, harvestable females (127-159mm CW), suggesting an evolutionary advantage to maturing at smaller sizes. I also used the model to estimate the efficacy of a proposed restriction on the commercial harvest of large females (>172mm CW), intended to increase the spawning potential of large females in order to increase population-wide recruitment, as well as the number of recruits that may possess a larger-size genotype. The proposed seasonal (Sept. ? Apr.) commercial harvest of large females produced an estimated 23.2 ? 35.1% increase in egg production over two spawning seasons. However, since the large females compose less than 2% of the population, on average, the estimated increase in spawning potential for the entire population was negligible (0.46%). Additionally, the 5% tolerance of the regulation allows for the harvest of the entire population of large females, suggesting that the proposed restriction will be ineffective.
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Min, Hojune. "Effects of nutrients from fish farms on culture of blue mussel (Mytilus edulis)." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14589.
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Intensive salmonid cage culture releases nutrients and organic matter that lead eutrophication of coastal waters. Integrated multi-trophic aquaculture (IMTA) is receiving great attention as a means of reducing organic/inorganic nutrient loads to the environment and increasing productivity by rearing viable secondary organisms. In this study blue mussels (Mytilus edulis) were cultured close to a salmon (Salmo salar) cage farm at Tristen, Bjugn in Sør Trøndelag, Central Norway from June 2010 to February 2011. 3 experimental stations at the fish farming area and 2 reference stations (1.8 and 3.6 km away from the fish farm, respectively) were positioned to test if the integrated mussel culture reduces the environmental impact from salmon cage culture.Highest water temperature recorded was 14.3 °C in July. Water temperature was above 10 °C until middle of October and the lowest was 3.1 °C in winter. Total particulate matter (TPM) and chlorophyll a contents varied 6.3 – 10.5 mg L-1 and 0.1 - 2.5 µg L-1, respectively. The mussel (n=450) length increased from 31.1±0.04 mm (standard length±SE) to 41.5±0.17 mm. The mussel growth was high in summer (June – September) and was close to zero in the winter (October – February). Multiple regression analysis showed that water temperature was the prime factor affecting condition index (CI) (meat dry weight/shell dry weight) and specific growth rate (SGR) of mussel. No differences were found in the environmental variables and food availabilities among the stations. Significantly higher CIs at the experimental stations (station 1, 2 and 3) than at the reference stations were caused by utilization of fish farm discharges by the mussels. Fatty acids 18:1 (n-9), 18:2 (n-6) and 20:5 (n-3) signatures and the ratio of n-3 to n-6 in the digestive gland tissue of mussels collected in February support the findings. SGR in shell length was highest at reference station 5 (0.29 % day-1 in summer and 0.02 % day-1 in winter). This result might be caused by slow current speed at the station.It is concluded that, mussels may play an important role reducing environmental impact from salmon farm and it gives a possibility to integrating mussels on the salmon cage culture.
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Mansour, Randa A. "Foraging ecology of the blue crab, Callinectes sapidus Rathbun, in lower Chesapeake Bay." W&M ScholarWorks, 1992. https://scholarworks.wm.edu/etd/1539616761.
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This study concurrently quantified blue crab feeding habits and preference, and examined the inter-relationships between diet, predator preference, and predator and prey abundance and distribution in three subestuaries of lower Chesapeake Bay--the James, York and Rappahannock Rivers, Virginia. Complementary laboratory investigations estimated the combined effect of the functional, aggregative and interference responses upon prey and predator survival and predator foraging rates for blue crabs and a common bivalve prey, Macoma balthica, in this system. Crab abundance, prey abundance and diet were correlated such that blue crabs aggregated in areas of highest preferred (i.e., bivalve) prey abundance, as determined through electivity analyses. Spatial and size-related differences in diet selection occurred. at least two trophic groups were distinguished, based on their relative consumption of bivalves and crabs, including conspecifics (i.e., older juveniles and adults) or polychaetes and small crustaceans (i.e., younger juveniles and new recruits). Spatial differences were reflected by proportional bivalve consumption: crabs always preferred bivalves, but in areas of relatively lower bivalve abundance, opportunistically expanded their diets to include other prey taxa. Cannibalism was common, but the frequency of occurrence varied with crab size, season, river, new juvenile recruit abundance, and the density of alternative preferred prey. Laboratory experiments assessed the joint effects of varying predator and prey densities upon predator foraging rates and prey survival. A full-factorial experimental design involved 2 prey and 3 predator densities with 6 trials per treatment combination. Blue crabs exhibited density-dependent foraging under all conditions: proportionally more clams were consumed at higher clam density. Furthermore, at the higher crab densities, mutual interference was evident in the incidence of wounds and deaths to crabs resulting from cannibalism or intraspecific aggression. The collective results indicate that both predator and prey densities must be examined experimentally for their joint impact upon predator-prey dynamics in marine systems.
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Johnson, Eric Gordon. "Population dynamics and stock assessment of the blue crab in North Carolina." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-06012004-095447/.
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The blue crab (Callinectes sapidus) is an ecologically important estuarine predator and represents North Carolina?s most important commercial fishery. Recent fishery-dependent and ?independent data suggest the population is declining. The goal of this study was to increase our understanding of the status and population dynamics of the blue crab in NC by addressing the following objectives: (1) estimate population demographics of blue crabs in salt marsh creeks, (2) construct a discontinuous model of blue crab growth in NC using growth rates estimated from free-ranging blue crabs, and (3) provide a comprehensive stock assessment for the blue crab in NC. A series of complimentary laboratory and field studies assessed the nursery role of salt marsh habitats for the blue crab (Callinectes sapidus). Population demographics and movement patterns of juvenile and adult blue crabs were quantified in two tidal salt marsh creeks near Beaufort, North Carolina, USA during June ? October 2001. While there are many studies that report estimates of population density, mortality rates, or movement rates for blue crabs, this study represents one of the first attempts to estimate all quantities concurrently. Juvenile crabs were mobile within the interstices of the vegetated marsh surface during flood tide, and were equally distributed buried in intertidal marsh and adjacent mud areas during ebb tide. Juvenile crabs may experience a spatial refuge from cannibalism in the marsh surface since adult conspecifics are physically impeded by dense vegetation and rarely move far into marsh habitats. This spatial refuge in the vegetated marsh surface may be significant, since cannibalism represents a large source of mortality for this species. The relatively high use of the marsh surface by juvenile blue crabs, combined with a general lack of sampling these complex habitats, suggest that crab densities may be even higher in salt marsh systems than previously thought. Growth models commonly used in fisheries and ecological modeling assume growth is a continuous function of age. While this approach is appropriate for finfish, the validity of these models for crustacean species, which grow discontinuously, has been questioned. There is a critical need to compare the predictions of discontinuous and continuous models simultaneously to identify if potential biases are introduced by the assumption of continuous growth for the blue crab. The blue crab stock in North Carolina currently sustains heavy exploitation by the commercial fishery, and information on the recreational fishery is generally lacking. There has been a systematic increase in commercial landings from 1987-1999, followed by a period of reduced landings from 2000-2002. During this period fishery-independent indices of abundance have remained stable, or have shown a significant decline. In no case have any indices of abundance shown an increasing trend. Moreover, adult and spawning stock abundance (SSB) during 2000-2001 were at the lowest levels recorded since 1987, and the mean size of mature females has declined significantly during 1987-2003. Increases in the index of relative SSB in 2002-2003, however, may indicate a recovery. We detected a significant stock-recruit relationship for the blue crab in North Carolina using certain estimates of recruit abundance and recommend an urgent need for conservation of the spawning stock. We encourage decision makers to use the information and recommendations in this dissertation as soon as possible to manage the blue crab fishery in NC in a sustainable manner.
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Reyns, Nathalie Brigitte. "Biophysical dispersal dynamics of the blue crab in Pamlico Sound, North Carolina." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-10312004-143755/.
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For many species such as the blue crab, Callinectes sapidus, successful estuarine recruitment to juvenile nursery habitats is dependent on the biophysical processes experienced during dispersal of the early life stages. The goal of this study was to determine how blue crab primary (postlarval) and secondary (early juvenile) dispersal occurs within a predominately wind-driven estuary, Pamlico Sound, North Carolina, USA. We (1) characterized circulation patterns in Pamlico Sound during the fall blue crab recruitment months over two consecutive years using current meters (2) sampled during multiple 24 h periods to relate spatiotemporal water column distributions of postlarval and early juveniles blue crabs with circulation patterns, and used a hydrodynamic model to recreate dispersal trajectories from eastern (inlet) to western sound nursery habitats and (3) examined the environmental (wind, diel cycle, tidal phase) and biological (ontogenetic, density-dependent) factors that contribute to early juvenile blue crab secondary dispersal from near-inlet nursery habitats. During our study, surface currents responded synchronously to wind-forcing by generally flowing in the same direction as the wind. Particle-tracking simulations suggested that dispersal from Oregon and Hatteras Inlets to across-sound nursery habitats resulted from the combined use of tidal and wind-driven currents. Simulation results and observed crab distributions further indicated that Oregon Inlet was the primary supplier of postlarval blue crabs (dispersing in surface waters at night) throughout Pamlico Sound, as postlarvae ingressing through Hatteras Inlet were not retained within our study area. Furthermore, Oregon Inlet supplied early juvenile blue crabs (dispersing in bottom waters at night) to northwestern sound habitats, while crabs from Hatteras Inlet dispersed to mid- and eastern-sound regions. Results from our study in near-inlet settlement habitats confirmed the importance of tides to mediating dispersal partway into Pamlico Sound, as early juvenile blue crabs responded to increasing conspecific density in settlement habitats by using flood-tide transport near the inlets to rapidly leave these habitats. Based on our findings, we make recommendations regarding the prioritization of nursery habitats for conservation and fisheries management.
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Bucci, John P. "Blue Crab Trophic Dynamics: Stable Isotope Analyses in Two North Carolina Estuaries." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-11222003-195124/.
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Eutrophication is increasing in estuaries as a result of anthropogenic activity along the land-sea margin. Human activities contribute large amounts of nitrogen and carbon compounds to watersheds, resulting in changes in resource availability through alteration of biogeochemical cycles. Although the effects of poor water quality on lower trophic level biota is well understood, the impact of nutrient waste on upper trophic levels, such as blue crabs (Callinectes sapidus), has not been well studied. Stable nitrogen (δ15N) and carbon (δ13C) isotope ratios can provide time and space integrated information about feeding relationships and energy flow through food webs. An isotopic comparison of the trophic structure of two North Carolina estuaries was undertaken to understand the impacts of anthropogenic runoff on blue crab tissue enrichment and feeding interactions. This study examined isotopic signatures of primary producers, as well as blue crab and their bivalve prey (Rangia cuneata & Corbicula fluminea) as indicators of potential changes in food web relationships in response to eutrophication. The Neuse River Estuary is an "impacted" system that experiences high nitrogen loading and drains areas of urban development, row crop agriculture, and concentrated animal operations. The Alligator River Estuary by comparison, is designated as a "less-impacted" system in this study. The Alligator River Estuary is classified as having "Outstanding Resource Waters" and low nutrient loading. In each estuary, samples were collected in the upper, middle and lower regions of the river. Bivalves collected from the Neuse River Estuary yielded a significant difference (p<0.0001) in mean nitrogen isotopic composition of tissue (10.4? ± 0.82; N=66) compared to the bivalves collected from the Alligator River Estuary (6.4? ± 0.63; N=45). Similarly, the Neuse River Estuary blue crabs had a mean nitrogen isotopic composition of 11.41? (± 1.3, N=77), which was significantly different (p<0.001) than the less-impacted Alligator River blue crabs (9.65? ± 0.6; N=77). The mean nitrogen isotopic ratios between blue crabs and bivalves were significantly different (p<0.0001) in the Neuse (1.01 ? ± 0.13) compared to the Alligator River Estuaries (3.2 ? ± 0.1). Linear regression analyses showed a significant inverse relationship between δ15N values of blue crab tissue and water quality for the Neuse River Estuary (R² = 0.7; p= 0.01). A generalized linear model was conducted using blue crab tissue δ15N as the dependent variable and river estuary as the independent variable of interest. This analysis showed a significant difference (p<0.0001) between rivers controlling for size, site, and the river by site interaction. The results of this study indicate that 1) a relationship exists between the uptake of anthropogenic nutrients by primary producers and the subsequent energy transfer to estuarine consumers, represented by δ15N and δ13C ratios, in two North Carolina estuaries; and 2) an inverse relationship exists between blue crab tissue enrichment and water quality in an impacted estuary.
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Olmi, Eugene J. III. "Immigration of blue crab (Callinectes sapidus) megalopae in the York River, Virginia: Patterns and processes." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539616798.
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Following larval development in coastal waters, the postlarval stage, the megalopa, of the blue crab enters estuaries and colonizes juvenile/adult habitats. I examined the dynamics of the immigration of blue crab megalopae in the York River, Virginia. Plankton samples were collected nightly during flood tide in the York River Jul-Nov 1987, 1988 and 1989 to quantify variation in abundance of blue crab megalopae during the recruitment season. The abundance of megalopae was highly episodic, and significantly correlated with wind stress to the west (1987, 1988 and 1989), wind stress to the north (1989), and observed tidal range at Gloucester Point (1987 and 1988). These factors accounted for 22-56% of the variation in megalopal abundance. Megalopal abundance was not correlated with current speed, water temperature, salinity, or Chesapeake Bay subtidal volume. While in the estuary, megalopae vertically migrated in response to light and tide. Blue crab megalopae were more abundant during flood than ebb, indicating that megalopae selectively occupy flood waters. Ascent of megalopae into the water column appeared to be light limited. at night, megalopae were concentrated at the surface; during day, they were concentrated near the bottom in deep water, but apparently did not ascend from the bottom in shallow water. Thus, megalopae utilize flood currents for transport up the estuary while reducing the risk of predation to visual predators. Spatial patterns of abundance of megalopal and juvenile blue crabs were not consistent across habitats (plankton, grassbeds, or artificial settlement substrates) or time (days, months). Densities of megalopae and first-stage juveniles in grass beds correlated with megalopal abundance in the plankton; settlement on artificial substrates did not. Total juvenile abundance exhibited lower spatial and temporal variability in grass beds than that of megalopae or first-stage juveniles, suggesting that high variability in settlement is tempered by post-settlement processes. In laboratory studies, sand shrimp, Crangon septemspinosa, consumed &>&99% of available megalopae, while grass shrimp, Palaemonetes pugio, consumed 37% of megalopae in the first trial and 5% in the second trial. Predation by grass shrimp was not related to the rate of metamorphosis of megalopae, but may have been related to water temperature.
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Garrison, Haley S. "Effects of Episodic Turbulence on Diatoms: with Comments on the use of Evans Blue Stain for Live-Dead Determinations." W&M ScholarWorks, 2013. https://scholarworks.wm.edu/etd/1539617938.
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Episodic turbulence is a short-lived, high-intensity phenomenon in marine environments produced by both anthropogenic and natural causes, such as boat propellers, strong winds, and breaking waves. Episodic turbulence has been shown to cause mortality in zooplankton, but its effects on marine phytoplankton have rarely been investigated. This study focused on two diatoms: Thalassiosira weissflogii and Skeletonema costatum. I found that exposure for 45 s to turbulence intensities above 2.5 cm2 s-3 caused 24-32% reduction in diatom abundance and increased the amount of intact dead cells to 22%. Turbulence also caused extracellular release of optically reactive DOM. At a turbulence level of 4.0 cm2 s-3, photosynthetic efficiency (Fv/Fm) decreased from 0.51 to 0.38 and 0.55 to 0.50 in T. weissflogii and S. costatum respectively. These turbulence levels are comparable to those under breaking surface waves and are much smaller than those generated by boat propellers.
Despite its relatively short duration, episodic turbulence has the potential to affect phytoplankton via lethal and sublethal effects. An improved technique using the Evans Blue stain was developed to enable visual live/dead plankton cell determinations. When used in conjunction with preservation and flow cytometry, this staining method allows the study of phytoplankton mortality due to turbulence and other environmental stresses.
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Chaves, Juan Carlos. "Biological and Operational Factors Causing Mortality in North Carolina's Soft-Shell Blue Crab Industry." NCSU, 2002. http://www.lib.ncsu.edu/theses/available/etd-07232002-164130/.
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Factors causing mortality in North Carolina's soft-shell blue crab industry were quantified and identified at 11 crab shedding systems across the state. Operators of crab shedding systems who shed peeler crabs (pre-molt crabs) that they had caught themselves (self-caught peeler crabs) experienced significantly lower crab mortality rates than operators who shed peelers that they had bought from different sources (purchased-peeler crabs). Molt stage had a significant effect on the mortality rates of self-caught peeler crabs, as early molt stage crabs (white-line peelers) suffered significantly higher mortality rates than late molt stage crabs (red-line peelers). Purchased male crabs experienced significantly higher mortality rates than purchased females crabs. Water quality did not have a significant effect on crab mortality. Male peeler crab mortality was not significantly affected by the presence or absence of female red-line peeler crabs. Male red-line peelers experienced significantly longer times to molt when male crab density was high. Results of this study may lead to improvements in crab shedding technology, increased profits, and better fishery management practices.
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McMahon, David Z. "The Effects of Various Salinities on the Growth, Reproduction, and Pathology of Blue Tilapia (Oreochromis aureus)." NSUWorks, 1998. http://nsuworks.nova.edu/occ_stuetd/327.
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Blue tilapia, Oreochromis aureus were cultured from fingerling through maturation, in outdoor tanks, at varying salinities, for a period of nine months, from September 19, 1997 to June 19, 1998. Twelve tanks were used for testing four different salinities, with three replicates each. Each tank had a surface area of 0.8 m2, a water depth of 48cm, and held a volume of 350 liters. Each tank was stocked with ten O. aureus, with a total mean weight of 100 grams, and fed 5% to 10% body weight per day depending on size throughout the study. Salinity was the only induced variable throughout the experiment. Three tanks were the freshwater control group and salinity was held at 0 ppt. Salinities in three tanks were maintained at 10 ± 2ppt. Salinities in three tanks were maintained at 20 ± 2ppt and the salinities for the remaining three tanks were maintained at 30 ± 2ppt. Complete water changes were done each month, and the fish were individually weighed and an estimate of uneaten food was done. Any morphological or behavioral changes were noted for each fish, and each was regularly checked for eggs.
During the ninth month, reproduction resulted in viable eggs occurring in the freshwater control group and two tanks with salinities of 10 ppt. Light orange colored eggs were found in the mouths of females in tanks with salinities of 20 ppt, but the eggs were not viable. The fish in one tank suffered a mass mortality in month seven, so it was removed from reproduction computations. Reproduction also occurred during the ninth month in the freshwater control groups. Light orange colored eggs were found in the mouths of females in tanks with salinities of 20 ppt, but the eggs were not viable. Eggs with a grayish tint were found in the mouths of females in tanks with salinities of 30 ppt, but the eggs were also not viable. One high salinity tank was removed after nine months due to disease, but females were holding eggs with a gray color and eggs were examined and found not to be viable. No reproduction occurred in tanks with salinities of 20 ppt or higher during the experiment. Weight gain was shown to be positive and linear with salinity. The control group had the least weight gain with a final mean weight gain of 565 grams per tank. In tanks with salinities of 10 ppt, final mean weight gain of the fish was 697 grams; and in tanks with water salinities of 20 ppt, a final mean weight gain of the fish was 815 grams at the close of the experiment. Fish within tanks with salinities of 30 ppt, showed the most gain, with a mean weight gain of 927 grams these differences were shown to be statistically significant (P< .004).
Morphological changes and the occurrence of disease were evident between the fish in the control tanks and the fish in all other tanks. Tank 3, with 20 ppt salinity developed bacterial septicemia, caused by Streptococcus sp .. This disease produced some lesions, enlarged heads and sunken bellies as well as a dark green cast to the dorsal area. During the eighth month, the fish in a tank with salinity of 30 ppt developed a toxic algae bloom and the fish contracted a disease, which manifested itself by producing epithelial erosion, highly suggestive of the dinoflagellate pathogen Pfiesteria piscicida. Within a week, nine of the ten fish suffered severe epithelial loss and were close to death. Other changes accompanying increased salinity were brighter red flashing on the dorsal and pectoral fins and tail.
Thus the results are consistent with a hypothesis that higher salinity severely restricts reproduction and increases growth rates, but it was also appears that increased disease accompanies increased salinity. Thus the use of saltwater does not appear to be advantageous for the culture of this species.
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Layman, Bruce Clare. "Role of Habitat Features and Chemical Cues in Substrate Selection by Blue Crab Megalopae: Evidence from Laboratory Experiments." W&M ScholarWorks, 1992. https://scholarworks.wm.edu/etd/1539617647.
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Dutton, Daniel J. "Habitat Utilization and Dive Characterization of Blue Marlin (Makaira nigricans) and White Marlin (Kajikia albida) in the Western Atlantic Ocean." W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539617891.
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Blue marlin Makaira nigricans and white marlin Kajikia albida (formerly Tetrapturus albidus) are overfished in the Atlantic Ocean, with the vast majority of fishing mortality resulting from the pelagic longline fishery that targets tunas (Thunnus spp.) and swordfish Xiphias gladius. Time series of catch-per-unit-effort (CPUE) data have been fundamental to assessments of blue marlin and white marlin stocks, but these time series have been affected by a shift over time in pelagic longline fishing practices from shallow to deeper sets. One method for adjusting CPUE data for changes in fishing practices is a habitat-based standardization that modifies fishing effort in proportion to the vertical distribution of the species of interest and the fishing gear. For these models to be successfully applied to population assessments, the vertical habitat utilized by blue marlin and white marlin must be known. Pop-up satellite archival tags (PSATs) provide a means of collecting high resolution vertical movement and distribution data for billfishes.
In my study, 62 blue marlin and 40 white marlin were caught in recreational fisheries off the U.S. mid-Atlantic, Yucatan Peninsula, northern Caribbean, Venezuela, and Brazil, tagged with Microwave Telemetry, Inc. PTT-100 HR PSATs, and released. Data were recovered from PSATs attached to 57 surviving blue marlin and 36 surviving white marlin. PSATs successfully transmitted 18-100% of the data they recorded (mean 72%). The minimum 10-day displacements of both species averaged 242 km (range 9 to 942 km) and varied significantly between tagging locations, but not between species. Blue marlin spent a significantly higher (62%) amount of time in the upper 10 m of water than white marlin (56%). Both species spent greater than 95% of the time in water that was within 8o C of the sea surface temperature. Only 3.1% of white marlin demonstrated diel differences in the maximum depth of dives, while 29% of blue marlin dove into deeper waters during the day. Variables identified as explaining the most variation in dives were total dive duration, bottom time, ascent time, number of wiggles, wiggle depth, interdive interval, skew of ascent and descent, % time ascending, and % time descending. Using these variables, two dive types were identified through cluster analysis: simple dives representing traditional "U" and "V" shapes, and complex dives with multiple descents, plateaus, and wiggles. There were significant differences in dive variables among locations, individuals, diel periods, and dive types. There was significant overlap in range, habitat use, and vertical movement patterns, and therefore no strong evidence of niche partitioning between blue marlin and white marlin. My analyses can be used to further define the physical and physiological factors limiting marlins' vertical movements and therefore improve stock assessments based on longline CPUE data by correcting for changes in fishing practices.
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Pardieck, Renee A. "The Influence of Location, Seagrass Species and Water Depth on the Settlement and Distribution of Early Stage Blue Crabs." W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539617708.
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Roche, Sylvain. "Réenchanter le maritime par la promesse énergétique : technologies, trajectoires, discours." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0064.
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Cette thèse analyse les dynamiques de changement du système énergétique en se focalisant sur les énergies marines renouvelables (EMR). A travers l’examen de dix études de cas (études à la fois sectorielles et territoriales), elle s’interroge sur les raisons du retour de ces technologies au tournant des années 2000. Mises à la marge du paradigme dominant de la production d’électricité des années 1980, nous montrons que les énergies marines renouvelables sont revenues sur le devant de la scène dans un contexte de crise systémique des 3E (environnementale, économique et énergétique). A l’interface des politiques énergétiques (celles de la transition énergétique) et des politiques maritimes (celles de la croissance bleue), les énergies marines renouvelables ont été légitimées au moment où la mer est devenue un terrain pour (re)construire des discours visionnaires, avant-gardistes et technopolitiques. Par ce biais, nous mettons en lumière l’importance des croyances et des représentations collectives sur l’activité technologique. Au regard de la diversité des trajectoires technologiques examinées (énergie des marées et des courants, énergie des vagues, énergie thermique des mers et éolien marin), nous montrons que « la filière » des énergies marines renouvelables se présente en France comme une construction politique sans cohérence technologique affirmée entre des univers techniques différents. Cette thèse permet également de relativiser la notion d’innovation de rupture et de destruction créatrice en mettant en évidence des phénomènes de résurgence technologique pouvant durer plusieurs décennies, voire plusieurs siècles, dans l’exploitation de sources d’énergies renouvelables. Enfin, en s’inscrivant dans une démarche rétro-prospective, cette thèse défend l’idée que les processus fondamentaux dans la dynamique de changement du système énergétique ne sont pas la création et la nouveauté mais plutôt l’actualisation et la réinterprétation. Elle entend ainsi apporter une contribution originale aux interrogations à la fois des économistes, des sociologues et des historiens des techniques, qui chacun dans leur domaine tentent de comprendre les trajectoires de l'innovation et les conditions de réussite des technologies de l’énergieThis thesis sheds light on the dynamics of change in the energy system by taking the example of marine renewable energies (MRE). By exploring ten case studies (both sectoral and territorial), it reflects on the reasons for the return of these technologies in the 2000’s. Previously excluded from the dominant paradigm of French electricity production, in the 1980s, marine renewable energies are currently making a comeback in the context of the systemic crisis of the 3Es (environmental, economic and energy). At the interface of energy policies (energy transition policies) and maritime policies (blue growth policies), marine renewable energies were legitimized when the sea became a new horizon for (re)building visionary, avant-garde and technopolitical discourses. Through this, we highlight the importance of beliefs and collective representations of technological activity. Through the diversity of technological trajectories discussed in this thesis (tidal stream and tidal range energy, wave energy, ocean thermal energy conversion and offshore wind energy), we show that, in France, the industry of marine renewable energies presents itself as a political construction without asserted technological consistency, at the interface between different technical worlds. This thesis put into perspective the notion of disruptive innovation and creative destruction by highlighting phenomena of technological rebirth, which can take several decades and even centuries. Through a retroprospective analysis, this thesis defends the idea that the dynamics of change of the energy system are not mainly driven by creation and novelty, but could, rather, be construed as a process of update and reinterpretation of existing technological principles. This thesis aims to provide insights to economists, sociologists and historians of technology who try to understand the trajectories of innovation and the conditions for success of energy technologies
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Carver, Adina Motz. "SELECTIVE FISHING PRESSURE ON LARGE MALE BLUE CRABS NEGATIVELY AFFECTSMALE SIZE, SEX RATIO, AND POPULATION REPRODUCTIVE POTENTIALIN THE UPPER CHESAPEAKE BAY." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20011116-104952.
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A male-focused size-selective fishing pressure has the potential to reduce the average size of the males in the population, reduce the density of males in the population, and/or raise the sex ratio of females to males. All of these may affect the mating dynamics of the population by reducing the amount of sperm that males provide to females and decreasing the number of males available for copulation. I used three different approaches to investigate the effect of the fishery on the population. First I collected paired and unpaired crabs from the field to investigate crab size and seminal stores in nature. This approach substantiated that male blue crabs subjected to heavier fishing pressure are smaller, and that smaller males pass less sperm and accessory fluid to females. It also demonstrated that although the most depleted males in the population are not mating, some that continue to form pre-copulatory pairs are as sperm depleted as males that had just completed copulation.My second approach involved the use of biotelemetry to monitor mating behaviors in the field. Tracked males demonstrated a proportionately greater amount of pairing behavior than tracked prepubertal females, which is consistent with expectations of crab behavior in a population with a female-biased Operational Sex Ratio. My third approach was to examine a long-term trawl data set for trends over time. A decline in the average size of mature males (carapace width >110 mm) and an increase in the operational sex ratio of pre-pubertal females to mature males (carapace width >110 mm) and pre-pubertal females to legally fished males (carapace width >127 mm) were found at one of the four trawl locations. The observed trends in size and sex ratio at that trawl location are as would be expected in a population where an increasingly intense fishery has been removing large males. Analysis of seminal stores in conjunction with the crab behaviors and population trends provides evidence that the fishery is in fact having a detrimental affect on the reproductive potential of the blue crab populatio
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Metcalf, Karen S. "The Relationship of Habitat and Spatial Scale Upon the Developmental State and Settlement of Blue Crab Postlarvae in Chesapeake Bay." W&M ScholarWorks, 1991. https://scholarworks.wm.edu/etd/1539617638.
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Moody, Kirt E. "Predation on juvenile blue crabs, Callinectes sapidus Rathbun, in lower Chesapeake Bay: Patterns, predators, and potential impacts." W&M ScholarWorks, 1994. https://scholarworks.wm.edu/etd/1539616782.
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Various investigations of the population dynamics of blue crabs in Chesapeake Bay indicate that predator-induced mortality in the juvenile phase may determine year-class strength. In a tethering study, which spanned three seasons in shallow-water habitats of the lower York River, daily mortality rates of juvenile crabs were measured across three variables: crab size (30-70 mm carapace width), habitat type (seagrass, mud, and sand), and month (May-November). Vulnerability to predation was consistently lower for larger crabs, approaching a size refuge from predation at approximately 90 mm carapace width. Predation was most intense in unvegetated sand habitats, and significantly lower in seagrass and unvegetated mud. The data also reflected a strong seasonal pattern in predation potential which was correlated with water temperature. Predators contributing to this pattern were identified and assessed using an underwater video-recording system to monitor tethered crabs. While a variety of potential predators appeared and attacked crabs frequently, only two species had a measurable impact on crab survival, adult conspecifics and northern puffers, Sphoeroides maculatus. These results were confirmed in large laboratory tanks using untethered crabs as prey. These studies indicate that the mechanisms behind seasonal variation in predation pressure may include both physiologically-linked activity rhythms and seasonal migration of predators. The potential impact of seasonally-varying predation pressure on the life history of blue crabs was explored in a modeling exercise, using concepts of dynamic optimization. The results suggest that the blue crab may exhibit behavioral adaptations which are reflected in optimal biological timing of recruitment and growth, thereby enhancing survival through the juvenile phase.
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Howard, Jason Lee. "PATTERNS OF CARBON METABOLISM, STORAGE, AND REMINERALIZATION IN SEAGRASS ECOSYSTEMS." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3719.
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Coastal marine sediments have recently been identified as globally important stocks of organic carbon (Corg) that, if compromised, could significantly exacerbate global greenhouse gas emissions. While resource managers and policy makers are eager to incorporate this ecosystem service into seagrass ecosystem valuation frameworks, similar to those already in existence for terrestrial forests, there has been insufficient information regarding how environmental conditions and seagrass ecology control carbon storage. These include the influence of the seagrass to the production and preservation of soil organic matter, the fate of stored carbon following conversion of coastal wetlands, and the interactions between organic and inorganic carbon cycling. This dissertation intends to to understand the drivers of Corg storage and preservation to better prioritize and evaluate the worth of seagrasses to large scale carbon cycles and greenhouse gas mitigation planning.
Long-term experiments and thorough field surveys reveal that seagrasses are not categorically necessary nor sufficient for long-term Corg storage. Soil Corg stocks as well as their recalcitrance and breakdown rates are all correlated with sediment grain size, where muddy, fine sediments have higher Corg stocks that are less likely to breakdown. Sediment grain size can be influenced by the presence of seagrasses at some sites, likely where the leaf canopy can modify local hydrology enough to create a depositional environmental that wouldn’t otherwise exist. However, similar depositional environments that collect and store Corg can be obtained through local geomorphological features and natural hydrology, independent of benthic flora. This distinction has important implications on how soil C is managed to continue its preservation.
The relation between seagrass Corg and CO2 can be blurred by calcification and carbonate dissolution processes that occur concurrently, and have direct but antagonistic effects on CO2. Carbonate processes are dependent on local environmental factors, though augmented by biological processes, thus the ability of carbonate processes to interfere with seagrass Corg storage and loss is limited to geographic areas where processes can occur. Warm, shallow waters, like those in Florida Bay, encourage calcification, though the magnitude of soil inorganic and organic carbon interaction can vary locally as well.
Seagrasses are declining globally thus additional ecosystem value via greenhouse gas mitigation could greatly benefit conservation efforts. To make conservation efforts worthwhile to greenhouse gas mitigation, these findings help to consider and prioritize sites where risk and impact of Corg lost is more severe.
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Pile, Adele J. "Effects of the Habitat and Size-Specific Predation on the Ontogenetic Shift in Habitat use by Newly Settled Blue Crabs, Callinectes sapidus." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539617655.
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O'Leary, Patricia Anne. "The Development of Fiddler Crabs (Uca Spp.) as a Comparative Model System for the Parasitic Dinoflagellate, Hematodinium Perezi and its Natural Host the Blue Crab, Callinectes Sapidus." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153657.
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Herein, I have completed several experiments which encompass developing fiddler crabs as a model system, as well as sentinel and temperature studies to investigate biotic and abiotic factors in parasite transmission. My studies show which factors prevent, delay, or accelerate transmission and progression of H. perezi. The fiddler crab experiments by chapter are as follows: Chapter 1. I screened adult and juvenile fiddler crab populations for naturally occurring H. perezi infections at endemic and non-endemic sites. No natural infections were found in the adult or juvenile populations (Chapter 1 and 3). I completed inoculation trials with U. minax, U. pugnax, and U. pugilator, demonstrating that the parasite can survive and replicate in these species. Fiddler crabs can live for several months with patent infections. For example, I successfully transferred H. perezi from blue crab to fiddler crab and back to blue crab. Through serial inoculations I was able to serially maintain the parasite in the lab year-round. Building on the above experiments, I completed minimum dose studies which showed that a minimum inoculum of 1,000 parasite cells was required for patent infections. Additionally, I evaluated parasite progression through studies using Uca minax. These studies which used an inoculum in the ameboid trophont and clump colony stages showed that H. perezi progresses through its life-history stages in fiddler crabs as it would in blue crabs, with the filamentous trophont stage first observed in the hemolymphs smears followed by the ameboid trophont stage. Chapter 2. Intertidal environments are well known as areas of environmental extremes, and accordingly the animals that reside there have adapted to those conditions out of necessity. One abiotic factor that can have large diel variation is temperature. to address the impact of temperature variation of the marsh and subtidal habitat on H. perezi, I developed laboratory temperature experiments with nascent infections (7 °C, 15°C, 20°C, 25°C, 30°C), with patent infections (10°C, 15°C, 20°C, 30°C), and a progression series over fine scale (15°C, 17°C, 19°C, 20°C) temperature increments. These studies demonstrated that growth of the parasite is limited at the higher and lower temperatures, and that H. perezi is eliminated from the host at 30°C. This was confirmed by hemolymph smears, histology, and PCR. Chapter 3. The successful laboratory inoculations and lack of infections in fiddler crabs from endemic areas led to additional field deployments. These experiments aimed to address the dissonance of the initial results. My sentinel studies included fiddler crabs deployed in a crab pot from a pier touching bottom, deployed from the pier approximately mid-tidal height, deployed mid-marsh in mesh cages without access to bury, and deployed mid-marsh with access to bury. Fiddler crabs can obtain H. perezi infections in the marsh when caged without access to bury or when fully or partially submerged from a pier. However, they do not obtain H. perezi infections when given access to bury. Natural behaviors, such as burying along with elevated marsh temperatures likely prevent the establishment of H. perezi in the natural fiddler crab population.
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Schneider, Lutz [Verfasser], Marcel [Akademischer Betreuer] Thum, and Ulrich [Akademischer Betreuer] Blum. "Alterung und Arbeitsmarkt : Eine Untersuchung zum Einfluss des Alters von Beschäftigten auf Produktivität, Innovation und Mobilität / Lutz Schneider. Gutachter: Marcel Thum ; Ulrich Blum. Betreuer: Marcel Thum." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://d-nb.info/1019001275/34.
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Mooney, Melissa. "A comparison of feeding physiology in cultured and wild blue mussels Mytilus edulis and M. trossulus." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0034/MQ62404.pdf.
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Stark, Tiara Elizabeth. "Phylogeography and Genetic Diversity of the Commercially-Collected Caribbean Blue-Legged Hermit Crab: Implications for Conservation." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543499269936318.
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Olsson, Björne. "Protein Expression in Baltic Sea Blue Mussels Exposed to Natural and Anthropogenic Stress : The use of stress inducible proteins in ecotoxicological studies." Doctoral thesis, Stockholm University, Department of Systems Ecology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-542.
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The focus of this thesis is the early detection of stress in the environment. It has been proposed that studies on the cellular level would detect stress reactions earlier in time compared to common physiological methods. In a series of experiments we investigated how different stress factors, both natural and introduced by man, affect levels of stress proteins. One- and two-dimensional gels were used to determine individual proteins and families of proteins. The two-dimensional gels were also used in a proteomic approach, were the presence and absence of proteins after treatment was observed, and the protein expression signatures (PES) were identified.
Baltic Mytilus edulis was used in all experiments and it is evident that earlier observed differences in physiological rates and pollution sensitivity, compared to marine mussels, is also manifested as lower concentrations of stress proteins after exposure to copper and cadmium. When the Baltic mussels were allowed to acclimate for one month the difference decreased, suggesting an environmentally induced difference (paper I). Pre-exposure to heat before exposure to either a second heat-shock or cadmium was found to enhance the levels of HSP70 and thus tolerance, significantly (paper II). Exposure to a mixture of stress factors (PCB, copper and lowered salinity) revealed synergistic, additive and antagonistic effects in induction of 6 different stress proteins. When analyzing a large number of proteins it was shown that it is possible to identify PES with this technique, and we hypothesize that it could be possible to separate responses to mixtures of stress factors (Papers III and IV). Different techniques were also applied to analyze the protein expression pattern when mussels were exposed to PAH- and PCB-fractions extracted from Baltic Sea sediments. In this experiment the protein assays were accompanied by physiological measurements. All methods indicated stressed conditions, but the variation between individual mussels within treatments was smaller in terms of protein response than for physiological parameters (paper V). It is concluded that measuring the induction of stress proteins is a reliable way to detect stressful conditions. Proteins visualized on a one dimensional gel give a “gross” picture of an organism’s condition. The major challenge is to identify the origin and severity of the elucidated stress response. Further mapping of two-dimensional gels suggested that protein patterns are specific to type and level of stress.
A most important future step is to establish links between sub-cellular protein response to well known physiological effects. This should include long term experiments where altered protein expression signatures are linked to life history characteristics like survival, growth and reproductive success.
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Howey, Lucy A. "Seasonal Movement Patterns, Migratory Behavior and Habitat Utilization of the Bblue Shark (Prionace glauca) in the Western North Atlantic." NSUWorks, 2010. http://nsuworks.nova.edu/occ_stuetd/217.
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The blue shark (Prionace glauca) is among the most abundant and widely distributed of all oceanic elasmobranchs. Millions of blue sharks are caught annually worldwide in pelagic long line fisheries, and it accounts for the largest component of auctioned fin weight in the international shark fin trade. There is growing concern about the depletion of its populations worldwide and impacts of such large scale removal of an apex predator on oceanic ecosystem stability. The fragmentary nature of life history information available for blue sharks, including on its detailed movement and migratory behavior, continues to limit management efforts that require such data for stock assessment and sustainable catch modeling. To assist in obtaining a better understanding of blue shark movement behavior in the western north Atlantic, I used satellite telemetry to investigate the detailed habitat utilization and movements of sharks during the summer months when the sharks form aggregations on the continental shelf off the Northeast United States, and during their fall , pelagic migrations. Thirty-one (26 male, 5 female) blue sharks were tagged with pop-up archival satellite transmitters. The transmitters reported data from a total of 1,656 combined days, yielding 74,163 depth recordings and 74,125 temperature recordings. Tracked sharks exhibited two distinct movement patterns: During the summer months, the sharks remained within a restricted geographical area south of Nantucket Island and spent nearly 80% of their time in the uppermost part of the water column in <20 m depth (mean depth of 8 m). During fall months (October and November) the sharks made fairly directed offshore and southerly movements, with several sharks associating with waters east of Bermuda. During their pelagic migrations, the sharks demonstrated markedly different water column utilization behavior. They occupied much greater depths (127 m mean depth) and exhibited a clear diel depth pattern, occupying deeper water during the day and shallower water at night, not observed on the shelf. The longest duration track was that of an immature female for nine months. The greatest distance traveled was by a mature male that moved from Martha's Vineyard, MA to waters near Puerto Rico (a linear distance > 4,000 km). There was some indication that the different demographic groups (mature males, immature males, and immature females) may display different movement behavior, especially during their pelagic migrations. This study provides the first detailed information on habitat utilization and movement patterns of blue sharks in the Western North Atlantic, and points to the need for further investigation of movement behavior by different demographic segments of the population.
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YUAN, YI-MOND. "Le ble concurrence t-il le riz dans les pays du sud-est asiatique : l'exemple d'une economie de marche, taiwan." Paris, Institut national d'agronomie de Paris Grignon, 1988. http://www.theses.fr/1988INAPA009.
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Evolution parallele de la demande en riz et ble, les 2 principales cereales consommees a taiwan, premier des nouveaux pays industrialises du sud-est asiatique pour son taux de croissance. Environnement geopoliticoeconomique de taiwan; dependance etrangere en matiere de cereales; reforme du systeme d'importations. Possibilites d'introduction sur ce marche pour d'autres pays producteurs et perspectives sur le marche d'extreme-orient
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Leleu, Kevin. "Suivi et évaluation de la pêche professionnelle au sein d'une Aire Marine Protégée : protocoles d'enquêtes et indicateurs de pression et d'impact. Application au Parc Marin de la Côte Bleue." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4011.
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La surexploitation des ressources halieutiques a conduit à une crise majeure du secteur de la pêche professionnelle. Dans ce contexte, les pêcheries artisanales, et notamment les pêcheries aux petits métiers côtiers, apparaissent comme des modes d'exploitation potentiellement durables des ressources côtières. La diversité des engins utilisés et des espèces ciblées rend néanmoins complexe le suivi de cette composante importante de la pêche professionnelle. L'activité de pêche artisanale reste ainsi très peu évaluée en Méditerranée, et notamment à l'échelle d'une Aire Marine Protégée (AMP). Les AMP sont pourtant de plus en plus utilisées comme des outils de gestion de ces pêcheries, les effets des différentes mesures de gestion mises en place étant à même de bénéficier aux pêcheurs professionnels. A l'heure où le nombre d'AMP se multiplie, il apparaît alors nécessaire pour les gestionnaires comme pour les scientifiques de disposer d'indicateurs permettant de suivre l'activité de pêche professionnelle sur le territoire d'une AMP, et d'évaluer les effets de la gestion sur cette activité. Un protocole d'enquête pour le suivi de la pêche artisanale aux petits métiers côtiers a ainsi été mis en place entre juillet 2009 et juin 2010 au sein du Parc Marin de la Côte Bleue (PMCB), AMP méditerranéenne française comprenant deux réserves marines d'âge et de taille différents. Les données récoltées ont permis d'identifier sept métiers principaux pratiqués par les pêcheurs du PMCB, et de les caractériser par un groupe d'espèces cibles, un engin, un territoire et une période de pêche. L'effort de pêche et les captures ont alors pu être estimés à partir de ces métiersThe overexploitation of fishery resources has led to a major fisheries crisis. In this context, artisanal fisheries, and in particular small-scale coastal fisheries, appear as relevant alternatives for a sustainable use of coastal resources. But the diversity of fishing gears and targeted species diversity make it difficult to assess this important component of the commercial fishery. Hence, the activity of small-scale artisanal fishing remains poorly known in the Mediterranean Sea and few studies focus on an assessment of this activity at the scale of a Marine Protected Area (MPA). MPAs are yet more and more used as management tools for these fisheries, as protection effects and targeted access regulations may benefit to commercial fishers. As many MPAs are going to be established in the short term, it seems necessary for managers and for scientists, to have indicators to monitor the artisanal small-scale coastal fishing activity within an MPA, and to estimate the effects of MPA management on this activity. A field protocol was defined and implemented between July 2009 and June 2010 within the Parc Marin de la Côte Bleue (PMCB), a French Mediterranean MPA including two marine reserves of different age and size. The collected data allowed identifying seven main métiers within the PMCB, and characterizing them by group of target species, type of gear, fishing grounds and fishing periods. Fishing effort and catch were estimated. In the Côte Bleue area, 3 512 fishing trips and 4645 fishing operations were performed by 30 active boats during the studied period, for a total of 10 300 km of immersed nets
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Bouffaut, Léa. "Detection and classification in passive acoustic contexts : application to blue whale low-frequency signals Passive stochastic matched filter for Antarctic blue whale call detection, in The Journal of the Acoustical Society of America 144 (2), 2018 Baleen whale distribution and seasonal occurrence revealed by an ocean bottom seismometer network in the Western Indian Ocean, in Deep Sea Research Part II: Topical Studies in Oceanography 161, March 2019." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0057.
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L’analyse des grands volumes de données générés par la surveillance par acoustique passive long-terme et continue des baleines bleues (BW) est améliorée par la détection automatisée des signaux d’intérêt. Le travail présenté dans cette thèse s’attaque au problème de la détection et classification de signaux stéréotypés dans un contexte passif basse fréquence où les signaux sont modifiés par le canal de propagation, bruités et où le SNR varie continuellement. Les méthodes développées sont appliquées à des enregistrements issus d’OBS déployés dans l'océan Indien occidental.Premièrement, le filtrage adapté stochastique (SMF) est étendu au contexte passif en adaptant l’estimation du bruit et du SNR. Ce filtre est appliqué avec succès pour la détection des calls de baleine bleue antarctique et est comparé aux MF et Z-detector sur données annotées présentant de nombreux bruits et d’importantes variations du SNR. Les excellentes performances du SMF passif permettent d’augmenter la portée de détection jusqu'à 100 km en présence de bruit de bateau.La détection simultanée de différentes espèces s’appuie sur un schéma de reconnaissance de formes où les signaux tonaux de BW sont extraits, caractérisés et classifiés pour la transcription automatique des chants.Les signaux ainsi identifiés sont ensuite reconstruits avec des formes d'onde distinctes reproduisant les chants sous-jacents. Le succès de la reconstruction repose sur la qualité de la détection de tonales: le détecteur de crêtes est choisi pour son efficacité. Les résultats d'apprentissage et la première application non supervisée de la transcription ont révélé des résultats prometteurs et son utilité pour l’analyse multi-espècesThe analysis of the large volumes of data resulting from continuous and long-term monitoring efforts of blue whales (BWs) benefits from the automated detection of target signals. This thesis investigates the challenging problem of the detection and classification of stereotyped signals in a low-frequency passive acoustic context where (1) signals traveling long distances are deteriorated by the propagation channel, (2) overlapping noises interfere and, (3) SNRs vary continuously. Developed methods are applied to recordings from ocean bottom seismometers deployed in the western Indian Ocean.First, the stochastic matched filter (SMF) is adapted to the passive context by overcoming noise estimation and estimating the SNR automatically. This filter is successfully applied to the detection of Antarctic blue whales calls and is compared to the MF and the Z-detector on an annotated ground-truth dataset exhibiting various SNRs and noises. The passive SMF showed better performances, increasing the detection range up to 100 km in the presence of ship noise.The problematic of the detection of concurrently calling species is addressed based on a pattern recognition development for the automatic transcription of BW songs where, tonal signals are extracted, characterized, and classified. The hence identified signals are then reconstructed as separate waveforms reconstructing of the underlying songs. The success of the reconstruction relies on the quality of the tonal detector: the ridge detector was chosen for its efficiency. Training and unsupervised application revealed promising results of the proposed transcription method and its utility for multi-species analysis
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Hill, Jennifer Marie. "Predator biomass and habitat characteristics affect the magnitude of consumptive and non-consumptive effects (NCEs): experiments between blue crabs, mud crabs, and oyster prey." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41172.
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Recent research has focused on the non-lethal effects of predator intimidation and fear, dubbed non-consumptive effects (NCEs), in which prey actively change their behavior and habitat use in response to predator chemical cues. Although NCEs can have large impacts on community structure, many studies have ignored differences in predator population structure and properties of the natural environment that may modify the magnitude and importance of NCEs. Here, I investigated the roles of predator size and density (i.e. biomass), as well as habitat characteristics, on predator risk assessment and the magnitude of consumptive and NCEs using blue crabs, mud crabs, and oyster prey as a model system. Predation experiments between blue crabs and mud crabs demonstrated that blue crabs consume mud crabs; however, the consumptive effects were dependent upon blue crab body size and habitat type. When mud crabs were exposed to chemical cues from differing biomasses of blue crabs in laboratory mesocosms, mud crab activity and predation on oysters was decreased in response to high biomass treatments (i.e. large and multiple small blue crabs), but not to low biomass predators (i.e single small blue crab), suggesting that risk associated with predator size is perceptible via chemical cues and is based on predator biomass. Further experiments showed that the perception of risk and the magnitude of the NCEs were affected by the sensory cues available and the diet of the blue crab predator. The NCE based on blue crab biomass was also demonstrated in the field where water flow can disperse cues necessary for propagating NCEs. Properties of water flow were measured within the experimental design and during the experiment and confirmed cage environments were representative of natural conditions and that patterns in NCEs were not associated with flow characteristics. These results affect species conservation and commercial fisheries management and demonstrate that we cannot successfully predict NCEs without considering predator size structure and the contexts under which we determine predator risk.
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Barber, Marcus. "Where the clouds stand Australian Aboriginal relationships to water, place, and the marine environment in Blue Mud Bay, Northern Territory /." Click here for electronic access, 2005. http://adt.caul.edu.au/homesearch/get/?mode=advanced&format=summary&nratt=2&combiner0=and&op0=ss&att1=DC.Identifier&combiner1=and&op1=-sw&prevquery=&att0=DC.Title&val0=Where+the+clouds+stand&val1=NBD%3A&submit=Search.
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SUL, Juliana Assunção Ivar do. "Contaminação ambiental por microplásticos em Fernando de Noronha, Abrolhos e Trindade." Universidade Federal de Pernambuco, 2014. https://repositorio.ufpe.br/handle/123456789/18853.
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Recentemente, a comunidade científica especializada vem concentrando seus esforços na identificação, caracterização e quantificação dos microplásticos, definidos pela literatura como partículas plásticas menores que 5 milímetros. Microplásticos então presentes na superfície dos oceanos, em praias arenosas e ambientes lamosos, desde o Equador até os Pólos, em praias urbanas e regiões remotas do globo, e ainda depositados em sedimentos profundos (>2.000m). Experimentos de laboratório indicam que estas partículas plásticas podem ser ingeridas por organismos de todos os níveis da teia trófica marinha. Poluentes orgânicos, como DDTs e PCBs, e inorgânicos presentes na água do mar podem estar adsorvidos a estes plásticos, transportando contaminantes químicos para diversas regiões do globo, ou sendo liberados quando no trato gastrointestinal de vertebrados e invertebrados se ingeridos, podendo ainda ser transportados ao longo da teia trófica marinha. Há mais de 10 anos relata-se que no Oceano Pacífico Norte microplásticos estão presentes principalmente no centro do giro subtropical, aparentemente influenciados por variáveis oceanográficas. Para o Oceano Atlântico tropical, evidências sobre a presença de microplásticos existiam apenas para as praias arenosas do Arquipélago de Fernando de Noronha (3°S, 32°W), e para as águas adjacentes ao Arquipélago de São Pedro e São Paulo. Para preencher esta lacuna, microplásticos foram o foco da amostragem em três importantes ambientes insulares no oeste do Oceano Atlântico tropical: Arquipélago de Fernando de Noronha, Arquipélago de Abrolhos (17°S, 38°W) e a Ilha da Trindade (20°S, 29°W) em 4 expedições científicas realizadas entre dezembro de 2011 e março de 2013. Plásticos flutuantes foram amostrados através de arrastos planctônicos (neuston) nas áreas marinhas adjacentes a estes ambientes. Um total de 160 arrastos foi realizado. Em Trindade, mais de 90% dos arrastos estavam contaminados por microplásticos, identificados como fragmentos duros, fragmentos moles, paint chips, linhas e fibras. Em Noronha e Abrolhos aproximadamente metade dos arrastos estava contaminada. Fragmentos plásticos duros foram os tipos de itens mais amostrados assim como em outros estudos de microplásticos em amostras de plâncton. Entre os fragmentos, >75% tinham 5mm ou menos. A contaminação média foi de 0,03 partículas por m3, inferior às quantidades previamente conhecidas no Oceano Pacífico. As amostras de microplásticos depositados na superfície do sedimento foram coletadas nas praias arenosas em cada uma das ilhas através de quadrantes. As amostras coletadas também foram analisadas quanto a granulometria predominante, já que estas informações ainda eram inexistentes para as ilhas estudadas. Em Abrolhos nenhuma partícula plástica foi amostrada. Fragmentos plásticos duros e esférulas plásticas foram identificados somente em Fernando de Noronha e Trindade, sendo que o lado mais exposto à ação de ventos e corrente superficias predominantes estava mais contaminado, quando comparado ao lado relativamente mais protegido nas ilhas estudadas. Estes resultados são os primeiros indícios da contaminação do oeste do Oceano Atlântico tropical em relação à contaminação por microplásticos. A presença destes microplásticos alerta para a vulnerabilidade destas ilhas e sua biota em relação á contaminação por plásticos.
Recently, the scientific community is focussed on the identification, characterization e quantification of microplastics, defined in the literature as those plastic particles with less than 5 millimetres. Microplastics are widespread on the ocean’s surface, on sand beaches and mud sediments, from the equator to the poles, on urban beaches and remote regions in the globe, and even deposited on deep sediments (>2,000m). Laboratory experiments indicate that organisms from every level of the marine food web potentially ingest microplastic particles. Organic, such as DDTs and PCBs, and inorganic pollutants available in seawater may adsorbed onto microplastics, transporting chemical contaminants to diverse regions in the globe, or being released in the gastrointestinal tract of vertebrates and invertebrates if ingested, when they are even transported along the marine food web. For more than 10 years, there were reports on the occurrence of microplastics in the North Pacific Ocean, mainly in the centre of the subtropical gyre, probably influenced by oceanographic variables. To the tropical Atlantic Ocean, however, evidences on the presence of microplastics were available only to sandy beaches in the Fernando de Noronha Archipelago (3°S, 32°W), and to waters around the São Pedro e São Paulo Archipelago. To fulfil this gap, microplastics were studied in three important insular environments in the western Atlantic Ocean: the Fernando de Noronha Archipelago, the Abrolhos Archipelago (17°S, 38°W) and the Trindade island (20°S, 29°W), during four scientific expeditions between December 2011 and March 2103. Floating plastics were collected by plankton tows (neuston) on the sea surface in the adjacent region to these environments. A total of 160 tows were conducted. In Trindade Island, more than 90% of the tows were contaminated with microplastics, identified as hard plastic fragments, soft fragments, paint chips, lines and fibres. In Fernando de Noronha and Abrolhos, approximately half of the tows were contaminated. Hard plastic fragments were the majority of the sampled items, as well as reported in other studies with plankton samples. Among plastic fragments, >75% had 5mm or less. The mean contamination pattern was 0.03 particles/m3, less than previously reported on the Pacific Ocean. Microplastics sampled on sediments were collected on sandy beaches in each island by quadrants dispoded in the strandline. Samples were also analysed in the relation to the main grain size of sediments because these information was still non-existent to the studied islands. In Abrolhos, no plastic particle was sampled. Hard plastic fragments and plastic pellets were identified in Fernando de Noronha and Trindade, where the windward side of the islans were significantly more contaminated when compared to the leeward side. These results are the first results indicating the occurrence of microplastic debris particles in the Western tropical Atlantic Ocean. The occurrence of microplastics highlights the vulnerability of these islands and their biota in relation to microplastic pollution.
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Patris, Julie. "Contributions en méthodes pour le suivi de mysticètes par acoustique passive." Electronic Thesis or Diss., Toulon, 2019. http://www.theses.fr/2019TOUL0016.
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La surveillance par acoustique passive est un outil d'importance croissante pour l'étude des mammifères marins. Cette thèse pose des nouveaux modèles pour l'étude du plus grand d'entre eux, la baleine bleue (Balaenoptera musculus), qui émet de très basses fréquences. Pour ce faire, nous avons enregistré un corpus inédit dans l'archipel de Humboldt au nord du Chili. Nos données révèlent un chant caractéristique de la baleine bleue 'chilienne', dont nous étudions la structure pulsée et l'évolution au cours des dernières décennies. Le classement en signal tonal ou non-tonal nous permet, en nous focalisant sur la fréquence fondamentale mise à jour, de quantifier la baisse en fréquence des chants et d'effectuer une comparaison des signaux au niveau mondial. Notre troisième contribution est une méthode de localisation mono-hydrophone basée sur des simulations de propagation par éléments spectraux. C'est à notre connaissance le premier modèle de ce type, implémenté en milliers d'heures de calcul haute performance. Nous concluons en soulignant l'intérêt des méthodes en bioacoustique comme moyen de suivi et de connaissance du milieu marinPassive acoustic monitoring has a growing importance in marine mammals studies. This work is concerned with the largest of marine mammals, the blue whale (Balaenoptera musculus). We obtained a new corpus of acoustic data in the northern part of Chile, in the Humboldt archipelago. We show the presence of a song characteristic of the 'Chilean' blue whale, formerly described in southern Chile and Galapagos islands. Based on this sang type, we propose new methods of analysing and classifying pulsed sounds. Using the fundamental frequency thus obtained, we analyse the blue whale's sang, showing a general evolution of the frequency on a decadal scale. We also construct a method of monohydrophone source localisation based on high performance simulation of the acoustic wave field, by spectral elements methods. We conclude emphasizing on the importance of bioacoustic for monitoring the marine world
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Monnet, Rodolphe. "La politique extérieure de l'Inde en Afrique." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCB025.
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Depuis 2001 et la recomposition des équilibres de puissance, l'Inde s'affirme comme l'un des acteurs qui compte dans un espace international de plus en plus multipolaire. Les mouvements de fond actuels provoquent une redistribution de cette puissance imposant de nouvelles alliances et de nouveaux jeux de pouvoirs. L'Inde n'est pas étrangère à cette tendance et encore plus depuis l'arrivée au pouvoir, en 2014, de l'actuel Premier ministre, Narendra Modi. Ce dernier conduit une politique extérieure ambitieuse pour que son pays accède à un statut de puissance mondiale. C'est dans ce cadre que se pose notre problématique qui est de savoir dans quelle mesure la place de l'Afrique dans la politique étrangère indienne permet-elle justement à l'Inde de parvenir à se hisser à ce statut de puissance. Pour y répondre, cette thèse investigue trois directions. D'abord, la place de l'océan Indien dans la relation indo-africaine doit rendre compte du rôle de l'Afrique dans la volonté indienne de faire de cet océan un espace pacifique et sécurisé sur lequel l'Inde puisse être un acteur incontournable face à des acteurs politiques puissants et hétérogènes. Ensuite, cette thèse s'attache à déterminer le rôle que l'Afrique joue dans la volonté de l'Inde d'être une puissance ayant une capacité d'influence politique sur la scène internationale au travers des instances internationales, de ses relations bilatérales avec les États africains et de la diaspora indienne installée dans ces pays. Enfin, cette recherche de statut passe par le champ économique et la nécessaire évaluation de l'empreinte économique que l'Inde souhaite imprimer en Afrique pour mieux asseoir ses capacités d'influence. Cette étude doit permettre de donner un éclairage sur la politique extérieure indienne à l'heure où les États-Unis réévaluent leur implication dans l'océan Indien, où la Chine met en place la « One Belt, One Road » et où l'Inde et le Japon viennent de s'unir pour proposer un nouveau partenariat à l'AfriqueSince 2001 and the reshuffling of the balance of power, India has become one of the influential actors in an increasingly multipolar international context. The current groundswells are reshuffling powers between Nations in shaping new alliances and new power games. India is, more than ever, involved in this trend since the current Prime Minister, Narendra Modi, came to power in 2014. He conducts an ambitious foreign policy as a means to make his country a global and respected power. The context of the issue detailed in this document is: to what extent does Africa's place in India's foreign policy enables India to reach this status of power? This thesis investigates the following three themes: Firstly, the Indian Ocean's place in the Indo-African relationship should reflect Africa's role in India's will to make the Indian Ocean region a peaceful and secured space in which India is a decisive player in front of powerful and heterogeneous political actors. Secondly, this thesis focuses on assessing Africa's role in India's initiatives to be an influential player on politics on the international agenda through international bodies, its bilateral relations with African states and the Indian diaspora settled down in these countries. Thirdly, India's search for that particular status goes through the economic area and the assessment of India's economic footprint in Africa to better establish its influence on that Continent. This study tries to shed the light on India's foreign policy while the United States are reassessing their involvement in the Indian Ocean, and while China is setting up its "One Belt, One Road" and India and Japan have just come together to propose a new partnership to Africa
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Vaz, Bárbara Maria Correia. "Development of downstream processes for pigment valorization: a step towards blue biorefinery." Master's thesis, 2021. http://hdl.handle.net/10773/33018.
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The guidelines of The 2030 Agenda for Sustainable Development were very clear. New strategies need to be found to ensure a sustainable future. In this way, marine resources emerge as natural and renewable feedstocks to integrate a blue biorefinery framework and a circular economy approach. Through biomass conversion an integrated production of biofuels and value-added compounds can be designed, allowing the recovery of multiple compounds with lower environmental impacts and a sustainable economic growth. Pigments are natural compounds used in high-end applications due to their colour and high biological interest that can be found in several marine resources. However, the conventional techniques to recover them require the use of complex and time-consuming methodologies that may lead to the degradation and/or loss of stability of the compounds, high energy consumption, and low yields of extraction. Alternative solvents such as aqueous solutions of surfactants and ionic liquids (ILs) appear as more sustainable options that can improve thermal and chemical stability of pigments, obtain higher extraction yields, while minimizing the environmental impacts of the process. In this work, two procedures were developed to recover different pigments using alternative solvents, to overcome the bottlenecks found in the conventional methodologies. In the first work, a solid-phase extraction technique was used to fragmentate chlorophylls from xanthophyll. Then, to elute chlorophylls from AmberLite™ HPR900 OH resin, aqueous solutions of ILs revealed to be efficient solvents to valorize simultaneously xanthophyll and chlorophylls while reusing the resin in several new cycles of purification. The second work focused on the extraction of bacterioruberin pigment from Haloferax mediterranei with aqueous solutions of surfactants, being the non-ionic class the one that showed higher extraction yields. Moreover, the purification of bacterioruberin was also addressed by inducing a simple precipitation with ethanol as anti-solvent to recover proteins as a second added-value compound. In both works easy to implement and environmentally friendly procedures using water-based solvents were successfully proposed, being the operational conditions optimized to reduce both economic and environmental impacts, and to reach higher yields.As diretrizes da Agenda 2030 para o Desenvolvimento Sustentável foram muito claras. Novas estratégias precisam de ser encontradas para garantir um futuro sustentável. Desta forma, os recursos marinhos surgem como matérias-primas naturais e renováveis para integrar uma estrutura de biorefinaria marinha e uma abordagem de economia circular. Através da conversão de biomassa, uma produção integrada de biocombustíveis e compostos de valor acrescentado pode ser projetada, permitindo a recuperação de vários compostos com impactos ambientais mínimos e um crescimento económico sustentável. Pigmentos são compostos naturais utilizados em aplicações de elevado padrão devido à sua cor e ao seu alto interesse biológico, podendo ser encontrados em diversos recursos marinhos. No entanto, as técnicas convencionais para recuperá-los requerem o uso de metodologias complexas e demoradas que podem levar à degradação e/ou perda de estabilidade dos compostos, alto consumo de energia e baixos rendimentos de extração. Solventes alternativos, como soluções aquosas de líquidos iónicos e surfactantes, aparecem como opções mais sustentáveis que podem melhorar a estabilidade térmica e química dos pigmentos, obter rendimentos de extração mais altos, enquanto minimizam os impactos ambientais do processo. Neste trabalho, foram desenvolvidos dois procedimentos para recuperar diferentes pigmentos utilizando solventes alternativos, a fim de superar as dificuldades encontradas nos métodos convencionais. No primeiro trabalho, uma técnica de extração em fase sólida foi usada para fracionar clorofilas e xantofilas. A seguir, para eluir as clorofilas da resina AmberLite™ HPR900 OH, as soluções aquosas de líquidos iónicos revelaram-se solventes eficientes para valorizar simultaneamente xantofilas e clorofilas, e reaproveitar a resina em vários novos ciclos de purificação. O segundo trabalho teve como foco a extração do pigmento bacterioruberina com soluções aquosas de surfactantes a partir da Haloferax mediterranei, sendo a classe dos não iónicos a que apresentou maiores rendimentos de extração. Além disso, a purificação da bacterioruberina também foi abordada através de uma simples precipitação induzida com etanol como anti-solvente para recuperar proteínas como um segundo composto de elevado valor comercial. Em ambos os trabalhos foram desenvolvidos com sucesso procedimentos de fácil implementação e ambientalmente sustentáveis recorrendo ao uso de solventes aquosos, sendo as condições operacionais otimizadas para reduzir os impactos económicos e ambientais, e permitir alcançar rendimentos mais elevados.
Mestrado em Engenharia Química
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Baptista, Silvia de Almeida. "Screening of polyhydroxyalkanoates producing bacteria isolated from marine ecosystems." Master's thesis, 2013. http://hdl.handle.net/10400.6/2945.
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Polyhydroxyalkanoates (PHAs) are biodegradable polyesters and environmentally friendly thermoplastics, which are accumulated as carbon and energy storage materials in various bacteria in limited growth conditions with excess carbon sources.
In this study, bacteria were isolated from samples taken from various marine ecosystems in the Archipelago of Madeira in the Atlantic Ocean, and screened for their ability to accumulate polyhydroxyalkanoates. These samples were taken from the seabed at depths of 30 and 1,700 meters to obtain a larger diversity of microorganisms and therefore, in an attempt to obtain new structures of PHAs. Strains were directly isolated from 612 mother plates where marine samples had been initially plated. A total of 724 isolates from mother plates were obtained, of which 174 were found PHA-positive using Nile red viable-colony screening. All synthesized intracellular inclusions during growth on starch carbon source. Twenty-five bacterial isolates in 25 mL-scale cultivation were proven promising for PHA production with PHA storage maximum 17.71 % for MD12-107 and 9.30 % for MD12-581 strain. The inclusions were predominantly identified as poly-β-hydroxybutyrate (PHB) using gas chromatography. Strains MD12-107 and MD12-581 were tested in 100 mL-scale and bioreactor cultivation. The best results were achieved with strain MD12-581 accumulated PHA storage 15.40 % in less than 6.5 hours with 5.5 g/L of cell dry weight and a specific growth rate was 0.24 h-1 when grown in medium containing 40 g/L of starch, 8 g/L of yeast extract and 4 g/L of peptone during batch cultivation.Os Polihidroxialcanoatos (PHAs) são biopoliésteres biodegradáveis e termoplásticos ecológicos, que são acumulados sob a forma de materiais de armazenamento de energia em várias bactérias em condições de crescimento limitado e fonte de carbono em excesso. Neste estudo, as bactérias foram isoladas a partir de amostras recolhidas a partir de vários ecossistemas marinhos no arquipélago da Madeira, no Oceano Atlântico e seleccionadas pela sua capacidade de acumular poli-hidroxialcanoatos. Estas amostras foram extraídas do fundo do mar a uma profundidade de 30 e 1,700 metros para se obter uma maior diversidade de microorganismos e, por conseguinte, numa tentativa de obter novas estruturas de PHAs. As estirpes foram directamente isoladas de 612 placas mãe onde as amostras marinhas tinham sido previamente espalhadas. Na totalidade foram isoladas 724 estirpes a partir das placasmãe, das quais 174 demonstraram resultado positivo durante o screening com o corante Vermelho do Nilo. Todas as estirpes com resultado positivo sintetizaram inclusões intracelulares durante o crescimento em amido como fonte de carbono. Vinte e cinco isolados bacterianos foram testados em cultura de 25 mL com resultados promissores quanto à produção de PHA com armazenamento de 17,71 % para a estirpe MD12-107 e 9,30 % para a estirpe MD12-581. As inclusões foram analisadas através da técnica de cromatografia gasosa como sendo predominantemente poli-β-hidroxibutirato (PHB). A produção a partir das estirpes MD12-107 e MD12-581 foi testada em 100 ml e em bioreactor. Os melhores resultados foram alcançados pela estirpe MD12-581 com um armazenamento de PHA de 15,40% em menos de 6,5 horas, com 5,5 g/L de concentração de biomassa e uma taxa específica de crescimento de 0,24 h-1 quando cultivada num meio contendo 40 g/L de amido, 8 g/L de extracto de levedura e 4 g/L de peptona durante a produção em bioreactor.
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Proteau, Philip J. "Oxylipins from temperate marine algae and a photoprotective sheath pigment from blue-green algae." Thesis, 1993. http://hdl.handle.net/1957/35584.
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Geldenhuys, Linda-Louise. "The influence of Blue Flag status on tourist decision-making in South Africa / Linda-Louise Geldenhuys." Thesis, 2014. http://hdl.handle.net/10394/11545.
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Marine tourism has been growing over the years to a diverse and large industry providing for a variety of markets. Across the world tourists enjoy activities of different types including kayaking, scuba diving, snorkelling, surfing and travelling to beaches for leisure reasons. Travelling to coastal towns with the purpose of visiting a beach has always been a great attraction for people across the world. Not only resulting in beaches becoming one of the tourism industry’s biggest markets but also a great contributor to local economies.
In 200,1 South Africa adopted the Blue Flag Programme, a beach award which focuses on clean bathing water and pollution free environments. The programme was first established on the French coastline in Europe by the Foundation for Environmental Education (FEE). Since then 244 beaches and 208 marinas across 10 countries now boast with a Blue Flag award. The award requires beaches to adhere to four sets of criteria. These are water quality, environmental management, environmental education and information and safety and security. The programme also has specific periods allocated to beaches in which the beach has to meet all the stipulated standards.
Previous research has stated that the programme has great drawing power for tourists.
In contrast, other studies revealed that it has no benefits for the tourism industry, whatsoever.
Some studies have stated that it is a symbol of quality recognised by all across the world.
The literature review conducted for this study revealed that the programme holds great benefits for conservation of the environment. Seen from a tourism point of view, however, it is still unclear whether the programme benefits the tourism industry or has any impact on it whatsoever.
The primary goal of this dissertation is to determine the influence of Blue Flag status on the decision-making process of beach visitors when they select a beach, thereby determining whether or not the Blue Flag programme adds any value to the tourism industry. A literature review was conducted on important aspects concerning this study, namely the Blue Flag Programme, the tourist decision-making process, travel behaviour of tourists and tourist behaviour, to gain insight into the type of research. Thereafter an empirical study was conducted on six beaches in KwaZulu-Natal which involved the distribution of a self-administered questionnaire. The sampling method used for the study was quantitative, probability sampling with systematic sampling which involved the fieldworkers to approach every second person/group of people on the beach. The survey took place from 28 March to 4 April 2013. A total of 572 usable questionnaires was collected from a sample of 600 beach visitors. The data was captured using Microsoft™ Excel™ 2010 and analysed using Statistical Package for Social Sciences (SPSS version 21). Exploratory factor analyses were performed as well as a linear mixed-effect model analysis to analyse the impact of the Blue Flag Programme on tourism. To achieve the goal set for this study, two articles were produced.
The aim of chapter 3 (article 1) was to determine the push and pull motives of beach visitors. The results revealed the profile of respondents to be female, married with an average age of 39 years and originating from Gauteng. They have a diploma or degree from a tertiary institute and like to visit the beach for an average of eight nights at a time. To identify the push and pull motives of beach visitors, the travel motives were first identified by means of a principal axis factoring analysis, with Oblimin and Kaiser Normalisation. The aspects yielded three factors, familiarity, family relaxation and escape and beach characteristics. The most important factor was determined to be familiarity. The analysis further revealed two push and two pull motives. The push factors are escape and relaxation (most important push motive) and familiarity. The pull motives are beach attributes (most important pull motive) and cognizance. This article showed that the familiarity of a beach plays an important role as to the motives of beach visitors as well as the fact that visitors to these beaches want to escape and relax away from everyday life.
The aim of the chapter 4 (article 2) was to identify the influence of Blue Flag status on visitors’ decision-making when selecting a beach as well as to determine whether any statistically significant differences exist between the visitors to Blue Flag beaches and visitors to non-Blue Flag beaches. A principal axis factoring analysis was conducted to determine the decision-making aspects of beach visitors. This analysis yielded five actors, environmental education, safety and access, cleanliness, landscape and popularity. The most important factor was identified as cleanliness with a mean value of 4.37. Furthermore, a linear mixed-effect model analysis was conducted which identified one statistically significant difference with the factor popularity, which has a p-value of 0.002. No other differences were identified. This study thus found that Blue Flag status does not influence visitors’ decision in selecting a beach. What was interesting was the fact that the aspects which are of importance to beach visitors (such as cleanliness) form part of the criteria on which the programme is based (environmental education and information, environmental management, safety and security and water quality). Thus having Blue Flag status does impact positively on tourism.
Since this was the first study of its kind in South Africa, it can benefit all beach destinations in the country. From the findings it is clear that marketing needs to be conducted regarding the Blue Flag programme and the benefits that could be reaped for both the local community and beach visitors. Furthermore, beach management can make use of the motives identified in chapter 3 as well as the decision-making aspects identified in chapter 4 to increase visitor numbers to the beach and gain competitive advantage. Tailor-made marketing strategies can be implemented which will improve the efforts of beach managers and municipalities as well as managers of the Blue Flag Programme to market the programme and raise awareness. Recommendations are made regarding further study on the Blue Flag programme to identify ways in which awareness of the programme amongst the public can be raised. Similar research can also be conducted on other environmental and tourism award systems, such as the Seaside award. This research contributes to the literature on marine tourism, seeing as this was the first time such a study was conducted in a South African setting.MCom (Tourism Management), North-West University, Potchefstroom Campus, 2014
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Costa, Diogo Balcão Reis Peão da. "The influence of oxygen fronts and mesoscale eddies on the foraging patterns and space-use of blue and mako sharks." Master's thesis, 2021. http://hdl.handle.net/10400.1/17438.
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As populações de predadores pelágicos de topo têm vindo a decrescer drasticamente nas últimas décadas, sendo a sobrepesca considerada a principal responsável por estes declínios. As repercussões destes decréscimos são especialmente graves para as populações de tubarões, uma vez que, dado o seu lento ciclo de vida, estas espécies apresentam uma maior dificuldade em restabelecer os seus números após períodos de pesca intensiva. Além disso, dada a sua posição de topo na cadeia trófica, a remoção de tubarões dos ecossistemas gera efeitos em cascata nos níveis tróficos inferiores, tendo consequências graves e imprevisíveis para todo o ecossistema. Os tubarões azul (Prionace glauca) e anequim (Isurus oxyrinchus) são as duas espécies de tubarões pelágicos mais pescadas no Oceano Atlântico, constituindo, em conjunto, mais de 95% de todos os tubarões pelágicos capturados anualmente neste oceano e estando, respetivamente, classificadas como “quase ameaçada” e “em perigo” pelo IUCN. No entanto, continuam a existir graves problemas ao nível da regulamentação, monitorização e reporte da pesca destas duas espécies, tendo apenas no ano passado (2020) sido estabelecida uma quota máxima para a captura de tubarão azul no Oceano Atlântico, enquanto o tubarão anequim continua sem qualquer quota a restringir a sua captura.
A determinação de áreas prioritárias para a conservação de predadores pelágicos de topo é complicada pela extrema mobilidade destes animais e a consequente dificuldade em identificar zonas de agregação devido à falta de dados fiáveis, uma vez que os estudos destas espécies estão historicamente restringidos a dados inerentes às pescas, sendo, por isso, extremamente enviesados. Porém, o advento da tecnologia de telemetria de satélite tem permitido descrever novos comportamentos, bem como uma melhor compreensão da real distribuição espacial e utilização de habitat, horizontal e vertical, destes predadores. Neste sentido, estudos anteriores utilizando dados de esforço de pesca e/ou telemetria de satélite têm sugerido a atração de uma grande variedade de predadores de topo por fenómenos dinâmicos de média dimensão, tais como frentes térmicas e vórtices oceânicos, que estará relacionada com movimentos de procura de alimento.
Neste estudo, os movimentos de procura de alimento de 34 tubarões azuis e 24 tubarões anequins foram analisados relativamente à presença de frentes de oxigénio dissolvido (OD), que até agora não tinham sido consideradas na literatura. Para tal, estes tubarões foram capturados em 5 localizações diferentes do Oceano Atlântico Norte (Açores, Cabo Verde, ao largo de Nova Iorque e a sudoeste de Portugal e Inglaterra) e marcados com transmissores de satélite SPOT, que são fixados à barabatana dorsal e permitem seguir os seus movimentos horizontais com elevada precisão. Todas as variáveis ambientais foram extraídas da plataforma CMEMS’s (Copernicus Marine Environment Monitoring Service) Ocean Products, que disponibiliza dados oceanográficos diários e mensais recolhidos através de uma combinação de medições de satélites e de boias à superfície e a meia água. Para identificar a presença de frentes, foram calculados os gradientes máximos de OD (e temperatura) entre células adjacentes.
Os resultados aqui apresentados sugerem que frentes de OD podem representar extensas zonas de alimentação para estas duas espécies, sendo esta relação particularmente evidente para os tubarões azuis. Dois tipos de frentes de OD foram identificadas como atrativas para estas espécies: frentes conjuntas de temperatura e OD, forte, persistente e verticalmente estruturadas, onde a grande produtividade existente cria importantes áreas de alimentação que, por sua vez, atraem predadores de níveis tróficos subsequentemente mais elevados; e frentes exclusivas de OD, associadas a zonas hipóxicas, onde a compressão de presas nas águas superficiais, mais oxigenadas, da coluna de água aumenta a probabilidade de encontro entre predador e presa. No entanto, apesar de ambas as espécies terem revelado afinidade para com estes fenómenos, diferenças importantes foram constatadas. Os tubarões azuis demonstraram uma maior relação com as frentes de OD que os tubarões anequins, enquanto o contrário se verificou em relação às frentes de temperatura, resultados que se coadunam com as diferentes estratégias metabólicas apresentadas pelas duas espécies. Presumivelmente, dada a menor taxa metabólica associada a uma estratégia ectotérmica, os tubarões azuis terão uma maior tolerância a diminuições momentâneas de oxigénio, explorando, por isso, zonas de frentes exclusivas de OD quando possível, tal como acontece nas zonas de oxigénio mínimo (ZOMs). Por outro lado, os tubarões anequins, dada a sua capacidade em manter uma temperatura corporal mais ou menos constante – endotermia - combinada com uma maior necessidade de oxigénio, tenderão a favorecer zonas de fortes gradientes térmicos.
Este estudo reforça ainda a importância dos vórtices oceânicos para a alimentação de predadores pelágicos em águas oligotróficas, tendo os tubarões anequins revelado uma clara preferência por vórtices ciclónicos (VCs). Por outro lado, os tubarões azuis demonstraram uma utilização mais equilibrada de VCs e vórtices anticiclónicos (VACs), corroborando parcialmente estudos anteriores que sugerem uma relação entre procura de alimento por parte de predadores de topo e VACs, apesar de estes, há muito, serem considerados apenas como “desertos biológicos”.
Os resultados aqui apresentados sugerem que a integração de frentes de OD em modelos utilizados para identificação e gestão de áreas prioritárias de conservação destas duas espécies poderá melhorar significativamente os seus resultados. Além disso, a adoção de medidas de gestão de stocks em tempo real, de acordo com a informação inferida destes modelos, tal como é feito, na Austrália, com o Atum Rabilho do Sul (Thunnus maccoyii), uma espécie ameaçada e com uma quota limite estabelecida, poderá melhorar significativamente a gestão e conservação destas espécies, sendo o mesmo, possivelmente, aplicável ao caso de outros predadores pelágicos de topo.
Finalmente, este estudo realça a importância da telemetria de satélite para a aquisição de informação relativa aos padrões ecológicos de movimentação a larga escala de grandes predadores marinhos. Acresce que a análise destes movimentos em conjunto com dados oceanográficos permite inferir com maior confiança quanto à importância de determinadas áreas e fenómenos para estas e outras espécies, possibilitando assim, decisões mais informadas no que respeita à gestão de stocks e proteção de habitats de extrema importância ecológica e económica. Pois apenas melhorando o conhecimento que temos sobre os hábitos destas espécies podemos almejar impedir uma total perda da biodiversidade e uma completa disrupção dos ecossistemas marinhos.Pelagic top predator populations worldwide have suffered sharp decreases in abundance over the last decades, with overfishing being the main cause of such declines. Blue (Prionace glauca) and mako sharks (Isurus oxyrinchus) are the two most caught pelagic shark species in the Atlantic Ocean, being classified, respectively, as “near-threatened” and “endangered” by the IUCN red list. However, their catches remain highly unregulated, unmonitored, and unreported. Identification of priority areas for pelagic top predators’ conservation is hampered by the high mobility of these animals and the consequent difficulty in determining aggregation areas, yet mesoscale dynamic features such as thermal fronts and eddies have been suggested to attract a variety of large apex predators while foraging. In this study, the foraging movements of 34 blue and 24 mako sharks, satellite-tagged across 5 different locations in the North Atlantic Ocean, were analysed in relation to dissolved oxygen (DO) fronts, which until now had not been considered. The results presented here suggest that DO fronts might represent extensive foraging areas for these two species, but particularly for blue sharks. Two different DO front types were noticed to attract these species: strong, persistent, and vertically structured thermal-oxygen fronts, where high productivity creates important foraging opportunities; and oxygen-only fronts associated with hypoxic areas where the compression of prey in the more oxygenated surface waters results in higher predator-prey encounters. This study also reinforces the importance of eddies for pelagic predators foraging in oligotrophic waters. In addition, mako sharks revealed a clear preference for cyclonic eddies (CEs) while blue sharks showed a more balanced usage of CEs and anticyclonic eddies. These results strongly suggest the integration of DO fronts in conservation and management modelling, as they can substantially improve the identification of priority conservation areas for these two sharks and, possibly, many other pelagic top predators.
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Pryor, Miranda Leigh. "Temporal and spatial distribution of larval and post-larval blue mussels (Mytilus edulis/Mytilus trossulus) and starfish (Asterias vulgaris) within four Newfoundland mussel culture sites /." 2004.
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Boucher, Sébastien. "Les ambitions maritimes de l’Inde dans l’océan Indien à l’aube du 21e siècle." Thèse, 2009. http://hdl.handle.net/1866/3504.
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Ce mémoire a pour objectif d’analyser la pertinence d’une culture stratégique particulière, celle de l’Inde. Au moins quatre variables culturelles à dimension sécuritaire – l’identité, les valeurs, les normes et les perceptions – permettent d’expliquer la conception de la sécurité et du pouvoir indiens.
L’hypothèse avancée dans ce mémoire est la suivante : à cause de l’influence de la culture stratégique indienne, l’océan Indien est perçu par l’élite indienne comme l’endroit où réside la principale menace à la sécurité de l’Inde. En outre, cette perception particulière de la menace permet de mieux comprendre les ambitions maritimes de l’Inde dans l’océan Indien à l’aube du 21e siècle. Afin de confirmer l’hypothèse, nous analysons l’influence de la culture stratégique indienne sur les approches stratégiques privilégiées par les décideurs Indiens au sein de l’océan Indien.
Nous concluons, sur la base de l’étude cas, que l’objectif stratégique de New Delhi est de devenir la puissance maritime dominante de l’océan Indien. Le moyen privilégié est la création d’une marine océanique puissante, capable de maintenir en permanence une escadre en patrouille loin de ses bases navales. Sur le plan théorique, les actions indiennes – qui ont surtout un caractère défensif – sont justifiées par une doctrine de non-ingérence des grandes puissances dans les affaires indiennes, doctrine calquée sur la doctrine Monroe. Selon la doctrine indienne, seules les puissances régionales sont à même de préserver la stabilité dans la région de l’océan Indien. Conséquemment, le Gouvernement indien œuvre à réduire l’ingérence des marines de guerre étrangères au sein de l’océan Indien.This thesis aims to analyze the relevance of a particular strategic culture, that of India. At least four cultural variables, each with a specific security dimension - identity, values, norms and perceptive lens - help us understand the Indian notions of security and power. The main hypothesis put forward in our paper is as follows: because Indian elite are deeply influenced by the prevailing Indian strategic culture, they perceive the Indian Ocean as the place where the main security threat to the country’s security lies. In addition, this particular security perception makes it possible to better understand India’s maritime ambitions in the Indian Ocean at the dawn of the 21st century. To confirm this, we analyze the influence of Indian strategic culture on strategic approaches privileged by Indian decision-makers within the Indian Ocean. We conclude that New Delhi’s strategic objective is to become the dominant maritime power in the Indian Ocean. The means to bring about this end is the creation of a strong blue water navy capable of sustaining a permanent squadron on patrol far from its naval bases. Furthermore, Indian naval activities - which are mainly defensive in nature - are justified by a doctrine of non-interference by major powers in Indian domestic affairs, a doctrine modeled on the Monroe Doctrine. According to the Indian doctrine, only the regional powers are able to preserve stability in the Indian Ocean region. Consequently, the Indian Government works to reduce the presence of foreign naval forces in the Indian Ocean.
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Nold, Marcel Friedrich [Verfasser]. "Expression and release of chemokines associated with apoptotic cell death in human promonocytic U-937 cells and peripheral blood mononuclear cells = Assoziation von Expression und Sekretion von Chemokinen mit apoptotischem Zelltod in promonozytischen U-937-Zellen und mononukleären Zellen aus peripherem Blut / vorgelegt von Marcel Friedrich Nold." 2004. http://d-nb.info/972098445/34.
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