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1
Winget, Danielle Marie. "The ecology and diversity of estuarine virioplankton". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 303 p, 2008. http://proquest.umi.com/pqdweb?did=1617912801&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Kaselowski, Tanja. "Physico-chemical and microalgal characteristics of the Goukamma Estuary". Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1011130.
Testo completoAbstract (sommario):
Estuaries are intrinsically complex and dynamic ecosystems that display marked spatial and temporal variability. Because estuaries are situated at the receiving end of catchment activities, they are at particular risk of alterations to their natural complexity. The overarching objective of this study was to gain an overview of the abiotic conditions and biotic response of the Goukamma Estuary, a small temporarily open/closed estuary (TOCE) which is situated in a relatively undisturbed catchment in the Southern Cape. Physico-chemical properties drive estuarine ecology, and together with biological indicators, are commonly assessed to determine the present status of an estuary. During the study, physico-chemical parameters reflected great spatial and temporal variability in response to the mouth state over a 13 month period. Parameters ranged within expected limits, as proposed by the conceptual model for water quality of TOCE’s (Snow and Taljaard 2007). Of particular importance was the prominent occurrence of salinity stratification and hypoxic conditions (dissolved oxygen [DO] < 3 mg l-1) during both open and closed mouth states. Data indicated that in the wide and shallow lower reaches, weak stratification gradients were present and oxygenated conditions (DO > 6 mg l-1) were maintained throughout the water column mainly by wind and tidal action. However, stratification increased towards the deeper, channel-like middle and upper reaches of the estuary, followed by a significant reduction in bottom DO concentrations and development of hypoxia and anoxia. Bottom water hypoxia commonly occurs in microtidal estuaries due to the limited influence of mixing forces, mainly by wind and tidal action. The Goukamma Estuary is a channel-like microtidal estuary where stratification effectively limited oxygenation of the bottom water which resulted in frequent occurrence of bottom water hypoxia. During June 2010 when the highest local rainfall (75 mm) was recorded for the region, salinity and DO data showed that this amount of rainfall was insignificant as it did not replenish the water column of oxygen. Only the surface 0.5 m layer was fresh and oxygenated while below this, the water column was completely hypoxic. In an unimpacted state, the Goukamma Estuary is a blackwater system and is expected to be nutrient poor; however, farming activities in the catchment have resulted in elevated nutrient concentrations. This study showed that significantly higher nutrient concentrations were measured in the middle and upper reaches of the estuary, adjacent to cattle farms situated in the floodplain of these reaches. Nutrient concentrations represented mesotrophic (dissolved inorganic nitrogen [DIN] > 500 μg l-1) to eutrophic conditions (dissolved inorganic phosphorus [DIP] > 25 μg l-1). Nutrient input stimulated phytoplankton to attain a significantly high biomass, ranging between 0.3 – 112 μg l-1 (~ 7.7 ± 1.3 μg l-1; n = 128) and 0.8 – 289 μg l-1 (~ 21.1 ± 4.4 μg l-1; n = 80) during the open and closed states, respectively. High organic loads are associated with high oxygen demands which consequently result in hypoxia following decomposition. Exacerbated by natural salinity stratification which effectively limits oxygenation of the water column, unnaturally high nutrient concentrations and coinciding organic loads place the estuary at particular risk of degradation. This study captured key patterns and processes by quantifying salinity, oxygen and nutrient concentrations in addition to biological indicators (phytoplankton biomass and community composition). Considering possible budget constraints, it is recommended that monthly salinity and oxygen concentrations should be monitored as well as seasonal nutrient concentrations. It is also recommended that riparian buffer zones should be established in the middle and upper reaches of the estuary, as these vegetation buffers have been well documented to contribute to nutrient attenuation and improved water quality from agricultural run-off.
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Moore, Stephanie Kay School of Biological Earth & Environmental Sciences UNSW. "Tracers and indicators of estuarine nutrients". Awarded by:University of New South Wales. School of Biological, Earth and Environmental Sciences, 2005. http://handle.unsw.edu.au/1959.4/21993.
Testo completoAbstract (sommario):
Three novel methods were examined to assess the effects of nutrient enrichment in three sub-tropical east Australian estuaries with differing levels of catchment disturbance. The Manning and Wallamba River catchments are 8927 and 500 km2 respectively and support intensive livestock agriculture and some residential development, whereas the smaller Wallingat River catchment is 185 km2 and is mostly forested. The Wallamba and Wallingat Rivers flow into Wallis Lake, which was the site of an environmental crisis in 1997 when the consumption of sewage-contaminated locally grown oysters caused an outbreak of Hepatitis A. This study contributes valuable and extensive water quality data to assess rehabilitative works in Wallis Lake, and in other estuaries, to reduce the input of nutrients such as sewage. The importance of various sources, loads and sinks and the dispersion and assimilation of nutrients were quantified and compared for each estuary. An ecological model coupled with a one-dimensional hydrodynamic box model revealed that nearly all of the nitrogen inputs to the modified Wallamba River entered as runoff from the intensively livestock farmed upper catchment. In contrast, in the forested Wallingat River nitrogen was generated internally from anoxic sediments and was also longitudinally dispersed upstream from the junction with the modified Coolongolook River. Bloom conditions of up to 59 mg m-3 were observed in the Wallamba River between 7 and 11 days after the storms, but in spite of high concentrations of biologically available nitrogen in the forested Wallingat River, phytoplankton biomass was low due to phosphate limitation. Longitudinal dispersion could not counter phytoplankton growth in the modified Wallamba River, in spite of large increases in river flow. Estimates of grazing pressure by the pygmy mussel, Xenostrobus securis, demonstrate that it could contribute up to half of the phytoplankton loss. The inter-tidal mangrove pneumatophore habitat of X. securis allows filtering of the upper water column from the lateral boundaries in a vertically stratified water column, exerting top-down control on phytoplankton biomass. The optical plankton counter (OPC) can provide an in situ, rapid assessment of zooplankton productivity over large temporal and spatial scales from the size distribution of zooplankton. High concentrations of sub-resolved particles, including suspended detritus, have hampered the use of the in situ OPC in estuaries. Up to 58 counts L-1 due to the coincidence of sub-resolved particles passing through 100 ??m mesh were detected by the laboratory OPC in Manning, Wallamba and Wallingat River water samples. The influence of these erroneous counts on in situ OPC measurements was assessed by comparison with measurements of simultaneously collected net zooplankton measured using the laboratory OPC. In situ OPC measurements of total zooplankton abundance could be corrected for erroneous counts of sub-resolved particles using laboratory OPC measurements of 100 ??m mesh filtered water samples from the same site, but estimates had large associated error and information on the size structure of the zooplankton community is sacrificed. In contrast to expected relationships, no meaningful or significant correlations were found between the number or biomass of sub-resolved particles and in situ light attenuance. Laboratory OPC measurements of net zooplankton in each estuary revealed that the modified Manning and Wallamba Rivers supported a greater biomass of zooplankton compared to the forested Wallingat River. The normalised biomass size spectra of net zooplankton responded to both production of small particles and predation and loss of large particles. The effect of catchment disturbance on the nitrogen and carbon stable isotope ratios (??15N and ??13C) of X. securis was investigated in the three estuaries. Manning and Wallamba River mussels were enriched in ??15N by an average of 3.2??? and 1.5??? respectively compared to mussels from the forested Wallingat River. The isotope values of particulate organic matter showed a similar pattern to mussels, indicating a direct link between them within each estuary. A multiple regression model of mussel ??15N using the fractions of land used for livestock agriculture and residential development within 5 km zones from river networks to a distance equivalent to a tidal ellipse from sites explained 67% of the variation in mussel ??15N with 95% of the differences lying within 1.6??? of observed values. Increasing fractions of land used for livestock agriculture in the regression equation depleted estimated mussel ??15N indicating the use of cow manure as a nutrient source with a value of 2.0???. Increasing fractions of land used for residential development enriched estimated mussel ??15N, indicating the use of human-derived waste with a value of 20.8???.
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Chuwen, Benjamin Michael. "Characteristics of the ichthyofaunas of offshore waters in different types of estuary in Western Australia, including the biology of black bream Acanthopagrus butcheri /". Murdoch University Digital Theses Program, 2009. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20100210.154423.
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Quinnell, Susan Elizabeth. "Estuarine Canaries: Macrobenthos Measures Pollution when Chemical Tests Cannot". Thesis, Griffith University, 2012. http://hdl.handle.net/10072/366573.
Testo completoAbstract (sommario):
Bramble Bay, an estuary with a long history of contamination, appears to have crossed multiple tipping points into a state of unstable biomass dominated by opportunistic species. In early 1996 mass mortality events began to affect the bay’s macrobenthic community within a few days of modest rainfall (30 mm) over the catchments. The numbers of wading birds and fish using the beach at such times greatly declined. Between mortality events the macrobenthos staged partial recoveries. However, 10 years later the beach had not attained the diversity of species it supported prior to 1996. Also, the riverine estuaries that drain the catchments had been severely affected. Monitoring in 1998 – 2000 showed that the abundance of riverine macrobenthos in six drainage systems was < 15% of that in 1972 – 1973 when these drainage systems were extensively surveyed and < 2.5% of that after extreme flooding in 1974. Remarkably, the variance of total abundance within estuaries had been reduced by 90 - 99%. Nearly all of the once-dominant peracarids had gone. Chemical tests could not explain this. Nor are other simplistic explanations credible, such as floods or changes in the rate of sedimentation, because only some components of the macrobenthos have been adversely affected. Most deposit feeders have been severely reduced, however, deposit-feeding annelids as well as suspension feeding molluscs and crustaceans have continued to thrive amongst the sediments.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text
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Helton, Rebekah R. "Ecology of benthic viruses in marine and estuarine environments". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 214 p, 2007. http://proquest.umi.com/pqdweb?did=1362525081&sid=14&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Wood, Tamara Michelle. "Numerical modeling of estuarine geochemistry /". Full text open access at:, 1993. http://content.ohsu.edu/u?/etd,240.
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Fruchter, Jesse. "DO LARGE, INFREQUENT DISTURBANCES RELEASE ESTUARINE WETLANDS FROM COASTAL SQUEEZING?" OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/923.
Testo completoAbstract (sommario):
As disturbance frequencies, intensities, and types have changed and continue to change in response to changing climate and land-use patterns, coastal communities undergo shifts in both species composition and dominant vegetation type. Over the past 100 years, fire suppression throughout the Northern Gulf of Mexico coast has resulted in shifts towards woody species dominance at the expense of marsh cover. Over the next 100 years, sea levels will rise and tropical storm activity is projected to increase; resultant changes in salinity could reduce cover of salt-intolerant fresh marsh species. Together, the effects of fire suppression upslope and rising salinities downslope could "squeeze" fresh marsh species, reducing cover and potentially threatening persistence. To mitigate the effects of fire suppression, the use of prescribed fire as a management tool to mimic historic conditions is becoming increasingly widespread and will likely gain further popularity during the 21st century. Ecological shifts that will result from changing disturbance regimes are unknown. It was hypothesized that two recent hurricanes, Ivan and Katrina in 2004 and 2005, respectively, and a prescribed fire, in 2010, differentially affected species along the estuarine gradient and drove overall shifts away from woody dominance. Overall community composition did not change significantly in the intermediate and fresh marsh zones. However, significant changes occurred in the salt and brackish marshes and in the woody-dominated fresh marsh-scrub ecotone zones. Relative to 2004, woody species abundance decreased significantly in all zones in 2006, following Hurricanes Ivan and Katrina, and 2012, following the hurricanes and fire, though woody species regeneration in the marsh-scrub ecotone had begun to occur by 2012. It is hypothesized that interacting changes in fire and tropical storm regimes could release upslope areas from coastal squeezing.
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Fritz, Alyce T. "Trophodynamics of estuarine (salt marsh) heterotrophic nanoplankton (microbial ecology, salt marsh ecology, choanoflagellates, Virginia)". W&M ScholarWorks, 1986. https://scholarworks.wm.edu/etd/1539616651.
Testo completoAbstract (sommario):
Seasonal occurrence and activity of heterotrophic nanoflagellates (HNANO or heteroflagellates) and bacteria were studied in a sheltered brackish water embayment of Chesapeake Bay wetlands (Virginia, USA) over a three year period (1981 - 1984). Epifluorescence direct counts and Scanning and Transmission Electron Microscopy (SEM and TEM) techniques were used for the description of organisms, enumeration, and biomass determinations. Seasonal bacterial growth rates and growth and grazing rates of bactivorous HNANO were estimated using diffusion chambers equipped with Nuclepore polycarbonate membrane filters in natural salt marsh tidal pools. Environmental monitoring of nanoplankton populations revealed a seasonal pattern of bacterial abundances with temperature while heteroflagellate abundances and growth rates showed no seasonal pattern nor correlation with fluctuations in bacterial densities. Heteroflagellate populations were dominated by 34 to 50 (mu)m('3) sized monads, choanoflagellates, bodonids, and Paraphysomonas sp., all found in varying abundances throughout the year. Blooms were concurrent with extended low tide or specific bacterial populations (i.e., cyanobacteria) typical of spring and autumn periods. Heteroflagellate growth in diffusion chambers reflected the environmental blooms and increased diversity of low water assemblages. Growth and grazing rates of heteroflagellates at ambient densities thus could account for 20 to 80% of daily bacterial carbon production. Although heteroflagellate ingestion rates did not regulate seasonal bacteria densities or vice versa, maximum growth of bacteria and heteroflagellates in chambers was closely coupled. Heteroflagellate grazing activity may regulate the rate of bacterial production by preventing substrate limitation and maintaining the population in an active growth phase. The seasonal study demonstrated the dynamic nature of nanoplankton populations during autumn and spring transitional periods. SEM photomicroscopy revealed that the dominant component of spring blooms may be composed of several members of the loricate choanoflagellate family, Acanthoecidae. Using modified EM techniques, eleven Acanthoecidae choanoflagellates species, identified from spring in situ chamber experiments, were described. In situ growth and grazing rates for the spring chamber populations ranged from 0.023 h('-1) to 0.196 h('-1) and 40 to 210 bacteria h('-1) respectively. These high rates represent an opportunistic response to optimum conditions and an expression of maximum grazing potential. (Abstract shortened with permission of author.).
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Vorsatz, Jeanne Pauline. "Ecological role of estuarine brachyuran crabs in mangrove and salt marsh estuaries, Eastern Cape, South Africa". Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1108.
Testo completoAbstract (sommario):
Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
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Childs, Amber-Robyn. "Movement patterns of spotted grunter, Pomadasys commersonnii (Haemulidae), in a highly turbid South African estuary". Connect to this title online, 2005. http://eprints.ru.ac.za/311/.
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Allison, Jeffrey Garner. "Dynamics of estuarine microphytobenthos in a shallow water sand bottom habitat". [Pensacola, Fla.] : University of West Florida, 2006. http://purl.fcla.edu/fcla/etd/WFE0000004.
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Thatcher, Lisa A. "Carbon remineralization and storage in estuarine wetland sediments /". Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/thatcherl/lisathatcher.pdf.
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Niture, S. K. "Biochemical ecology of fusarium moniliforme isolated from an estuarine environment". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2002. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2830.
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Jelbart, Jane E., University of Western Sydney, of Science Technology and Environment College e School of Environment and Agriculture. "The influence of seascape spatial features on the fish and macroinvertebrates in seagrass beds". THESIS_CSTE_EAG_Jelbert_J.xml, 2004. http://handle.uws.edu.au:8081/1959.7/492.
Testo completoAbstract (sommario):
Seagrass beds of Zostera capricorni are an integral part of the estuarine landscape along the east coast of Australia forming important habitats for juvenile fish and macroinvertebrates. Seagrass beds can vary in their spatial structural such as their size, shape and patchiness of seagrass cover. They can also be located within the estuarine landscape context such as their proximity to other habitats or their location within the estuary. The influence or correlation of these landscape or seascape spatial features of seagrass beds on the assemblages of seagrass fauna (fish and macroinvertebrates) was tested in this thesis. It was found that the spatial structure of seagrass beds (size and shape), their patchiness of the seagrass cover and location within the estuary (close or far from estuary mouth) were correlated with the assemblages of fish within seagrass beds. In particular it was demonstrated that there were greater densities of small fish species in the small compared to the large beds of Z. capricorni. This occurred regardless of the placement of the seagrass bed within the estuary context, its proximity to other habitats or patchiness of cover. Further experimentation using artificial seagrass patches demonstrated that this effect of patch size was independent of the perimeter length or perimeter to area ratio of the seagrass beds. It was hypothesised that the greater density of small fish species in small seagrass beds could be attributed to the greater proportion of edge habitats in small beds i.e. edge-mediated effects. However, the number of fish species per net haul in edges and inner regions of small and large seagrass beds were measured and found not to be different. The outcomes of this research suggest that to conserve the small fish species within an estuary, it is essential to protect even the small and patchy seagrass beds. A network of seagrass beds from all regions of the estuary is also required and the adjacent mangrove forests must be includedDoctor of Philosophy (PhD)
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Mazik, Krystina. "The influence of a petrochemical discharge on the bioturbation and erosion potential of an intertidal estuarine mudflat (Humber estuary, UK)". Thesis, University of Hull, 2004. http://hydra.hull.ac.uk/resources/hull:7047.
Testo completoAbstract (sommario):
The influence of sedimentary variables on the structure and function of infaunal estuarine and marine communities is well studied but less is known of the influence of biota on sediment properties. Feeding and burrowing activity, locomotion, the production of faecal pellets and biological secretions (bioturbation) have important implications for sediment structure, chemistry, transport characteristics and the flux of nutrients and contaminants. Although spatial and temporal patterns in bioturbation have been studied to some extent, little attention has been given to the effects of pollution. The present study examines the effects of an intertidal petrochemical discharge into the Humber estuary (UK), from BP chemicals (Saltend) Ltd on the structure and function of the communities. Field and laboratory techniques were used to determine the effects of community change on bioturbation potential. In addition, a laboratory flume was constructed to measure sediment erosion potential with field measurements being taken using a Cohesive Strength Meter (CSM). The physico-chemical properties of the sediment, changes to the infaunal community structure, bioturbation potential and the interaction of these variables were used to explain differences between the erosion potential of sediments subject to varying levels of contamination. The main study was carried out on the Saltend mudflats near Hull, with sites at various distances from the outfall being used. A further set of control sites on the adjacent, and largely unaffected, mudflat at Paull were also used. In terms of the sediment properties, sites closest to the outfall showed the greatest degree of anoxia and the highest chlorophyll-a and carbohydrate concentrations, with all three parameters being seasonally influenced. No consistent spatial or temporal patterns were found for any of the other parameters (water and organic content, particle size). Whilst the infaunal communities were characteristic of estuarine areas, macrobenthic community response followed the Pearson & Rosenberg (1978) model for organic discharges with high abundance and low species diversity being associated with the more polluted sediments. Close to the discharge, there was an impoverished community consisting predominantly of highly abundant oligochate worms. With increasing distance from the outfall, species diversity and biomass increased with Hediste diversicolor becoming increasingly dominant and the appearance of Corophium volutator, Streblospio shrubsolii and Macoma balthica. Bioturbation potential was significantly reduced (in terms of depth and burrow volume and density) by increasing effiuent concentrations and with proximity to the discharge. The diversity of both feeding and sediment modification guilds was also reduced as a result of the discharge. Both field and laboratory studies indicated a stabilising effect of this type of pollution. Using the CSM, critical shear stress values were found to be significantly lower from unpolluted sites, indicating higher erosion potential, than those from sites close to the discharge. As a result of this, the total mass of sediment eroded from unpolluted sites was significantly higher than that from polluted areas. A similar trend was observed in the laboratory with sediments treated with an effluent concentration of 32% being considerably more stable than untreated sediments. Flume studies also indicated the stabilising effect of pollution with suspended particulate matter (SPM) concentrations and mass of sediment being transported as bedload being significantly higher for unpolluted sediments. These differences in erosion potential were attributed to the direct effects of the effiuent on the physico-chemical properties of the sediment, the effects of the effiuent and sediment type on macrofaunal community structure and function and the differences in bioturbation potential between sites. The implications of these findings in the wider context of coastal management are discussed.
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Akoto, William. "Valuing preferences for freshwater inflows into selected Western and Southern Cape estuaries". Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/915.
Testo completoAbstract (sommario):
An estuary is the last stage of a river. It is where the river meets the sea. Estuaries are one of the most significant features of the South African coastline. In recent years, South Africa has witnessed an increase in the demand for freshwater for both industrial and domestic purposes. At the same time, there has been a gradual deterioration of river systems and their catchments. To add to this, there has been a gradual reduction in the amount of recorded rainfall, which is the primary source of freshwater for rivers. This has resulted in decreased freshwater inflow into estuaries, a situation which poses a serious threat to the biological functioning of these estuaries and the services rendered to its recreational users. A deterioration of estuary services reduces the yield for subsistence households and their appeal for recration. This study uses the contingent valuation method as its primary methodology to elicit users' willingness-to-pay to reduce the negative impacts of reduced freshwater inflow into selected western and southern Cape estuaries. Eight estuaries were selected for this study; the Breede, Duiwenhoks, Great Berg, Kleinemond West, Mhlathuze, Swartvlei and Olifants estuaries. The contingent valuation (CV) method is widely used for studies of this nature because of its ability to capture active, passive and non-use values. The CV method involves directly asking people how much they would be willing to pay for specific environmental services. In this case, users were asked what they would be willing to pay to sustain freshwater inflows into selected estuaries in order to prevent the negative impacts of reduced inflows. The travel cost method (TCM) was uesed to generate an alternative comparative set of values for the purposes of convergence testing. This is because convergence testing is highly desirable as a validity test for CV estimates.
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Everett, Jason D. School of Biological Earth & Environmental Science UNSW. "Biogeochemical dynamics of an intermittently open estuary: a field and modelling study". Awarded by:University of New South Wales. School of Biological, Earth and Environmental Science, 2007. http://handle.unsw.edu.au/1959.4/30555.
Testo completoAbstract (sommario):
This thesis presents a combined modelling and observational study of an intermittently open and closed lake or lagoon (ICOLL) in south-eastern Australia. ICOLLs are a common, yet vulnerable type of estuary characterised by low freshwater inflow leading to a sand berm being formed across the entrance preventing oceanic flushing. The accumulation of nutrients during the closed phase, and the increased water residence time, can have detrimental effects on the estuary if the nutrient load cannot be assimilated. The general aim of this study was to develop a quantitative understanding of ecological processes in Intermittently Closed and Open Lakes or Lagoons (ICOLLs) through a combination of field work and ecological modelling. The field-based component of the studied was completed in Smiths Lake, NSW Australia. The field data shows that concentrations of NH3, NOx and Chlorophyll a in Smiths Lake gradually increases over time between the two studied opening events, before declining while the lake is open to the ocean. Phosphorus concentration is relatively low throughout both cycles. Of the 2 opening events, one was long (~ 3.5 months) and one was short (~3 weeks). Initially ammonia concentrations following this short open period were 2-4 times higher than the initial values from the previous 2 closures. The reduced open phase also resulted in more persistent stratification. The observations show that the duration of the open/closed phases will influence the physiochemical characteristics of the water column. A spatially resolved, eleven-box ecological model was developed for Smiths Lake. The process descriptions in the ecological model are based on a combination of physical and physiological limits to the processes of nutrient uptake, light capture by phytoplankton and predator/prey interactions. An inverse model is used to calculate mixing coefficients from salinity observations. When compared to field data, the ecological model obtains fits for salinity, nitrogen, phosphorus, chlorophyll a and zooplankton that are within 1.5 standard deviations of the mean of the field data. Simulations show that nutrient limitation (nitrogen and phosphorus) is the dominant factor limiting growth of the autotrophs during both the open and closed phases of the lake. The model is characterised by strong oscillations in phytoplankton and zooplankton abundance,typical of predator-prey cycles. A sensitivity analysis was completed using a simplified 1-box configuration, coupled with the existing ecological model. When small perturbations in the initial conditions of DIN, phytoplankton and zooplankton are implemented, the standard deviations of the state variables strongly attract to a declining oscillation, showing the variation between runs decreasing with time. The most sensitive parameters in the model were the feeding efficiency of small and large zooplankton, and the mortality of epiphytes and small zooplankton which all had normalised sensitivities of 1.28, 1.11, 1.01 and 1.05 respectively for a 10% change in parameter value. The non-linearity of the model is illustrated by increasing the percentage change of the parameter. For a 25% change in feeding efficiency of small and large zooplankton, the normalised sensitivity increased to 1.28 and 1.15 respectively, and for a 50% change, they increased further to 1.78 and 1.35 respectively. The ecological state variables were also sensitive to increased catchment loads and depths. The modelled system switches from seagrass dominated to algal dominated at loads over 10?? the current loads, with increased plankton biomass and suspended solids shading the seagrass. The spatially resolved ecological model is run for a variety of open/closed cycles to assess the impact of various opening regimes on the model state variables. The results indicate that Smiths Lake is capable of assimilating its current nutrient loads without persistent phytoplankton blooms or a decrease in seagrass biomass. When catchment loads are increased by 10?? or the duration of the lake open/closed cycle is increased there is a corresponding increase in seagrass biomass. In contrast, small and large phytoplankton both increase in biomass as the duration of the open phase increases. Small and large phytoplankton growth is generally limited by phosphorus, and seagrass growth is limited by nitrogen under normal catchment loads. Due to the shallow depths and low phytoplankton biomass, seagrass only becomes light limited when the nutrient and suspended solids loads are increased 10??. This switch to light limitation only decreases the biomass for short periods.
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Batten, Sonia Dawn. "Correlative studies of the ecophysiology and community structure of benthic macrofauna". Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241219.
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Strydom, Nadine Amelia. "Dynamics of early stage fishes associated with selected warm temperate estuaries in South Africa". Thesis, Connect to this title online, 2002. http://eprints.ru.ac.za/25/.
Testo completo
21
Gilmour, Fiona Louise. "The effect of salinity and ammonia on nitirifier function and distribution in estuarine sediments". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59375.
Testo completo
22
Lindsey, Jacqueline Kimberly. "Estuarine habitat use by the California sea otter (Enhydra lutris nereis)". Thesis, San Jose State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10255129.
Testo completoAbstract (sommario):
As the southern sea otter (Enhydra lutris nereis) range expands into northern and southern California, it will encounter estuaries that have been historically occupied by sea otters. Understanding how otters use re-colonized estuarine environments will inform how estuaries might be managed to encourage future sea otter range expansion. This project addressed the question: how do southern sea otters use space in the unique estuarine habitats of Elkhorn Slough? I compared the locations and behaviors of 25 individual sea otters of different status (male, female, and female with pup) among eelgrass, saltmud, saltmarsh, tidal creek, and main channel habitats in Elkhorn Slough. From these data I created a synoptic model to predict space use for resident otters of Elkhorn Slough based on sex, behavior, home range, and habitat distribution. Ninety percent home ranges calculated from the model indicated that females used larger home ranges than males in the slough, but both sexes had smaller home range areas than otters using the rocky outer-coast habitats of the Monterey Peninsula. In Elkhorn Slough, important habitats associated with resting included tidal creeks (for females only) and eelgrass, whereas the main channel was important for foraging behaviors of both sexes. Although using land habitats, sea otters were most likely to be found within 50 m of water. Protection of similar resting and foraging habitats in prey-rich estuaries colonized in the future will promote southern sea otters recovery by allowing them to re-colonize historically important estuarine habitats.
23
Hewitt, Chad LeRoy. "Marine biological invasions : the distributional ecology and interactions between native and introduced encrusting organisms". Thesis, Thesis (Ph. D.)--University of Oregon, 1993, 1993. http://hdl.handle.net/1794/9974.
Testo completo
24
Zagars, Matiss. "Estuarine mangrove fish communities in southwestern Thailand : trophic ecology and movement patterns". 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/160976.
Testo completo
25
Williams, Simon. "Microbial ecology of anammox bacteria in estuarine and oxygen minimum zone environments". Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/61716/.
Testo completoAbstract (sommario):
Anammox (anaerobic ammonium oxidation) is an environmentally significant process with great importance for global biogeochemical cycles. This process is mediated by a unique suite of phylogenetically distinct chemolithoautotrophic bacteria which demonstrate novel physiological and metabolic characteristics. However, despite the importance of these organisms, there is still much which is poorly understood about them, specifically the diversity and distribution of these bacteria and their controlling environmental factors. Furthermore, genomic studies and observations from the field suggest that anammox bacteria may have a far greater metabolic diversity than previously thought, suggesting that the current understanding of these organisms is incomplete. This study aimed to elucidate these aspects of the ecology of anammox bacteria in estuarine and OMZ (oxygen minimum zone) environments. A clear community shift was observed in estuarine environments from Ca. Brocadia spp. dominated freshwater sites to Ca. Scalindua spp. dominated marine sites. The OMZ was dominated by Ca. Scalindua spp. though diversity within this clade was observed between organisms in the upper oxycline and those within the core of the OMZ. Microcosm experiments amended with organic substrates suggested that some anammox organisms (namely Ca. Brocadia spp., Ca. Jettenia spp. and Ca. Kuenenia spp.) may have the ability to assimilate carbon directly from organic substrates such as dimethylamine and urea. However, these data were inconclusive and further investigations are required to prove or disprove the hypothesis that anammox bacteria can utilise organic substrates. Nevertheless, this study improves the understanding of the ecology of anammox organisms in estuarine and OMZ environments, providing an unprecedented depth of data as to the diversity and distribution and unique insights into potentially novel metabolic capabilities of these organisms.
26
Veldhuis, Helen Anne. "An analysis of factors controlling the distribution of zooplankton in the Knysna estuary, South Africa". Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/22015.
Testo completoAbstract (sommario):
The Knysna estuary system, on the south coast of South Africa, was sampled for zooplankton over period of one year. All species were recorded and an attempt was made at relating the distribution of populations to physical factors within the estuary. Over 50 species were identified. Pseudodiaptomus hessei, Acartia(Paracartia) longipatella and A.(Acartiella) natalensis were the dominant copepods in the upper estuary. Paracalanus spp. were dominant near the mouth. Zooplankton distribution was found to be related to tidal exchange. The zooplankton displayed a seasonal cycle of abundance, with maximum numbers occuring during summer. P. hessei displayed no pronounced seasonal cycle in abundance. Its abundance was strongly related to freshwater inflow. Seasonal succession was evident between A. natalensis, the summer dominant, and A. longipatella, the winter dominant. The controlling factors for this cyclical dominance were not clear. Diel vertical migration behaviour was shown to various degrees by virtually all zooplankton populations. The stimulus for this behaviour could not be definitely identified.
27
Masefield, Vincent Antony. "A preliminary assessment linking altered catchment land-cover to the health of four temporarily open/closed South African estuaries". Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1013096.
Testo completoAbstract (sommario):
Estuaries worldwide are being subjected to various degrees of catchment degradation, which is having severe consequences on the integrity of these aquatic ecosystems and their ability to function properly. This thesis investigated the relationship between catchment land-cover and estuarine health in four temporarily open/closed estuarine systems (TOCEs) in South Africa, namely the Groot Brak, East Kleinemonde, Mdloti and Tongati. GIS techniques were employed to delineate catchments, lower sections of catchments, 1 km and 100 m buffer zones, and to quantify the extent of land-cover classes present within these delineations. Anthropogenic activities outlined by the Department of Water Affairs and Forestry (DWAF) Resource Directed Measures (RDM) studies and their associated land-cover classes were described. The possible links between catchment and buffer zone land-cover class composition and health of the estuaries were explored. Results indicated that there was a relationship between catchment and estuarine health within the Coastal Protection Zone (CPZ) (1 km and 100 m) buffers, but not at a broader catchment level. Out of natural, urban built-up and cultivation land-cover classes, natural land was determined to be the best predictor of estuarine health within the CPZs. A method of rapidly assessing South African TOCE condition was applied and could be used to prioritise these estuaries for rehabilitation and/or conservation.
28
Zharikov, Yuri. "Feeding ecology of shorebirds (Charadrii) spending the non-breeding season on an Australian subtropical estuarine flat /". St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16734.pdf.
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Mcgaw, Iain James. "Behavioural responses of the shore crab Carcinus maenus to salinity variation". Thesis, Bangor University, 1991. https://research.bangor.ac.uk/portal/en/theses/behavioural-responses-of-the-shore-crab-carcinus-maenus-to-salinity-variation(b75f6f70-c663-4702-a955-0eb37bb01e25).html.
Testo completoAbstract (sommario):
Behavioural responses of the colour forms of Carcinus maenas to salinity variation were investigated, and related to their physiology and distribution in an estuary. Red males, characterised by a thicker carapace were unable to survive in as low salinities as green males; this was reflected in their poorer osmoregulatory capabilities. Haemolymph osmolality and ion concentrations of red crabs decreased at a faster rate and reached lower levels than in green crabs. Haemolymph osmolality and choice behaviour did not vary with size. In the tidally mixed estuary male and female crabs occurred in roughly similar proportions. Most were green and generally smaller than their open shore counterparts. Migration out of the estuary in winter was reversed in late spring. Differences in salinity tolerance of red and green crabs were reflected in salinity preference behaviour. Green crabs persisted longer in the lowest range of salinities tested, especially if a shelter was available. Prior acclimation affected the timing of choice behaviour; the lower the salinity of acclimation the faster the time of exit from the lowest range of salinities tested, and vice versa. Estuarine green crabs exhibited endogenous locomotor activity of circatidal periodicity and were less responsive to episodes of low salinity than open shore red and green crabs. Constant low salinity initiated a rhythm of circatidal periodicity in arhythmic red and green crabs; red crabs reacted faster and were more active upon salinity change than green crabs. The amount of locomotor activity induced after prior acclimation was similar within each acclimation salinity tested. Carcinus detected salinity variation by responding to the concentrations of Na and Cl in seawater, and was able to differentiate between salinities separated by as little as 0.5ppt., - General physiological changes appear to occur before behavioural responses are mediated; they probably act as cues for the behavioural responses, which appear not to be triggered by specific receptors. Behavioural and physiological responses combing to enhance, the survivability of crabs in changing salinities.
30
Chege, Jedidah. "Valuing preferences for freshwater inflows into five Eastern Cape and Kwazulu-Natal estuaries". Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/932.
Testo completoAbstract (sommario):
An estuary, according to the National Water Act of 1998, is a partially or fully enclosed body of water which is open periodically or permanently to the sea within which the sea water can be diluted, to an extent that is measurable with freshwater from inland. Estuaries and the lands surrounding them are places of transition from land to sea, and from freshwater to saltwater. Although influenced by the tides, estuaries are protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that surround them. South Africa’s estuaries are important and irreplaceable habitats, especially for prawns, fish, wading birds and mangroves. They are home to numerous plants and animals that live in water that is partly fresh and partly salty. Estuaries are also homes to growing coastal communities as increasing number of people occupy watersheds. However, estuaries are also threatened. One of the threats is reduced river water inflow. This study applies the contingent valuation method (CVM) to elicit user’s willingness to pay to mitigate the negative impacts of reduced freshwater inflow into selected five Eastern Cape and Kwazulu-Natal estuaries: the Sundays, Gamtoos, Mdloti, Mgeni and Mvoti estuaries. In addition to the contingent valuation method, the travel cost method was used to generate comparative values. The contingent valuation method is a technique to establish the value of a good (or service) that is not bought or sold in an actual market. The CVM establishes the economic value of the good by asking the users of an environmental good to state their willingness to pay (WTP) for a hypothetical project to prevent, or bring about, a change in the current condition of the environmental good. The users’ WTP is aggregated to establish a total willingness to pay (TWTP) for the population of the users of the environmental good.
31
Cooper, Margaret Anne. "Population biology of Spartina maritima and Spartina anglica monocultures in estuarine salt marshes". Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336180.
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32
Mazumder, Debashish, e res cand@acu edu au. "Contribution of Saltmarsh to Temperate Estuarine Fish in Southeast Australia". Australian Catholic University. School of Arts and Science (NSW, 2004. http://dlibrary.acu.edu.au/digitaltheses/public/adt-acuvp47.09042006.
Testo completoAbstract (sommario):
Saltmarsh is an important coastal habitat located in the littoral zone of estuaries. Australian saltmarsh area is decreasing due to agricultural and urban development and invasion by mangrove. The aim of the study was to assess the contribution made by saltmarsh as a habitat and a source of food items for fish. Three saltmarsh sites were studied, with Towra Point chosen as a site for detailed ecological study. When corrected for water volume, fish densities were found to be higher within the saltmarsh compared to the adjacent mangrove. Although the fish assemblages in saltmarshes differed significantly from mangroves the overall ratio between commercially and ecologically valuable species in these habitats are similar, a result suggesting the importance of temperate saltmarsh as habitat for economically important fish. Significant export of crab larva from saltmarsh (average crab larval abundance 2124.63 m-3 outgoing water) is a positive contribution to the estuarine food chain supplementing the nutritional requirements of estuarine fish. While the diet of the crabs producing this larvae seems dependant on the saltmarsh environment (given the contrasting isotopic signatures of Sesarma erythrodactyla in saltmarsh and mangrove, and the similarity of isotopic signatures in the saltmarsh for Sesarma erythrodactyla and Helograpsus haswellianus), the crabs do not seem to be dependent on any of the common species of saltmarsh plant, but rather depend on particulate organic matter (POM) derived from local and other sources. Crab larva are a prey item for many estuarine fish, including commercially important species, as evidenced by gut content analysis of fish visiting the saltmarsh flats during spring tides. The results strongly suggest that emphasis be given to ecosystembased management for an estuary rather than component (e.g., vegetation) based managed as defined by the Fisheries Management Act (1994) and the State Environmental Planning Policy 14.
33
Young, Ruth Anne. "Biotic Responses to Urbanisation in Mangrove Dominated Estuaries". Thesis, Griffith University, 2009. http://hdl.handle.net/10072/367651.
Testo completoAbstract (sommario):
Increasing urbanisation of coastal areas is placing unprecedented pressure on
estuarine environments. Impacts associated with urbanisation can alter the health of
estuarine ecosystems, reducing their capacity to provide valuable ecosystem services.
In order protect these environments, relationships between estuarine health and
urbanisation should be understood and applied to sustainable urban planning in coastal
areas. Responses measured in estuarine biota offer much potential for providing
pragmatic and sensitive means for the detection of urban impacts in estuaries.
I assessed the responses of estuarine biota to increasing levels of urbanisation
in the rapidly developing coastal region of southeast Queensland, Australia. I
measured a suite of biotic indicators, namely: the δ15N of mangroves and crabs as a
tracer for urban N sources, sediment chlorophyll a concentration (Chl a) as an
estimate of the biomass of microphytobenthos (MPB), and a condition index in crabs,
measured as the hepatosomatic index (HI). Urbanisation was estimated as the
percentage of catchment covered by impervious surfaces (impervious cover, IC).
Increases in impervious surfaces such as roads, footpaths and car parks are closely
linked to urbanisation. These surfaces concentrate and convey pollutants generated
from urban activities into coastal waterways and estuaries, thus making IC a useful
indicator of urban impact.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text
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Jafta, Nolusindiso. "The botanical importance and health of the Bushmans estuary, Eastern Cape, South Africa". Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1255.
Testo completoAbstract (sommario):
The Bushmans Estuary is one of the few permanently open estuaries in the Eastern Cape that is characterized by large intertidal salt marshes. Freshwater inflow to the estuary has decreased as a result of abstraction by more than 30 weirs and farm dams in the catchment. The mean annual run-off is naturally low (38 x 106 m3 y-1) and thus abstraction and reduction of freshwater inflow to the estuary is expected to cause a number of changes. The aims of this study were to determine the current health/status of the estuary based on the macrophytes and microalgae and identify monitoring indicators for the East London Department of Water Affairs, River Health Programme. Changes in the estuary over time were determined from available historical data which were compared with present data. This analysis showed that under normal average conditions freshwater inflow to the estuary is very low, less that 0.02 m3 s-1 most of the time. Under these conditions the estuary is in a homogenous marine state. Vertical and horizontal salinity gradients only form when high rainfall and run-off occurs (> 5 m3.s-1). Salinity gradients from 30.1 PSU at the mouth to 2.2 PSU in the upper reaches were measured in 2006 after a high flow event. However the estuary quickly reverted back to its homogenous condition within weeks after this flood. This study showed that freshwater inflow increased nutrient input to the estuary. Total oxidised nitrogen (TOxN) and soluble reactive phosphorus (SRP) concentrations were higher in August 2006, after the flood, than during the other low flow sampling sessions. TOxN decreased from a mean concentration of 21.6 μM in 2006 to 1.93 μM in February 2009. SRP decreased from 55.3 μM to 0.2 μM respectively. With the increased nutrient availability, the response in the estuary was an increase in phytoplankton biomass. After the 2006 floods the average water column chlorophyll-a was 9.0 μg l-1, while in the low freshwater inflow years it ranged from 2.1 to 4.8 μg l-1. The composition of the phytoplankton community was always dominated by flagellates and then diatoms, with higher cell numbers in the nutrient-enriched 2006 period. Although the water column nutrient data indicated that the estuary was oligotrophic, benthic microalgal biomass (11.9-16.1 μg.g-1) in the intertidal zone was comparable with nutrient rich estuaries. Benthic species indicative of polluted conditions were found (Nitzschia frustulum, Navicula gregaria, Navicula cryptotenelloides). These benthic species were found at the sites where wastewater / sewage seepage had occurred. Benthic diatom species also indicated freshwater inflow. During the high flow period in 2006 the dominant diatoms were fresh to brackish species that were strongly associated with the high concentrations of TOxN and SRP (Tryblionella constricta, Diploneis smithii, Hippodonta cf. gremainii, and Navicula species). During the freshwater limited period of 2008 and 2009 the benthic diatom species shifted to a group responding to the high salinity, ammonium and silicate concentrations. The species in this group were Nitzschia flexa, Navicula tenneloides, Diploneis elliptica, Amphora subacutiuscula and Nitzschia coarctata. Ordination results showed that the epiphytic diatom species responded to different environmental variables in the different years. Most of the species in 2008/2009 were associated with high salinity, temperature, dissolved oxygen, ammonium and silicate concentrations while the response was towards TOxN and SRP in 2006. The dominant species were Cocconeis placentula v euglyphyta in 2006; Nitzschia frustulum in 2008; and Synedra spp in 2009. The average biomass of the epiphytes was significantly lower in May 2008 than in both August 2006 and February 2009; 88.0 + 17.7 mg.m-2, 1.7 + 0.8 mg.m-2, and 61.8 + 14.4 mg.m-2 respectively. GIS mapping of past and present aerial photographs showed that submerged macrophyte (Zostera capensis) cover in 1966 and 1973 was less than that mapped for 2004. Salt marsh also increased its cover over time, from 86.9 ha in 1966 to 126 ha in 2004, colonizing what were bare sandy areas. Long-term monitoring of the health of the Bushmans Estuary should focus on salinity (as an indicator of inflow or deprivation of freshwater), benthic diatom identification and macrophyte distribution and composition (for the detection of pollution input), and bathymetric surveys (for shallowing of the estuary due to sedimentation).
35
Vosloo, Mathys Christiaan. "Network analysis of trophic linkages in two sub-tropical estuaries along the South-East coast of South Africa". Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1010966.
Testo completoAbstract (sommario):
Estuaries are some of the most productive yet threatened ecosystems in the world. Despite their importance they face significant threats through changes to river flow, eutrophication, rapid population growth long the caost and harvesting of natural resources. A number of international studies have been conducted investigating the structure and functioning of an array of ecosystems using ecological network analysis. Energy flow networks have been contsructed for coastal, lagoonal, intertidial and, most notably, permantently open estuaries. Despite the valualble insights contributed by these and other studies, a lack of information on the majority of estuarine ecosystems exists.
36
Hambelton, R. G. "The use of artificial substrates as a method of monitoring estuarine benthic invertebrate populations". Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372155.
Testo completo
37
Gibson, Glenn R. "The ecology and physiology of sulphate-reducing bacteria in anaerobic marine and estuarine sediments". Thesis, University of Dundee, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282962.
Testo completo
38
Iriarte, Arantza. "Picophytoplankton : ecological and physiological studies in culture and in natural coastal and estuarine waters". Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358363.
Testo completo
39
Crump, Byron C. "Bacterial activity and community structure in the Columbia River estuarine turbidity maxima /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10989.
Testo completo
40
Hinchey, Elizabeth K. "Autoecology of Paraprionospio pinnata (Polychaeta: Spionide) along an Estuarine Gradient". W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539617709.
Testo completo
41
Campfield, Patrick Anthony. "Ichthyoplankton community structure and feeding ecology in the Patuxent River estuarine transition zone". College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1751.
Testo completoAbstract (sommario):
Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
42
Usmar, Natalie R. "Ontogeny and ecology of snapper (Pagrus auratus) in an estuary, the Mahurangi Harbour /". e-Thesis University of Auckland, 2009. http://hdl.handle.net/2292/5642.
Testo completoAbstract (sommario):
Thesis (PhD--Marine Science)--University of Auckland, 2009." A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Marine Science." Includes bibliographical references (leaves 161-173).
43
Veldkornet, Dimitri Allastair. "Morphological variation and species diversity of South African Estuarine macrophytes". Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1013001.
Testo completoAbstract (sommario):
Studies on morphological variation are important as it can depict the relationship with environmental factors clearly and convey an understanding of the manner, mechanism and factors influencing plant adaptation and evolution. Although many studies have been conducted on South African salt marsh plant physiology and phytosociology there are at present very few morphological studies on estuarine plants. The aim of this study was to compare the morphological variation of estuarine macrophytes in three different estuary types in the warm temperate biogeographic zone of South Africa and to compare characters used in the taxonomic descriptions of species with those measured in the field. Permanently open estuaries investigated were Ngqusi (WC), Kowie (KW) and Swartkops (SW) estuaries. The Knysna Estuary (KN) was the estuarine bay investigated and the temporarily open/ closed estuaries (TOCEs) were the East Kleinemonde (EK) and Great Brak (GB) estuaries. Macrophytes were morphologically different across different estuary types. This suggests that there were different factors operating between these estuary types that would directly influence the morphology of species. The variation of plant height with different estuary types can be attributed to the fact that smaller salt marshes also have smaller habitat ranges compared to larger ones. The variation in morphological characteristics such as plant height can also be attributed to biogeographical range. Most morphological characteristics measured in the field fall within previously published ranges, and so these characters are useful in delimiting species. There were significant relationships between phenotypic variables and multivariate environmental variables. The most important of these variables were soil electrical conductivity, soil organic content and soil water content. Specifically, plant height increased with water content and decreased with salinity, flower stalk length had strong significant positive correlations with moisture content, organic content and pH while there were strong significant correlations with redox potential and electrical conductivity. Salt marshes are considered ideal for studying variation of species due to the explicit environmental gradients and plants occurring in salt marshes are halophytes that exhibit a range of morphological traits that allows for growth and reproduction under the stressful and extreme conditions. Considering recent climate change predictions and the consequent effects on South African estuaries this study provides significant information with regard to the response of species to a changing environment. The study was also aimed at updating the existing botanical database for South African estuaries in terms of species occurrence in South African estuaries, taxonomic name changes of existing species, new species, common names and habitats. Species diversity indices were also calculated for different estuaries, estuary types and biogeographic zones and diagnostic descriptions of the dominant salt marsh species were developed. The objective of this was that these data should provide baseline information for determining habitat richness and plant species diversity of South African estuaries which in turn should be used in determining priority estuaries for conservation and management. The identification key, developed using the DELTA software, would also aid researchers, managers and laymen in identifying salt marsh species. Results showed that the total number of macrophyte species, including intraspecific taxa and macroalgae, was 242 in 53 estuaries that were updated . There was an increase in the number of taxa recorded in the database primarily due to 1) research focus and full taxonomic surveys on larger estuaries and the big research projects has led to the identification of more species, 2) the addition of species that are not characteristically known as estuarine species, 3) the addition of 50 macroalgal taxa and 4) minor changes due to taxonomic revisions of species and the addition of newly described species. The Shannon diversity index showed that greater species diversity was found in the Berg (Groot) Estuary (4.220) and the Uilkraals Estuary (4.025). The cool temperate bioregion was the most diverse in the number of taxa (58) with the highest Shannon index (4.736). Permanently open estuaries were the most diverse in the number of unique taxa (56) with the highest Shannon index (4.867). Estuarine managers need to be aware of the species diversity in different estuarine types as well as the associated impacts on them. Conservation planning must therefore include species. Diagnostic features of INTKEY indicated that all 57 taxa were distinguishable from each other. Contrary to expectations plant height and not floral morphology was the best diagnostic characteristic. Ecological information such as the estuarine habitat, where different life forms occur, was important in delimiting species.
44
Hubbard, C. E. "Population studies of Spartina angelica in the Dee Estuary". Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381195.
Testo completo
45
Ritter, Mary Christine. "Benthic succession in a Texas estuary : the influence of hypoxia, salinity fluctuations, and disturbance frequency /". Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Testo completo
46
Mohd, Abdullah Maizah. "Ecological Studies of the Mangrove-Associated Meiofauna in Southeast Queensland, Australia". Thesis, Griffith University, 2016. http://hdl.handle.net/10072/367507.
Testo completoAbstract (sommario):
Meiofauna are ubiquitous but poorly-studied components of soft-bottom marine communities around the world, including mangroves. However, information on the ecological role of the meiofauna in subtropical intertidal habitats is scarce compared to knowledge of the benthic macrofauna. The dynamic environmental conditions and heterogeneous sediments of mangroves present challenges to understanding the structure of mangrove meiofaunal assemblages at various spatial and temporal scales. This study was designed to elucidate the ecological role of the meiofauna in mangroves by studying their three main ecological elements: 1) assemblages structure; 2) top-down interaction with macrofauna; and 3) bottom-up interaction in terms of nutrient utilisation.
Firstly, how meiofaunal assemblage respond to estuarine sediment conditions was described by analysing the assemblages associated with different mangrove species (Avicennia marina, Rhizophora stylosa and Aegiceras corniculatum) at three locations in sub-tropical Southeast Queensland, Australia. Secondly, the significance and nature of top-down control on the density of meiofauna based on their interactions with deposit- feeding crabs was investigated in a mangrove and the adjoining sandflat.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text
47
Tweddle, Gavin Paul. "Population dynamics of selected ichthyofaunal components in the temperate, temporarily open/closed Kasouga Estuary, South Africa". Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1005428.
Testo completoAbstract (sommario):
The spatial and temporal pattern of ichthyofaunal community composition in relation to selected physico-chemical (temperature and salinity) and biological variables (chlorophyll-a and zooplankton) was investigated at ten stations in the temperate temporarily open/closed Kasouga estuary. In addition, the food web structure in the estuary was investigated using stable carbon isotope analysis. Results of the 5 metre seine net survey indicated that ichthyofaunal composition and biomass in the Kasouga estuary was largely determined by seasonality and mouth condition. Maximum abundance and biomass of ichthyofauna was recorded during summer or during those periods when overtopping occurred. Overtopping coincided with the recruitment of marine estuarine dependant species, which dominated the catches both numerically and in biomass. The recruitment of these species resulted in an increase in diversity of the ichthyofaunal community. There were no significant spatial patterns in the distribution of smaller ichthyofauna (<50mm SL) identified in Bray-Curtis similarity matrices using cluster analysis (Primer 5 v5.2.4). Spearman’s correlation analysis revealed that there were no significant correlations between abundance and biomass of ichthyofauna and selected physico-chemical and biological variables other than salinity (P>0.05 in all other cases). There were two distinct spatial patterns in the distribution of the larger ichthyofauna (>50mm SL). These corresponded to a grouping associated with the mouth region and a grouping associated with the remaining regions of the estuary. Stable isotope analysis indicated that the primary source of carbon utilised by the ichthyofauna of the Kasouga estuary was derived from the channel, most likely microphytobenthic algae. The contributions of the riparian and salt marsh vegetation to the total carbon flow appear to be minimal.
48
Gillett, David James. "Effects of habitat quality on secondary production in shallow estuarine waters and the consequences for the benthic-pelagic food web". W&M ScholarWorks, 2010. http://www.vims.edu/library/Theses/Gillett10.pdf.
Testo completo
49
Snow, Gavin Charles. "Contributions to the use of microalgae in estuarine freshwater reserve determinations". Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/709.
Testo completoAbstract (sommario):
The ecologist Garrett Hardin (1968) introduced a useful concept called the tragedy of the commons, which describes how ecological resources become threatened or lost. The term “commons” is based on the commons of old English villages and is symbolic of a resource that is shared by a group of people. If every person were to use each resource in a sustainable fashion it would be available in perpetuity. However, if people use more than their share they would only increase their personal wealth to the detriment of others. In addition, an increase in the population would mean that the size of each share would have to decrease to accommodate the larger number of people. As a result, resources are threatened by personal greed and uncontrolled population growth. Freshwater is an example of a common resource that is under threat in South Africa where the average annual rainfall is less than 60 percent of the global average (Mukheibir & Sparks 2006). The increasing demands for freshwater as well as its eutrophication are major concerns with regards to estuarine health, environmental resource management and human health. The correct management of water is necessary to ensure that it is utilised in a sustainable manner. The National Water Act (No. 36 of 1998) has provided the rights to water for basic human needs and for sustainable ecological function; the Basic Human Needs Reserve and Ecological Reserve are both provided as a right in law. The amount of water necessary for an estuary to retain an acceptable ecological status, known as the Estuarine Ecological Reserve, is determined through the implementation of procedures (rapid, intermediate or comprehensive) compiled by the Department of Water Affairs and Forestry (1999) in its Resource Directed Measures (RDM) for the Protection of Water Resources. The impact of restricted flow on estuaries can be reduced by manipulating the water released from impoundments, the regulation of water abstractions within the river catchment or both (Hirji et al. 2002). The reserve assessment method is designed to evaluate ecosystem requirements by employing groups of specialists from different disciplines. In South Africa, this includes hydrologists, sedimentologists, water chemists and biologists (including microalgae specialists). The use of microalgae in ecological assessments has largely been based on research that was initiated at the Nelson Mandela Metropolitan University (formerly University of Port Elizabeth) and subsequently at Rhodes University (Grahamstown) and the University of KwaZulu Natal (Durban). The microalgal research can be divided into two main focus areas; phytoplankton and benthic microalgae
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Naidoo, Lyndle Sherae. "Identification and classification of micro-estuaries using selected abiotic and biotic characteristics along the Eastern Cape coast, South Africa". Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/11920.
Testo completoAbstract (sommario):
Many of the larger estuaries along the South African coastline are highly degraded due to human impacts, highlighting the need to conserve pristine systems. There are approximately 100 micro-estuaries along our coastline which have not yet been identified or classified and hence their ecological functioning is unknown. The aim of this study was to identify and classify micro-estuaries along the Eastern Cape coast. Specific objectives of the study were to: 1) map the distribution of estuarine habitats in a selection of micro-estuaries and assess changes over time; 2) measure the physico-chemical characteristics of the micro-estuaries in the field; 3) investigate the distribution of vegetation, identify macrophyte species and habitat integrity and classify the micro-estuaries sampled using abiotic and botanical characteristics. A total of 30 systems were identified of which 10 were selected for sampling which took place seasonally (2015-2016). A relationship between open water surface area and short term rainfall was only evident in Cunge, Sandy Bottom and Ichabana. In the field it was observed that after heavy rainfall, open water surface area increased and mouth breaching occurred. Salinity was the only water column characteristic that showed differences; salinity increased in response to over wash events. Sand was dominant in all systems and there were no differences in sediment characteristics. A total of 8 macroalgal species, 16 estuarine macrophyte species, six freshwater species and 72 riparian plant species were found. Seed bank reserves were low in all systems despite them being vegetated. Only abiotic characteristics were used for classification using Principle Components Analysis since there were no botanical differences between systems. Micro-estuaries were larger (> 0.03 ha), had a higher salinity (oligohaline, mesohaline and polyhaline conditions) and a constant water body. Micro-outlets were smaller (< 0.03 ha), had a lower salinity (oligohaline conditions were most common) and showed periods of drying. Five micro-estuaries (Shelbertsstroom, Kwesani, Cunge, Mtwendwe and Mtendwe) and five micro-outlets (Stromatolite, Sandy Bottom, Ichabana, Palm Tree and Black Rock) were classified. This study has shown that the micro-estuaries along the Eastern Cape coast are pristine (i.e. intact riparian zone and catchment), untouched and highly dynamic systems (i.e. great variation in water surface area and mouth condition) highlighting their need for protection.