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Artykuły w czasopismach na temat "Algal Grazing"
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Swamikannu, Xavier, i Kyle D. Hoagland. "Effects of Snail Grazing on the Diversity and Structure of a Periphyton Community in a Eutrophic Pond". Canadian Journal of Fisheries and Aquatic Sciences 46, nr 10 (1.10.1989): 1698–704. http://dx.doi.org/10.1139/f89-215.
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Periphyton diversity was highest at low to intermediate levels of grazing by the freshwater snail Physella and suppressed at high grazer densities, in partial support of the intermediate disturbance hypothesis. For the first time, the response curve of algal biomass versus a range of snail densities was used to establish low, intermediate, and high levels of community disturbance. Physella densities corresponding to these levels were added to net enclosures in a small eutrophic pond, to examine differences in attached algal cell densities and diversity after 20 d. Algal standing crop was enhanced in low and depressed in intermediate and higher grazer treatments. Five categories of attached algal response to grazing were identified: (1) filamentous algae suppressed at high grazing pressure; (2) rosette or filamentous taxa suppressed at moderate to high levels of grazing; (3) algae resistant to grazing via sediment-associated recruitment; (4) low profile algae with highest densities at moderate grazing, and; (5) prostrately attached taxa enhanced at moderate and high grazing levels, in contrast to marine macroalgal communities, the primary mechanism mediating community response to different levels of grazing was the morphology of algal attachment.
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Nakpan, Apisara, Jaruwan Mayakun i Kringpaka Wangkulangkul. "Population Ecology and Habitat use of the Sea Slug Elysia pusilla (Bergh, 1872) (Sacoglossa) in A Tropical Halimeda macroloba Decaisne Meadow". Trends in Sciences 20, nr 1 (25.11.2022): 6402. http://dx.doi.org/10.48048/tis.2023.6402.
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Relationship between abundance of specialist marine herbivores and their food sources is poorly known because these herbivores are relatively rare in marine systems. The relationship between the cryptic sea slug Elysia pusilla (Bergh, 1872) and its host alga, Halimeda macroloba Decaisne, was evaluated in terms of spatial association and habitat utilization in a tropical algal meadow in southern Thailand that exclusively comprised of H. macroloba. The density of H. macroloba and of E. pusilla egg masses varied temporally throughout the sampling period, but temporal variation was not detected in the density of E. pusilla individuals, which was generally low with a maximum of 4 individuals per 400 cm2. Analysis suggests that the occurrence of the slug and its egg masses might be determined by the availability of the algal host. The slug was more likely to be observed in dense patches of algae that which offered a large total algal surface area. Occurrence of the slug was also higher when the algae were abundant. The numbers of slugs, egg masses and grazing marks were higher on mature thalli, which have larger surface areas than younger thalli. Egg masses and grazing marks were observed more often on segments at terminal positions on thalli. According to previous works, these segments contain low levels of accumulated calcium carbonate and high levels of secondary metabolites, which are sequestered by the slug and used to deter predators. The findings provide an insight into the life history of E. pusilla and variations in a natural population which that were previously little known.
HIGHLIGHTS
The relationship between the cryptic sea slug Elysia pusilla (Bergh, 1872) and its host alga, Halimeda macroloba Decaisne, was evaluated in terms of spatial association and habitat utilization in a tropical algal meadow in southern Thailand
The slug pusilla was more likely to be observed in dense patches of its algal host H. macroloba
Occurrence of the slug was also higher when the algae were abundant
The numbers of slugs, egg masses and grazing marks were higher on mature thalli
Egg masses and grazing marks were observed more often on segments at terminal positions on thalli
GRAPHICAL ABSTRACT
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Fisher, Carolyn L., Pamela D. Lane, Marion Russell, Randy Maddalena i Todd W. Lane. "Low Molecular Weight Volatile Organic Compounds Indicate Grazing by the Marine Rotifer Brachionus plicatilis on the Microalgae Microchloropsis salina". Metabolites 10, nr 9 (4.09.2020): 361. http://dx.doi.org/10.3390/metabo10090361.
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Microalgae produce specific chemicals indicative of stress and/or death. The aim of this study was to perform non-destructive monitoring of algal culture systems, in the presence and absence of grazers, to identify potential biomarkers of incipient pond crashes. Here, we report ten volatile organic compounds (VOCs) that are robustly generated by the marine alga, Microchloropsis salina, in the presence and/or absence of the marine grazer, Brachionus plicatilis. We cultured M. salina with and without B. plicatilis and collected in situ volatile headspace samples using thermal desorption tubes over the course of several days. Data from four experiments were aggregated, deconvoluted, and chromatographically aligned to determine VOCs with tentative identifications made via mass spectral library matching. VOCs generated by algae in the presence of actively grazing rotifers were confirmed via pure analytical standards to be pentane, 3-pentanone, 3-methylhexane, and 2-methylfuran. Six other VOCs were less specifically associated with grazing but were still commonly observed between the four replicate experiments. Through this work, we identified four biomarkers of rotifer grazing that indicate algal stress/death. This will aid machine learning algorithms to chemically define and diagnose algal mass production cultures and save algae cultures from imminent crash to make biofuel an alternative energy possibility.
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Riley, Lesilie, Mark Dybdahl i Robert Hall, Jr. "Grazing Effects of the New Zealand Mud Snail Across a Productivity Gradient in the Greater Yellowstone Ecosystem". UW National Parks Service Research Station Annual Reports 29 (1.01.2005): 96–104. http://dx.doi.org/10.13001/uwnpsrc.2005.3623.
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Accurately predicting the effects of introduced species on native commumtles and ecosystems is a challenge. Utilizing methods of food web ecology, we measured grazing effects of the invasive freshwater New Zealand mud snail, Potamopyrgus antipodarum, in streams within the Greater Yellowstone Ecosystem. Previous results indicate that P. antipodarum can significantly reduce algal standing stocks in less than one week, but it is not yet known if grazing effects vary across streams differing in benthic algae production. In this study, we measured the strength of P. antipodarum grazing on algal resources across six streams varying widely in ambient primary production. In field enclosure experiments within each stream, we estimated direct grazing effects of snails on algae by measuring chlorophyll a, gross primary production and chlorophyll a-specific primary production. In most streams, P. antipodarum decreased overall algal standing stocks, as measured by chlorophyll a, even though gross primary production was not affected. As a result, chlorophyll-a specific primary production increased in productive streams. Finally, standardized comparisons of P. antipodarum-algae interactions indicated that grazing effects were largest in the most productive streams. The overall impact of P. antipodarum on native stream communities will be greatest in the most productive streams if these assemblages are also capable of supporting dense P. antipodarum populations.
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Reese, Kristen L., Carolyn L. Fisher, Pamela D. Lane, James D. Jaryenneh, A. Daniel Jones, Matthias Frank i Todd W. Lane. "Abiotic and Biotic Damage of Microalgae Generate Different Volatile Organic Compounds (VOCs) for Early Diagnosis of Algal Cultures for Biofuel Production". Metabolites 11, nr 10 (15.10.2021): 707. http://dx.doi.org/10.3390/metabo11100707.
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Open microalgal ponds used in industrial biomass production are susceptible to a number of biotic and abiotic environmental stressors (e.g., grazers, pathogens, pH, temperature, etc.) resulting in pond crashes with high economic costs. Identification of signature chemicals to aid in rapid, non-invasive, and accurate identification of the stressors would facilitate targeted and effective treatment to save the algal crop from a catastrophic crash. Specifically, we were interested in identifying volatile organic compounds (VOCs) that can be used to as an early diagnostic for algal crop damage. Cultures of Microchloropsis gaditana were subjected to two forms of algal crop damage: (1) active grazing by the marine rotifer, Brachionus plicatilis, or (2) repeated freeze–thaw cycles. VOCs emitted above the headspace of these algal cultures were collected using fieldable solid phase microextraction (SPME) fibers. An untargeted analysis and identification of VOCs was conducted using gas chromatography-mass spectrometry (GC-MS). Diagnostic VOCs unique to each algal crop damage mechanism were identified. Active rotifer grazing of M. gaditana was characterized by the appearance of carotenoid degradation products, including β-cyclocitral and various alkenes. Freeze–thaw algae produced a different set of VOCs, including palmitoleic acid. Both rotifer grazing and freeze–thawed algae produced β-ionone as a VOC, possibly suggesting a common stress-induced cellular mechanism. Importantly, these identified VOCs were all absent from healthy algal cultures of M. gaditana. Early detection of biotic or abiotic environmental stressors will facilitate early diagnosis and application of targeted treatments to prevent algal pond crashes. Thus, our work further supports the use of VOCs for monitoring the health of algal ponds to ultimately enhance algal crop yields for production of biofuel.
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Mitra, Aditee, i Kevin J. Flynn. "Promotion of harmful algal blooms by zooplankton predatory activity". Biology Letters 2, nr 2 (marzec 2006): 194–97. http://dx.doi.org/10.1098/rsbl.2006.0447.
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The relationship between algae and their zooplanktonic predators typically involves consumption of nutrients by algae, grazing of the algae by zooplankton which in turn enhances predator biomass, controls algal growth and regenerates nutrients. Eutrophication raises nutrient levels, but does not simply increase normal predator–prey activity; rather, harmful algal bloom (HAB) events develop often with serious ecological and aesthetic implications. Generally, HAB species are outwardly poor competitors for nutrients, while their development of grazing deterrents during nutrient stress ostensibly occurs too late, after the nutrients have largely been consumed already by fast-growing non-HAB species. A new mechanism is presented to explain HAB dynamics under these circumstances. Using a multi-nutrient predator–prey model, it is demonstrated that these blooms can develop through the self-propagating failure of normal predator–prey activity, resulting in the transfer of nutrients into HAB growth at the expense of competing algal species. Rate limitation of this transfer provides a continual level of nutrient stress that results in HAB species exhibiting grazing deterrents protecting them from top-down control. This process is self-stabilizing as long as nutrient demand exceeds supply, maintaining the unpalatable status of HABs; such events are most likely under eutrophic conditions with skewed nutrient ratios.
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Wang, Zheng, Guangjian Xu, Lu Zhao, Yangyang Gao, Abdullah Al Mamun i Henglong Xu. "A community-based approach to identifying defence of microalgae against protozoan grazing". Journal of the Marine Biological Association of the United Kingdom 98, nr 4 (3.03.2017): 665–72. http://dx.doi.org/10.1017/s002531541700008x.
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It has increasingly been recognized that defence of microalgae against predator grazing is a passive response to increase algal population density by excreting chemicals with a change in physical properties. As common biological pollutants in the cultivation of the microalgae, the community-based method was used to identify the ability of two microalgae, Chlorella sp. and Nannochloropsis oceanica, to defend against protozoan grazing. Mature protozoan samples with 14-day age were collected, using microscopy glass slides, in coastal waters of the Yellow Sea, northern China. For both microalgae, a gradient of concentrations was designed as 100 (control), 104, 105, 106 and 107 cell ml−1, respectively. Results showed that both test algal species represented strong defence effects on protozoan grazing, especially at high density levels. Species richness, abundance and taxonomic distinctness of the protozoan assemblages showed a sharp decrease at high concentration level (107 cell ml−1) of both algae. A significant variation in protozoan community structures was found to be driven by the gradient of the algal concentrations. The paired taxonomic distinctness indices of the protozoan communities showed an increasing trend of departure from the expected taxonomic pattern with increase of algal concentrations. Based on the results, we suggest that the community-based bioassay might be used as a feasible tool for identifying defence against protozoan grazing of microalgae.
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Yang, Grace Y., i David Dudgeon. "Dietary variation and food selection by an algivorous loach (Pseudogastromyzon myersi: Balitoridae) in Hong Kong streams". Marine and Freshwater Research 61, nr 1 (2010): 49. http://dx.doi.org/10.1071/mf09032.
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The algivorous balitorid loach Pseudogastromyzon myersi is abundant in Hong Kong streams where it may exert top-down control on benthic algal assemblages as reported for grazing fish in temperate and neotropical streams. Dietary selectivity by P. myersi was investigated in two shaded and two unshaded streams during the wet and dry seasons, thereby allowing for variation in the potential bottom-up influences of light and flow on algae. Fish stomach contents were compared with the benthic algal assemblages to assess selectivity and to test whether algal growth form influenced susceptibility to grazing. Diatoms and filamentous cyanobacteria dominated the diets of the fish, regardless of stream or season; most of the remainder of the stomach contents comprised fine particulate organic matter (FPOM). Stalked diatoms (Gomphonema) and filamentous cyanobacteria (Homeothrix) were the most important dietary items, with the former selected during the dry season and the latter in the wet season. Adherent diatoms (Achnanthes) were underrepresented in the diet, and filamentous chlorophytes were rarely eaten. Seasonal changes in diet were minor. Interstream variations reflected differences in the proportions of Gomphonema, Homeothrix and FPOM ingested, and were unrelated to shading. Grazing by P. myersi may influence algal composition and productivity by removing loosely attached diatoms and facilitating growth of filamentous cyanobacteria.
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Evans, Marlene S., Richard D. Robarts i Michael T. Arts. "Predicted versus actual determinations of algal production, algal biomass, and zooplankton biomass in a hypereutrophic, hyposaline prairie lake". Canadian Journal of Fisheries and Aquatic Sciences 52, nr 5 (1.05.1995): 1037–49. http://dx.doi.org/10.1139/f95-102.
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We compared the accuracy of various regression models in predicting algal production, algal biomass and composition, and zooplankton biomass in a hypereutrophic, hyposaline prairie lake. The total phosphorus (TP) models investigated underestimated mean summer algal biomass and inedible biomass: the models overestimated mean summer edible algae biomass and annual primary production in the euphotic zone. Differences between predicted and actual biomass values are attributed to intense zooplankton grazing on the edible algal community and to the gradual accumulation of slow-growing, inedible algae. The TP model investigated provided an accurate prediction of zooplankton biomass. The algal biomass model overestimated zooplankton biomass, possibly because edible algae accounted for a very small fraction of algal biomass in Humboldt Lake during the ice-free season. The chlorophyll model investigated underestimated zooplankton biomass, apparently because Humboldt Lake algae have a relatively low chlorophyll content. The use of a 0.01 conversion factor to estimate algal biomass on the basis of chlorophyll appears to be inadequate and requires further study. There was no evidence that hyposaline Humboldt Lake has a relatively high zooplankton to phytoplankton biomass ratio when compared with freshwater lakes.
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Fisher, Carolyn L., Michelle V. Fong, Pamela D. Lane, Skylar Carlson i Todd W. Lane. "Storage and Algal Association of Bacteria That Protect Microchloropsis salina from Grazing by Brachionus plicatilis". Microorganisms 11, nr 3 (18.03.2023): 786. http://dx.doi.org/10.3390/microorganisms11030786.
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Loss of algal production from the crashes of algal mass cultivation systems represents a significant barrier to the economic production of microalgal-based biofuels. Current strategies for crash prevention can be too costly to apply broadly as prophylaxis. Bacteria are ubiquitous in microalgal mass production cultures, however few studies investigate their role and possible significance in this particular environment. Previously, we demonstrated the success of selected protective bacterial communities to save Microchloropsis salina cultures from grazing by the rotifer Brachionus plicatilis. In the current study, these protective bacterial communities were further characterized by fractionation into rotifer-associated, algal-associated, and free-floating bacterial fractions. Small subunit ribosomal RNA amplicon sequencing was used to identify the bacterial genera present in each of the fractions. Here, we show that Marinobacter, Ruegeria, and Boseongicola in algae and rotifer fractions from rotifer-infected cultures likely play key roles in protecting algae from rotifers. Several other identified taxa likely play lesser roles in protective capability. The identification of bacterial community members demonstrating protective qualities will allow for the rational design of microbial communities grown in stable co-cultures with algal production strains in mass cultivation systems. Such a system would reduce the frequency of culture crashes and represent an essentially zero-cost form of algal crop protection.
Rozprawy doktorskie na temat "Algal Grazing"
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Madikiza, Liwalam Onwabile. "The role of grazers and basal sustrate cover in the control of intertidal algal distribution". Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&.
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Graham, Sylvia Lynne. "Growth and grazing of microzooplankton in response to the harmful alga Heterosigma akashiwo in prey mixtures /". Online version, 2008. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=305&CISOBOX=1&REC=8.
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VENULEO, MARIANNA. "Algal responses to abiotic and biotic environmental changes". Doctoral thesis, Università Politecnica delle Marche, 2017. http://hdl.handle.net/11566/245503.
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L’eterogeneità delle risposte fisiologiche delle microalghe ai cambiamenti ambientali rappresenta uno dei fattori più importanti nel determinare le interazioni tra le specie in ambiente. La mia ricerca ha rivelato che specie differenti sono diversamente inclini a modificare la propria composizione cellulare in risposta ai cambiamenti ambientali. La scelta tra acclimatazione e omeostasi dipende anche dal tipo e dalla durata della perturbazione in esame. La maggior parte delle alghe considerate nel mio studio, per esempio, ha mostrato una risposta omeostatica ai cambiamenti nelle concentrazioni ambientali di CO2 e nella forma di azoto disponibile. Non è stato ritrovato nessun legame tra la strategia di risposta e la tassonomia delle alghe.
Particolare attenzione è stata rivolta a Chromera velia, parente prossima dei parassiti Apicomplexa e probabile simbionte di coralli dell’ordine Scleractinia. C. velia si è dimostrata perfettamente in grado di vivere ad alta CO2. Questa condizione ha stimolato la produzione di C organico da parte di C. velia, incrementato la sua efficienza di utilizzo dei nutrienti e ha determinato cambiamenti nei rapporti stechiometrici tra gli elementi. Si può ipotizzare, dunque, che l’elevata concentrazione di CO2 rinvenuta all’interno dei tessuti del corallo che circondano il simbionte possa facilitare la vita di quest’alga in simbiosi.
Infine, ho potuto dimostrare che le interazioni tra alghe e ambiente possono avere conseguenze nei rapporti tra alghe e loro predatori. I miei esperimenti hanno mostrato che i copepodi (ma non i rotiferi) possono discriminare tra alghe che sono identiche in ogni aspetto tranne che nella composizione cellulare. La storia nutrizionale delle alghe, dunque, essendo uno dei principali determinanti della loro composizione cellulare, risulta un elemento di grande importanza nelle relazioni tra alghe e predatori.Algae exhibit a large variety of physiological responses to the environmental changes. Such heterogeneity of responses, which is a major determinant of species interaction in natural algal assemblages, was the target of my research. My results show that different species are differently prone to change their cell composition in response to environmental changes, depending on the type and duration of the perturbation. When algae are exposed to changes in the N source and in the CO2 availability, for instance, homeostasis appears as a much more common strategy than usually believed. No link between the response modes and the taxonomy of the examined species was found. I paid special attention to Chromera velia, a photosynthetic relative of apicomplexan parasites that is likely involved in symbiotic associations with scleractinian corals. This alga seems perfectly capable of copying with very high CO2. Life at high CO2 stimulates the overall organic C production of C. velia, increases its nutrient use efficiency and changes the stoichiometric relationships among elements within the cell. The high CO2 concentrations that has been reported in the animal tissue surrounding the photosynthetic cells may therefore facilitate C. velia life in symbiosis. Finally, I have demonstrated that the interactions between algae and environment can affect the relationships between algae and their grazers. My experiments show that the copepods are able to discriminate among algae identical in all aspects but in cell composition, while the rotifers are not. Therefore, the nutritional history of algae, which has the potential to affect algal cell composition, appears as a major determinant of the relationships between algae and grazers.
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Vost, L. M. "The influence of grazing by the sea urchin Echinus esculentus L. on subtidal algal communities". Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372713.
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Rosser, S. M. Jane Horner. "Phytoplankton ecology in the upper Swan River estuary, Western Australia: with special reference to nitrogen uptake and microheterotroph grazing". Thesis, Curtin University, 2004. http://hdl.handle.net/20.500.11937/1562.
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Phytoplankton succession and abundance in estuaries is known to be influenced by the relative strengths of various seasonally changing physical and chemical factors. Previous studies of Swan River Estuary phytoplankton biomass and composition have identified salinity, temperature, rainfall and nutrients as the most important controlling factors. These conclusions are generally based on analysis of data from river length transects and depth integrated day-time sampling. They describe influences ,affecting whole system phytoplankton abundance and succession. Many of the typical seasonal bloom that develop are ephemeral and only extend over relatively small areas. The focus of this study is a single site, Ron Courtney Island, considered typical of the upper estuary region. This region of the estuary was chosen as representative of the section of river most influenced by allochthonous nutrient input. It has been the region of most frequent and intense algal blooms over the past decade. The factors, physical, biological or physiological, that have the greatest influence on controlling phytoplankton biomass under various ambient conditions for this system are determined. While previous studies have recognised the importance of nitrogen to phytoplankton growth in the Swan River Estuary, they have focused on NO;, with only anecdotal reference to the importance of the alternative nitrogen source, NH4+. This is the first study to explore the influence of different nitrogen source fluxes on phytoplankton biomass in the upper Swan River Estuary. The roles of physiological adaptation to, and preferences for, 'new' (NO,), recycled (NH4+) and organic (urea) nitrogen sources in relation to ambient nutrient levels are explored.Specific uptake rates (v), normalised to chlorophyll a, for NO;, NH4+ and urea were 0.2 ± 0.04 - 1831.1 ± 779.19, 0.5 ± 0.26 - 1731.6 ± 346.67 and 3.0 ± 0.60 - 2241.2 ± 252.56 ng N μg Chla-1 respectively. Urea concentration (14.8 - 117.7 μg urea-N 1-1) remained relatively constant over the 12 month study period. Measured ambient specific uptake rates for urea represent between 27.5% and 40.4% of total N uptake over the annual period February 1998 -January 1999. Seasonal nitrate uptake over the same period constituted only 11.3% (±10.77%, n=12) to 24.4% (± 13.02%, n=12) with the highest percentage during winter, when nitrate levels are elevated. It is suggested that urea provides a nutrient intermediary over the spring - summer period during transition from autotrophic to heterotrophic dominated communities. Grazing ,and nitrogen recycling are intricately connected by simultaneously providing top-down biomass control and bottom-up nutrient supply. Zooplankton (> 44 μm) grazing has been shown to reduce up to 40% of phytoplankton standing stock at times. Microheterotrophs (<300 pm) can reduce phytoplankton biomass production by up to 100% (potential production grazed, 11.1% day' - 99.6 % day-1) over an annual cycle. This correlated to mean seasonal day-time grazing loss of 80.47 ± 3.5 ngN μg Chla-1 in surface waters and 20.17 ± 9.7 ngN μg Chla-1 at depth (4.5m). Night time grazing for surface and bottom depths resulted in similar nitrogen loss rates (13.03 ± 4.84 ngN μg Chla-1).Uptake rates for nitrate (r2 0.501) and urea (r2 0.512), doing with temperature (r2 0.605) were shown to have the greatest influence on phytoplankton distribution over depth and time. This research emphasises the need for more detailed investigations into the physiology of nutrient uptake and the effects of nutrient fluxes on phytoplankton biomass and distribution. Further research into the roles of organic nitrogen and pico and nanoplankton in this system is recommended.
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Kennedy, Matthew R. "The Role of Microzooplankton and Mesozooplankton Grazing During the Planktothrix-Dominated Cyanobacterial Blooms in Sandusky Bay, Lake Erie". Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1589546747826657.
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Rosser, S. M. Jane Horner. "Phytoplankton ecology in the upper Swan River estuary, Western Australia: with special reference to nitrogen uptake and microheterotroph grazing". Curtin University of Technology, Department of Environmental Biology, 2004. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16266.
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Phytoplankton succession and abundance in estuaries is known to be influenced by the relative strengths of various seasonally changing physical and chemical factors. Previous studies of Swan River Estuary phytoplankton biomass and composition have identified salinity, temperature, rainfall and nutrients as the most important controlling factors. These conclusions are generally based on analysis of data from river length transects and depth integrated day-time sampling. They describe influences ,affecting whole system phytoplankton abundance and succession. Many of the typical seasonal bloom that develop are ephemeral and only extend over relatively small areas. The focus of this study is a single site, Ron Courtney Island, considered typical of the upper estuary region. This region of the estuary was chosen as representative of the section of river most influenced by allochthonous nutrient input. It has been the region of most frequent and intense algal blooms over the past decade. The factors, physical, biological or physiological, that have the greatest influence on controlling phytoplankton biomass under various ambient conditions for this system are determined. While previous studies have recognised the importance of nitrogen to phytoplankton growth in the Swan River Estuary, they have focused on NO;, with only anecdotal reference to the importance of the alternative nitrogen source, NH4+. This is the first study to explore the influence of different nitrogen source fluxes on phytoplankton biomass in the upper Swan River Estuary. The roles of physiological adaptation to, and preferences for, 'new' (NO,), recycled (NH4+) and organic (urea) nitrogen sources in relation to ambient nutrient levels are explored.Specific uptake rates (v), normalised to chlorophyll a, for NO;, NH4+ and urea were 0.2 ± 0.04 - 1831.1 ± 779.19, 0.5 ± 0.26 - 1731.6 ± 346.67 and 3.0 ± 0.60 - 2241.2 ± 252.56 ng N μg Chla-1 respectively. Urea concentration (14.8 - 117.7 μg urea-N 1-1) remained relatively constant over the 12 month study period. Measured ambient specific uptake rates for urea represent between 27.5% and 40.4% of total N uptake over the annual period February 1998 -January 1999. Seasonal nitrate uptake over the same period constituted only 11.3% (±10.77%, n=12) to 24.4% (± 13.02%, n=12) with the highest percentage during winter, when nitrate levels are elevated. It is suggested that urea provides a nutrient intermediary over the spring - summer period during transition from autotrophic to heterotrophic dominated communities. Grazing ,and nitrogen recycling are intricately connected by simultaneously providing top-down biomass control and bottom-up nutrient supply. Zooplankton (> 44 μm) grazing has been shown to reduce up to 40% of phytoplankton standing stock at times. Microheterotrophs (<300 pm) can reduce phytoplankton biomass production by up to 100% (potential production grazed, 11.1% day' - 99.6 % day-1) over an annual cycle. This correlated to mean seasonal day-time grazing loss of 80.47 ± 3.5 ngN μg Chla-1 in surface waters and 20.17 ± 9.7 ngN μg Chla-1 at depth (4.5m). Night time grazing for surface and bottom depths resulted in similar nitrogen loss rates (13.03 ± 4.84 ngN μg Chla-1).
Uptake rates for nitrate (r2 0.501) and urea (r2 0.512), doing with temperature (r2 0.605) were shown to have the greatest influence on phytoplankton distribution over depth and time. This research emphasises the need for more detailed investigations into the physiology of nutrient uptake and the effects of nutrient fluxes on phytoplankton biomass and distribution. Further research into the roles of organic nitrogen and pico and nanoplankton in this system is recommended.
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Manley, Nicola Louise. "Polyphenolic compounds in intertidal fuciod algae and their effectiveness as grazing deterrents". Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333575.
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Rowcliffe, J. Marcus. "The population ecology of brent geese and their food plants". Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365866.
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Schwinnen, Chad Robert. "Impacts of a Herbivorous Fish, Campostoma anomalum (central stoneroller), on Nitrogen Fixation by Benthic Algae". Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1284993489.
Pełny tekst źródłaKsiążki na temat "Algal Grazing"
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Konar, Brenda. Role of grazers on the recolonization of hard-bottom communities in the Alaska Beaufort Sea. [Fairbanks, Alaska]: Coastal Marine Institute, University of Alaska Fairbanks, 2006.
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Toth, Gunilla B. Inducible chemical responses and herbivore resistance in seaweeds. Göteborg: Inst. för Marin Ekologi, Göteborgs Universitet, 2002.
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Romanowski, Nick. Wetland Habitats. CSIRO Publishing, 2010. http://dx.doi.org/10.1071/9780643100220.
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Wetland Habitats is a practical and easy to use manual for wetland restoration and conservation of diverse animal species. Covering all the recent work in this field, among other significant issues it discusses making the most of dams and created wetlands; reversing the effects of drainage, grazing, weirs, deteriorating water quality, and associated algal problems; captive breeding and reintroduction; and controlling weeds and vermin.
The book describes a range of potential problems encountered during restoration efforts and approaches to dealing with them, so that readers will be able to make informed decisions about wetlands on their own properties. It also explains how to set realistic targets for wetland restoration as well as longer-term goals for management, and includes colour photographs of diverse wetland habitats and the animals that rely on them.
The examples draw on a wide range of wetland animals including some which aren’t often found in wetlands on private properties, but the primary emphasis is on the ecology, interactions and management of species and other aspects of management that will be of most use to landholders with wetlands in need of rejuvenation.
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Sheppard, Charles R. C., Simon K. Davy, Graham M. Pilling i Nicholas A. J. Graham. The main reef builders and space occupiers. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198787341.003.0002.
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Corals are the main reef builders on tropical reefs. They make their own substrate, much of which remains as consolidated rock, the remainder becoming broken down to form extensive sediment beds. Soft corals, sea fans and sponges are other major occupiers of substrate but deposit only minimal quantities of rock. All are important ecological components of coral reefs, although the greatest biodiversity of macrofauna are found amongst the fish, cryptic invertebrates and microorganisms. Amongst the algae, the microalgae symbiotic with corals are of key importance in the nutrition of the reef, but macroalgae are generally scarce on healthy reefs, partly due to grazing. Some algae generate large quantities of limestone and assist in reef construction. Growth and reduction by bioerosion are generally closely balanced in a healthy reef, and reef growth depends, of course, on growth exceeding erosion by a small margin.
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Kirchman, David L. The ecology of viruses. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0010.
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In addition to grazing, another form of top-down control of microbes is lysis by viruses. Every organism in the biosphere is probably infected by at least one virus, but the most common viruses are thought to be those that infect bacteria. Viruses come in many varieties, but the simplest is a form of nucleic acid wrapped in a protein coat. The form of nucleic acid can be virtually any type of RNA or DNA, single or double stranded. Few viruses in nature can be identified by traditional methods because their hosts cannot be grown in the laboratory. Direct count methods have found that viruses are very abundant, being about ten-fold more abundant than bacteria, but the ratio of viruses to bacteria varies greatly. Viruses are thought to account for about 50% of bacterial mortality but the percentage varies from zero to 100%, depending on the environment and time. In addition to viruses of bacteria and cyanobacteria, microbial ecologists have examined viruses of algae and the possibility that viral lysis ends phytoplankton blooms. Viruses infecting fungi do not appear to lyse their host and are transmitted from one fungus to another without being released into the external environment. While viral lysis and grazing are both top-down controls on microbial growth, they differ in several crucial respects. Unlike grazers, which often completely oxidize prey organic material to carbon dioxide and inorganic nutrients, viral lysis releases the organic material from hosts more or less without modification. Perhaps even more important, viruses may facilitate the exchange of genetic material from one host to another. Metagenomic approaches have been used to explore viral diversity and the dynamics of virus communities in natural environments.
Części książek na temat "Algal Grazing"
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Arfi, Robert, i Daniel Guiral. "Chlorophyll budget in a productive tropical pond: algal production, sedimentation, and grazing by microzooplankton and rotifers". W Studies on the Ecology of Tropical Zooplankton, 239–49. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0884-3_17.
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Norton, Trevor A., i Nicola L. Manley. "The Characteristics of Algae in Relation to their Vulnerability to Grazing Snails". W Behavioural Mechanisms of Food Selection, 461–78. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75118-9_23.
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Arvola, L., K. Salonen, P. Kankaala i A. Lehtovaara. "Vertical distributions of bacteria and algae in a steeply stratified humic lake under high grazing pressure from Daphnia longispina". W Dissolved Organic Matter in Lacustrine Ecosystems: Energy Source and System Regulator, 253–69. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2474-4_18.
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"Effects of Urbanization on Stream Ecosystems". W Effects of Urbanization on Stream Ecosystems, redaktorzy Marina Potapova, James F. Coles, Elise M. P. Giddings i Humbert Zappia. American Fisheries Society, 2005. http://dx.doi.org/10.47886/9781888569735.ch19.
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<em>Abstract.</em>—Patterns of stream benthic algal assemblages along urbanization gradients were investigated in three metropolitan areas—Boston (BOS), Massachusetts; Birmingham (BIR), Alabama; and Salt Lake City (SLC), Utah. An index of urban intensity derived from socioeconomic, infrastructure, and land-use characteristics was used as a measure of urbanization. Of the various attributes of the algal assemblages, species composition changed along gradients of urban intensity in a more consistent manner than biomass or diversity. In urban streams, the relative abundance of pollutiontolerant species was often higher than in less affected streams. Shifts in assemblage composition were associated primarily with increased levels of conductivity, nutrients, and alterations in physical habitat. Water mineralization and nutrients were the most important determinants of assemblage composition in the BOS and SLC study areas; flow regime and grazers were key factors in the BIR study area. Species composition of algal assemblages differed significantly among geographic regions, and no particular algal taxa were found to be universal indicators of urbanization. Patterns in algal biomass and diversity along urban gradients varied among study areas, depending on local environmental conditions and habitat alteration. Biomass and diversity increased with urbanization in the BOS area, apparently because of increased nutrients, light, and flow stability in urban streams, which often are regulated by dams. Biomass and diversity decreased with urbanization in the BIR study area because of intensive fish grazing and less stable flow regime. In the SLC study area, correlations between algal biomass, diversity, and urban intensity were positive but weak. Thus, algal responses to urbanization differed considerably among the three study areas. We concluded that the wide range of responses of benthic algae to urbanization implied that tools for stream bioassessment must be region specific.
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"Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity". W Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity, redaktorzy Darcie L. Quamme i Patrick A. Slaney. American Fisheries Society, 2003. http://dx.doi.org/10.47886/9781888569445.ch12.
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<em>Abstract.</em>—The relationship between added soluble nutrient concentration and the abundance and taxonomic composition of stream insects was determined in an experiment using streamside troughs. Target phosphorus (P) concentrations were 0, 0.5, 2.5, 5, 10, and 50 µg/L at a N:P ratio of 1:1 (wt.:wt.). All treatments were replicated three times except 50 µg/ L, which was unreplicated. Peak algal biomass (PB) increased with nutrient concentration linearly to 7.4 mg/m<sup>2</sup> at 2.5 mg P/L and reached an asymptote at 9.2 mg/m2 (2.7× the controls) at 10 µg P/L. Adult baetid mayflies increased 2- and 4-fold when caught in drift nets and emergent insect traps, respectively, at a phosphorus concentration of 10 µg/L compared with controls. Numbers of benthic baetids, nemourid, and perlodid stoneflies and hydroptilid and polycentripodid trichopterans increased 1.6, 2.3, 2.9, 2.8, and 1.2-fold, respectively, at 10 µg P/L compared with controls. Adult and nymphal baetids and benthic nemourids, perlodids, and hydroptilids initially increased rapidly at nutrient concentrations of 0–2.5 µg P/L and reached asymptotes at concentrations of 2.5–10 µg P/L. Exclusion of insects from a single unfertilized trough suggested that grazing limited peak biomass of periphyton to low levels. Increased abundances of aquatic insects resulted from greater periphyton availability at relatively low dissolved-nutrient additions ranging from 0.5 to 10 µg P/L.
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Morél, Andre. "Optics from the Single Cell to the Mesoscale". W Ocean Optics. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195068436.003.0009.
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The inherent optical properties of a water body (mesoscale), namely, the absorption coefficient, the scattering coefficient, and the volume scattering function combine with the radiant distribution above the sea to yield the apparent optical properties (Preisendorfer, 1961). The radiative transfer equation is the link between these two classes of optical properties. Locally, the inherent properties of seawater are governed by, and strictly result from, the sum of the contributions of the various components, namely, the water itself, the various particles in suspension able to scatter and absorb the radiant energy, and finally the dissolved absorbing compounds. Analyzing these contributions is an important goal of optical oceanography. Among these particles, the phytoplanktonic cells, with their photosynthetic pigments, are of prime importance, in particular in oceanic waters far from terrestrial influence. They also are at the origin of other kinds of particles, such as their own debris, as well as other living “particles” grazing on them (bacteria, flagellates and other heterotrophs). Studying optics at the level of single cells and particles is therefore a requirement for a better understanding of bulk optical properties of oceanic waters. Independently of this goal, the study of the individual cell optics per se is fundamental when analyzing the pathways of radiant energy, in particular the light harvesting capabilities and the photosynthetic performances of various algae or their fluorescence responses. The following presentation is a guidline for readers who will find detailed studies in the classic books Light Scattering by Small Particles by van de Hulst (1957) and Light and Photosynthesis in Aquatic Ecosystems by Kirk (1983), as well as in a paper dealing specifically with the optics of phytoplankton by Morel and Bricaud (1986). This chapter is organized according to the title, with first a summary of the relevant theories to be applied when studying the interaction of an electromagnetic field with a particle, and then, as a transition between this scale and that of in vitro experiments, some results concerning the optical behavior of pure algal suspensions; finally the more complicated situations encountered in natural environments are briefly described to introduce the “nonlinear biological” effect (Smith and Baker, 1978a) upon the optical coefficients for oceanic waters, and to examine some of the empirical relationships, as presently available, between the pigment concentration and the optical properties of the upper ocean at mesoscale and global scale.
Raporty organizacyjne na temat "Algal Grazing"
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Hackbarth, Carolyn, i Rebeca Weissinger. Water quality in the Northern Colorado Plateau Network: Water years 2016–2018 (revised with cost estimate). National Park Service, listopad 2023. http://dx.doi.org/10.36967/nrr-2279508.
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Water-quality monitoring in National Park Service units of the Northern Colorado Plateau Network (NCPN) is made possible through partnerships between the National Park Service Inventory & Monitoring Division, individual park units, the U.S. Geological Survey, and the Utah Division of Water Quality. This report evaluates data from site visits at 62 different locations on streams, rivers, and reservoirs in or near ten NCPN park units between October 1, 2015 and September 30, 2018. Data are compared to state water-quality standards for the purpose of providing information to park managers about potential water-quality problems. The National Park Service does not determine the regulatory status of surface waters; state water quality agencies determine whether waters comply with the Clean Water Act. Evaluation of water-quality parameters relative to state water-quality standards indicated that 17,997 (96.8%) of the 18,583 total designated beneficial-use evaluations completed for the period covered in this report met state water-quality standards. The most common exceedances or indications of impairment, in order of abundance, were due to elevated nutrients, elevated bacteria (E. coli), elevated water temperature, elevated trace metals, elevated total dissolved solids (and sulfate), elevated pH, and low dissolved oxygen. While some exceedances were recurring and may have been caused by human activities in the watersheds, many were due to naturally occurring conditions characteristic of the geographic setting. This is most apparent with phosphorus, which can be introduced into surface water bodies at elevated levels by natural weathering of the geologic strata found throughout the Colorado Plateau. Higher phosphorus concentrations could also be attributed to anthropogenic activities that can accelerate erosion and transport of phosphorus. Some activities that can increase erosional processes include grazing, logging, mining, pasture irrigation, and off-highway vehicle (OHV) use. Exceedances for total phosphorus were common occurrences at nine out of ten NCPN park units, where at least one site in each of these parks had elevated phosphorus concentrations. At these sites, high levels of nutrients have not led to algal blooms or other signs of eutrophication. Sites monitored in Arches National Park (NP), Black Canyon of the Gunnison NP (BLCA), Bryce Canyon NP (BRCA), Capitol Reef NP (CARE), Curecanti National Recreation Area (CURE), Dinosaur National Monument (DINO), and Zion NP (ZION) all had E. coli ex-ceedances that could be addressed by management actions. While many of these sites already have management actions underway, some of the actions necessary to bring these waters into compliance are beyond the control of the National Park Service. Changes to agricultural practices to improve water quality involves voluntary participation by landowners and/or grazing permittees and their respective states. This could be the case with lands upstream of several parks with E. coli contamination issues, including Red Rock Canyon (BLCA); Sul-phur, Oak, and Pleasant creeks (CARE); Blue Creek and Cimarron River (CURE); Brush and Pot creeks (DINO); and North Fork Virgin River (ZION). Issues with E. coli contamination at Yellow Creek (BRCA) seemed to be resolved after the park boundary fence downstream of the site was repaired, keeping cattle out of the park. At North Fork Virgin River, E. coli exceedances have been less frequent since the State of Utah worked with landowners and grazing permittees to modify agricultural practices. Continued coordination between the National Park Service, state agencies, and local landowners will be necessary to further re-duce E. coli exceedances and, in turn, improve public health and safety in these streams. Selenium concentrations in Red Rock Canyon (BLCA) continued to exceed the state aquat-ic-life standard at both the upstream and downstream sites. Although selenium weathers naturally from bedrock and...