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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.
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Suzuki, H., Y. Kubo, E. Inomata, Y. Agatsuma i MN Aoki. "Effects of herbivorous gastropod grazing on the sedimentation and succession of subtidal macroalgal assemblages". Marine Ecology Progress Series 656 (10.12.2020): 123–38. http://dx.doi.org/10.3354/meps13582.
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The subtidal zone on cold temperate rocky coasts is an environment exposed to much less physical disturbance than the intertidal, and sediment deposition is continuous. Removal of this sediment by gastropod grazers is therefore presumed to affect the structure of subtidal algal communities. This concept was investigated by evaluating the grazing effects of the dominant herbivorous gastropod Omphalius rusticus by exclusion experiments in the field. Settlement plates of both exclusion and control treatments were placed every month from November 2014, and immersed for 1 mo. Algae colonized from May and tended to increase in biomass toward summer. No marked differences were observed in the algal composition of exclusion and control. Sediment deposition showed no apparent seasonal changes. Cumulative successional plates of both exclusion and control treatments were placed in November 2014, and immersed for 1 to 9 mo. The colonization of algae started in February and the species number peaked earlier in the exclusion and later in the control. Sediment load and algal biomass were high from February to May in the exclusion, and from April to July in the control. Seedlings of Sargassum confusum were found in both plots starting in July. We conclude that O. rusticus constantly removed sediments by its grazing activity and had a large impact on the formation of the macroalgal community by controlling sediment deposition. Its presence delayed the colonization of early-successional turf algal species, but did not affect colonization of late-successional canopy-forming algae such as S. confusum.
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Iken, K., E. R. Barrera-Oro, M. L. Quartino, R. J. Casaux i T. Brey. "Grazing by the Antarctic fish Notothenia coriiceps: evidence for selective feeding on macroalgae". Antarctic Science 9, nr 4 (grudzień 1997): 386–91. http://dx.doi.org/10.1017/s0954102097000497.
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In Potter Cove, King George Island, Antarctica, macroalgae provide a significant food resource for herbivores. The demersal fish Notothenia coriiceps feeds on macroalgae. Eighteen algal species were identified in stomach contents: two chlorophytes, ten rhodophytes and six phaeophytes. Among these the rhodophyte Palmaria decipiens, the phaeophyte Desmarestia menziesii and the chlorophyte Monostroma hariotii comprised the greatest proportions of algal biomass. A food selection study showed four algae to be preferred (P. decipiens, M. hariotii, D. menziesii, Iridaea cordata) and two species to be avoided (Desmarestia anceps and Himantothallus grandifolius) by N. coriiceps. The present investigation indicates that this fish feeds not only intentionally, but also selectively, on macroalgae. Preference for particular algal species is not related to associated epifaunal biomass or to associated amphipod biomass.
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Himmelman, John H., i Henri Nédélec. "Urchin Foraging and Algal Survival Strategies in Intensely Grazed Communities in Eastern Canada". Canadian Journal of Fisheries and Aquatic Sciences 47, nr 5 (1.05.1990): 1011–26. http://dx.doi.org/10.1139/f90-116.
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We examine relationships between food preferences of the urchin, Strongyhcentrotus droebachiensis, and such properties of fleshy macroalgae as dry mass, ash content, calorific value, and phenolic content. Grazing resistant algae characteristic of urchin dominated habitats rank low in attraction, reflecting the ability of urchins to detect and locate them in the field. They fall into two groups, (1) reds, Phycodrys rubens, Turnerella pennyi, and Ptilota serrata, with a high proportion of dry matter and low phenolic content, and (2) browns, Desmarestia viridis and Agarum cribrosum with low to intermediate calorific values. Algae susceptible to grazing fall into two additional groups, (3) algae with high dry mass which strongly attract urchins and are consumed at an intermediate rate (mostly annuals), and (4) readily eaten perennials which attract urchins to an intermediate degree and have high ash and low phenolic content. The susceptible algae survive through spatial and temporal escapes, mainly in shallow water where the effectiveness of urchin grazing is reduced. The urchin is a selective feeder and its ability to locate preferred algae promotes intake of foods (algae in the subtidal algal fringe and drift algae) that enhance fitness by favouring somatic and gonadal growth.
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Chow-Fraser, Patricia. "An Empirical Model to Predict in situ Grazing Rates of Diaptomus minutus Lilljeborg on Small Algal Particles". Canadian Journal of Fisheries and Aquatic Sciences 43, nr 5 (1.05.1986): 1065–70. http://dx.doi.org/10.1139/f86-133.
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Grazing rates of Diaptomus minutus were measured in situ in six lakes in south-central Ontario using the tracer species Chlorella vulgaris and Scenedesmus ovalis. An empirical model was constructed to predict grazing rate as a function of the relative proportion of small (<10 μm)to large (10–30 μm) algal particles in the nanoplankton. It accurately predicted diaptomid grazing rates for three lakes in an independent lake set; however, it produced overestimates for two other lakes. There was also a significant positive correlation between grazing rate and the biomass concentration of small algae in the lakes. Difference in ambient lake temperature did not contribute significantly towards explained variation in grazing rate; prosome length was also a poor predictor of grazing rate. In parallel experiments, diaptomid grazing rates were higher when Pediastrum was used than when Scenedesmus was used as the tracer; in a similar set of experiments, grazing rates were higher when Chlamydomonas was used than when Scenedesmus was used.
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Pearson, H. W., D. D. Mara, S. W. Mills i D. J. Smallman. "Physico-Chemical Parameters Influencing Faecal Bacterial Survival in Waste Stabilization Ponds". Water Science and Technology 19, nr 12 (1.12.1987): 145–52. http://dx.doi.org/10.2166/wst.1987.0139.
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In situ studies on waste stabilization ponds (in Portugal) showed that faecal coliform numbers were lowest at positions in the water column where pH, temperature, dissolved oxygen and algae were high. Numbers were not always lowest at the surface where light intensities were highest or in ponds where light penetration had increased through algal grazing by Daphnia. Laboratory studies showed that pH values approaching 9.0 or above increased faecal coliform die-off particularly under nutrient-poor conditions. Elevated temperatures enhanced the pH effect but the level of dissolved oxygen made little difference. Streptococcus, Salmonella and Campylobacter isolates all behaved similarly to the faecal coliforms. Daphnia grazing of the algal population in maturation ponds may reduce the microbial quality of the final effluent. These findings are discussed in relation to pond design.
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Hill, Nicole A., Craig Blount, Alistair G. B. Poore, Duncan Worthington i Peter D. Steinberg. "Grazing effects of the sea urchin Centrostephanus rodgersii in two contrasting rocky reef habitats: effects of urchin density and its implications for the fishery". Marine and Freshwater Research 54, nr 6 (2003): 691. http://dx.doi.org/10.1071/mf03052.
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The sea urchin Centrostephanus rodgersii plays an important role in determining the abundance and composition of benthic macroalgae in New South Wales. Centrostephanus rodgersii is commonly found in areas devoid of foliose algae (termed 'barrens habitat'), which abruptly change into areas rich in foliose algae (termed 'fringe habitat'). Complementary experiments were used to investigate the impact of C. rodgersii grazing on algal assemblages at a range of densities in the barrens and fringe habitats. Although 33% of the natural density of C.�rodgersii maintained barrens areas relatively free of foliose algae, only densities exceeding natural densities within barrens habitat cleared areas dominated by macroalgae. The impact of grazing was not linearly related to density in either habitat, which suggests that both the barrens and fringe habitats are stable and will persist unless there is a dramatic decrease in urchin densities in barrens areas or a large influx into fringe areas. These findings have significant implications for the commercial harvesting of C. rodgersii. They imply that reducing urchin densities in barrens habitats, or translocating urchins from barrens to fringe habitats in order to improve roe quality, will not significantly alter the algal assemblage of either habitat in the short term (less than 3 months).
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PHILBEY, AW, IJ LINKS i GC MORRICE. "Algal infection in sheep grazing irrigated pasture". Australian Veterinary Journal 79, nr 3 (marzec 2001): 212–14. http://dx.doi.org/10.1111/j.1751-0813.2001.tb14583.x.
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Paul, A. J., D. W. Schindler, A. K. Hardie i P. R. Leavitt. "Direct and indirect effects of predation by a calanoid copepod (subgenus: Hesperodiaptomus) and of nytrients in a fishless alpine lake". Canadian Journal of Fisheries and Aquatic Sciences 52, nr 12 (1.12.1995): 2628–38. http://dx.doi.org/10.1139/f95-852.
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The calanoid copepod Diaptomus (subgenus: Hesperodiaptomus) arcticus is a keystone predator in fishless alpine lakes of the Canadian Rockies. We quantified the effects of predation by D. arcticus on other copepods, rotifers, and algae in large mesocosm experiments (2250 L) using two levels of predator (present and absent) and two levels of nutrient addition (ambient and 4×). Standing stocks of algal taxa were assessed by high performance liquid chromatography of phytoplankton pigments. Diaptomus arcticus suppressed the biomass of rotifers and cyclopoid nauplii at both nutrient levels. The indirect effect of D. arcticus on algal biomass was minimal under ambient nutrient conditions, possibly owing to high rates of nutrient recycling by grazers. Biomass of algae, cyclopoid nauplii, and rotifers responded positively to nutrient additions. Nutrient addition increased algal standing crop 2- to 4-fold and changed dominance from diatoms and chrysophytes to blue-green algae. Diaptomus arcticus accelerated these changes, possibly by eliminating grazing by rotifers. These results suggest that in the absence of increased nutrients D. arcticus directly limits the biomass of herbivorous zooplankton but the indirect effect on phytoplankton is minimal.
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Tsai, Jeng-Wei, Yi-Li Chuang, Zih-Yi Wu, Mei-Hwa Kuo i Hsing-Juh Lin. "The effects of storm-induced events on the seasonal dynamics of epilithic algal biomass in subtropical mountain streams". Marine and Freshwater Research 65, nr 1 (2014): 25. http://dx.doi.org/10.1071/mf13058.
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Information concerning the drivers of seasonal variation in algal biomass in subtropical mountain streams is limited. To identify the drivers of biomass dynamics for epilithic algae, a 20-month study was conducted in mountain streams in Taiwan, an area characterised by different levels of riparian vegetation coverage and agricultural activity, in which a process-based model was optimally fit to field data. We found that episodic typhoon-induced floods were the major drivers shaping the seasonal variations in algal biomass. Flow-induced detachment was frequently observed in periods of higher algal biomass. In contrast, an increased flow stimulated algal growth during periods with slower flow rates. Increased temperature stimulated algal growth at sites with an open canopy cover and higher light availability but constrained biomass at sites with dense canopy shading. Overall, scraper biomass exerted less influence on algal biomass than did environmental factors. The effects of grazing were visible only at the pristine, low-stream-order site in winter. The effects of minimal algal biomass required for recovery was comparable to environmental factors only at sites with intermediate canopy cover, moderate discharge, and higher nutrient concentrations. We suggest that agricultural activity and riparian vegetation can affect epilithic algal biomass in subtropical mountain streams.
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Sautour, Benoît, i Jacques Castel. "Grazing activity of mesoplanktonic copepods in a shallow bay during an algal spring bloom (Marennes-Oléron Bay, France)". Journal of the Marine Biological Association of the United Kingdom 79, nr 1 (luty 1999): 73–84. http://dx.doi.org/10.1017/s0025315498000083.
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In situ grazing activity of mesoplanktonic copepods was investigated by the fluorometric method during an algal spring bloom in a zone of oyster farming in Marennes-Oléron Bay. The grazing activity of copepods was overall higher during the night than during the day for three species (Temora longicornis, Paracalanus parvus and Acartia clausi), but peaks also appeared during the day for all of them. Individual ingestion rates and daily rations were higher during neap tide (low suspended particulate matter (SPM) concentrations) than during spring tide (high SPM concentrations). During ebb tide (when SPM concentrations were the lowest) the feeding activity of T. longicornis, P. parvus and A. clausi was significantly negatively correlated with algal concentration. Our work suggests that during the algal spring bloom in the farming area of Marennes-Oléron Bay the pressure exerted by mesoplanktonic copepods on the algal stock was very low, as a consequence of: (i) high algal concentrations in the field (resuspension and high phytoplanktonic production); (ii) low ingestion rates when high algal concentrations were observed. The likely ingestion of non-fluorescent particles by copepods is discussed.
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Lafforgue, Michel, Wojciech Szeligiewicz, Jean Devaux i Michel Poulin. "Selective mechanisms controlling algal succession in Aydat lake". Water Science and Technology 32, nr 4 (1.08.1995): 117–27. http://dx.doi.org/10.2166/wst.1995.0173.
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Aydat lake is a dimictic eutrophic lake where Cyanophycean blooms occur. In order to study with accuracy this lake functioning, a one-dimensional vertical model (Licorne 2 model) was developed. This model takes into account physical, chemical and biological interactions and simulates the algal succession of the five main phytoplankton algae for two different years (1984 and 1985). It appears that the growth rate, the sedimentation rate, or the death rate do not explain by themselves the algal succession, and more specially the blue-green blooms. However, a good correlation between field data and Licorne 2 results are obtained by introducing specific advantages of blue-green algae such as buoyancy regulation mechanisms, capacity to fix atmospheric nitrogen and to grow at high pH value and toxin production. In the view of these results, a new understanding of the Aydat lake algal succession is then possible, where competition for light, food and limitation of the losses (sedimentation, grazing) take an important place in a thermal and chemical vertical stratified environment.
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Korzen, Leor, Alvaro Israel i Avigdor Abelson. "Grazing Effects of Fish versus Sea Urchins on Turf Algae and Coral Recruits: Possible Implications for Coral Reef Resilience and Restoration". Journal of Marine Biology 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/960207.
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Herbivory is an important structuring factor in coral reefs, influencing seaweed abundance, competitive interactions between seaweeds and corals, and coral reef resilience. Despite reports of a drastic increase in the cover of benthic algae and turf dominancy in the coral reefs of Eilat, Red Sea, very little is known about the factors responsible for this phenomenon or the possible effects of herbivory on turf algae and coral recruits. Here, we examine the effects of herbivory by experimentally exposing turf algae and coral recruits to grazing activities of herbivorous fish and sea urchins. Using remote video cameras to document removal of algae and coral spats, we show that the main grazing impact is due to daily grazing by fishes, whereas the significant impact of sea urchins is mainly expressed in their adverse effect on the survival of coral recruits, with a relatively low effect on algal biomass. These findings contribute to our understanding of the factors influencing turf algae establishment and proliferation, and the survival of coral recruits on the coral reefs of Eilat. The clear differences between the impact of herbivorous fish and that of sea urchins, on the Eilat reefs, have critical implications for reef resilience and restoration measures.
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Riley, Leslie, Mark Dybdahl i Robert Hall. "Fertilization of Algal Resources By an Exotic Snail May Facilitate Invasion". UW National Parks Service Research Station Annual Reports 27 (1.01.2003): 116–22. http://dx.doi.org/10.13001/uwnpsrc.2003.3555.
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We studied positive and negative effects of snail consumers on their resource to determine if positive consumer effects may be facilitating invasion. Consumer- resource interactions often focus on losses to the resource, even though the resource might benefit if consumers recycle nutrients. The New Zealand mudsnail, Potamopyrgus antipodarum, an exotic in western U.S. rivers, attains high densities and dominates macroinvertebrate communities. In one well-studied river, it consumes the majority of primary productivity, cycles most nitrogen and can grow faster at higher densities. In field experiments, we tested the hypothesis that this invasive grazer stimulates algal growth via nitrogen excretion, which might explain its self-facilitation and invasiveness. Using in-stream cages subdivided into "with snails" and "without snails" sections, we examined the response of periphytic algae to snail grazing and excretion and snail excretion alone at various levels of snail biomass. We found that chlorophyll a and GPP (gross primary production) decreased as the biomass of snails increased in the grazed sections. Snail excretion, in the absence of grazing, increased both chlorophyll a and GPP, demonstrating a positive effect of snails on the resource, consistent with the nutrient recycling and enrichment hypothesis. We found no evidence for increased algal growth at intermediate snail densities in grazed treatments, as predicted by the Herbivore Optimization Curve hypothesis. However, the difference in chlorophyll a between "with snails" and "without snails" treatments increased as snail biomass increased. This suggests that snail compensation of the resource, through excretion, decreases at extremely high levels of grazing pressure and the net effect of snail grazing becomes negative. Together, these results suggest that invasiveness in some rivers may be fostered by this self-facilitation and recycling of essential nutrients.
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Havens, Karl E. "Acidification Effects on the Algal–Zooplankton Interface". Canadian Journal of Fisheries and Aquatic Sciences 49, nr 12 (1.12.1992): 2507–14. http://dx.doi.org/10.1139/f92-277.
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An in situ mesocosm experiment was done to assess the impacts of acidification on algal and zooplankton biomass and C assimilation, and on the efficiency of energy transfer in the grazing food chain. Triplicate mesocosms were left untreated (pH 8.5), or were acidified to pH 6.5, 5.5, or 4.5 with H2SO4 over 9 d. Algal biomass was reduced at pH 6.5 and lower, but showed no further decline across the gradient of pH 6.5–4.5. Algal C assimilation rates consistently declined with decreasing pH, reflecting a shift in dominance to larger, less productive cells at pH 5.5 and 4.5. Zooplankton biomass and productivity also declined with decreasing pH, as nearly all crustacean herbivores became extinct. In the low-pH treatments, only cyclopoids and rotifers persisted. Overall, there were significant reductions in the ratios of zooplankton/algal biomass and zooplankton/algal C assimilation (ecological transfer efficiency) with declining pH. The latter was a result of reduced grazer biomass, rather than reduced grazing efficiency; the mean zooplankton P/B ratio at pH 4.5 exceeded that measured in the higher pH treatments.
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Idrisi, Nasseer, Edward L. Mills, Lars G. Rudstam i Donald J. Stewart. "Impact of zebra mussels (Dreissena polymorpha) on the pelagic lower trophic levels of Oneida Lake, New York". Canadian Journal of Fisheries and Aquatic Sciences 58, nr 7 (1.07.2001): 1430–41. http://dx.doi.org/10.1139/f01-070.
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We analyzed a data series on nutrients, phytoplankton, zooplankton, and young-of-the-year fish from Oneida Lake, New York, to test several hypotheses relating the response of the pelagic food web to grazing by zebra mussels (Dreissena polymorpha). System-wide grazing rates increased by one to two orders of magnitude after zebra mussel introduction. The most dramatic change associated with dreissenid grazing was increased water clarity and overall decrease in algal biovolume and Chl a. Contrary to predictions, primary production did not decline. We attribute the lack of whole water column decline in primary productivity to the compensating effect of increased water clarity resulting in deeper penetration of photosynthetically active radiation. We observed no change in total or dissolved phosphorus concentrations. Although algal standing crop declined, Daphnia spp. biomass and production did not, but dominance shifted from Daphnia galeata mendotae to Daphnia pulicaria. Consistent with our findings in the lower food web, we found no evidence that zebra mussels had a negative impact on young yellow perch (Perca flavescens) growth, biomass, or production. Thus, despite the order of magnitude increase in grazing rates and associated decrease in algal biomass, pelagic production at primary, secondary, and tertiary levels did not decline in association with zebra mussels.
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Strom, SL, TA Morello i KJ Bright. "Protozoan size influences algal pigment degradation during grazing". Marine Ecology Progress Series 164 (1998): 189–97. http://dx.doi.org/10.3354/meps164189.
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Riegman, R. "Nutrient-related selection mechanisms in marine phytoplankton communities and the impact of eutrophication on the planktonic food web". Water Science and Technology 32, nr 4 (1.08.1995): 63–75. http://dx.doi.org/10.2166/wst.1995.0167.
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A general increase in nutrient discharges during the last few decades has caused various changes in the algal community structure along the European continental coast. Coincidentally and maybe consequently, the foodweb structure and functioning has altered in local areas causing various phenomena like oxygen depletion, mortality of groups of organisms, foam on beaches, and an increase in the productivity of benthic communities and some commercial fish species. The observed increases in algal biomass and shifts in species composition are discussed in relation to the involved key mechanisms: resource competition and selective grazing. Along the Dutch coastal zone of the North Sea eutrophication has caused a doubling of the yearly averaged algal biomass during the past three decades. The sudden appearance of Phaeocystis summer blooms coincided with a shift from P-limitation towards N-limitation in the Dutch coastal area due to a stronger increase in P-discharge relative to the increase in N-discharge. Competition experiments in continuous cultures showed Phaeocystis to become dominant under N-limitation. Additionally, the large Phaeocystis colonies, which can reach a diameter up to one centimetre, escape from microzooplankton grazing. A computer model is presented which demonstrates a shift from bottom-up towards top-down control if the pelagic environment becomes eutrophicated. Implementation of this concept in a size-differential phytoplankton control model generates the prediction that algal blooms are dominated by species that escape from grazing by those zooplankton species which have a high potential numerical response. In marine environments these are microzooplankton species. These organisms mainly feed on cyanobacteria, prochlorophytes and some nano-algal species. One of the consequences for foodweb structure and the carbon fluxes in marine foodwebs is that eutrophication will lead to the dominance of poorly edible algal species. Eutrophication favours the downward transport of carbon and nutrients towards the sediments not only due to higher algal biomasses but also as a consequence of a shift towards larger algal species with higher sedimentation characteristics. An example is given how these new insights can be used for water quality management purposes.
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Hernández, José Carlos, María Candelaria Gil Rodríguez, Guacimara Herrera López i Alberto Brito. "Diet of the “key herbivore” Diadema antillarum in two contrasting habitats in the Canary Islands (Eastern-Atlantic)". Vieraea Folia scientiarum biologicarum canariensium 35, Vieraea 35 (2007): 109–20. http://dx.doi.org/10.31939/vieraea.2007.35.11.
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We analyzed the gut content of 30 sea urchins of the species Diadema antillarum which were collected seasonally over the course of two years from two different marine environments (barren grounds and grazing fronts) in the Canary Islands (Tenerife). Results show the influence of these two habitats on the diet of the sea urchin Diadema antillarum. No annual variations in diet were recorded; however we did find seasonal variations in diet in both barren and grazing front habitats. D. antillarum is mainly an herbivorous grazer but it also consumes invertebrates, especially in barren areas where seaweeds are scarce. Within the gut contents, filamentous algae were found in larger proportion than any other algal or animal group, independent of environment, month or year
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Puk, LD, N. Cernohorsky, A. Marshell, J. Dwyer, K. Wolfe i PJ Mumby. "Species-specific effects of herbivorous fishes on the establishment of the macroalga Lobophora on coral reefs". Marine Ecology Progress Series 637 (5.03.2020): 1–14. http://dx.doi.org/10.3354/meps13262.
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Herbivory is a key ecosystem function that influences ecosystem trajectories. However, interactions between plants and herbivores are species-specific and change throughout the plants’ lifetime. On coral reefs, herbivorous fishes reduce competition between corals and macroalgae through their grazing activity, thereby regulating the ecosystem state. Grazing vulnerability of marine algae generally decreases with increasing algal size. Therefore, the removal of newly settled recruits by herbivorous fish is likely important in preventing macroalgal blooms and reducing competition with corals. We studied the grazing susceptibility of recruits of the brown macroalga Lobophora to multiple fish species through a combination of feeding observations and manipulative in situ and ex situ experiments. Further, we recorded short-term Lobophora growth patterns and adult survival over 9 wk. Lobophora recruits were more susceptible to herbivory than adults, likely owing to their smaller size. However, recruit mortality was driven by only 3 of the studied species: Acanthurus nigrofuscus, Scarus niger and Chlorurus spilurus, whereas other common herbivores did not remove any Lobophora recruits. Our data also suggest variable growth and recruitment among months. These findings point to a possible increase in grazing resistance with age for Lobophora. As such, a decrease in grazing pressure by key fish species controlling Lobophora recruits could permit Lobophora to establish more grazing-tolerant adult populations.
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ASPLUND, Johan, i Yngvar GAUSLAA. "The gastropod Arion fuscus prefers cyanobacterial to green algal parts of the tripartite lichen Nephroma arcticum due to low chemical defence". Lichenologist 42, nr 1 (26.11.2009): 113–17. http://dx.doi.org/10.1017/s0024282909990284.
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AbstractAlthough the tripartite terricolous lichen Nephroma arcticum is easily accessible to lichen-feeding gastropods, grazing marks are mainly restricted to localized cephalodia with N-fixing Nostoc. We tested if this gastropod preference for cephalodia can be explained by differences in carbon based secondary compounds (CBSCs) in cyanobacterial versus green-algal tissues. CBSCs were non-destructively removed from air-dry thalli by 100% acetone. Compound deficient and control thallus parts were offered to the slug Arion fuscus and grazing preferences were quantified by area measurements in ArcGIS™. The concentrations of CBSCs (phenarctin, usnic acid, nephroarctin and methyl gyrophorate) in thallus parts with and without cephalodia were quantified with HPLC. Compared to purely green-algal parts, cephalodial parts with adjoining fungal tissues contained less defensive compounds, and were preferred by A. fuscus. The cephalodia themselves do not contain any CBSCs. After acetone rinsing, A. fuscus did not discriminate between green-algal and cyanobacterial parts. The results were consistent with the hypothesis that CBSCs in green-algal parts of N. arcticum play a herbivore-defensive role. It is further hypothesized that grazing of cephalodia may lead to N-starvation and reduced growth of N. arcticum thalli in southern portions of its range where lichenivorous gastropods are more abundant. This may play a role in shaping the southern distribution limit of this arctic-boreal lichen species.
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Tank, Suzanne E., i David W. Schindler. "The role of ultraviolet radiation in structuring epilithic algal communities in Rocky Mountain montane lakes: evidence from pigments and taxonomy". Canadian Journal of Fisheries and Aquatic Sciences 61, nr 8 (1.08.2004): 1461–74. http://dx.doi.org/10.1139/f04-080.
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We investigated changes in the community structure of epilithic (rock-dwelling) algae brought about by ultraviolet-A and -B radiation (UV-A and UV-B, respectively), using measurements of biovolume of individual taxa, and taxonomically diagnostic photosynthetic pigments. We undertook our study in four Canadian Rocky Mountain montane lakes, where downwelling ultraviolet radiation (UVR) can be intense. Although taxonomic counts revealed significant decreases in algal community diversity under UV-A and UV-B exposure, they revealed no other significant trends in algal community composition. Instead, redundancy analysis using these counts suggested that variations in nutrient concentrations were most important in structuring these communities. Photosynthetic pigments decreased significantly under UV-A and UV-B exposure. This decrease was much more striking for carotenoid than for chlorophyll concentrations, despite the photoprotective properties of many carotenoid pigments. Grazed carotenoids have been shown to be more resistant to degradation than grazed chlorophylls. We suggest that an observed increase in grazing pressure in our UVR-shielded communities counteracted increases in algal growth, but that increased algal growth rates were reflected by increased concentrations of slowly degrading carotenoids. Our study suggests that other factors, such as nutrients and grazers, are more important than UVR for structuring epilithic algal communities in our study lakes.
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Stock, Marsha S., i Amelia K. Ward. "Establishment of a Bedrock Epilithic Community in a Small Stream: Microbial (Algal and Bacterial) Metabolism and Physical Structure". Canadian Journal of Fisheries and Aquatic Sciences 46, nr 11 (1.11.1989): 1874–83. http://dx.doi.org/10.1139/f89-236.
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Patterns of epilithic algal and bacterial productivity were examined in a developing community on newly exposed stream bedrock for a period of 10 wk and in an undisturbed bedrock community used as a seasonal control. Physical and chemical changes were minimal over the experimental period. Bacterial colonization occurred initially and was rapidly followed by the development of a monolayer of adnate diatoms. Subsequent bacterial development coupled with maximum rates of bacterial productivity may have depended upon the algal cells for physical refugia, mucilage production, and/or other growth-promoting substrates present in algal photosynthate. After the diatom monolayer, filamentous algae developed despite the presence of high densities of snail grazers. By the end of the experiment, community composition on both substrata was generally similar although filamentous blue-green algae were a more important component of the native communities. Communities on newly exposed rock had higher total levels of epilithic productivity than on native rock where bacterial numbers averaged 2.26 × 1011 cells/m2. On native rock epilithic bacterial productivity averaged 72 mg C∙m−2∙d−1, yielding an average turnover time of 0.56 d; algal productivity averaged 224 mg C∙m−2∙d−1. These data suggested that epilithic production was not quantitatively limiting as a food resource for grazing snails in this stream during the summer months.
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Alves, Filipe M. A., Luis M. Chícharo, Ester Serrao i António D. Abreu. "Grazing by Diadema antillarum (Philippi) upon algal communities on rocky substrates". Scientia Marina 67, nr 3 (30.09.2003): 307–11. http://dx.doi.org/10.3989/scimar.2003.67n3307.
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Buschmann, A. H. "Amphipod Food Preference and Iridaeaspp. (Rhodophyta) Spore Release and Dispersal". Journal of the Marine Biological Association of the United Kingdom 71, nr 4 (listopad 1991): 891–97. http://dx.doi.org/10.1017/s0025315400053546.
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Using laboratory experiments, this study examines the nature of the grazing relationship between the amphipod Hyale hirtipalma (Dana) and the red algae Iridaea spp., and the potential effects of grazing on the release and dispersal of algal spores. The results indicate that Hyale hirtipalma has a significant food preference for the cystocarpic stage of Iridaea laminarioides Bory when compared with consumption of Ulva rigida C. Ag. Hyale hirtipalma also shows a significantly greater food preference for cystocarpic tissues of Iridaea laminarioides and I. ciliata Kützing than for other karyological stages of these algae. By consuming the cystocarpic tissues, H. hirtipalma significantly increases the number of carpospores which are released and which settle at all measured distances from the mature cystocarpic I. laminarioides frond where measurements were taken. This evidence, together with information previously published, indicates that several Hyale species show similar food preferences towards the cystocarpic stage of Iridaea spp., and probably have the same ecological role as spore releasers and dispersal agents.
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Costa, Diogo Fleury Azevedo, Joaquín Miguel Castro-Montoya, Karen Harper, Leigh Trevaskis, Emma L. Jackson i Simon Quigley. "Algae as Feedstuff for Ruminants: A Focus on Single-Cell Species, Opportunistic Use of Algal By-Products and On-Site Production". Microorganisms 10, nr 12 (22.11.2022): 2313. http://dx.doi.org/10.3390/microorganisms10122313.
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There is a wide range of algae species originating from a variety of freshwater and saltwater habitats. These organisms form nutritional organic products via photosynthesis from simple inorganic substances such as carbon dioxide. Ruminants can utilize the non-protein nitrogen (N) and the cell walls in algae, along with other constituents such as minerals and vitamins. Over recent decades, awareness around climate change has generated new interest into the potential of algae to suppress enteric methane emissions when consumed by ruminants and their potential to sequester atmospheric carbon dioxide. Despite the clear potential benefits, large-scale algae-livestock feedstuff value chains have not been established due to the high cost of production, processing and transport logistics, shelf-life and stability of bioactive compounds and inconsistent responses by animals under controlled experiments. It is unlikely that algal species will become viable ingredients in extensive grazing systems unless the cost of production and practical systems for the processing, transport and feeding are developed. The algae for use in ruminant nutrition may not necessarily require the same rigorous control during the production and processing as would for human consumption and they could be grown in remote areas or in marine environments, minimizing competition with cropping, whilst still generating high value biomass and capturing important amounts of atmospheric carbon. This review will focus on single-cell algal species and the opportunistic use of algal by-products and on-site production.
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Reinertsen, Helge, Arne Jensen, Arnfinn Langeland i Yngvar Olsen. "Algal Competition for Phosphorus: The Influence of Zooplankton and Fish". Canadian Journal of Fisheries and Aquatic Sciences 43, nr 6 (1.06.1986): 1135–41. http://dx.doi.org/10.1139/f86-141.
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Interspecific competition for phosphorus between the blue-green alga Anabaena flos-aquae and the green alga Staurastrum luetkemuelleri was studied in enclosure experiments. Both algal populations increased in number upon introduction of fish, but addition of herbivorous zooplankton led to an increase solely in the Staurastrum population. This could not be attributed to grazing by zooplankton, chemical or physical conditions (light, pH, inorganic carbon), or the total supply or rate of supply of phosphorus. The observed differences were apparently due to the patchy release of phosphorus by the fish, and the more homogenous release of this nutrient by the zooplankton. This would allow the Anabaena species, which was capable of rapid uptake of temporary pulses of phosphate, to coexist with Staurastrum in the enclosures with fish.
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Leavitt, P. R., i S. R. Carpenter. "Regulation of Pigment Sedimentation by Photo-Oxidation and Herbivore Grazing". Canadian Journal of Fisheries and Aquatic Sciences 47, nr 6 (1.06.1990): 1166–76. http://dx.doi.org/10.1139/f90-136.
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Reversed-phase high pressure liquid chromatography was used to show that algal carotenoid sedimentation is regulated by photo-oxidation and herbivore grazing in three unproductive, north-temperate lakes. Comparison of algal carotenoid and biovolume standing stocks revealed that carotenoid concentrations in epilimnetic waters were influenced by nonplanktonic inputs of pigments as well as phytoplankton community composition. Sediment traps did not record weekly events in the water column. Pigments that were incorporated in zooplankton feces and sank rapidly (e.g. alioxanthm and pheophorbide a) were overrepresented in trap material relative to epilimnetic pigment standing stocks. Differential decay of pigments in traps could not account for this observed bias. Chlorophyll mass–balance budgets corroborated the important influence of grazing by large-bodied zooplankton on pigment sedimentation. Interannual differences in pigment sedimentation were caused by changes in zooplankton community structure and the vertical zonation of phytoplankton communities. In the absence of fecal transportation, photo-oxidation destroyed carotenoids prior to their sedimentation from the photic zone. Therefore, sedimentary carotenoid composition is regulated by loss processes as well as changes in algal community composition.
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Arango, Clay Porter, Leslie Anne Riley, Jennifer Leah Tank i Robert Ogden Hall,. "Herbivory by an invasive snail increases nitrogen fixation in a nitrogen-limited stream". Canadian Journal of Fisheries and Aquatic Sciences 66, nr 8 (sierpień 2009): 1309–17. http://dx.doi.org/10.1139/f09-079.
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Despite anthropogenic nitrogen contributions, nitrogen fixation contributes half of biosphere inputs but has rarely been quantified in streams. Herbivory controls algal biomass and productivity in streams, and we hypothesized that herbivory could also control nitrogen fixation. We released periphyton from herbivory in nitrogen-limited Polecat Creek, Wyoming, where heavy grazing by the invasive New Zealand mudsnail ( Potamopyrgus antipodarum ) dominates nitrogen cycling. One and two weeks after releasing periphyton, we found higher rates of nitrogen fixation on heavily grazed rocks (two-way analysis of variance (ANOVA), p = 0.012). Time elapsed after snail manipulation had no effect (two-way ANOVA, p = 0.24). Grazing changed periphyton composition by reducing the proportion of green algae and increasing the proportion of nitrogen-fixing diatoms (multivariate ANOVA, p = 0.001). Nitrogen fixation rates increased disproportionately to nitrogen-fixing algal cells, indicating that snails increased nitrogenase efficiency, probably by improving light and (or) nutrient availability to nitrogen fixers. We incorporated our nitrogen fixation rates into a published nitrogen budget for Polecat Creek and found that nitrogen flux into the periphyton was 50% higher when we included nitrogen fixation. Herbivory can increase nitrogen fixation in streams, and future studies should measure nitrogen fixation for a more thorough understanding of stream nitrogen cycling.
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Sculley, John B., Rex L. Lowe, Charles A. Nittrouer, Tina M. Drexler i Mary E. Power. "Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core". Proceedings of the National Academy of Sciences 114, nr 38 (5.09.2017): 10155–59. http://dx.doi.org/10.1073/pnas.1611884114.
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Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass ofCladophorasurveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by “top-down” (consumer release) rather than “bottom-up” (growth promoting) controls.
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Barbee, Nicole C. "Grazing insects reduce algal biomass in a neotropical stream". Hydrobiologia 532, nr 1-3 (styczeń 2005): 153–65. http://dx.doi.org/10.1007/s10750-004-9527-z.
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Gleitz, Markus, Sönnke Grossmann, Renate Scharekm i Victor Smetacek. "Ecology of diatom and bacterial assemblages in water associated with melting summer sea ice in the Weddell Sea, Antarctica". Antarctic Science 8, nr 2 (czerwiec 1996): 135–46. http://dx.doi.org/10.1017/s095410209600020x.
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The fate of ice biota released via meltwater into pools of seawater trapped between melting ice floes (crack pools) was followed in late January in the southern Weddell Sea. Low salinity crack pools shared the following features: nitrate exhaustion, high pH and POC/PON ratios, high bacterial biomass composed of large cells, and a dense algal assemblage dominated to over 90% by only two diatom species. It is suggested that this “climax stage” evolved from a nutrient rich, moderate biomass situation prevailing in high salinity crack pools, and is representative of summer succession of sea ice biota. “Overflow” production following nitrate exhaustion by the algae resulted in internal (lipid) and external (presumably mucus) carbon pools. The latter must fuel bacterial biomass build-up, as algal mortality appeared to be low. The large algal and bacterial stocks point to low grazing pressure exerted by phagotrophic protists, presumably due to poor food quality (e.g. high C/N ratios) and/or excessive mucus production. It is concluded that environmental selection of the abundant ice algal species occurs under conditions prevailing in the disintegrating ice cover during summer, which differ drastically from those generally referred to as characteristic of the sea ice habitat at large (a combination of low temperature, low light and high salinity).
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Cuddington, K., i P. R. Leavitt. "An individual-based model of pigment flux in lakes: implications for organic biogeochemistry and paleoecology". Canadian Journal of Fisheries and Aquatic Sciences 56, nr 10 (1.10.1999): 1964–77. http://dx.doi.org/10.1139/f99-108.
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Vertical fluxes of pigments are used in limnology to monitor phytoplankton abundance, herbivore grazing, ecosystem efficiency, and historical changes in production. However, significant pigment degradation can occur during algal sedimentation. We used an individual-based model of pigment flux to quantify the relative importance of production and degradation as controls of pigment sedimentation. Pigment deposition increased with production, sinking rate, and phytoplankton depth and declined as lake depth and the depth of oxygen penetration increased. Unexpectedly, pigment sedimentation rate was not sensitive to variation in photooxidation rates, even though bleaching accounted for the second greatest amount of pigment loss. Digestion by zooplankton caused the most pigment degradation, but grazing increased pigment deposition when digestive losses were less than those due to oxidation of pigments in ungrazed cells. The model suggests that algal production may be underestimated in sedimentation studies that do not consider variability in water column depth. Further, comparisons with paleoecological analyses suggest that some inferred increases in production during lake ontogeny may arise from changes in regulation of pigment fluxes rather than from increased algal production.
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O'Brien, John M., Kira A. Krumhansl i Robert E. Scheibling. "Invasive bryozoan alters interaction between a native grazer and its algal food". Journal of the Marine Biological Association of the United Kingdom 93, nr 5 (5.03.2013): 1393–400. http://dx.doi.org/10.1017/s0025315412001683.
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The epiphytic bryozoan Membranipora membranacea encrusts the surface of kelp blades, causing recurrent large-scale defoliation events in kelp beds off the Atlantic coast of Nova Scotia, Canada. The gastropod Lacuna vincta grazes kelp, creating perforations that weaken blade tissues and increase the fragmentation rate. We assess the interaction between M. membranacea and L. vincta by measuring the grazing rate of snails on bryozoan-encrusted and non-encrusted kelp (Saccharina latissima) in no-choice and choice experiments in the laboratory conducted in November and December 2010. There was no effect of diet on grazing rate in no-choice experiments. In choice experiments, however, L. vincta grazed significantly more non-encrusted than encrusted kelp (7.1 versus 1.1 mg snail−1 d−1), and grazing rate of non-encrusted kelp was almost twice that in the no-choice experiment (3.8 mg snail−1 d−1), indicating that snails may avoid colonies of M. membranacea on partially encrusted kelp blades. We found no effect of diet on growth, reproduction and survival of snails maintained for four weeks on encrusted or non-encrusted kelp. By concentrating grazing damage on non-encrusted areas of blades, L. vincta may act synergistically with M. membranacea to increase the likelihood of blade breakage and canopy loss. This indirect effect of the invasive bryozoan could augment its direct effect on the standing biomass of native kelp beds and detrital export to adjacent communities.
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Scholten, M., i J. Kuiper. "THE EFFECTS OF OIL AND CHEMICALLY DISPERSED OIL ON NATURAL PHYTOPLANKTON COMMUNITIES". International Oil Spill Conference Proceedings 1987, nr 1 (1.04.1987): 255–57. http://dx.doi.org/10.7901/2169-3358-1987-1-255.
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ABSTRACT The effects of various crude oils and chemically dispersed oil on natural phytoplankton communities were tested in several experiments using marine mesocosms. Elevated algal biomass concentrations were found in most of the experiments, despite the long-term inhibition of primary productivity per unit chlorophyll. This result is due to reduced grazing upon algae as a consequence of oil-induced mortality of copepods or bivalves. A rapid succession from a diatom-dominated algae community to one dominated by microflagellates can be observed after an oil spill, owing to the more rapid exhaustion of silicate. If silicate is not being exhausted, a prolonged abundance of diatoms is observed. Treatment of oil with dispersant generally will aggravate effects, because of high dissolved oil concentrations in the water.
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Zheng, Yan Lin, i Zhuo Ying Lv. "Study on the Selective Grazing of Zooplankton in Plankton Ecosystem". Advanced Materials Research 864-867 (grudzień 2013): 17–21. http://dx.doi.org/10.4028/www.scientific.net/amr.864-867.17.
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Harmful algal blooms (Habs) caused great harm to the human environment. Habs occurrence was connected with other types of plankton. This relationship may be restrictive, and may also be promotional. Selectivity of zooplankton grazing has an important influence on the Habs. The behavior of zooplankton selective grazing was studied in the plankton ecosystem formed by three populations of nontoxic phytoplankton-toxic phytoplankton-zooplankton (NTP-TTP-Z) system. The selective grazing function of zooplankton on toxic phytoplankton and non-toxic phytoplankton was built based on Holling type IV functional response. Numerical simulation was given depending on the laboratory data. Results show that the models nicely explained the selective grazing behavior of zooplankton in the three species ecosystem, and provided key parameters for the marine ecosystem dynamics models.
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Tuchman, Nancy C., i R. Jan Stevenson. "Effects of Selective Grazing by Snails on Benthic Algal Succession". Journal of the North American Benthological Society 10, nr 4 (grudzień 1991): 430–43. http://dx.doi.org/10.2307/1467668.
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Graba, Myriam, Sabine Sauvage, Nabil Majdi, Benoît Mialet, Frédéric Y. Moulin, Gemma Urrea, Evelyne Buffan-Dubau, Michèle Tackx, Sergi Sabater i José-Miguel Sanchez-Pérez. "Modelling epilithic biofilms combining hydrodynamics, invertebrate grazing and algal traits". Freshwater Biology 59, nr 6 (21.02.2014): 1213–28. http://dx.doi.org/10.1111/fwb.12341.
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Williams, S. L., i R. C. Carpenter. "Grazing effects on nitrogen fixation in coral reef algal turfs". Marine Biology 130, nr 2 (15.12.1997): 223–31. http://dx.doi.org/10.1007/s002270050242.
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Hart, David D. "Grazing Insects Mediate Algal Interactions in a Stream Benthic Community". Oikos 44, nr 1 (marzec 1985): 40. http://dx.doi.org/10.2307/3544041.
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Worm, Boris, i Heike K. Lotze. "Effects of eutrophication, grazing, and algal blooms on rocky shores". Limnology and Oceanography 51, nr 1part2 (styczeń 2006): 569–79. http://dx.doi.org/10.4319/lo.2006.51.1_part_2.0569.
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