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Helmut Hillebrand - One of the best experts on this subject based on the ideXlab platform.
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meta analysis of Grazer control of periphyton biomass across aquatic ecosystems 1
Journal of Phycology, 2009Co-Authors: Helmut HillebrandAbstract:Grazer control of periphyton biomass has been addressed in numerous experimental studies in all kinds of aquatic habitats. In this meta-analysis, the results of 865 experiments are quantitatively synthesized in order to address the following questions: (i) Do lotic, lentic, and marine ecosystems differ in their degree of Grazer control of periphyton biomass? (ii) Which environmental variables affect the degree of Grazer control? (iii) How much does the result of these experiments depend on facets of experimental design? Across all ecosystems, the Grazers removed on average 59% of the periphyton biomass, with grazing being significantly stronger for laboratory (65%) than for field (56%) experiments. Neither field nor lab experiments showed a significant difference among lotic, lentic, and coastal habitats. Among different taxonomic consumer groups, crustaceans (amphipods and isopods) and trichopteran larvae removed the highest proportion of periphyton biomass. Grazer effects increased with increasing algal biomass, with decreasing resource availability and with increasing temperature, especially in field experiments. Grazer effects also increased with increasing total Grazer biomass in field experiments but showed the opposite trend in lab experiments, indicating a tendency toward overcrowded lab experiments. Other aspects of experimental design, such as cage type, size, and duration of the study, strongly affected the outcome of the experiments, suggesting that much care has to be placed on the choice of experimental design.
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selectivity and competitive interactions between two benthic invertebrate Grazers asellus aquaticus and potamopyrgus antipodarum an experimental study using 13c and 15n labelled diatoms
Freshwater Biology, 2005Co-Authors: Nicole Aberle, Helmut Hillebrand, Jonathan Grey, Karen Helen WiltshireAbstract:1. Tracer experiments with two diatoms labelled with 13C (Nitzschia palea) and 15N (Fragilaria crotonensis), were conducted to investigate feeding selectivity and interspecific competition between the Grazers Asellus aquaticus (Isopoda, Crustacea) and Potamopyrgus antipodarum (Hydrobiidae, Gastropoda). Conventional methods, such as cell counts and estimated biovolume, were used first to detect feeding preferences within the different Grazer treatments. 2. The results revealed a significant decline in algal biovolume in all Grazer treatments and no indications of active selectivity were observed. In contrast to conventional methods, measurements based on isotope signatures showed strong differences in tracer uptake, thus indicating different degrees of assimilation and digestion by the two Grazers. 3. The selectivity index Q, which provides information on the uptake ratio of 13C to 15N, showed a significant time effect for both Grazer species and a significant difference between single- and mixed-Grazer treatments for P. antipodarum. Thus, this technique enabled the direct quantification of the uptake by Grazers and, therefore, served as an ideal tool for the detection of passive selectivity. 4. Our results indicate a shift in feeding preferences related to between-species competition and a potential divergence of trophic niches when species coexist.
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top down versus bottom up control of autotrophic biomass a meta analysis on experiments with periphyton
Journal of The North American Benthological Society, 2002Co-Authors: Helmut HillebrandAbstract:AbstractNutrient supply and herbivore presence can regulate plant biomass. The relative impact of both of these factors, and their interactions, on periphyton biomass were examined in a quantitative meta-analysis. A literature survey revealed 85 experiments with factorial and replicated manipulation of Grazer access and nutrient supply. Two measures of effect sizes were calculated for each experiment, one based on final biomass yields (Hedges’ d) and the other on rates (Δr). Grazers significantly reduced periphyton biomass across all experiments, whereas nutrient addition significantly increased periphyton biomass. Effect sizes were very large for both factors. Thus, periphyton can be viewed as highly controlled by top-down and bottom-up mechanisms. Grazer effects were greater than nutrient effects. This result would be expected because nutrient enrichment represents a relative relief from nutrient limitation, whereas Grazer exclusion represents a categorical removal of grazing pressure. Moreover, nutrien...
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effect of grazing and nutrient supply on periphyton biomass and nutrient stoichiometry in habitats of different productivity
Limnology and Oceanography, 2001Co-Authors: Helmut Hillebrand, Maria KahlertAbstract:The impact of grazing and nutrient supply on epilithic periphyton was investigated in factorial field experiments in four seasons at three Swedish sites of different productivity and herbivore composition (Lake Limmaren, Lake Erken, and Vaddo ¨, a low salinity coastal site). Nutrient supply was enhanced by a granulose fertilizer containing nitrogen (N) and phosphorus (P), and Grazer density was manipulated by exclusion cages. Algal biomass was increased by nutrient enrichment and reduced by Grazer presence, but effects were highly variable between sites and seasons. Generally, Grazers had stronger effects on algal biomass than nutrient enrichment, but there was no overriding effect of either grazing or nutrients. This indicated a simultaneous top-down and bottom-up control of algal biomass. Taxonomic composition of the periphyton was more affected by Grazer presence than by nutrients. Internal nutrient ratios of the algae indicated N limitation at two of the sites. At all sites, the content of N and P in the periphytic assemblage was enhanced by the experimental nutrient enrichment, resulting in decreased C : N and C : P ratios. The presence of herbivores also increased periphytic nutrient content (decreased N : P and C : P ratios) in some experiments, suggesting an increase in algal P due to excretion. The effect strength of Grazers and nutrients on periphyton was affected by different abiotic characteristics such as light availability, nutrient concen- trations, and temperature. However, single environmental characteristics were not sufficient to explain the relative importance of grazing and nutrients.
Thi Kim Hue Nguyen - One of the best experts on this subject based on the ideXlab platform.
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low doses of the quaternary ammonium salt cetyltrimethylammonium bromide can be used as a pesticide to control Grazers in microalgal cultures
Algal Research-Biomass Biofuels and Bioproducts, 2019Co-Authors: Bert Deruyck, Thi Kim Hue Nguyen, Ramasamy Praveenkumar, Koenraad MuylaertAbstract:Contamination of large-scale microalgal cultures by Grazers can cause huge losses in biomass productivity. Here we propose the use of a quaternary ammonium salt cetyltrimethylammonium bromide (CTAB) to eradicate three types of commonly occurring Grazers in microalgal cultures: the rotifer Brachionus, the ciliate Sterkiella and the flagellate Paraphysomonas. Low, premicellar doses (≤3 μM) of CTAB rapidly eradicated (within 1–2 d) all three tested Grazers from microalgal cultures without significant losses (p < 0.05) in microalgal productivity. However, doses exceeding 5 μM also negatively affected microalgal growth. The optimal dose of CTAB that resulted in complete eradication of the Grazers with minimum impact on microalgal productivity was 3 μM for Brachionus, 2 μM for Sterkiella and 3 μM for Paraphysomonas. Thus, being a readily available chemical, CTAB has the potential to be used as a fast-acting, low-cost control agent against a range of frequently occurring Grazer types in large-scale microalgal cultures.
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Low doses of the quaternary ammonium salt Cetyltrimethylammonium bromide can be used as a pesticide to control Grazers in microalgal cultures
'Elsevier BV', 2019Co-Authors: Deruyck Bert, Thi Kim Hue Nguyen, Praveenkumar Ramasamy, Muylaert KoenraadAbstract:© 2019 Elsevier B.V. Contamination of large-scale microalgal cultures by Grazers can cause huge losses in biomass productivity. Here we propose the use of a quaternary ammonium salt cetyltrimethylammonium bromide (CTAB) to eradicate three types of commonly occurring Grazers in microalgal cultures: the rotifer Brachionus, the ciliate Sterkiella and the flagellate Paraphysomonas. Low, premicellar doses (≤3 μM) of CTAB rapidly eradicated (within 1–2 d) all three tested Grazers from microalgal cultures without significant losses (p < 0.05) in microalgal productivity. However, doses exceeding 5 μM also negatively affected microalgal growth. The optimal dose of CTAB that resulted in complete eradication of the Grazers with minimum impact on microalgal productivity was 3 μM for Brachionus, 2 μM for Sterkiella and 3 μM for Paraphysomonas. Thus, being a readily available chemical, CTAB has the potential to be used as a fast-acting, low-cost control agent against a range of frequently occurring Grazer types in large-scale microalgal cultures.status: publishe
Koenraad Muylaert - One of the best experts on this subject based on the ideXlab platform.
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low doses of the quaternary ammonium salt cetyltrimethylammonium bromide can be used as a pesticide to control Grazers in microalgal cultures
Algal Research-Biomass Biofuels and Bioproducts, 2019Co-Authors: Bert Deruyck, Thi Kim Hue Nguyen, Ramasamy Praveenkumar, Koenraad MuylaertAbstract:Contamination of large-scale microalgal cultures by Grazers can cause huge losses in biomass productivity. Here we propose the use of a quaternary ammonium salt cetyltrimethylammonium bromide (CTAB) to eradicate three types of commonly occurring Grazers in microalgal cultures: the rotifer Brachionus, the ciliate Sterkiella and the flagellate Paraphysomonas. Low, premicellar doses (≤3 μM) of CTAB rapidly eradicated (within 1–2 d) all three tested Grazers from microalgal cultures without significant losses (p < 0.05) in microalgal productivity. However, doses exceeding 5 μM also negatively affected microalgal growth. The optimal dose of CTAB that resulted in complete eradication of the Grazers with minimum impact on microalgal productivity was 3 μM for Brachionus, 2 μM for Sterkiella and 3 μM for Paraphysomonas. Thus, being a readily available chemical, CTAB has the potential to be used as a fast-acting, low-cost control agent against a range of frequently occurring Grazer types in large-scale microalgal cultures.
Erik Selander - One of the best experts on this subject based on the ideXlab platform.
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fight and flight in dinoflagellates kinetics of simultaneous Grazer induced responses in alexandrium tamarense
Limnology and Oceanography, 2012Co-Authors: Tony Fagerberg, Sylke Wohlrab, Erik Selander, Henrik PaviaAbstract:We monitored the kinetics of Grazer-induced responses in the marine dinoflagellate Alexandrium tamarense. Chemical cues from each of three calanoid copepods (Calanus sp., Centropages typicus, and Acartia tonsa) induced increased toxicity and suppressed chain formation in A. tamarense. Both chemical and morphological responses augmented over 3 d. Toxicity subsequently averaged 299% higher than controls, and average biovolume 24% lower than controls because of suppression of chain formation in grazed treatments. Grazer-induced toxicity returned to control levels after approximately 11 d, equivalent to five cell divisions, and average biovolume returned to control levels within 1 to 4 d (one to two cell divisions). This suggests that dinoflagellates simultaneously reduce Grazer encounter rates and increase chemical defense levels in the presence of copepod Grazers. Media replacement experiments showed that the inducing cue(s) attenuate rapidly in seawater, which allows A. tamarense to adjust resource allocation to Grazer-induced responses to follow fluctuations in Grazer density. Grazer-induced responses, however, develop too slowly to be accounted for in short-term grazing experiments with laboratory cultures.
Ramasamy Praveenkumar - One of the best experts on this subject based on the ideXlab platform.
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low doses of the quaternary ammonium salt cetyltrimethylammonium bromide can be used as a pesticide to control Grazers in microalgal cultures
Algal Research-Biomass Biofuels and Bioproducts, 2019Co-Authors: Bert Deruyck, Thi Kim Hue Nguyen, Ramasamy Praveenkumar, Koenraad MuylaertAbstract:Contamination of large-scale microalgal cultures by Grazers can cause huge losses in biomass productivity. Here we propose the use of a quaternary ammonium salt cetyltrimethylammonium bromide (CTAB) to eradicate three types of commonly occurring Grazers in microalgal cultures: the rotifer Brachionus, the ciliate Sterkiella and the flagellate Paraphysomonas. Low, premicellar doses (≤3 μM) of CTAB rapidly eradicated (within 1–2 d) all three tested Grazers from microalgal cultures without significant losses (p < 0.05) in microalgal productivity. However, doses exceeding 5 μM also negatively affected microalgal growth. The optimal dose of CTAB that resulted in complete eradication of the Grazers with minimum impact on microalgal productivity was 3 μM for Brachionus, 2 μM for Sterkiella and 3 μM for Paraphysomonas. Thus, being a readily available chemical, CTAB has the potential to be used as a fast-acting, low-cost control agent against a range of frequently occurring Grazer types in large-scale microalgal cultures.
