Journal articles: 'Algal Grazers'

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Albini, Dania, Mike S. Fowler, Carole Llewellyn, and Kam W. Tang. "Turning defence into offence? Intrusion of cladoceran brood chambers by a green alga leads to reproductive failure." Royal Society Open Science 7, no. 9 (September 2020): 200249. http://dx.doi.org/10.1098/rsos.200249.

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Microalgae are the foundation of aquatic food webs. Their ability to defend against grazers is paramount to their survival, and modulates their ecological functions. Here, we report a novel anti-grazer strategy in the common green alga Chlorella vulgaris against two grazers, Daphnia magna and Simocephalus sp. The algal cells entered the brood chamber of both grazers, presumably using the brood current generated by the grazer's abdominal appendages. Once inside, the alga densely colonized the eggs, significantly reducing reproductive success. The effect was apparent under continuous light or higher light intensity. The algal cells remained viable following removal from the brood chamber, continuing to grow when inoculated in fresh medium. No brood chamber colonization was found when the grazers were fed the reference diet Raphidocelis subcapitata under the same experimental conditions, despite the fact that both algal species were readily ingested by the grazers and were small enough to enter their brood chambers. These observations suggest that C. vulgaris can directly inflict harm on the grazers' reproductive structure. There is no known prior example of brood chamber colonization by a microalgal prey; our results point to a new type of grazer–algae interaction in the plankton that fundamentally differs from other antagonistic ecological interactions.

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Fisher, Carolyn L., Pamela D. Lane, Marion Russell, Randy Maddalena, and Todd W. Lane. "Low Molecular Weight Volatile Organic Compounds Indicate Grazing by the Marine Rotifer Brachionus plicatilis on the Microalgae Microchloropsis salina." Metabolites 10, no. 9 (September 4, 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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Minuti, JJ, and BD Russell. "Functionally redundant herbivores: urchin and gastropod grazers respond differently to ocean warming and rising CO2." Marine Ecology Progress Series 656 (December 10, 2020): 239–51. http://dx.doi.org/10.3354/meps13416.

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Future ocean CO2 and temperatures are predicted to increase primary productivity across tropical marine habitats, potentially driving a shift towards algal-dominated systems. However, increased consumption of algae by benthic grazers could potentially counter this shift. Yet, the response of different grazer species to future conditions will be moderated by their physiologies, meaning that they may not be functional equivalents. Here, we experimentally assessed the physiological response of key grazers—the sea urchin Heliocidaris crassispina and 2 gastropod species, Astralium haematragum and Trochus maculatus—to predicted CO2 concentrations (400, 700 and 1000 ppm) and temperature conditions (ambient, +3 and +5°C). In line with metabolic theory, we found that urchin metabolic rate increased at future temperatures regardless of CO2 conditions, with evidence of metabolic acclimation to higher temperatures. The metabolic rate of A. haematragum was depressed only by CO2, whereas T. maculatus initially had elevated metabolic rates at moderate CO2, which were depressed by the combination of the highest CO2 concentration and temperatures. Taxa showed differential survival, with no urchin mortality under any future conditions but substantial mortality of both gastropods under elevated temperatures regardless of CO2 concentration. Importantly, all species had substantially reduced algal consumption in response to elevated CO2, though the urchins only demonstrated an energetic mismatch under combined future CO2 and temperature. Therefore, despite sharing an ecological niche, these key grazers are likely to be differentially affected by future environmental conditions, potentially reducing the strength of ecological compensatory responses depending on the functional redundancy in this grazing community.

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Grutter, AS, S. Bejarano, KL Cheney, AW Goldizen, T. Sinclair-Taylor, and PA Waldie. "Effects of the cleaner fish Labroides dimidiatus on grazing fishes and coral reef benthos." Marine Ecology Progress Series 643 (June 11, 2020): 99–114. http://dx.doi.org/10.3354/meps13331.

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Territorial and roving grazing fishes farm, and feed on, algae, sediment, or detritus, thus exerting different influences on benthic community structure, and are common clients of cleaner fish. Whether cleaners affect grazing-fish diversity and abundance, and indirectly the benthos, was tested using reefs maintained free of the bluestreak cleaner wrasse Labroides dimidiatus for 8.5 yr (removals) compared with controls. We quantified fish abundance per grazing functional group, foraging rates of roving grazers, cleaning rates of roving grazers by L. dimidiatus, reef benthos composition, and fouling material on settlement tiles. Abundances of ‘intensive’ and ‘extensive’ territorial farmers, non-farmers, parrotfishes and Acanthurus spp. were lower on removal than control reefs, but this was not the case for ‘indeterminate’ farmers and Ctenochaetus striatus. Foraging rates of Acanthurus spp. and C. striatus were unaffected by cleaner presence or cleaning duration. This suggests some robustness of the grazers’ foraging behaviour to loss of cleaners. Acanthurus spp. foraged predominantly on sediment and detritus, whereas C. striatus and parrotfishes grazed over algal turfs. Nevertheless, benthic community structure and amount of organic and inorganic material that accumulated over 3.5 mo on tiles were not affected by cleaner presence. Thus, despite greater abundances of many roving grazers, and consequently higher grazing rates being linked to the presence of cleaners, the benthos was not detectably affected by cleaners. This reveals that the positive effect of cleaners on fish abundance is not associated with a subsequent change in the benthos as predicted. Rather, it suggests a resilience of benthic community structure to cleaner-fish loss, possibly related to multiple antagonistic effects of different grazer functional groups. However, losing cleaners remains a problem for reefs, as the lack of cleaning has adverse consequences for fish physiology and populations.

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Jordan, J., and PS Lake. "Grazer-epilithon interactions in an Australian upland stream." Marine and Freshwater Research 47, no. 6 (1996): 831. http://dx.doi.org/10.1071/mf9960831.

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Effects of macroinvertebrate grazers on the distribution of their food resource, epilithon, were examined in a south-eastern Australian stream. The hypothesis that grazers would significantly alter the development of epilithon was tested experimentally: macroinvertebrates were excluded from some experimental substrata and allowed to colonize others. Epilithic chlorophyll a concentration, organic matter content and total diatom density were used to monitor the effects of the grazer assemblage over 35 days. As predicted, epilithon density was higher on bricks with exclusion barriers than on bricks open to colonization by grazers. Similarly, diatom densities were significantly higher on bricks from the grazer-exclusion treatment. Patterns in the development of epilithon over time point to the importance of prevailing abiotic conditions in determining the outcome of macroinvertebrate grazing. Differences in total epilithon biomass, algal biomass and diatom density between treatments clearly indicate the independent importance of macroinvertebrate grazing to the microdistribution of epilithon in upland streams.

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Tank, Suzanne E., and 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, no. 8 (August 1, 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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Heard, Stephen B., and Corinne K. Buchanan. "Grazercollector facilitation hypothesis supported by laboratory but not field experiments." Canadian Journal of Fisheries and Aquatic Sciences 61, no. 6 (June 1, 2004): 887–97. http://dx.doi.org/10.1139/f04-022.

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Grazing invertebrates in streams feed by harvesting algal cells from surfaces, and in doing so release fine particulate organic matter (FPOM). The "grazercollector facilitation hypothesis" holds that FPOM production by grazers facilitates growth and (or) survival of FPOM-collecting invertebrates. We tested for grazercollector facilitation in laboratory and field experiments. In recirculating flumes in the laboratory, we tested for facilitation of the collector Hydropsyche slossonae by the grazers Physa gyrina, Glossosoma intermedium, and Baetis tricaudatus. All three grazers increased FPOM levels in flume water, but only Physa facilitated Hydropsyche growth. In the field, we manipulated Physa and Glossosoma densities to test for facilitation (at a local scale) of natural collector assemblages in an eastern Iowa stream. We did not detect facilitation of any collector by either grazer in the field, despite high power to detect such interactions. We suspect that grazercollector facilitation was not observed in the field because (unlike in our laboratory flumes) field FPOM levels are often high and extremely variable in time and space and because organic particles can arise from sources other than grazer activity (= grazer-independent processing). Therefore, at local scales, collectors may not be significantly limited by the supply of grazer-derived FPOM.

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Connelly, S. J., E. A. Wolyniak, K. L. Dieter, C. E. Williamson, and K. L. Jellison. "Impact of Zooplankton Grazing on the Excystation, Viability, and Infectivity of the Protozoan Pathogens Cryptosporidium parvum and Giardia lamblia." Applied and Environmental Microbiology 73, no. 22 (September 14, 2007): 7277–82. http://dx.doi.org/10.1128/aem.01206-07.

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ABSTRACT Very little is known about the ability of the zooplankton grazer Daphnia pulicaria to reduce populations of Giardia lamblia cysts and Cryptosporidium parvum oocysts in surface waters. The potential for D. pulicaria to act as a biological filter of C. parvum and G. lamblia was tested under three grazing pressures (one, two, or four D. pulicaria grazers per 66 ml). (Oo)cysts (1 × 104 per 66 ml) were added to each grazing bottle along with the algal food Selenastrum capricornutum (6.6 × 104 cells per 66 ml) to stimulate normal grazing. Bottles were rotated (2 rpm) to prevent settling of (oo)cysts and algae for 24 h (a light:dark cycle of 16 h:8 h) at 20°C. The impact of D. pulicaria grazing on (oo)cysts was assessed by (i) (oo)cyst clearance rates, (ii) (oo)cyst viability, (iii) (oo)cyst excystation, and (iv) oocyst infectivity in cell culture. Two D. pulicaria grazers significantly decreased the total number of C. parvum oocysts by 52% and G. lamblia cysts by 44%. Furthermore, two D. pulicaria grazers significantly decreased C. parvum excystation and infectivity by 5% and 87%, respectively. Two D. pulicaria grazers significantly decreased the viability of G. lamblia cysts by 52%, but analysis of G. lamblia excystation was confounded by observed mechanical disruption of the cysts after grazing. No mechanical disruption of the C. parvum oocysts was observed, presumably due to their smaller size. The data provide strong evidence that zooplankton grazers have the potential to substantially decrease the population of infectious C. parvum and G. lamblia in freshwater ecosystems.

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Jacobucci, G. B., M. O. Tanaka, and F. P. P. Leite. "Factors influencing temporal variation of a Sargassum filipendula (Phaeophyta: Fucales) bed in a subtropical shore." Journal of the Marine Biological Association of the United Kingdom 89, no. 2 (March 2009): 315–21. http://dx.doi.org/10.1017/s0025315409002306.

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In the present study, we evaluate the influence of biotic and abiotic factors on temporal fluctuations of Sargassum filipendula in a subtropical shore. Monthly algal samples, abiotic components, amphipod grazer density, and epiphyte biomass were obtained from a Sargassum bed in south-eastern Brazil. Density of S. filipendula fronds decreased during the sampling period, whereas dry mass was more constant, although with a noticeable reduction in the warmer months. Hypnea musciformis was the most frequent epiphyte on S. filipendula, occurring in all sampling periods, although with significant temporal variation. Sargassum filipendula density and dry mass were both influenced by epiphyte dry mass, temperature, and amphipod grazers. Sargassum filipendula biomass negatively influenced total epiphyte biomass, whereas H. musciformis biomass was positively influenced by phosphate, nitrite, and S. filipendula density and negatively influenced by S. filipendula dry mass and amphipod grazer abundance. Algal temporal fluctuations can be related to local abiotic and biotic factors, but the variation observed for S. filipendula and its epiphytes suggest that these factors have quite distinct effects for these algae.

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Khan, Najmus Sakib. "Ecological Potentiality of Plankton: A Perspective on Nutrition, Toxicity and Bio-Indication." Environmental Sciences and Ecology: Current Research (ESECR 2, no. 7 (December 7, 2021): 1–4. http://dx.doi.org/10.54026/esecr/1040.

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The base of aquatic energy is initiated and concreted by plankton such as primary photosynthetic algae and consequently their immediate secondary grazers as zooplankton. The nutritional features of algae or phytoplankton are controlled by aquatic nutrients (e.g. nitrogen, phosphorus, silica and other essential minerals). Moreover, the biochemical content of zooplankton reflects their diet profiles (e.g. bacteria and algae). The promising and sustainable fisheries prospects are crucially subjective by nutritional quality and quantity of plankton (e.g. algal bloom). Additionally, both algae and zooplankton are efficient as auspicious biological tools for indicating the aquatic environments.

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Hata, Hiroki, and Makoto Kato. "A novel obligate cultivation mutualism between damselfish and Polysiphonia algae." Biology Letters 2, no. 4 (August 7, 2006): 593–96. http://dx.doi.org/10.1098/rsbl.2006.0528.

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In cultivation mutualisms, farming animals prepare fields for cultivars, enhance their growth and harvest them. For example, in terrestrial ecosystems, plant–herbivore cultivation mutualisms arose between humans and their crops only relatively recently. We discovered an obligate cultivation mutualism between a damselfish and an alga in a coral reef ecosystem. The damselfish, Stegastes nigricans , manages algal farms through territorial defence against the invading grazers and through weeding of unpalatable algae. As a result, the algal farms of S. nigricans are dominated by one species, Polysiphonia sp. We performed an exhaustive survey of algal assemblages inside and outside the territories of five damselfish species around the Ryukyu Islands, Japan, using molecular and morphological characteristics. Polysiphonia sp. 1 grew exclusively inside the farms of S. nigricans , and never elsewhere. Since only Polysiphonia sp. 1 is harvested and consumed by the damselfish as a staple food, this interdependent relationship is an obligate cultivation mutualism. This is the first record of an obligate plant–herbivore cultivation mutualism in a marine ecosystem. Our data also suggest that three other Polysiphonia species are facultatively mutual with, commensal with, or parasitic on other damselfish species.

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Albini, Dania, Mike S. Fowler, Carole Llewellyn, and Kam W. Tang. "Reversible colony formation and the associated costs in Scenedesmus obliquus." Journal of Plankton Research 41, no. 4 (July 2019): 419–29. http://dx.doi.org/10.1093/plankt/fbz032.

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AbstractGrazer-induced colony formation as a defense strategy in microalgae such as Scenedesmus species has been widely reported, but the associated costs and reversibility of the colonies are rarely studied. We experimentally showed that Scenedesmus obliquus formed chained colonies in the presence of a predator, including predators separated from the algae by a membrane, but quickly reverted to single cells after the removal of the predator—a defining characteristic of an inducible defense. We detected stress indicators—astaxanthin esters—in the algal populations in the presence of grazers but not when grazers were absent. We found significant costs associated with S. obliquus colony formation in terms of lower population growth rate, lower photosystem II efficiency and lower cellular chlorophyll a content. These results together show that colony formation as an inducible defense in S. obliquus against grazers comes at a substantial cost such that the defense must be switched off and the colonies revert to single cells when the predation risk disappears.

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Korosi, Jennifer B., Samantha M. Burke, Joshua R. Thienpont, and John P. Smol. "Anomalous rise in algal production linked to lakewater calcium decline through food web interactions." Proceedings of the Royal Society B: Biological Sciences 279, no. 1731 (September 28, 2011): 1210–17. http://dx.doi.org/10.1098/rspb.2011.1411.

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Increased algal blooms are a threat to aquatic ecosystems worldwide, although the combined effects of multiple stressors make it difficult to determine the underlying causes. We explore whether changes in trophic interactions in response to declining calcium (Ca) concentrations, a water quality issue only recently recognized in Europe and North America, can be linked with unexplained bloom production. Using a palaeolimnological approach analysing the remains of Cladocera (herbivorous grazers) and visual reflectance spectroscopically inferred chlorophyll a from the sediments of a Nova Scotia (Canada) lake, we show that a keystone grazer, Daphnia , declined in the early 1990s and was replaced by a less effective grazer, Bosmina , while inferred chlorophyll a levels tripled at constant total phosphorus (TP) concentrations. The decline in Daphnia cannot be attributed to changes in pH, thermal stratification or predation, but instead is linked to declining lakewater [Ca]. The consistency in the timing of changes in Daphnia and inferred chlorophyll a suggests top-down control on algal production, providing, to our knowledge, the first evidence of a link between lakewater [Ca] decline and elevated algal production mediated through the effects of [Ca] decline on Daphnia . [Ca] decline has severe implications for whole-lake food webs, and presents yet another mechanism for potential increases in algal blooms.

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Paul, A. J., D. W. Schindler, A. K. Hardie, and 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, no. 12 (December 1, 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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Alfaro, Andrea. "Diet of the pulmonate gastropod Onchidella nigricans in the intertidal rocky shore, New Zealand." Animal Biology 59, no. 2 (2009): 231–40. http://dx.doi.org/10.1163/157075609x437736.

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AbstractGut content analyses and stable isotopes (δ13C and δ15N) were used to investigate the food consumption and assimilation of the pulmonate, Onchidella nigricans, within a rocky intertidal platform at Waiwera, northern New Zealand. Analyses of gut contents indicate that this species is a generalist herbivore, which may consume a variety of micro- and macro-algae, although small zooplankton may be ingested, when present. Gut contents of individuals collected from different intertidal habitats (bare rock, Hormosira banksii, green filaments, and coralline algae) reflected the dominant algal species within each habitat, suggesting that food availability does not restrict the grazer's distribution across its range. The radular morphology and small size of this gastropod also support the notion that O. nigricans is a non-selective microphagous feeder. However, stable isotopes on O. nigricans from the four habitats and the dominant algal food types indicate a strong assimilation preference for microalgae. The δ13C values (-15 to -13‰) of O. nigricans were consistent with signatures for intertidal grazers, but δ15N values (8 to 9‰) were relatively high, which may indicate the presence of bacteria and microfaunal detritus in the diet. Clusters of isotopic signatures of individuals from different habitats suggest feeding preferences, which also may be attributed to differences in detrital and bacterial consumption. This study illustrates the importance of using parallel techniques in diet studies.

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Day, John G., Naomi J. Thomas, Undine E. M. Achilles-Day, and Raymond J. G. Leakey. "Early detection of protozoan grazers in algal biofuel cultures." Bioresource Technology 114 (June 2012): 715–19. http://dx.doi.org/10.1016/j.biortech.2012.03.015.

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Ho, Susie S., Nick R. Bond, and P. Sam Lake. "Comparing food-web impacts of a native invertebrate and an invasive fish as predators in small floodplain wetlands." Marine and Freshwater Research 62, no. 4 (2011): 372. http://dx.doi.org/10.1071/mf10222.

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Gambusia holbrooki is an invasive predatory poeciliid fish in wetlands of south-eastern Australia, where it coexists with the native waterbug Anisops thienemanni (Notonectidae). Gambusia has been shown to produce trophic cascades, leading to increased algal biomass following invasion, whereas these effects relative to the often-dominant invertebrate predator Anisops are unknown. Given its flexible diet, we predicted that Gambusia would feed more broadly than Anisops, thereby reducing the abundance of zooplankton grazers, and increasing chlorophyll a. We tested this hypothesis in experimental 110-L wetland mesocosms, using Gambusia and Anisops alone and in combination, in addition to no-predator treatments. We ran two experiments lasting 91 and 35 days, respectively. Both fish and macroinvertebrates generated weak trophic cascades, resulting in minor increases in chlorophyll a above concentrations in control treatments. Gambusia, in lowering total zooplankton abundances, triggered a larger, although still relatively small, algal response relative to Anisops. Impacts of both predators on dominant invertebrate grazers (e.g. Simocephalus spp., copepod nauplii) were similar, although Anisops was associated with an increase in ostracod (Newnhamia sp.) numbers. The similar trophic role of the two predators on algae was unexpected, given their different effects on planktonic communities and their very different taxonomic positions and zoogeographic origins.

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Tramonte, Rafael Prandini, Nicolli Cristina Osório, Flávio Henrique Ragonha, Gisele Daiane Pinha, Liliana Rodrigues, and Roger Paulo Mormul. "Periphyton consumption by an invasive snail species is greater in simplified than in complex habitats." Canadian Journal of Zoology 97, no. 1 (January 2019): 13–21. http://dx.doi.org/10.1139/cjz-2017-0359.

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Habitat complexity may stabilize consumer–resource interactions and reduce the probability of invasion in aquatic habitats. We tested the hypotheses that (i) higher habitat complexity reduces resource consumption independently of grazer species, but that (ii) invasive grazers have a greater influence on decreasing resources independently of habitat complexity. We performed an experiment using artificial substrates to simulate different complexity levels. We evaluated Melanoides tuberculata (O.F. Müller, 1774) and Aylacostoma chloroticum Hylton Scott, 1954 consumption of specific algal groups and the interaction between habitat complexity and grazer species. Moreover, we evaluated grazer activity on the different substrates during the experiment. The results support only the first hypothesis and indicate lower resource consumption on complex substrates compared with simpler substrates. Additionally, the effect of the grazing of the invasive species on taxon richness was greater in simplified than in complex habitats. The grazing activity on the substrate suggests a relationship between resource exploitation and habitat complexity in which the invasive grazing species visited the simple habitat less frequently. However, the effects of invasive grazers on food resources were higher on the simple substrate. The effects of grazing activity on food resources depend on the interaction between habitat complexity and grazer species. In this way, the introduction of an invasive species may have negative impacts on the structure and function of periphytic communities, mainly in simplified aquatic ecosystems.

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Reese, Kristen L., Carolyn L. Fisher, Pamela D. Lane, James D. Jaryenneh, A. Daniel Jones, Matthias Frank, and 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, no. 10 (October 15, 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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Uryupova, Ekaterina F., Vassily A. Spiridonov, and Dmitry G. Zhadan. "Amphipods (Crustacea: Amphipoda) associated with red algae (Rhodophyta) in Kandalaksha Bay (the White Sea, Russia)." Journal of the Marine Biological Association of the United Kingdom 92, no. 2 (December 6, 2011): 265–73. http://dx.doi.org/10.1017/s0025315411001676.

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Amphipods' assemblages living in the red algae communities were studied in Velikaya Salma Strait (Kandalaksha Bay, north-western White Sea) in the depth range of 3–11 m. Sampling sites were located along the depth and shore exposure gradients in the areas with a significant number of rhodophytes. In total 12 species of amphipods were found with Ampithoe rubricata and Crassicorophium bonellii being most common and abundant. Gammaropsis melanops and Pleusymtes glaber were revealed as subdominant species. As an algal grazer A. rubricata appeared to be the species most closely associated with various algal assemblages. Crassicorophium bonellii were found on substrates being a deposit feeder predominantly inhabiting mixed assemblages of red algae where deposition and accumulation of seston most likely took place. Gammaropsis melanops and P. glaber are known as grazers but they preferred the habitats with both red algae and sponges. None of the species can be considered as obligate inhabitants of red algae hosts. Ampithoe rubricata and C. bonellii occurred in red algae communities in the shallow area (about 4 m). The most diverse and quantitatively rich amphipod assemblages were found at depths of 8–9 m in the area protected from waves and surf by the islands. Three of the most common and abundant species A. rubricata, C. bonellii and P. glaber are considered as amphiboreal while most of the species associated with rhodophytes belong to the Arctic-boreal ones. Amphiboreal species are presumably adapted to a broader temperature-range, in particular to higher summer temperature, than the Arctic-boreal species; they most likely have an advantage when occupying biotopes at shallow subtidal depth with local conditions in the White Sea.

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Suzuki, H., Y. Kubo, E. Inomata, Y. Agatsuma, and MN Aoki. "Effects of herbivorous gastropod grazing on the sedimentation and succession of subtidal macroalgal assemblages." Marine Ecology Progress Series 656 (December 10, 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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Stock, Marsha S., and 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, no. 11 (November 1, 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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Agrawal, Anurag A. "Algal defense, grazers, and their interactions in aquatic trophic cascades." Acta Oecologica 19, no. 4 (July 1998): 331–37. http://dx.doi.org/10.1016/s1146-609x(98)80037-4.

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Birtel, Julia, and Blake Matthews. "Grazers structure the bacterial and algal diversity of aquatic metacommunities." Ecology 97, no. 12 (December 2016): 3472–84. http://dx.doi.org/10.1002/ecy.1612.

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Sculley, John B., Rex L. Lowe, Charles A. Nittrouer, Tina M. Drexler, and 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, no. 38 (September 5, 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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Taylor, Brad W., Angus R. McIntosh, and Barbara L. Peckarsky. "Reach‐scale manipulations show invertebrate grazers depress algal resources in streams." Limnology and Oceanography 47, no. 3 (May 2002): 893–99. http://dx.doi.org/10.4319/lo.2002.47.3.0893.

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Havens, Karl E. "The importance of rotiferan and crustacean zooplankton as grazers of algal productivity in a freshwater estuary." Archiv für Hydrobiologie 122, no. 1 (August 28, 1991): 1–22. http://dx.doi.org/10.1127/archiv-hydrobiol/122/1991/1.

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McCormick, Paul V. "Direct and Indirect Effects of Consumers on Benthic Algae in Isolated Pools of an Ephemeral Stream." Canadian Journal of Fisheries and Aquatic Sciences 47, no. 10 (October 1, 1990): 2057–65. http://dx.doi.org/10.1139/f90-230.

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Artificial pools were used to test for interactions among dominant consumer and producer populations that coexist in isolated pools of an ephemeral stream each summer. Nitrogen and/or phosphorus were supplied to one set of pools; herbivorous snails and crayfish and a predaceous centrarchid were added in different combinations to other pools. Algal growth was measured inside and outside wire cages placed in pools to exclude herbivores and/or predators. Algal biomass and the abundance of most algal species were increased by nitrogen enrichment. Algal biomass was also enhanced by addition of consumers. There were few differences in structure between algal assemblages inside and outside cages in any treatment. Under conditions of nitrogen limitation, moderate levels of herbivory can enhance algal growth. Positive effects are greatest at the microsite level and may depend on the ability of algal species to resist digestion by grazers. Predators may affect the algal assemblage indirectly by reducing herbivore survival or activity and directly by converting nutrients stored in herbivore biomass into a form available for algal growth. Because the importance of different trophic connections may vary among ecosystems, experimentation must consider all those that are potentially important.

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Caron, Vanessa, Ariel Greiner, Krista Ransier, and Bryna Cameron-Steinke. "The Relationship between Large Herbivore Abundance and Algal Cover on Coral Reefs on West Coast Barbados." McGill Science Undergraduate Research Journal 11, no. 1 (April 13, 2016): 11–15. http://dx.doi.org/10.26443/msurj.v11i1.162.

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Background: Over the past few decades, climate change and the intensification of coastal development significantly contributed to the degradation of coral reefs across the Caribbean Sea. Widespread increase in algal cover on coral reefs since the 1970s has made it difficult for the corals to recover. Thus, algae regulating factors, such as herbivorous grazers and groundwater nutrient concentrations, have important implications for the conservation of coral reefs. In this study we conducted a small-scale assessment of the relationship between the abundance of two families of herbivorous fishes, Scaridae and Acanthuridae, and algal cover on the coral reefs of West Coast Barbados was conducted, and we hypothesized that a direct negative correlation exists between them. Methods: Herbivorous fish abundance and percent algal cover were quantified for three different coral reefs, and the data was analyzed using linear regressions and analyses of variance. Results: We found that although there were no significant relationship between herbivorous fish abundance and algal cover, there was a significant difference between them across the three reefs studied. These results suggest the presence of other factors influencing algal cover. One such factor could potentially be ground- water input levels, which was found to differ at each of the three sites studied. Limitations: The limited timeframe of this study did not allow for extensive sampling. Conclusion: In order to effectively protect the coral reefs in Western Barbados, Further studies are needed to increase the understanding of the relationship between herbivory and algal cover in Western Barbados as well as to further investigate the role of groundwater seepage on algal growth.

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Brocks, Jochen J. "The transition from a cyanobacterial to algal world and the emergence of animals." Emerging Topics in Life Sciences 2, no. 2 (June 29, 2018): 181–90. http://dx.doi.org/10.1042/etls20180039.

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The Neoproterozoic, 1000–541 million years (Myr) ago, saw the transition from a largely bacterial world to the emergence of multicellular grazers, suspension feeders and predators. This article explores the hypothesis that the first appearance of large, multicellular heterotrophs was fueled by an elevated supply of nutrients and carbon from the bottom of the food chain to higher trophic levels. A refined record of molecular fossils of algal sterols reveals that the transition from dominantly bacterial to eukaryotic primary production in open marine habitat occurred between 659 and 645 Myr ago, in the hot interlude between two Snowball Earth glaciations. This bacterial–eukaryotic transition reveals three characteristics: it was rapid on geological timescales, it followed an extreme environmental catastrophe and it was permanent — hallmarks of an ecological hysteresis that shifted Earth's oceans between two self-stabilizing steady states. More than 50 million years of Snowball glaciations and their hot aftermath may have purged old-world bacterial phytoplankton, providing empty but nutrient-rich ecospace for recolonization by larger algae and transforming the base of the food web. Elevated average and maximum particle sizes at the base of the food chain may have provided more efficient energy and nutrient transfer to higher trophic levels, fueling an arms race toward larger grazers, predators and prey, and the development of increasingly complex feeding and defense strategies.

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Caroline, Soizic, Jacky, and Claude. "Impact of Zirconium on Freshwater Periphytic Microorganisms." Environments 6, no. 10 (October 1, 2019): 111. http://dx.doi.org/10.3390/environments6100111.

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The majority of studies on biofilms have focused on autotrophic and bacterial taxa, without considering the potential effects on biofilm grazers. In this work, we investigated the effects of realistic environmental concentrations of zirconium (Zr) on periphyton algal growth and micromeiofauna biodiversity. Glass slides were submerged in a pond for four weeks to colonize biofilms and exposed for four weeks in aquaria to targeted Zr concentrations of 0, 1, and 10 nM, which were monitored over time (average measured concentrations were 0.2 ± 0.1, 0.5 ± 0.3, and 2.9 ± 0.3 nM Zr). The four-week exposure to the highest concentration (3 nM) affected the micromeiofauna structure of biofilms and modified the autotrophic biofilm structure by increasing the proportion of green algae and decreasing the abundance of cyanobacteria and brown algae. Rotifers and the ciliate Aspidisca cicada appeared to be the most sensitive organisms among the observed micromeiofauna. A toxic effect of Zr on rotifers could explain such results. Indirect effects, such as reduced food availability given the reduced algal growth in the presence of Zr, could also play a role in the changes of micromeiofauna community structure. These results are among the few published data on the effects of Zr.

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Day, John G. "Grazers: the overlooked threat to the sustained production of future algal biofuels." Biofuels 4, no. 5 (September 2013): 459–61. http://dx.doi.org/10.4155/bfs.13.29.

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BOTTS, P. SILVER. "The impact of small chironomid grazers on epiphytic algal abundance and dispersion." Freshwater Biology 30, no. 1 (August 1993): 25–33. http://dx.doi.org/10.1111/j.1365-2427.1993.tb00785.x.

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Wang, Yifei, Maria Castillo-Keller, Everett Eustance, and Milton Sommerfeld. "Early detection and quantification of zooplankton grazers in algal cultures by FlowCAM." Algal Research 21 (January 2017): 98–102. http://dx.doi.org/10.1016/j.algal.2016.11.012.

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Toporowska, Magdalena, Jacek Rechulicz, Małgorzata Adamczuk, and Michał Niedźwiecki. "The role of abiotic and biotic environmental factors in shaping epiphyton on common reed in shallow, hydrologically transformed, temperate lakes." Knowledge & Management of Aquatic Ecosystems, no. 419 (2018): 18. http://dx.doi.org/10.1051/kmae/2018005.

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Epiphytic algae are an important group of organisms involved in primary productivity, nutrient cycling, and energy transfer in littoral food webs. However, multifactorial studies conducted on epiphyton on the same substrate across a spectrum of environmental parameters are very limited. Here, we present first complex field study on the role of abiotic and biotic factors in shaping the species richness, diversity, abundance, and biomass composition of epiphyton on common reed in four shallow lakes with different trophic status, water and fish management, and the abundance and structure of potential algal grazers: littoral crustaceans and fish. The obtained results revealed that the algal taxa richness was the lowest in the hypertrophic lake and the highest in the meso-eutrophic lake. Epiphyton abundance (predominated by pennate diatoms) and biomass were found to be the highest in eutrophic water bodies. Biomass consisted primarily of diatoms, but we found the seasonal predominance of filamentous Chlorophyta (in the eutrophic lakes) and Chlorophyceae (in the meso-eutrophic lake). Redundancy analysis (RDA) showed that the frequency of water level fluctuations was the most significant variable in the composition of epiphyton. RDA also revealed the importance of grazing pressure of fish. Thus, in hydrologically transformed lakes, man-made factors may be of great relevance in the development of epiphytic algae.

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Geller, Jonathan B. "Gastropod grazers and algal colonization on a rocky shore in northern California: the importance of the body size of grazers." Journal of Experimental Marine Biology and Ecology 150, no. 1 (July 1991): 1–17. http://dx.doi.org/10.1016/0022-0981(91)90102-3.

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Papadakis, O., K. Tsirintanis, V. Lioupa, and S. Katsanevakis. "The neglected role of omnivore fish in the overgrazing of Mediterranean rocky reefs." Marine Ecology Progress Series 673 (September 2, 2021): 107–16. http://dx.doi.org/10.3354/meps13810.

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Sea urchins are considered the most important grazers in Mediterranean shallow sublittoral rocky reef ecosystems, but fish can also have an important role in overgrazing and the reduction of habitat complexity. In this study, the trophic behavior of fish was recorded when provided access to experimental surfaces with increased macroalgal biomass and associated benthic fauna, created by herbivore exclusion cages. After a sufficient period for substantial algal growth, the cages were removed and the activity of fish on these surfaces was recorded for 3 h by an automated photographic camera system. Control surfaces with no restriction on grazers were defined on similar substrates for comparison. To quantify the effects of fish feeding activity on macroalgal coverage, photographic samples were taken immediately after the opening of the cages and after each 3 h recording. The response of fish when the cages were removed was immediate and intense. Feeding activity by 13 different fish species was recorded in total, of which the most frequent were the omnivores Diplodus vulgaris, Coris julis and Thalassoma pavo, and to a lesser extent the herbivore Sarpa salpa. The coverage of erect algae was substantially decreased on the experimental surfaces due to fish feeding activity. The algae were either directly consumed by the fish or cut off when the fish were feeding on macroinvertebrates. We conclude that in addition to grazing by herbivores, fish of higher trophic levels can also significantly affect macroalgal assemblages and restrict the recovery of erect algae in overgrazed reefs where prey is scarce.

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Barak-Gavish, Noa, Miguel José Frada, Chuan Ku, Peter A. Lee, Giacomo R. DiTullio, Sergey Malitsky, Asaph Aharoni, et al. "Bacterial virulence against an oceanic bloom-forming phytoplankter is mediated by algal DMSP." Science Advances 4, no. 10 (October 2018): eaau5716. http://dx.doi.org/10.1126/sciadv.aau5716.

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Emiliania huxleyiis a bloom-forming microalga that affects the global sulfur cycle by producing large amounts of dimethylsulfoniopropionate (DMSP) and its volatile metabolic product dimethyl sulfide. Top-down regulation ofE. huxleyiblooms has been attributed to viruses and grazers; however, the possible involvement of algicidal bacteria in bloom demise has remained elusive. We demonstrate that aRoseobacterstrain,SulfitobacterD7, that we isolated from a North AtlanticE. huxleyibloom, exhibited algicidal effects againstE. huxleyiupon coculturing. Both the alga and the bacterium were found to co-occur during a naturalE. huxleyibloom, therefore establishing this host-pathogen system as an attractive, ecologically relevant model for studying algal-bacterial interactions in the oceans. During interaction,SulfitobacterD7 consumed and metabolized algal DMSP to produce high amounts of methanethiol, an alternative product of DMSP catabolism. We revealed a unique strain-specific response, in whichE. huxleyistrains that exuded higher amounts of DMSP were more susceptible toSulfitobacterD7 infection. Intriguingly, exogenous application of DMSP enhanced bacterial virulence and induced susceptibility in an algal strain typically resistant to the bacterial pathogen. This enhanced virulence was highly specific to DMSP compared to addition of propionate and glycerol which had no effect on bacterial virulence. We propose a novel function for DMSP, in addition to its central role in mutualistic interactions among marine organisms, as a mediator of bacterial virulence that may regulateE. huxleyiblooms.

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Lasley-Rasher, Rachel S., Kathryn Nagel, Aakanksha Angra, and Jeannette Yen. "Intoxicated copepods: ingesting toxic phytoplankton leads to risky behaviour." Proceedings of the Royal Society B: Biological Sciences 283, no. 1829 (April 27, 2016): 20160176. http://dx.doi.org/10.1098/rspb.2016.0176.

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Understanding interactions between harmful algal bloom (HAB) species and their grazers is essential for determining mechanisms of bloom proliferation and termination. We exposed the common calanoid copepod, Temora longicornis to the HAB species Alexandrium fundyense and examined effects on copepod survival, ingestion, egg production and swimming behaviour. A. fundyense was readily ingested by T. longicornis and significantly altered copepod swimming behaviour without affecting copepod survival or fitness. A. fundyense caused T. longicornis to increase their swimming speed, and the straightness of their path long after the copepods had been removed from the A. fundyense treatment. Models suggest that these changes could lead to a 25–56% increase in encounter frequency between copepods and their predators. This work highlights the need to determine how ingesting HAB species alters grazer behaviour as this can have significant impacts on the fate of HAB toxins in marine systems.

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Aires, Tania, Alexandra Serebryakova, Frédérique Viard, Ester A. Serrão, and Aschwin H. Engelen. "Acidification increases abundances ofVibrionalesandPlanctomycetiaassociated to a seaweed-grazer system: potential consequences for disease and prey digestion efficiency." PeerJ 6 (March 30, 2018): e4377. http://dx.doi.org/10.7717/peerj.4377.

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Ocean acidification significantly affects marine organisms in several ways, with complex interactions. Seaweeds might benefit from rising CO2through increased photosynthesis and carbon acquisition, with subsequent higher growth rates. However, changes in seaweed chemistry due to increased CO2may change the nutritional quality of tissue for grazers. In addition, organisms live in close association with a diverse microbiota, which can also be influenced by environmental changes, with feedback effects. As gut microbiomes are often linked to diet, changes in seaweed characteristics and associated microbiome can affect the gut microbiome of the grazer, with possible fitness consequences. In this study, we experimentally investigated the effects of acidification on the microbiome of the invasive brown seaweedSargassum muticumand a native isopod consumerSynisoma nadejda. Both were exposed to ambient CO2conditions (380 ppm, pH 8.16) and an acidification treatment (1,000 ppm, pH 7.86) for three weeks. Microbiome diversity and composition were determined using high-throughput sequencing of the variable regions V5-7 of 16S rRNA. We anticipated that as a result of acidification, the seaweed-associated bacterial community would change, leading to further changes in the gut microbiome of grazers. However, no significant effects of elevated CO2on the overall bacterial community structure and composition were revealed in the seaweed. In contrast, significant changes were observed in the bacterial community of the grazer gut. Although the bacterial community ofS. muticumas whole did not change,OceanospirillalesandVibrionales(mainlyPseudoalteromonas) significantly increased their abundance in acidified conditions. The former, which uses organic matter compounds as its main source, may have opportunistically taken advantage of the possible increase of the C/N ratio in the seaweed under acidified conditions.Pseudoalteromonas,commonly associated to diseased seaweeds, suggesting that acidification may facilitate opportunistic/pathogenic bacteria. In the gut ofS. nadejda,the bacterial genusPlanctomycetiaincreased abundance under elevated CO2. This shift might be associated to changes in food (S. muticum) quality under acidification.Planctomycetiaare slow-acting decomposers of algal polymers that could be providing the isopod with an elevated algal digestion and availability of inorganic compounds to compensate the shifted C/N ratio under acidification in their food.In conclusion, our results indicate that even after only three weeks of acidified conditions, bacterial communities associated to ungrazed seaweed and to an isopod grazer show specific, differential shifts in associated bacterial community. These have potential consequences for seaweed health (as shown in corals) and isopod food digestion. The observed changes in the gut microbiome of the grazer seem to reflect changes in the seaweed chemistry rather than its microbial composition.

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Buskey, Edward J. "How does eutrophication affect the role of grazers in harmful algal bloom dynamics?" Harmful Algae 8, no. 1 (December 2008): 152–57. http://dx.doi.org/10.1016/j.hal.2008.08.009.

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Liess, Antonia, and Maria Kahlert. "Gastropod grazers and nutrients, but not light, interact in determining periphytic algal diversity." Oecologia 152, no. 1 (February 7, 2007): 101–11. http://dx.doi.org/10.1007/s00442-006-0636-4.

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Pan, Yangdong, and Rex L. Lowe. "Independent and interactive effects of nutrients and grazers on benthic algal community structure." Hydrobiologia 291, no. 3 (October 1994): 201–9. http://dx.doi.org/10.1007/bf00014709.

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Ingrid, Gismervik, Tom Andersen, and Olav Vadstein. "Pelagic food webs and eutrophication of coastal waters: Impact of grazers on algal communities." Marine Pollution Bulletin 33, no. 1-6 (January 1996): 22–35. http://dx.doi.org/10.1016/s0025-326x(96)00134-8.

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Doi, Hideyuki, Izumi Katano, and Eisuke Kikuchi. "The use of algal-mat habitats by aquatic insect grazers: effects of microalgal cues." Basic and Applied Ecology 7, no. 2 (March 2006): 153–58. http://dx.doi.org/10.1016/j.baae.2005.04.009.

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Santelices, B., and E. Martínez. "Effects of filter-feeders and grazers on algal settlement and growth in mussel beds." Journal of Experimental Marine Biology and Ecology 118, no. 3 (June 1988): 281–306. http://dx.doi.org/10.1016/0022-0981(88)90079-2.

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47

Tummon Flynn, P., KD Lynn, DK Cairns, and PA Quijón. "Mesograzer interactions with a unique strain of Irish moss Chondrus crispus: colonization, feeding, and algal condition-related effects." Marine Ecology Progress Series 669 (July 8, 2021): 83–96. http://dx.doi.org/10.3354/meps13737.

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Marine macroalgae are exposed to multiple sources of stress. As a result, perennial macroalga habitats have become depleted in many coastlines. Here, we investigated the role of mesograzers in the sharp decline of a unique strain of Chondrus crispus (the giant Irish moss) found solely in a lagoon in Atlantic Canada. This study was prompted by damage resembling grazing scars that appeared on the fronds as the population declined, for which no grazer had been identified. We identified potential grazers of the seaweed by deploying 4 types of experimental clumps of giant Irish moss and sampling the epifauna that colonized them. Laboratory assays were then run with an abundant species, the amphipod Gammarus oceanicus, to measure feeding rates and test whether this mesograzer is capable of consuming the alga and creating measurable damage. G. oceanicus readily consumed the Irish moss at a grazing rate of 5.24 mg amphipod-1 d-1 and created deep lateral grazing wounds similar to those observed in the field. An additional experiment was conducted to assess whether a co-acting stressor in the lagoon, the accumulation of fine sediments, could explain the appearance and spatially patchy distribution of the damage in the population. Giant Irish moss fronds that had been buried under sediment lost twice as much biomass as those that had not. These results suggest that grazer activity and declining conditions in the lagoon have a negative and additive effect on this unique strain of Irish moss, with clear implications for its restoration.

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Price, Karen, Arlene Suski, Joanna McGarvie, Barbara Beasley, and John S. Richardson. "Communities of aquatic insects of old-growth and clearcut coastal headwater streams of varying flow persistence." Canadian Journal of Forest Research 33, no. 8 (August 1, 2003): 1416–32. http://dx.doi.org/10.1139/x03-089.

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Headwater streams, varying in flow persistence from ephemeral to intermittent to perennial, provide the tightest coupling between water and land, yet they often receive the least protection during forest management. We described communities of aquatic insects in perennial, intermittent, and ephemeral channels surrounded by old-growth forest and 4- to 8-year-old clearcuts in Clayoquot Sound, British Columbia, to determine whether temporary streams have unique aquatic communities and to examine the short-term impacts of harvesting. We measured flow persistence, stream size, canopy cover, organic detritus, and algal biomass in 19 streams. We sampled aquatic invertebrates with a combination of emergence cages and kicknet samples. Temporary and old-growth streams had more organic detritus and a higher abundance of shredders. Perennial and clearcut streams had a higher abundance of some algal grazers, but not higher algal biomass. Insect richness was similar in intermittent and perennial streams of each seral stage but lower in ephemeral streams. Intermittent streams contained four taxa not found in the other stream classes; perennial and ephemeral streams had none. Communities of aquatic insects differed between streams surrounded by clearcuts and old growth, and varied with continuity of flow.

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Harvey, Ben P., Sylvain Agostini, Koetsu Kon, Shigeki Wada, and Jason M. Hall-Spencer. "Diatoms Dominate and Alter Marine Food-Webs When CO2 Rises." Diversity 11, no. 12 (December 16, 2019): 242. http://dx.doi.org/10.3390/d11120242.

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Diatoms are so important in ocean food-webs that any human induced changes in their abundance could have major effects on the ecology of our seas. The large chain-forming diatom Biddulphia biddulphiana greatly increases in abundance as pCO2 increases along natural seawater CO2 gradients in the north Pacific Ocean. In areas with reference levels of pCO2, it was hard to find, but as seawater carbon dioxide levels rose, it replaced seaweeds and became the main habitat-forming species on the seabed. This diatom algal turf supported a marine invertebrate community that was much less diverse and completely differed from the benthic communities found at present-day levels of pCO2. Seawater CO2 enrichment stimulated the growth and photosynthetic efficiency of benthic diatoms, but reduced the abundance of calcified grazers such as gastropods and sea urchins. These observations suggest that ocean acidification will shift photic zone community composition so that coastal food-web structure and ecosystem function are homogenised, simplified, and more strongly affected by seasonal algal blooms.

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WELLNITZ, TODD, and N. LEROY POFF. "Herbivory, current velocity and algal regrowth: how does periphyton grow when the grazers have gone?" Freshwater Biology 51, no. 11 (November 2006): 2114–23. http://dx.doi.org/10.1111/j.1365-2427.2006.01644.x.

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Journal articles on the topic 'Algal Grazers'

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