Grazing resistance in phytoplankton

Abstract

Phytoplankton is confronted with a variable assemblage of zooplankton grazers that create a strong selection pressure for traits that reduce mortality. Phytoplankton is, however, also challenged to remain suspended and to acquire sufficient resources for growth. Consequently, phytoplanktic organisms have evolved a variety of strategies to survive in a variable environment. An overview is presented of the various phytoplankton defense strategies, and costs and benefits of phytoplankton defenses with a zooming in on grazer-induced colony formation. The tradeoff between phytoplankton competitive abilities and defenses against grazing favor adaptive trait changes-rapid evolution and phenotypic plasticity-that have the potential to influence population and community dynamics, as exemplified by controlled chemostat experiments. An interspecific defense-growth trade-off could explain seasonal shifts in the species composition of an in situ phytoplankton community yielding defense and growth rate as key traits of the phytoplankton. The importance of grazing and protection against grazing in shaping the phytoplankton community structure should not be underestimated. The trade-offs between nutrient acquisition, remaining suspended, and grazing resistance generate the dynamic phytoplankton community composition.

Phytoplankton of the Curonian Lagoon as a New Interesting Source for Bioactive Natural Products. Special Impact on Cyanobacterial Metabolites

“…Daphnia sp. is an important organism in the food chains; it grazes on phytoplankton organisms [61]. In many acute toxicity assays, relatively high concentrations of samples are used, which do not always reflect the real situation in the aquatic environment.…”

Bacterial CRISPR-Cas Abundance Increases Precipitously at Around 45°C: Linking Antivirus Immunity to Grazing Risk

“…In addition, prey bacteria are not entirely passive to be grazed, and they could evolve grazing-resistance capacities, like high motility, large size, and biofilm formation. [40][41][42] In a long-term arms race between prey bacteria and grazing protists/bacteria, the prey bacteria might, in some periods, be free of grazing risk and grazing-caused mortality because of newly evolved grazing-resistance strategies. In this case, viral lysis becomes dominant in bacterial mortality, and the bacteria experience an intense selective pressure to have CRISPR-Cas systems.…”

Can Top-Down Controls Expand the Ecological Niche of Marine N2 Fixers?

“…Top-down control by grazers ( Prowe et al, 2012a ; Vallina et al, 2014 ) and mortality by viral infection ( Suttle, 2007 ; Weitz et al, 2015 ) are thought to exert a major control on plankton diversity and coexistence, driving adaptation and evolution. For example, grazing can drive changes in cell size and morphology ( Fenchel, 1980 ; Branco et al, 2020 ) as well as defense mechanisms ( Lürling, 2021 ). Selective mortality, via grazing or viral-lysis, leads to increased diversity and coexistence ( Thingstad, 2000 ), contributing, together with the spatial and temporal heterogeneity of the environment, to maintain plankton diversity ( Hutchinson, 1961 ) on seasonal to centennial time scales ( Barton et al, 2010 ; Tsakalakis et al, 2018 ; Dutkiewicz et al, 2020 ).…”

“…Zooplankton specific ingestion rates generally decrease with size of the predator ( Kiørboe and Hirst, 2014 ), reflecting an increase in prey handling time with large sizes and complex morphologies ( Wirtz, 2012 ). Size and morphological changes can be induced by grazing pressure and are achieved, e.g., via the formation of colonies and aggregates in phytoplankton, likely at the cost of reduced growth rates ( Van Donk et al, 2011 ; Lürling, 2021 ).…”