We have developed a trait-based model to describe how the size of organisms and the environmental conditions interact to determine trophic strategies of unicellular plankton.
Unicellular plankton employ trophic strategies ranging from pure photoautotrophs over mixotrophy to obligate heterotrophs (phagotrophs), with cell sizes from 10-8 to 1 𝜇gC. A full understanding of how trophic strategy and cell size depend on resource environment and predation is lacking. To this end, we develop a trait based model for unicellular planktonic organisms characterized by four traits: cell size and investments in phototrophy, nutrient uptake, and phagotrophy. We identify two mixotrophic strategies: ‘generalist mixotrophs’ investing in all three investment-traits, and ‘obligate mixotrophs’ investing only in phototrophy and phagotrophy. We formulate two conjectures: 1) most cells are limited by organic carbon, however, small unicellulars are co-limited by organic carbon and nutrients, and only large photoautotrophs and smaller mixotrophs are nutrient limited; 2) trophic strategy is bottom-up selected by the environment, while optimal size is top-down selected by predation
The paper can be read here.
Chakraborty, S., Nielsen, L., and Andersen, K. (2017) Trophic strategies of unicellular plankton. American Naturalist 189 (4), E000-E000.