In an outdoor replicated whole-pond experiment, we aim to understand the relative contributions of ecological species turnover and evolutionary adaptation in phytoplankton communities to changes in ecosystem functioning in response to eutrophication and the presence or absence of two foundation species: the invasive freshwater mussel Dreissena polymorpha and the aquatic plant, Myriophyllum spicatum. In our first publication on this project, we found that when each foundation species occurs by itself, they can reduce phytoplankton biomass, clarify the water and help to promote recovery from nutrient disturbances. However, when they are found together the two species make the ponds more productive, turbid and unstable. This was associated with an increase in dominance of single species of cyanobacterium and a dramatic loss of trait evenness. In turn, these changes in the phytoplankton community affected a number of ecosystem properties, including grazer abundance, dissolved oxygen and turbidity.
It has been shown that phytoplankton can evolve rapidly, and that evolutionary adaptation can fundamentally alter their ecological interactions. We are currently following up on the first part of this project by quantifying the relative contributions of ecological and evolutionary change in the phytoplankton community to these observed changes in algal production and stability.