The effects of freshwater phytoplankton germination at population and community scales

Dormancy, a process by which an organism enters a reversible state of low metabolic activity, is an important shared trait across phytoplankton taxonomic groups as both a bet hedging strategy and a method to survive unfavorable conditions. Phytoplankton use dormancy in response to many biotic and abiotic cues, including temperature and light. The ecological effects of germination from dormant individuals in benthic sediments are largely unknown. We conducted experiments to investigate: (1) how environmental conditions and sediment age affect the abundance and identity of germinating phytoplankton, and (2) how strongly contributions from sediment affect community assembly and dynamics.  We created a series of microcosms by incubating alpine lake sediment samples from 0 to 86 years old under different temperature and light conditions. Age of sediment, incubation temperature, and photoperiod affected overall community growth and composition, with functional groups like diatoms and green algae responding favorably to different temperatures and photoperiods. To investigate how such germination affects the whole microalgal community, we also need to understand how germinants interact with the contemporary phytoplankton community. In a second microcosm experiment, we added sediment to unfiltered lake water, using sediment or lake water alone as controls. Over three weeks, we observed differences in the growth rate and composition of these communities, likely influenced by different assembly patterns.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Hannah Larson, University of Connecticut (hannah.larson@uconn.edu)

Authors:

Hannah Larson, University of Connecticut  (hannah.larson@uconn.edu)

Celia Symons, University of California, Irvine  (csymons@uci.edu)

Charlotte Melnitsky, University of Connecticut  (charlotte.melnitsky@uconn.edu)

Colin Kremer, University of Connecticut  (colin.kremer@uconn.edu)