On thin ice- implications of shorter winters for the future of freshwater phytoplankton phenology and function

Lakes around the world face rapidly warming temperatures coupled with shorter winters, which affects ice cover, and can alter phytoplankton dynamics. Increased phytoplankton blooms, including both cyanobacteria and eukaryotic taxa, threaten water quality, drinking water supplies, recreation, and energy flow through food webs. Despite the risks, current ecological theory and field sampling methods are not well equipped to predict alterations to phytoplankton structure and function over the entire year, including winter. We present a project overview for our new NSF Macrosystems grant, where our main objective is to study the transition from ice covered to ice free winters and assess the effects on freshwater ecosystem structure and function. Our study will compare lakes across a latitudinal gradient (Ontario to Florida) to span a variety of ice cover conditions, ranging from long ice cover to intermittent to ice-free. Our gradient also contains lakes with varying degrees of summer phytoplankton blooms. We focus on how ecosystem memory of winter conditions may result in altered spring and summer ecosystem conditions, including changes in cyanobacteria biomass,toxin production, and lake metabolism. We present plans for field surveys, experiments, and predictive modeling using high-frequency environmental sensors. We will also provide information and invite collaborators to participate in a global summer and winter lake sampling campaign commencing in summer 2025. This project assesses how changes in climate will ultimately affect basal ecosystem structure and function.

Presentation Preference: Poster

Primary Presenter: David Richardson, SUNY New Paltz (richardsond@newpaltz.edu)

Authors:

Meredith Holgerson, Cornell University  (meredith.holgerson@cornell.edu)

Ana Morales-Williams, University of Vermont  (Ana.Morales@uvm.edu)

Rebecca North, University of Missouri  (northr@missouri.edu)

Isabella Oleksy, University of Colorado Boulder  (isabella.oleksy@colorado.edu)

Anila Ajayan, University of Vermont  (anila.ajayan@uvm.edu)