Changes in Ice Cover Regimes Influence Zooplankton Community Structure in Subalpine Castle Lake, California

ERIN SUENAGA; FACUNDO SCORDO; JOSHUA CULPEPPER; SUDEEP CHANDRA; CARINA SEITZ

Grand Rapids

Congreso; Joint Aquatic Sciences Meeting 2022 in Grand Rapids, Colorado; 2022

American Fisheries Society (AFS) - Association for the Sciences of Limnology and Oceanography (ASLO) - Coastal and Estuarine Research Federation (CERF) - Freshwater Mollusk Conservation Society (FMCS) - International Association for Great Lake Research

Climate change, in particular increasing air temperatures, results in shorter ice cover duration and warmer water temperatures in temperate lake ecosystems. The duration of ice cover impacts the physical and chemical conditions of a lake and subsequently influences the ecological processes occurring in the following seasons. We compare the succession of zooplankton community composition and biomass along with primary productivity (PPr) throughout the ice-free season in the subalpine Castle Lake (zmax=35m), California, after early, late, and average ice-off years between 1968 and 2020. The mean ice-off during the study period is ordinal day 133, with earliest ice-off dates recorded on ordinal days 51 and 57 (2015 and 2014, respectively) and the latest ice-off dates recorded on ordinal days 178 and 187 (2011 and 1983, respectively). We found evidence of compositional differences in the zooplankton communities in the early summer months between early, average, and late ice-off years, with higher abundances of cyclopoid copepods and cladocerans in years with earlier ice-off, but no difference in total zooplankton biomass. We observed higher net rates of PPr in the epilimnion (0-5m) in years with earlier ice-off throughout the ice-free season relative to average and late ice-off years. This study highlights the importance of changing snowpack and ice-cover duration for freshwater ecosystem functioning and productivity.