Freshwater ecosystems are increasingly affected by rising annual mean temperatures and extreme heatwaves. While heatwaves are expected to have more dramatic effects than mean temperature increases on local communities, comparative experimental studies are largely lacking. We conducted a mesocosm experiment to test the effect of different warming scenarios, constantly raised temperatures (+3°C), and recurring heatwaves (+6°C) on plankton communities. We specifically tested how shifts in zooplankton trait composition and functional groups are reflected in ecosystem functioning (top-down control on primary producers). We found that heatwaves had a stronger and more immediate effect on trait and functional group compositions. We found that heatwaves had a negative impact on Rotifer, and the decrease of micrograzers. This resulted in weaker top-down control, leading to elevated algal biomass. Altogether, our results highlight the importance of the indirect effects of heatwaves via inducing shifts in zooplankton functional groups and trait composition, which may foster periodic algal blooms.

Primary Presenter: Thu Huong Huynh Ngoc, Institute of Aquatic Ecology, Centre for Ecological Research, National Multidisciplinary Laboratory for Climate Change, Centre for Ecological Research, Doctoral School of Biology, Institute of Biology, Eotvos Lorand University (thuhuong14es@gmail.com)

Authors:

Thu Huong Huynh Ngoc,  Institute of Aquatic Ecology, Centre for Ecological Research, National Multidisciplinary Laboratory for Climate Change, Centre for Ecological Research, Doctoral School of Biology, Institute of Biology, Eotvos Lorand University  ()

Zsofia Horvath,  Institute of Aquatic Ecology, Centre for Ecological Research, Hungary ; National Multidisciplinary Laboratory for Climate Change, Centre for Ecological Research, Budapest, Hungary ; Eotvos Lorand University  ()

Karoly Palffy, Institute of Aquatic Ecology, Centre for Ecological Research, Hungary ; National Multidisciplinary Laboratory for Climate Change, Centre for Ecological Research  ()

Vivien Kardos, Institute of Aquatic Ecology, Centre for Ecological Research, Hungary   ()

Beata Szabo,  Institute of Aquatic Ecology, Centre for Ecological Research, Hungary ; National Multidisciplinary Laboratory for Climate Change, Centre for Ecological Research, Budapest, Hungary  ()

Peter Dosoby,  Institute of Aquatic Ecology, Centre for Ecological Research, Hungary ; Eotvos Lorand University, Budapest, Hungary  ()

Csaba Vad, Institute of Aquatic Ecology, Centre for Ecological Research, Hungary ; National Multidisciplinary Laboratory for Climate Change, Centre for Ecological Research, Budapest, Hungary ; Eotvos Lorand University  ()