Assessing the effects of freshwater salinization and heatwaves on zooplankton community biomass and size structure.

Awareness of the impact of multiple stressors on freshwater ecosystems is increasing. For example, heatwaves are increasingly common due to climate change, and chloride (Cl^-) concentrations are rising in inland waters due to human activities. Both stressors threaten freshwater wildlife, biodiversity, and ecosystem services, individually and in tandem. Zooplankton are primary consumers that play important roles in ecosystems, such as regulating algal growth and nutrient cycling. The mechanisms by which heatwaves and Cl^- affect zooplankton biomass, composition, and body size are not well known. We evaluated how fluctuations in zooplankton biomass could be attributed to (H1) abundance declines, (H2) compositional shifts in community size structure, or (H3) intraspecific size responses. We also tested for synergistic interactive effects when elevated temperatures and salinity co-occurred (H4). We performed a 6-week experimental study using nine indoor mesocosms to assess plankton responses to heatwaves and elevated Cl^- conditions with a pulse treatment design. Preliminary results indicate that zooplankton biomass generally remained unaffected by treatments. However, zooplankton community-weighted mean body size decreased in response to elevated Cl^-, alone or combined with heatwaves. Heatwaves alone only affected zooplankton body size after the first pulse, suggesting increased community resistance upon subsequent pulses. Overall, this work will provide insight into the mechanisms that drive zooplankton community responses to co-occurring stressors in freshwater ecosystems.

Presentation Preference: Oral

Primary Presenter: Hannah Cane, Rubenstein Ecosystem Science Laboratory, University of Vermont (hcane@uvm.edu)

Authors:

Hannah Cane, Rubenstein Ecosystem Science Laboratory, University of Vermont  (hcane@uvm.edu)

Marie-Pier Hébert, Rubenstein Ecosystem Science Laboratory, University of Vermont/ Université du Québec à Chicoutimi  (mphebert4@gmail.com)

Miles Nippes, Rubenstein Ecosystem Science Laboratory, University of Vermont  (miles.nippes@uvm.edu)

Samantha Gonsalves, Rubenstein Ecosystem Science Laboratory, University of Vermont  (samantha.gonsalves@uvm.edu)

Adebukola Abiodun Aborigho, Rubenstein Ecosystem Science Laboratory, University of Vermont  (adebukola.aborigho@uvm.edu)

Allie Shiers, Rubenstein Ecosystem Science Laboratory, University of Vermont  (ashiers135@gmail.com)

Lisette Senerpont Domis, Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW)  (l.desenerpontdomis@nioo.knaw.nl)

Sven Teurlincx, Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW)  (s.teurlincx@nioo.knaw.nl)

Jason Stockwell, Rubenstein Ecosystem Science Laboratory, University of Vermont  (jason.stockwell@uvm.edu)