FRESHWATER ZOOPLANKTON DIEL VERTICAL MIGRATION AND CARBON FLUX UNDER VARYING LEVELS OF PLANKTIVORY: A MESOCOSM-BASED APPROACH

Zooplankton often exhibit diel vertical migration (DVM) in lakes, whereby they reside in deeper waters during the day to avoid fish predation and migrate to surface waters at night to feed on phytoplankton. Zooplankton are expected to exhibit more pronounced DVM behavior in lakes with higher predation risk from planktivorous fish. However, zooplankton trait-based groups differ in their evasion capabilities, which may drive diverse behavioral responses to planktivory. Zooplankton DVM behavior contributes to the downward transport of organic carbon to deep waters and sediments in the ocean, but DVM-mediated carbon flux has not been quantified in freshwater systems. We manipulated densities of planktivorous fish in 14 large enclosures (9 m diameter x 20 m deep) at the LakeLab in Lake Stechlin, Germany for six weeks in spring 2023 to investigate differences in DVM behavior of zooplankton functional groups, and to quantify impacts of DVM on carbon cycling. DVM was quantified using AI-supported high-resolution in situ video (MDPI). Preliminary results indicate stronger migration responses for larger individuals and taxa with weaker evasion capabilities. We use zooplankton respiration and fecal pellet production models, combined with physical parameters and particulate and dissolved carbon concentrations, to investigate how DVM drives carbon flux dynamics through changes in respiration and excretion across time and space. Our results will contribute to better understanding impacts of fish community changes on zooplankton behavioral dynamics and roles in lake ecosystem function.

Primary Presenter: Anna Schmidt, University of Vermont (anna.schmidt@uvm.edu)

Authors:

Anna Schmidt, University of Vermont  (anna.schmidt@uvm.edu)

Christian Dilewski, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (christian.dilewski@igb-berlin.de)

Harrison DuBois, Northeastern University  (dubois.h@northeastern.edu)

Lars Ganzert, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (lars.ganzert@igb-berlin.de)

Tiare Huízar Hernández, University of Kaiserslautern-Landau  (3atiare@gmail.com)

Elžbieta Kazanavičiūtė, Lancaster University  (elzkazanaviciute@gmail.com)

Amelia McReynolds, University of Vermont  (amelia.mcreynolds@uvm.edu)

Sabine Wollrab, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (sabine.wollrab@igb-berlin.de)

Gülce Yalçın, Middle East Technical University  (g.saydam7@gmail.com)

Hans-Peter Grossart, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (hanspeter.grossart@igb-berlin.de)

Stella Berger, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (stella.berger@igb-berlin.de)

Jens Nejstgaard, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (jens.nejstgaard@igb-berlin.de)

Jason Stockwell, University of Vermont  (jason.stockwell@uvm.edu)