EFFECTS OF WATER RESIDENCE TIME ON PHYTOPLANKTON DYNAMICS IN CONNECTED LAKE ECOSYSTEMS - A LARGE-SCALE ENCLOSURE EXPERIMENT

Lake ecosystems face severe anthropogenic forcing through land use alterations and climate change, which influence lake connectivity, compromise water quality and provision of ecosystem services. Effective lake management to sustain ecosystem functioning requires a mechanistic understanding of how ecosystems respond to environmental stressors. These responses are influenced by lake features, but also by connectivity to their surrounding catchment and neighbouring lakes and rivers. To test how lake connectivity drives synchrony of biological dynamics in lake chains, we conducted a mesocosm experiment in the IGB-LakeLab, installed in Lake Stechlin, Germany. Six experimental circular chains of four enclosures each were set up to mimic short and long water residence times observed in lake chains of the region. Water residence times were manipulated by pumping epilimnetic water between connected enclosures. Following an initial nutrient loading event in the head-enclosure, we monitored phytoplankton dynamics and ecosystem-scale processes related to ecosystem functioning by combining high-resolution in-situ multi-sensor profiles with high-throughput image-based flowcytometry (FlowCam). Our results indicate that short residence times synchronized the epilimnetic plankton community after four weeks, while long residence times led to pronounced differences in phytoplankton communities. This mesocosm experiment improves our understanding of biological dynamics in river-connected lakes and hold great promises for future lake monitoring and management.

Presentation Preference: Oral

Primary Presenter: Stella Berger, Leibniz Institute of freshwater Ecology and Inland Fisheries (IGB) (stella.berger@igb-berlin.de)

Authors:

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

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

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

Isimemen Osemwegie, University of Bonn, Germany  (iosemweg@uni-bonn.de)

Christine Kiel, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Germany  (christine.kiel@igb-berlin.de)

Igor Ogashawara, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Germany  (igor.ogashawara@igb-berlin.de)

Andreas Jechow, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (andreas.jechow@th-brandenburg.de)

Katrin Kohnert, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (Katrin.Kohnert@expertenrat-klima.de)

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

Franz Hölker, Leibniz Institute of Freshwater Ecology and Inland Fisheries  (franz.hoelker@igb-berlin.de)

Gabriel Singer, University of Innsbruck, Austria  (gabriel.singer@ulbk.ac.at)