Climate change is increasing the frequency and amplitude of extreme events such as heavy rainfall or storm-induced mixing which result in a temporally variable input and availability of nutrients and DOM for plankton communities in lakes. This leads to changes in the phytoplankton C:N:P elemental composition which impacts consumer growth and thus the energy transfer in the aquatic food-web. However, the current understanding of run-off impacts on producers and consumers is limited as studies on variability in run-off events including multiple trophic levels are rare. Here, we conducted a mesocosm experiment within the AQUACOSM-plus network at Lake Erken (SITES AquaNet) in Sweden to simulate a rainfall period with different amplitudes and frequencies of nutrient and cDOM pulses. The experimental treatments ranged from one extreme to multiple intermediate and low pulses of nitrate, phosphate and cDOM, with the same total addition, over a period of 20 days. This was followed by a 17-day recovery period without any input. Our results show that the extreme nutrient pulse enables fast recovery of phytoplankton biomass and C:N ratios but leads to phosphorus-driven decreases in C:P and N:P ratios compared to both higher frequency pulses. These effects translate into consumer level with differences between the functional groups of zooplankton (cladocerans and copepods). Overall, our study demonstrates that stoichiometric resilience and recovery not only depend on the amount of nutrient and DOM input but also the amplitude and frequency with which it is introduced into the ecosystem.

Primary Presenter: Anika Happe, University of Oldenburg (anika.happe@uni-oldenburg.de)

Authors:

Anika Happe, University of Oldenburg, Germany  (anika.happe@uni-oldenburg.de)

Gabriela Ágreda López, Uppsala University, Sweden  ()

Stella Berger, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Germany  ()

Berenike Bick, Uppsala University, Sweden  ()

Bence Buttyán, Eötvös Loránd University, Hungary  ()

Eleni Charmpila, Charles University, Czech Republic  ()

Bence Gergácz, Eötvös Loránd University, Hungary  ()

Silke Langenheder, Uppsala University, Sweden  ()

Clara Mangold, University of Innsbruck, Austria  ()

Jens Nejstgaard, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Germany  ()

Katerina Symiakaki, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Germany  ()

Maren Striebel, University of Oldenburg, Germany  ()