Kurzzeitdynamik des Sediment-Phytoplankton-Nährstofftransports in Flachgewässern
Zusammenfassung der Projektergebnisse
Algal blooms remain a persistent challenge in shallow lakes, driven by "legacy" nutrients in sediments that release nutrients even after external loads are reduced. These pulses, intensified by warming-induced stratification and anoxia, immensely impact algal growth and species composition, yet the short-term dynamics of these nutrients’ pulses are poorly understood due to limitations in high-resolution in-situ measurement methods. This project focused on measuring, analyzing, and conceptualizing the short-term effects of benthic nutrient dynamics on algal dynamics, including species composition and physiology, under in-situ conditions at high frequency. Investigations were conducted in two contrasting shallow systems: Lake Müggelsee, a eutrophic freshwater lake, and Grabow, a brackish lagoon influenced by hypertrophic inner lagoon waters and the nutrient-rich Baltic Sea. Using high-frequency wet chemistry analyzer (P), ion-selective electrodes (N), and advanced phytoplankton monitoring devices (in-situ flow cytometry and pulse-amplitude-modulated fluorometers), seasonal and short-term variability of abiotic and phytoplankton parameters were monitored over a full vegetation period. Key Findings: 1. High-frequency in-situ monitoring revealed frequent, short-lived peaks in nutrient release that conventional sampling often misses, highlighting the importance of continuous monitoring for capturing dynamic nutrient fluxes. 2. Nutrient release patterns in Müggelsee and Grabow were strongly influenced by redox conditions, with Müggelsee showing higher nutrient release potential due to greater seasonal porewater gradients and reactive sediment P forms. 3. Stratification-mixing cycles were identified as key drivers of nutrient dynamics. Prolonged stratification promoted anoxic phosphorus release from sediments, while subsequent mixing events triggered significant nutrient pulses. 4. Short-term variability in algal and physical variables showed that SRP pulses primarily drive short-term algal growth, particularly for cyanobacteria. Chlorophyll-a dynamics in Müggelsee and Grabow were characterized by complex interactions among physical, chemical, and biological factors, with site-specific drivers such as calcite precipitation in Müggelsee and wind-driven mixing in Grabow playing critical roles. To the best of our knowledge, no studies have combined high-temporal-resolution nutrient release with phytoplankton eco-physiology. These findings therefore provide new insights into nutrient cycling and algal dynamics at fine temporal scales, with implications for managing eutrophication, designing effective monitoring programs, and addressing knowledge gaps for future research.
Projektbezogene Publikationen (Auswahl)
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Internal loading in slowmotion: High resolution in-situ monitoring of benthic nutrient fluxes reveals pulsed regimes in a polymictic lake. 36th Congress of the International Society of Limnology (SIL) 100, 7– 10 August 2022 · Berlin, Germany
Dadi T., Köhler J., Friese K., Kaligatla R.B., Schubert H. & Rinke R.
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High-frequency soluble reactive phosphorus in-situ analysis in lakes. Ecological Indicators, 157, 111221.
Dadi, Tallent; Rinke, Karsten; Balzer, Laura; Kaligatla, Rokhya; Köhler, Jan; Schubert, Hendrik; Shen, Qiushi & Friese, Kurt
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High-resolution phytoplankton dynamics in a polymictic shallow lake. ASLO Aquatic Sciences Meeting 2023, 4– 9 June 2023 · Palma de Mallorca, Spain
Kaligatla R.B., Dadi T., Köhler J., Friese K., Rinke K. & Schubert H.
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Internal loading in slowmotion: High resolution in-situ monitoring of benthic nutrient fluxes reveals pulsed regimes in a polymictic lake. ASLO Aquatic Sciences Meeting 2023, 4–9 June 2023 · Palma de Mallorca, Spain
Dadi T., Köhler J., Friese K., Kaligatla R.B., Schubert H. & Rinke R.
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High-frequency in-situ monitoring of phosphorus reveals pulsed regimes in a polymictic lake, International Phosphorus Workshop (IPW10), 26–30 August 2024, Dundee, Scotland
Dadi T., Graeber D., Friese K., Kaligatla R.B., Köhler J., Schubert H., Shatwell T & Rinke R.
