Investigation of the Effects of Salinity, Global Warming and Eutrophication on Lake Ecosystem Structure, Processes and Biodiversity Under Different Climatic Conditions via Simultaneous Mesocosm Experiment (TuzIuSıcakÖtrofik)

Short Name: TuzIuSıcakÖtrofik

Type / Supporting Institution: TÜBİTAK 1001 – The Scientific and Technological Research Projects Funding Program

Project Period/Planned duration: 36 months (approx. 2025–2028)

Principal Investigator: Prof. Dr. Meryem Beklioğlu – Middle East Technical University, Department of Biological Sciences

Host Institution: Middle East Technical University (METU)

General Information

The TuzIuSıcakÖtrofik project is a large-scale mesocosm study aiming to understand the individual and combined effects of salinity increase, global warming, and eutrophication in lake ecosystems that have become fragile under climate change and human pressure.

Within the scope of the project, identical mesocosm systems located in two different climatic regions of METU are being used:

Ankara: cold semi-arid climate

Mersin (Erdemli): hot Mediterranean climate

In a total of 48 mesocosms at these two sites:

• 6 different salinity levels (0–40 g/L),
• 2 temperature scenarios (ambient temperature and +4.5 °C warming),
• 2 nutrient levels (low and high N–P loading)

are being tested together. Thus, the effects of three main stress factors frequently seen together in lakes (warming × salinization × eutrophication) as multiple stressors on ecosystem structure, biodiversity, and ecosystem functioning (TSEF) are being investigated.

During the experiments:

• Physical parameters such as water temperature, salinity, dissolved oxygen, pH, and water clarity,
• Chemical variables such as nutrient salts (TN, TP, NO₃, NO₂, SRP), TOC/DOC,
• Species composition, biomass, and diversity of planktonic communities such as phytoplankton, ciliates, rotifers, and meso-zooplankton (Cladocera, Copepoda)

are monitored with weekly samplings. Plankton communities are analyzed with FlowCAM imaging technology in addition to classical microscopic methods; thus, high-resolution plankton visual libraries belonging to Turkey's saline lakes are also being created.

By quantitatively revealing the simultaneous effects of salinization, warming, and eutrophication, especially for lakes in the semi-arid and Mediterranean climate zones, the project results will:

• Provide scientific infrastructure for lake management and restoration strategies,
• Provide input to climate change adaptation policies,
• Produce high-impact scientific publications and datasets at national and international levels.

Figure 1. The relationship between climate change and eutrophication, this figure is adapted from Moss et al. (2011).

Figure 2. Schematic summary of phytoplankton and zooplankton diversity and biomass responses to increasing salinity; this figure is adapted from Afonina and Tashlykova (2024).