Response of water quality to short and long-term warming under different salinities and climatic conditions: two synchronized mesocosm experiments in Turkey

Salinisation due to excessive water use for irrigation in dry landscapes may dramatically affect functioning of shallow lake ecosystems, which may further be complicated by climate warming and heatwave events. We conducted two synchronized experiments for the effects of short and long-term heating at two different salinities (4 and 40 ppt) in 32 identical outdoor mesocosms located in two different climatic zones (semi-arid cold-dry steppe Ankara and Mediterranean Mersin, 16 mesocosms per location) mimicking shallow lake ecosystems. Each mesocosm had 5m³ volume, 1.2 m water depth and inoculated with natural sediment and biotic communities. The first experiment focused on the effects of a short heatwave event (ambient temperature vs a two-week long heatwave of +6 °C) and was conducted between 29 August and 3 November 2022. The second experiment focused on the effects of long-term heating (ambient temperature and constant +4.5 °C heating), conducted between 29 August and 30 November 2023. Temperature treatments in both experiments were crossed with two salinities, all having four replicates. Both experiments revealed significant response in water quality and nutrient concentrations to salinity treatment and climatic zones (between Mersin and Ankara). No pronounced effect of short-term heatwave was observed, whereas long-term heating induced significant response in water quality and nutrient chemistry. Long-term heating decreased chlorophyll-a concentrations, oxygen, and pH, especially at higher salinities and warmer climates. Both mesocosm experiments revealed predominantly negative effects of salinisation and climatic warming on water quality, although latter was conditional on duration of heating.

Primary Presenter: Korhan Özkan, MIDDLE EAST TECHNICAL UNIVERSITY / INSTITUTE OF MARINE SCIENCES (korhan.ozkan@gmail.com)

Authors:

Korhan Özkan, Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Türkiye  (korhan.ozkan@gmail.com)

Gültekin Yılmaz, Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Türkiye  (tekinims@gmail.com)

Cihelio Amorim, Department of Biological Sciences, Middle East Technical University, 06800 Ankara, Türkiye  (alvescihelio@gmail.com)

Mustafa Korkmaz, Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Türkiye  (korkmaz.hidro@gmail.com)

Meltem Koru, Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Türkiye  (korumeltem99@gmail.com)

İrem Arık, Department of Biological Sciences, Middle East Technical University, 06800 Ankara, Türkiye  (igamzearik@gmail.com)

Masum Billah, Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Türkiye  (masum_imsf07@yahoo.com)

Zeynep Uyar, Department of Biological Sciences, Middle East Technical University, 06800 Ankara, Türkiye  (zeynepdilbeuyar@gmail.com)

Tolga Coşkun, Department of Biological Sciences, Middle East Technical University, 06800 Ankara, Türkiye  (tolgaa.coskunn@gmail.com)

Onat Arıkan, Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Türkiye  (onat.arikan@yandex.com)

Archana Manjunath, Institute of Marine Sciences, Middle East Technical University, 33731 Mersin, Türkiye  (archanamanjunath007@gmail.com)

Meryem Beklioğlu, Department of Biological Sciences, Middle East Technical University, 06800 Ankara, Türkiye  (meryem@metu.edu.tr)

Erik Jeppesen, Department of Biological Sciences, Middle East Technical University, 06800 Ankara, Türkiye  (ej@ecos.au.dk)