Impact of salinization on ecosystem structure, function and diversity in shallow lakes using a gradient design synchronized mesocosm experiments

The widespread salinization of freshwater ecosystems is among the major grand challenges that poses a major threat to ecosystem structure, function and biodiversity that .is especially common in arid and semi arid areas coupled with excessive water use for irrigation of water-thirsty crops e.g. Central Anatolian Türkiye. To understand the effects of salinization on shallow lakes, we performed synchronized long-term gradient design mesocosm experiments between September 2021 to May 2022 with 16 different salinities (0-50 g/L), in two places with different climate conditions in Türkiye (Ankara, mean temperature: 12.6°C; and Mersin, mean temperature: 20.1°C). The experiments were divided into three periods: increasing (30 days), stable (six months), and decreasing (40 days) salinity. In both places, the concentrations of nutrients, especially phosphorus, chlorophyll-a, turbidity and suspended solids increased, which was more pronounced after 20 g/l of salinity. Overall, the increase was much higher in the warmer Mersin mesocosms. Increasing salinity led to a linear decrease in water clarity in Ankara while it did not cause a change in Mersin mesocosms during the increasing salinity period. At stable levels, intermediate salinities showed higher water transparency in both places. Increased salinity shifted phytoplankton community structure to more Cyanobacteria and diatoms dominated. Zooplankton biomass and richness decreased largely with increasing salinity. Changes took place along the salinity gradient in two different climatic zones will be discussed in depth

Presentation Preference: Oral

Primary Presenter: Meryem Beklioglu, Middle East Technical University (meryem@metu.edu.tr)

Authors:

Cihelio Amorim, Middle East Technical University, Biological Sciences Department  (alvescihelio@mail.com)

İrem Arık, Middle East Technical University, Biological Science Department  (igamzearik@gmail.com)

Tolga Coskun, Middle East Technical University, Biological Science Department  (tolgaa.coskun@gmail.com)

Gultekin Yilmaz, Middle East Technical University, Institute of Marine Sciences  (tekin.ims@gmail.com)

Mustafa Korkmaz, Middle East Technical University, Biological Science Department  (m.korkmaz@gmail.com)

Arda Çolak, Middle East Technical University  (ardac@gmail.com)

Can Ozen, Middle East Technical University  (dr.can.ozen@gmail.com)

Korhan Ozkan, Middle East Technical University, Institute of Marine Science  (korhan.ozkan@gmail.com)

Erik Jeppesen, 5Aarhus University, Department of Ecoscience and Middle East Technicla University  (ej@ecos.au.dk)