Influences of climate and nutrient enrichment on the multiple trophic levels of Turkish shallow lakes

ABSTRACT

Climate warming threatens the structure and function of shallow lakes, not least those in the Mediterranean climate. We used a space-for-time substitution approach to assess the response of trophic and community structures as well as the richness and evenness of multiple trophic levels to temperature, hydrological, and nutrient constraints. We selected 41 lakes covering wide climatic, hydrological, and nutrient gradients within a short distance for reducing the effect of biogeographical factors in the western Anatolian plateau of Turkey. Generalized linear model analyses revealed that temperature was overall the most important driving variable, followed by total nitrogen (TN) and salinity. The chlorophyll a:total phosphorus ratio, the cyanobacteria:total phytoplankton biovolume ratio, the fish:zooplankton biomass ratio, the proportion of small fish, and fish richness increased with increasing temperature, whereas macrophyte plant volume inhabited (PVI, %), richness, and evenness decreased. Grazing pressure, macrophyte coverage, piscivore biomass, phytoplankton richness, and evenness decreased significantly with both increasing TN and temperature. Temperature and nutrients also separated the northern highland lakes from other lakes in a non-metric multidimensional scaling analysis. Additionally, salinity reduced richness and evenness of phytoplankton and zooplankton. Our results indicate major changes in lake structure and functioning with warming and eutrophication, and highlight the need for strict control of nutrients and water use.

KEYWORDS:

• drought
• elevation
• land use
• richness
• salinity
• small fish

Acknowledgements

Most of us are part of the “Moss Scientific Family,” and we wish to take this opportunity to dedicate our paper on the ecology of Turkish shallow lakes to the memory of our dearest Brian Moss. He was a world leading pioneer and scientist on the ecology of shallow lakes as well as a great mentor, and although he is no longer with us he continues to inspire us.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Middle East Technical University-BAP programme (BAP.07.02.2009–2012); FP-7 REFRESH (Adaptive strategies to Mitigate the Impacts of Climate Change on European Freshwater Ecosystems), under Contract Number 244121; and MARS (Managing Aquatic ecosystems and water Resources under multiple Stress), under the 7th EU Framework Programme, Theme 6 (Environment including Climate Change), Contract Number 603378 (http://www.mars-project.eu). AİÇ, ÜNT, EEL, GB and KÖ were supported by TÜBİTAK-ÇAYDAG projects (Project nos.: 105Y332 and 110Y125); TB and NF were supported by TÜBİTAK 2211 Scholarship Programme; and AÖ and SE were supported by the METU-ÖYP Programme. EJ, MB and KÖ were further supported by TÜBİTAK BIDEB 2232 – Outstanding researchers programme. SB was supported by the TUBITAK 2221–Visiting Scientist Fellowship Program and by the Marie Curie Intra European Fellowship no. 330249 (CLIMBING). We thank C. Can Bilgin for his valuable suggestions and contribution regarding the use and estimation of bioclimatic values and Anne Mette Poulsen for her valuable editorial comments.