Eutrophication continues to be the most important problem preventing a favorable environmental state and detrimentally impacting the ecosystem services of lakes. The current study describes the results of analyses of 20 year monitoring data from two interconnected Anatolian lakes, Lakes Mogan and Eymir, receiving sewage effluents and undergoing restoration. The first step of restoration in both lakes was sewage effluent diversion. Additionally, in hypertrophic Lake Eymir, biomanipulation was conducted, involving removal of benthi-planktivorous fish and prohibition of pike fishing. The monitoring period included high (H) and low (L) water levels (WL) enabling elucidation of the effects of hydrological changes on lake restoration. In shallower Lake Mogan, macrophyte abundance increased after the sewage effluent diversion in periods with low water levels even at turbid water. In comparatively deeper Lake Eymir, the first biomanipulation led to a clear water state with abundant macrophyte coverage. However, shortly after biomanipulation, the water clarity declined, coinciding with low water level (LWL) periods during which nutrient concentrations increased. A second biomanipulation was conducted, mostly during high water level (HWL) period, resulting in a major decrease in nutrient concentrations and clearer water, but without an expansion of macrophytes. We conclude that repetitive fish removal may induce recovery but its success may be confounded by high availability of nutrients and adverse hydrological conditions.

Microplastic pollution has increased rapidly over recent decades and accepted as an emerging thread. However, the effects and dimensions of microplastic pollution on aquatic ecosystems have not been fully understood yet. Most of these few studies have been carried out in marine ecosystems and the number of studies on freshwater are very limited. In this study, microplastic (<5 mm) pollution level of surface water samples taken from Cevdet Pond (Yozgat/Turkey) was investigated. Water samples (150 L) were taken from 5 stations and microplastic particles were extracted via density separation method. Random particles were examined both visually and spectrophotometrically (µ-Raman). According to station averages, there were 233 microplastic particles in 1 m3 of the pond water. Highest number of MP particles observed in 100-250 µm (56%) size class. Most abundant microplastic type and colour are fiber (91%) and blue (36%) respectively. Polypropylene (50%) and polyethylene (40%) were the most abundant type of polymers according to µ-Raman analysis. The presence of microplastic pollution in an area where human impact is relatively low, indicates the prevalence of microplastic pollution in freshwater ecosystems.

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.

The present study investigates microplastic (MP) contamination in the gills and gastrointestinal tract (GIT) of common carp (Cyprinus carpio), mirror carp (Cyprinus carpio carpio) and European perch (Perca fluviatilis) specimens obtained from Gelingüllü Reservoir (Türkiye). MP particles were found in 58 (75.3%) of the 77 fish examined. The percentages of MP contamination identified in the GITs of common carp, mirror carp, and perch were 46.4% (1.2 ± 1.8 MPs/ind.), 30% (0.5 ± 0.9 MPs/ind.), and 47.4% (0.9 ± 1.1 MPs/ind.), respectively. The differences observed between the three groups were not statistically significant (p > 0.05). On the other hand, the percentages of MP contamination identified in the gills of common carp, mirror carp, and perch were 46.4% (0.7 ± 0.9 MPs/ind.), 53.3% (0.7 ± 0.8 MPs/ind.), and 68.4% (0.8 ± 0.7 MPs/ind.), respectively (p > 0.05). There was no statistically significant effect of habitat preference or diet on MP contamination (p > 0.05). The most frequently observed colours in the gills and GIT were blue and black. The most common size category identified in all samples was 0–100 µm, while the 100–200 µm category was predominantly observed only in the common carp gill samples. In addition, all particles observed were fibers, except for the common carp gill sample where 78.9% were fibers and the remaining 21.1% were fragments. The identified spectra were determined to be 50% polystyrene, 25% polyester and 25% polypropylene. This study is significant as the first microplastic research in the Gelingüllü ecosystem, contributing to limited freshwater studies. Moreover, it holds national and international importance due to its role in fish production and export.