Kemal Çelik

Seasonal Dynamics of Phytoplankton Assemblages across Nutrient Gradients in Shallow Hypertrophic Lake Manyas, Turkey

Abstract Species composition, abundance and size distribution (the average measure of the longest cell dimension and surface area to volume ratio) of phytoplankton in the shallow hypertrophic Lake Manyas, Turkey were studied between January 2003 and December 2004. A total of 165 species were recorded during the study. Diatoms and Cyanobacteria were the dominant taxa at most stations. Nitrate and phosphate values showed a decreasing gradient with the distance from Sigirci Inlet to Karadere Outlet. Bacillariophyta dominated the phytoplankton in spring, while Cyanobacteria prevailed in summer. Each summer, a peak of Euglenophyta was also observed at Sigirci Inlet. Nutrient gradients seemed to have a greater control over overall density than of species composition. The size distribution of the Cyanobacteria showed positive correlations with nutrient levels, while green algae and diatoms did not. There was a negative correlation between the average cell dimension of the phytoplankton cells and the surface area to volume ratio in general. The objective of this study was to determine the seasonal dynamics of species composition, abundance and size distribution of phytoplankton assemblages across nutrient gradients along a distance in the shallow hypertrophic Lake Manyas, Turkey.

Seasonal variations in the length of zooplankton related to certain physicochemical variables in two freshwater reservoirs

Seasonal variations in the body length of zooplankton were studied in relation to water temperature, nitrate (NO3), soluble reactive phosphorus (SRP), total chlorophyll, Secchi disk depth, pH, conductivity, and oxidation-reduction potential (ORP) in a mesotrophic (Ikizcetepeler) and a eutrophic (Caygoren) reservoir from February 2007 to March 2008. During the study, the body lengths of a total of 7590 zooplankton specimens (1110 rotifers, 3270 cladocerans, and 3210 copepods) were measured. The length of the majority of the species was significantly smaller in summer than in winter, fall, and spring, including that of the most dominant species, Asplanchna priodonta, Daphnia galeata, Daphnia longispina, Diaphanosoma brachyurum, Bosmina longirostris, Leptodora kindtii, Ceriodaphnia pulchella, Cyclops vicinus, Metacyclops gracilis, and Acanthocyclops robustus (F > 5, p < 0 . 05 ). Correspondence analysis (CA) showed that the body length of the zooplankton studied was inversely related to water temperature, whereas it was positively related to ORP and pH. The results of our study suggest that, although nutrients (NO3 and SRP) apparently have an effect on zooplankton body length only in the mesotrophic reservoir, temperature influences the body length in both the mesotrophic and the eutrophic reservoir.

The Vertical and Seasonal Distribution of Chlorophyll and Main Nutrients in a Mesotrophic Freshwater Reservoir

The mesotrophic Ikizcetepeler Reservoir was sampled monthly from February 2007 to June 2008 at three stations. Thermal stratification occurred in the reservoir from May to September. The results revealed high bands of chlorophyll in the epilimnion and metalimnion of the reservoir during summer and winter. Results suggest that high chlorophyll accumulation was a result of the increase in available light levels in spring and deep mixing, providing phytoplankton with the nutrients needed for grow in summer. Correlation analyses were used to determine the relationships between chlorophyll (μg/L), water temperature (C), total nitrogen (mg/L), total phosphorus (mg/L) and Secchi disk depth (m). Differences in chlorophyll, total phosphorus, total nitrogen and in Secchi disk transparency were not significant among sampling stations (p>0.01), but they were significant among seasons (p<0.01). Successful control of eutrophication requires an understanding of how nutrients, physical conditions and biological processes interact to affect algal growth and since the utility of chlorophyll in estimating algal biomass world-wide, this study was conducted to determine how variations in water temperature, total nitrogen, total phosphorus and water transparency affected the the vertical and seasonal distribution of chlorophyll in Ikizcetepeler Reservoir. KeywordsIkizcetepeler Reservoir; phytoplankton biomass; total nitrogen; total phosphorus; water transparency