Dams interrupt the longitudinal connectivity of rivers by impeding the movement of water, sediments and organisms, which, in turn, could affect aquatic biodiversity and food web ecology. Using stable isotope analysis, we examined spatiotemporal variation in food web structure at four sites in the upper Yeşilırmak River, Anatolia Peninsula, Turkey, in relation to environmental parameters and a dam. It was apparent that the dam created discontinuity in the longitudinal fluvial gradient of fish species richness, with more species observed at upstream sites. Fish assemblages from different sites and seasons occupied distinct areas of isotopic space. Isotopic niche space, trophic diversity, variation in δ13C of basal resources and assemblage redundancy were all higher for the fish assemblage at the site downstream from the dam compared with the site above the dam, a possible indication of greater interspecific dietary variation. Food chain length (the range in δ15N) was lower at the downstream site, possibly resulting from a greater tendency towards omnivory. The findings strongly suggest that the dam affects not only environmental conditions and fish diversity, but also trophic ecology. The results of the present study emphasise the need for research to assess potential effects of new dams in Anatolia on aquatic communities and ecosystem dynamics in rivers.

This study analyzed variation in stable isotope ratios of aquatic and terrestrial primary producers and two common cyprinid fishes (Capoeta banarescui and Squalius cephalus) at seven sites in the upper Yeşilırmak River Basin, Turkey, to estimate relative contributions of basal production sources to fish biomass. We hypothesized that seasonal and spatial variation in fish assimilation of basal production sources would be affected by hydrological variation, with results for a reach downstream from a reservoir differing from those from upstream sites. Carbon and nitrogen isotopic ratios of primary producers and S. cephalus and d 15 N of C. banarescui revealed significant spatial variation. d 13 C of primary producers, d 15 N of S. cephalus, and both d 13 C and d 15 N of C. banarescui revealed significant seasonal variation. C. banarescui biomass in the river channel was mostly derived from terrestrial herbaceous plants, and its biomass in the reservoir derived mostly from aquatic plants. Estimated proportional contributions of herbaceous plants to both species were greatest at the downstream site during spring, and declined during summer in the case C. banarescui. Overall, the influence of the dam was small relative to effects from watershed characteristics and seasonal changes in temperature and hydrology.

Collected blue-green algae (cyanobacteria) from freshwater sites throughout Tokat province and its outlying areas were isolated in laboratory environment and their morphological systematics were determined and also their species identifications were studied by molecular methods. Seven different species of blue-green algae collected from seven different sites were isolated by purifying in cultures in laboratory environment. DNA extractions were made from isolated cells and extracted DNAs were amplified by using PCR. Cyanobacteria specific primers were used to amplify 16S rRNA and phycocyanine gene regions using PCR. Phylogenetic identification of species were conducted by evaluation of obtained sequence analysis data by using computer software. According to species identification by sequence analysis, it was seen that molecular data supports morphological systematics.

Cyanobacterium samples were collected from fresh water of Tokat city in Turkey, and then isolation and cultivation of Chroococcus minutus were achieved successfully. TLC (Thin layer chromatography) and HPLC (High Performance Liquid Chromatography) analyses revealed that the C. minutus consisted of norharmane as a major product. So amount of norharmane was determined during the growth process. Growth and norharmane production of C. minutus were executed under salt stress and pH stress conditions. The most growth and the highest production of norharmane were detected at 16 th day. Therefore inoculation process was performed at 16 th day. Salt stress was evaluated at 0.5, 1.0, 3.0 and 5.0 M concentrations. The most norharmane was synthesized by C. minutus at 5 M concentration. The norharmane production and the growth were higher at pH 9 than that of the pH 5. Most norharmane was produced at pH 7.

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