In order to compare the ostracod species composition of the Zonguldak and Bartın regions of Turkey, samples were collected from 105 aquatic sites with 7 different habitats during June 2013. Thirteen and 18 species were identified from Bartın and Zonguldak, respectively. While all of the species are new reports for Bartın, 11 species are new for Zonguldak. Twenty-two species were common in both regions, with 40.9% similarities. Species abundance (49.2 individuals/site) was found to be greater in Zonguldak than in Bartın (33 individuals/site), but the number of species per sampling site was higher in Bartın (0.48 spp./site) than in Zonguldak (0.42 spp./site). Increasing the numbers of sampling sites did not increase the numbers of species. Among the habitat types, the numbers of species per site was the lowest in troughs (0.35 spp./site). Canonical correspondence analyses explained 78.3% of the correlation with relatively low variance (9.8%) between the 15 most common species and 4 environmental variables in the regions, where water temperature (F = 3.216; P = 0.002) and electrical conductivity (F = 2.525; P = 0.018) displayed strong correlation with the species. However, water temperature per se did not show a significant effect on the numbers of species (P > 0.05). Cosmopolitan species showed relatively high tolerance and optimum values to different environmental variables.

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To complete the first long-term study on freshwater ostracods and estimate their alpha and beta species diversity in a newly established Seben-Taşlıyayla Reservoir (Bolu, Turkey) along with nine different environmental variables, monthly samp les were collected from 15 stations located around the reservoir between August 2013 and September 2014. A total of 19 taxa (10 living and 9 subfossils) was reported for the first time from the reservoir. Cypridopsis vidua was the most frequently occurring species with a wide ecological ranges and seasonal distribution. Numbers of living ostracods (the alpha diversity) were found lower than the average numbers of species per lake in Turkey (13.2 spp./lake). When the alpha diversity of the reservoir (2.079) was in the medium, beta diversity (5.2) was ranged from low to medium. Results exhibited natural aquatic habitats showed relatively higher dissimilarities in species composition than small man-made habitats and the reservoir. A possible implication of finding such low numbers of species in such artificial habitats may depend on the age of the reservoir. Finding most of the cosmopolitan (and cosmoecious) species from the reservoir is the indication of ostracods primary succession. Accordingly, long-term studies are recommended to understand possible changes in species assemblages in future.