Abstract
To investigate the relationship between ostracod occurrence patterns, community assemblage, and abiotic factors, we sampled five sites on lake Karamurat (Bolu, Turkey) and two nearby rheocrene springs. Thirteen ostracod taxa (10 from the lake, three from the springs) were collected. Species exhibited clear habitat preferences, and lake and spring ostracods showed clear differences in their monthly and seasonal occurrences. Darwinula stevensoni and Cypria ophtalmica were the dominant species for the lake and Psychrodromus cf. fontinalis and P. olivaceus were only reported from the springs. Ostracod Watch Model illustrated that a rare species, Notodromas monacha, was only found in May to August from the lake while two species (D. stevensoni, C. ophtalmica) were encountered from all year around. Common species also exhibited relatively high levels of ecological tolerances to multiple environmental variables. Canonical correspondence analyses explained about 91% of correlation between species and environmental variables and indicated that four variables (water temperature, dissolved oxygen, pH and electrical conductivity) most strongly influenced species occurrences. Also, binary data of sample medians showed significant (P < 0.01) differences between ostracod assemblages from 13 lakes and reservoirs compared to Lake Karamurat. A significant correlation was detected between Lake Karamurat and two other lakes (Abant and Yeniçağa) located in the same region. The Pseudorichness Ratio (noncosmopolitan/cosmopolitan species) of the lake was very low (Pr = 0.25), indicating dominancy of cosmopolitan species over noncosmopolitans. Conservation efforts should be considered to addressed increasing anthropogenic impacts to Lake Karamurat.