Relationships of the Cyprideis torosa (Ostracoda, Crustacea) with Seasonal Occurrences, Carapace Type and Physicochemical Variables in Kocaçay Delta (Turkey)

To understand spatial and temporal continuing occurrence patterns and relationships of Cyprideis torosa to several physicochemical variables, monthly samples from seven stations were collected from Kocaçay Delta (Bursa, Turkey) between 2018 and 2019. Four (C. torosa, Koencypris ornata, Candona lindneri, Candona meerfeldiana) of 14 ostracod taxa are new records for the ostracod fauna of Bursa province where total numbers of recent species increased to 33. Cyprideis torosa was the only dominant species found in almost all samples throughout the sampling. Based on carapace type of the species, three groups can be divided as i) Type-1 (smooth carapaces), ii) Type-2 (noded carapaces), and iii) Type-3 (carapaces noded on one valve and smooth on the other). Different occurrence patterns of the species with overlapping ecological ranges were observed among the stations. Except for station 1, all the types were encountered from other stations. Beginning from December 2018, nearly all populations had mostly Type-1 individuals until the end of March. During April-May, individuals with Types-2 and 3 appear to increase until the end of October while individuals in Type-2 group were solely found from three stations (2, 3 and 5) in March and May 2018. There was a significant difference in salinity, magnesium, and calcium values among the stations (P < 0.05) but only total nitrogen, temperature and calcium showed a medium correlation to carapace type. In all cases, populations with noded individuals were found in narrower ecological ranges for those variables than other populations with smooth individuals.