Ecological requirements of freshwater Ostracoda (Crustacea) in two limnocrene springs (Bolu, Turkey)

Abstract

Ecological requirements of ostracods in two limnocrene springs (Usta and Çetin Bey) were investigated between January 2000 and July 2002 in Bolu, Turkey. Ten taxa (Candona neglecta, Darwinula stevensoni, Eucypris virens, Eucypris sp., Heterocypris incongruens, Herpetocypris sp., Ilyocypris bradyi, Potamocypris sp., Scottia pseudobrowniana, Tonnacypris lutaria) were found. Canonical correspondence analysis (CCA) showed that species with wide cosmopolitan distribution could tolerate high levels of changes in environmental variables. CCA explained about 80 % and 77 % of the relationships between species and environmental variables in Usta and Çetin Bey springs, respectively. Electrical conductivity and dissolved oxygen were the two most influential factors on species occurrence in each spring. According to Spearman correlation analysis, there were no significant relationships between the numbers of species and environmental variables in both springs. When dissolved oxygen showed significant negative correlations to electrical conductivity, water and air temperature in Usta spring, such correlation was only negatively significant (P < 0.05, r = -0.46) between electrical conductivity and dissolved oxygen in Çetin Bey spring. Clustering analysis (UPGMA) of presence/absence data divided species into four main groups. Results may suggest that anthropogenic activities were responsible for decreasing water quality of these springs and reducing species richness. Although increasing incentives for conservation of natural springs were proposed, Çetin Bey spring and especially Usta spring are now highly degraded.