Distribution and relationships of non-marine ostracods (Crustacea, Ostracoda) with water quality variables in Amasya province (Türkiye)

We assessed the relationships between non-marine ostracods and water quality by collecting samples from 80 randomly selected sites between 18–22 May 2022 in the Amasya province. A total of 28 taxa (18 recent) were recorded from 59 sites, and 25 of them were new for the Amasya province. The most common species were Ilyocypris bradyi, Heterocypris incongruens, and Prionocypris zenkeri. Only 5% of the sampled sites had poor and unsuitable water status. We found ostracods in a range of water conditions, from excellent to unsuitable. Heterocypris salina, along with the most common species, was found in site 41 with unsuitable waters. The Shannon diversity index and abundance of ostracods showed non-linear relationships with the water quality index value (WQI). Although P. zenkeri did not display a linear relationship with WQI, it tended to occur in waters with increasing WQI values, indicating lower water quality. Water temperature and pH were found to be the most influential variables on species distribution, while the number of species indicated positive and negative relationships with chloride and sulphate, respectively. The functional richness values indicated that species in dams had developed swimming setae on the second antennae, while species in streams had reduced setae. The functional evenness values exposed that the functional distance between species in dams and troughs was more regular compared to streams. These results suggest that functional diversity indices can be used to evaluate the function and indicator potential of ostracod species in aquatic systems.