Research of the relationship between the ostracoda (crustacea) fauna of lake manyas and the pressure of ecological variables

Freshwater resources are extremely important for meeting the most basic needs of life. Periodic sampling plays a crucial role in diagnosing and monitoring the degree of degradation of these resources due to increasing industrial and agricultural activities. Lake Manyas (Kuş) (Bandırma, Balıkesir), which provides a valuable habitat for faunistic studies with its rich biodiversity, is one of Türkiye's most important aquatic ecosystems. Ostracods, which can be found in almost every aquatic habitat in the world, are crustaceans with high species diversity and wide tolerance levels to environmental variables. Their many species have clearly defined environmental tolerance profiles and are therefore considered reliable bioindicators. Monthly samples were collected between December 2020 and November 2021 to determine the Ostracoda species in Lake Manyas (Kuş) and the effects of ecological variables on these species. As a result of the identifications, 25 species belonging to total of 38 taxa were identified and increasing the total number of known species in the lake from 13 to 27. Among these species, Cypria ophtalmica, Darwinula stevensoni, Ilyocypris gibba, Limnocythere inopinata, Neglecandona neglecta, and Physocypria kraepelini are present in the lake year-round, while other species have been observed intermittently or only once. Regarding the relationship between species and environmental factors, according to CCA results, a direct relationship between the distribution of Heterocypris salina, Herpetocypris chevreuxi, and Neglecandona neglecta and electrical conductivity is evident, while an opposite relationship with dissolved oxygen concentration was found for Fabaeformiscandona fabaeformis, Candonopsis kingsleii, and Pseudocandona compressa. Additionally, it has been detected that electrical conductivity reaches levels of 2537 µScm−1 in Sığırcı Creek, located in the northern part of the lake where industrial and manufacturing facilities are situated. Finally, the Ostracoda Almanac Model (OAM) concept was proposed to determine the extent to which species are affected by seasonality by observing them each month throughout the year.