Ostracods response to environmental anthropogenic disruption in a neotropical karstic lake in southern Mexico

Ostracods are sensitive to environmental changes and represent a powerful tool to assess anthropogenic impact such as land use changes and deforestation. In this work we present ostracod, ephippia, diatom and geochemical data of Lake San Lorenzo sediments dating from 1956 to 2013. The ostracod assemblage consists of Darwinula stevensoni, Cypridopsis okeechobei, Cytheridella ilosvayi and an unidentified species. This Unknown species rapidly adapted to the new environmental conditions of enhanced nutrients levels and variable oxygen, whereas the other ostracods were absent in the sediments dating from around 1982 to 1992. Overall, D. stevensoni, C. okeechobei and C. ilosvayi are benthic species that occur in shallow waters or littoral zones with rich vegetation. However, we suggest C. ilosvayi was the most sensitive to oxygen variations as it is only present in sediments dating to ∼1978. The lack of ostracod preservation in the sedimentary record, especially during ∼1995–2013 could be result of anoxic lake bottom conditions caused by high organic matter content during periods of anthropogenic catchment disturbance. Finally, we suggest that analysis and description of live specimens with soft parts of the Unknown species are strongly necessary to determine this species and its environmental preferences. •Ostracods reflect high sensibility to dissolved oxygen variations in Lake San Lorenzo.