The long-term changes in plankton composition: Is Bay Sivash transforming back into one of the world's largest habitats of Artemia sp. (Crustacea, Anostraca)?

摘要

Bay Sivash was a hypersaline lagoon but after construction of the North Crimean canal, it shifted to a brackish water state. In 2014, the canal was closed; a salinity increase started. In 2018 and 2019, plankton sampling was conducted in the bay at salinity from 30 to 100 g/L. A decrease in taxonomic diversity and total abundance was observed. Before November of 2018, Harpacticoida and chironomid larvae were the most common and abundant groups. Different stages of Artemia were consumed by invertebrate predators and fish at that time. In November 2018, Artemia stages contributed more than 90% to total zooplankton abundance at all sites excepting with salinity lower than 55 g/L. In June-July 2019, adult Artemia were at all sites with salinity higher than 82 g/L when there was no suppression by predators. A self-sustaining Artemia population in the bay may recover in 2 or 3 years, when the average salinity would reach 80-90 g/L; total abundance of the active Artemia stages may reach 3000-5000 ind. M-3 between April and August. The lagoon may become one of the world main habitats of Artemia having a significant impact to provide world's supply by its cysts.