The calanoid copepod Acartia italica Steuer, phenomenon in the small saline Lake Rogoznica (Eastern Adriatic coast)

Lake Rogoznica, near ibenik, Croatia, is a salt coastal lakewith a maximum depth of about 15 m. During most of the year,this small, naturally eutrophied lake is highly stratified,with hypoxia/anoxia occurring in the bottom layer. Total anoxia,with the presence of hydrogen sulphide, was recorded on September27, 1997. At that moment, massive mortality of all planktonicand benthic organisms was observed. After the anoxia, Acartiaitalica, the only planktonic copepod species of the lake, re-establishedquickly. Before anoxia, the population dynamics of the A.italicapopulation depended primarily on predator/prey relationships.However, in the post-anoxic period, nutrient–phytoplankton–copepodrelationships became more important, as there was no longerany predation pressure. From all accounts, it would appear thatonly A.italica is adapted to the extreme conditions which appearfrom time to time in the lake, and that this species has animportant role in the functioning of the lake ecosystem. Acartiaitalica was very important for the gradual normalization oflife in the lake after total anoxia.