Strong biopollution in the southern Caspian Sea: the comb jelly Mnemiopsis leidyi case study.
The invasive ctenophore Mnemiopsis leidyi was first recorded in the Caspian Sea in 1995 in the southern part of the sea (Iranian waters). This study assesses the magnitude of the M. leidyi bioinvasion impacts on the region's ecosystem using the biopollution level (BPL) index. For this purpose, biomass and distribution range of the invasive ctenophore were analyzed for the period 1996-2010. In addition, the impacts of the IAS on native species, communities, habitats and ecosystem functioning were assessed. The BPL for the period of our study remained relatively stable at the level 4 (massive). The BPLs caused by M. Leidyi in the southern Caspian Sea were compared with those of the Black and Baltic Seas. The method used in this study seems to be applicable for evaluating spatial and temporal variations of the invasive impacts of gelatinous zooplankton in other marine regions.