Plankton biodiversity in surface sediments of Siracuse Bay (Western Ionian Sea, Mediterranean).

The occurrence and abundance of plankton resting stages were investigated for the first time at a Ionian locality along the south-eastern coast of Sicily, subject to spring-summer harmful algal events. Forty one different cyst morphotypes were recognized, 83% of them produced by dinoflagellates. Total densities of living cysts ranged from 43 to 857 cysts g-1 of dry weight sediment, with the highest numbers registered at the most confined station. The cyst occurrence in Syracuse sediments confirmed the overall importance of benthic-pelagic coupling in the dynamics of planktonic blooms and highlighted, for the first time in the study site, the role of benthic resting stages for the initiation of dinoflagellate blooms in this area, highly susceptible to harmful algal events, including blooms of species producing PST (Paralyzing Shellfish Toxins) and shellfish contamination.