An annotated checklist of dinoflagellates in the Black Sea

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Courtesy of Planktonlab

The Black Sea (∼41–46◦ N) is a semi-enclosed basin whose only connection to the world’s oceans is through narrow straits (<110 m depth), the Dardanelles and the Bosphorus, both opening to the Marmara Sea. The fresher waters of the Black Sea (salinity ∼17) flow to the Mediterranean Sea by means of an upper layer flow; saltier Mediterraneanwaters (∼38.5) flow to the Black Sea in a lower current. A permanent halocline is maintained by colder low-salinity surface water averaging 17.5–19 overlying deep waters with salinity about 22. Low near-surface salinity is maintained by the influx of freshwater from rivers and decreases to <13 near the mouths of the Danube and Dnieper rivers (see references in Sorokin, 2002).  In the last decades the Black Sea basin has experienced huge changes in water quality caused by human interventions both on the hydraulic regime of the rivers and on the nutrient and pollutant discharge.  Significant changes on phytoplankton, zooplankton, zoobenthos and fisheries have been reported (Bakan & Buyukgungor, 2000). The high nitrate and phosphate to silicate ratios as well as organic material provide competitive advantage for mixo- or heterotrophic dinoflagellates compared to autotrophic diatoms, with high dinoflagellates to diatoms ratio (Humborg et al., 1997). A change in dominant species was observed as well as an increase in red tide events (Bologa et al., 1995; Mihnea, 1997). The high degree of eutrophication in the Black Sea could favour invasive species (i.e., via ballast waters; Moncheva & Kamburska, 2002) to compete for niches. Among phytoplankton taxa, dinoflagellates with more than 200 potential toxic species (Sournia, 1995) require special attention.

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