Coccolithophore export production from Eastern Mediterranean and Black Sea sites: biogeographic trends and biogenic carbonate fluxes

Α sediment trap mooring has been deployed for one year (10/2007- 9/2008) at 1000 m water depth, in western Black Sea. The maximum coccosphere fluxes, with almost monospecific assemblage of Emiliania huxleyi, have been recorded during May and June. The seasonally controlled coccolithophore patterns are strongly related to those of sea surface temperature and accumulated rainfall in the area, triggering riverine nutrient input. Coccosphere fluxes in North Aegean Sea have been calculated from a sediment trap deployment at 500 m (1/2011-12/2011). E. huxleyi is the dominant species, followed by Syracosphaera pulchra, Rhabdosphaera clavigera as minor assemblage components. Maximum fluxes have been observed in between May-June. A single mooring with two sediment traps (500 and 1700 m) was deployed at the southern margin of the Cretan Sea (1/2001-2/2002) [1]. The results obtained from 500 m depth show that the highest productivity season was recorded from January till late September with the highest flux values observed between late March to late June. During this period the pattern was characterized by three main phases that correlate well with the gradual increase in SST from January till September. Coccosphere sinking assemblages were characterized by high abundances of E. huxleyi, followed by Florisphaera profunda, R. clavigera and Syracosphaera spp. Six moorings have been deployed at different sites along the south–west margin of Crete, providing a total of eight sediment-trap time series (6/2005- 5/2006) [2]. Maximum coccosphere fluxes were recorded in between March to June, featured by dominance of E. huxleyi and subordinate Helicosphaera carteri, Umbilicosphaera spp. and S. pulchra; intermediate fluxes from June to November, with high abundance of the deep photic zone species Algirosphaera robusta, F. profunda, Gladiolithus flabellatus; and low fluxes from November to February, with high flux of A. robusta, S. pulchra and Syracosphaera spp. These three periods correspond to the seasonal changes in sea surface temperature and surface mixed layer depth. Coccolithophore fluxes from the central part of the Ionian Sea have been studied from a sediment trap mooring (9/1999-6/2001) at 500 and 2800 m water depth [3]. Peak coccolithophore export production is observed in May, a secondary peak is observed in September-October. The assemblages is dominated year-round by the cosmopolitan species E. huxleyi, followed by the deep-dwelling F. profunda and by several minor species (Syracosphaera pulchra, R. clavigera, A. robusta, G. flabellatus, Calcidiscus leptoporus, Umbellosphaera tenuis and small Syracosphaera spp.) which are most abundant during the summer period of upper water column stratification. A high seasonal pattern characterizes the coccolithophore assemblages from all the investigated areas of eastern Mediterranean and Black seas. The export production and biogenic carbonate fluxes are strongly dependent on the nutrient influx, the vertical mixing and sea surface temperatures of the water column, in a north-south and east-west transient.