Coccolithophores in Water Samples and Fossil Assemblages in Sedimentary Archives of the Mediterranean Sea: A Review. In: Martorino, L., Puopolo, K.,. New Oceanography Research Developments: Marine Chemistry, Ocean Floor Analyses and Marine Phytoplankton.

Coccolithophores are unicellular planktonic algae belonging to the phylum Haptophyta, and have been one of the most important contributors to calcium carbonate production in the oceans since the Middle-Late Mesozoic. They are attracting growing attention in the light of their potentiality in evaluating the response of marine organisms' calcification to ocean acidification. We present a review of living coccolithophores in the Mediterranean Sea and of the assemblages stored in the underlying surface sediments. Thus, we provide a case history from the Sicily Channel, a key area for Mediterranean oceanographic and palaeoceanographic studies. It deals with fossil coccolithophore (calcareous nannofossil) assemblages over the last 430,000 years, whose data were collected at a centennial-scale resolution. Water samples demonstrate that coccolithophore production in the Mediterranean Sea is seasonally controlled (Knappertsbusch, 1993). In winter, the nutrient uptake is rapidly exploited by r-strategist taxa such as placolith-bearing species. In summer, the productivity is at least one order of magnitude lower and the occurrence of a seasonal thermocline leads to the development of a vertical zonation. Lower photic zone species can still profit from a rising nutrient flux at the base of the thermocline, while a typical K-strategist community grows in the surface waters of the mixed layer. Such a seasonal configuration, with the development of a summer vertical zonation, is identical to what is observed in today's oceans at low-middle latitudes.