Ecosystem functioning nearby the largest steelworks in Europe and the main Italian naval base: the study case of the Mar Piccolo of Taranto.

To contribute to promote ecosystem-based management in a densely populated area, the ecosystem functioning of the Mar Piccolo of Taranto was evaluated. Six sampling sites were chosen and four sampling campaigns were carried out. Structural chemical parameters were determined in water samples and sediments. The planktonic trophic web was evaluated (autotrophic and heterotrophic fractions of picoplancton, nanoplancton, microplankton and mesoplankton) together with primary production and prokaryotic secondary production. Benthic biodiversity (prokaryotes, microphytobenthos, meiofauna, macrofauna) along with primary and secondary production, benthic community respiration and exoenzymatic activities were estimated and related to contamination. Primary production rates reached 20.07 ? 3.12 µg C l-1 h-1 in June. This major photosynthetic rate was ascribable to the nanoplanktonic fraction rather than to the microplanktonic one. High photoautotrophic densities caused phosphate depletion in the water column. In surface sediments the estimated rates were almost negligible and the exoenzymatic degradative activities were quite low. Although the Mar Piccolo is very shallow, the water column is much more productive than the surface sediments where the accumulated contaminants likely interfere with the proper functioning of the benthic ecosystem.