Who are the planktonic phototrophic primary producers in Mar Piccolo of Taranto?

Mar Piccolo is a semi-enclosed basin in the Ionian Sea. It is liable to pollution since it receives a considerable amount of sewage and industrial waste. In order to comprehend the influence of anthropogenic contamination on the dynamics of phototrophic primary producers in the water column, four sampling campaigns were carried out on a seasonal basis in the period between June 2013 and April 2014. Sampling was performed in six sampling sites characterized by different levels of contamination. The abundance and biomass of planktonic phototrophs were investigated at surface and bottom depth and associated with physicochemical features of the water column in order to detect their seasonal dynamics. The lowest abundance of all planktonic photoautotrophs was detected in February 2014 whereas the dynamics among different size-classes widely varied for the rest of the study period. In June 2013 autotrophic nanoplankton reached its maximum abundance with respect to all campaigns and their distribution was generally characterized by decreasing surface-bottom gradient. In October the picophytoplankton peaked to 109 cells L-1, thus reaching their maximum abundance in the entire area and largely prevailing over the nanoplanktonic fraction, with higher abundances detected in the inner inlet. The condition encountered in April favoured the proliferation of larger phototrophs, in particular micro-sized and partly nano-sized. In that survey microphytoplankton reached abundances up to 285-folds those observed during other campaigns with higher proliferation that was found towards the inner part of the Mar Piccolo.