Primary production and seasonal succession of different photoautotrophs (pico-, nano and microplankton) in the Mar Piccolo of Taranto

In order to detect their seasonal dynamics, the abundance of planktonic phototrophs was investigated and associated with physical-chemical features of the water column and primary production. The lowest abundance of all planktonic photoautotrophs was detected in February 2014. In April 2014 the proliferation of the largest, micro-sized fraction, was observed. In June 2013, primary production (PP) rates were high, up to 10.14 +- 1.45 µg C l-1 h-1 in the first inlet and 20.07 +- 3.12 µg C l-1 h-1 in the centre of the second inlet. This major photosynthetic rate was likely ascribable to the nanoplanktonic fraction that reached its maximum abundance over the study period. In October the picophytoplankton peaked to 109 cells L-1, with higher abundances detected in the inner inlet. High densities of all photoautotrophic organisms caused phosphate depletion, especially in June 2013. Our results indicate a clear seasonal succession of plankton phototrophs in the very productive system of the Mar Piccolo.