Σωματιδιακή και διαλυτή πρωτογενή παραγωγή κατά μήκος μιας υδρογραφικής και τροφικής διαβάθμισης (Σύστημα Τουρκικών Στενών – Β.Α. Αιγαίο)

The rates of particulate (PPp) and dissolved (PPd) primary production were estimated along a trajectory of variable environmental regimes, following the course of Black Sea waters passing through the Turkish Straits System (TSS) into the Aegean Sea (BS-AS outflow). Seven stations in total were sampled, covering a transect from the eastern edge of the Marmara Sea to the NE Aegean Sea, during two consecutive cruises performed in October 2008, within the framework of the EU SESAME project. Along the BS-AS outflow of the surface-layer water masses, integrated (0-30 m) PPp decreased considerably from 91 to <16 mg C m^-2 h^-1 whereas PPd increased from 3 to 10 mg C m^-2 h^-1. As a consequence, the relative importance of PPd over total production (percentage extracellular release, PER) increased from 6% (±3% sd) in the Marmara Sea to 37% (±4% sd) in the Aegean Sea. Total chlorophyll a concentration gradually decreased and phytoplankton community size-structure was modified, with pico-phytoplankton chlorophyll a contribution from a moderate level in the Marmara Sea (35 ± 9%) gradually becoming dominant in the NE Aegean (77 ± 2 %), substituting large nano- (>5 μm) and micro-phytoplankton cells. The study showed that PER increased under oligotrophic conditions, probably due to nutrient limitations, and that it was closely linked to phytoplankton size-structure.