Phytoplankton community structure changes during autumn and spring in response to environmental variables in Methana, Saronikos Gulf, Greece.

Phytoplankton community was investigated during two contrasting periods using offshore plankton samples in the volcanic area of Methana peninsula (Saronikos Gulf): the first at early autumn (warm period, September 2016) and the second one at early spring (cold period, March 2017). In order to investigate the phytoplankton community structure in the complex geo-biochemical conditions of the area, samples were collected from stations near the CO hydrothermal vents, at the hydrothermal sulfur and radioactive springs and at a fishery nearby Methana town. Three major phytoplankton groups, Bacillariophyceae, Dinophyceae, and Prymnesiophyceae, were studied, using inverted microscopy.

Coccolithophore community response along a natural CO2 gradient off Methana (SW Saronikos Gulf, Greece, NE Mediterranean).

A natural pH gradient caused by marine CO2 seeps off the Methana peninsula (Saronikos Gulf, eastern Peloponnese peninsula) was used as a natural laboratory to assess potential effects of ocean acidification on coccolithophores. Coccolithophore communities were therefore investigated in plankton samples collected during September 2011, September 2016 and March 2017. The recorded cell concentrations were up to ~50 x103 cells/l, with a high Shannon index of up to 2.