BACTERIA-PHYTOPLANKTON INTERACTIONS IN A COASTAL MEDITERRANEAN AREA AFFECTED BY HARMFUL ALGAL BLOOMS

In order to understand bacteria-phytoplankton interactions in harbor environments, trophic conditions (nutrient, chlorophyll, organic matter), microbial enzyme activities and phytoplankton and bacterial abundances were studied seasonally from September 2018 to August 2019 in the Syracuse Gulf (Ionian Sea), a Mediterranean area often experiencing Harmful Algal Blooms. During spring, dinoflagellate bloom was coupled with high microbial activity rates that recycled nutrients to sustain phytoplankton growth; conversely, in the other seasonal periods, phytoplankton and bacterial abundances were uncoupled. This suggested that bacterial-phytoplankton interactions modulated differently microbial metabolism in terms of enzyme production depending on the variable trophic conditions (bloom or not-bloom periods).