Pollution Indicators and HAB-Associated Halophilic Bacteria Alongside Harmful Cyanobacteria in the Largest Mussel Cultivation Area in Greece

Taking into consideration the essential contribution of <i>Mytilus galloprovincialis</i> farming, it is of rising importance to add knowledge regarding bacterial species occurrence in water samples from aquaculture zones from the point of view of both the organism and public health. In the present study, we investigated the bacterial community existing in water samples from six <i>Mytilus galloprovincialis</i> aquaculture areas in the Thermaikos gulf, northern Greece, that may provoke toxicity in aquatic organisms and humans and may indicate environmental pollution in mussel production as well as algal blooms. Bacterial species were identified molecularly by sequencing of a partial 16s rRNA segment and were analyzed phylogenetically for the confirmation of the bacterial taxonomy. The results obtained revealed the presence of four bacterial genera (<i>Halomonas</i> sp., <i>Planococcus</i> sp., <i>Sulfitobacter</i> sp., and <i>Synechocystis</i> sp.). Members of the <i>Halomonas</i> and <i>Sulfitobacter</i> genera have been isolated from highly polluted sites, <i>Planococcus</i> bacteria have been identified in samples derived directly from plastic debris, and <i>Synechocystis</i> bacteria are in line with microcystin detection. In this context, the monitoring of the bacteria community in mussel aquaculture water samples from the Thermaikos gulf, the largest mussel cultivation area in Greece, represents an indicator of water pollution, microplastics presence, algal blooms, and toxin presence.