Phytoplankton carried by ballast water is a threat in coastal areas receiving commercial ships. In Barcelona Bay, there is traffic of ships transporting hydrocarbons, and it is important to monitor the phytoplankton in ballast water. In this sense, the oil port José Antonio Anzoátegui represents an increase in the risk of introducing invasive species through ballast water, with the potentially dangerous risk for the biological balance of the different local ecosystems. In the present study, ballast water from 33 tankers that arrived at the port between January and May 2023 was monitored. Measurements of temperature and salinity parameters were taken in both the water in the tanks and the surface water of the bay. Samples were collected with bottles (125 ml) for microscopic examination using the Utermohl method. Sixty-one species of phytoplanktonic organisms were identified, distributed in 8 cyanobacteria, 5 chlorophyta, 39 diatoms, 6 dinoflagellates, 2 coccolithophorids and 1 silicoflagellate. Diatoms were the most representative group (54%), followed by cyanobacteria (38%). The predominant genera were Trichodesmium, Navicula, Nitzschia, Synedra and Gymnodinium. The samples did not show excessive phytoplankton abundance and no potentially toxic species were detected. This research constitutes the beginning of a baseline for a possible temporal monitoring of species that are regularly transported on tankers in that port.
