Plankton community of trafficked ports as a baseline reference for non indigenous species arrivals. Case study of the Port of Bar (South Adriatic Sea)

Abstract

Plankton (ichthyoplankton, zooplankton and phytoplankton) communities were studied in the temperate, shallow waters of the Port of Bar, one of the main cargo ports on the south-eastern Adriatic coast. Sampling was undertaken in February, April, June and October of 2015 at 12 stations using the BALMAS Port Baseline Survey protocol. The research was conducted to determine the presence of invasive and potentially toxic plankton species in the port as a result of the discharge of ballast water by ships. The most dominant species of ichthyoplankton were the eggs and larvae of the families Engraulidae, Bothidae and Sparidae, with a dominance of Engraulis encrasicolus, Arnoglossus laterna and Diplodus annularis. In addition to ichthyoplankton, sampling of phytoplankton and zooplankton was performed to assess the abundance and diversity of the species. The most numerous zooplankton species throughout the investigated period were Penilia avirostris, Euterpina acutifrons, Oithona nana, Acartia clausi, Centropages kroyeri, Paracalanus parvus, Oncaeidae and the larvae of Bivalvia. One very unusual occurrence was the spawning of parrotfish, Sparisoma cretense (Linnaeus, 1758), a species with Atlantic origins and tropical affinities, whose presence throughout the Mediterranean has shown an increasing trend over the last decade. The most dominant species of phytoplankton were the diatoms Chaetoceros affinis and Chaetoceros spp., Asterionellopsis glacialis, Pseudo-nitzschia spp., Thalassionema nitzschioides, and the dinoflagellates Gymnodinium spp. and Prorocentrum triestinum. Potentially toxic species from the genus Pseudo-nitzschia reached an abundance of 104 cells L-1. The toxic dinoflagellates Prorocentrum cordatum and P. micans reached values of 103 cells L-1. Although there were no HAOP species found during the survey, the presence of several potentially toxic and toxic phytoplankton species, whose impact is not sufficiently known, indicates the necessity of introducing regular monitoring activities and defining preventive protection measures.