Fouling assemblages from two Maltese ports studied as part of the portal project

Abstract

Within the context PORTAL project, which was initiated by CIESM in 2003, a wharf in the Grand Harbour, and a fuel jetty and buoy in Marsaxlokk Harbour were sampled to collect baseline data on alien species. 86 species belonging to 7 targeted taxa were collected, with Crustacea being the dominant taxon in terms of both species richness and individual abundance. The highest species richness and evenness values were recorded at 3 m at both sites. Multivariate analyses and SIMPER showed that the degree of separation of fouling assemblages between the two sites was minimal. The fouling assemblages investigated are broadly similar to those occurring in Italian waters. The only alien species found in the samples was a single juvenile of the grapsid Percnon gibbesi. Introduction PORTAL is a research programme of the International Commission for the Scientific Exploration of the Mediterranean Sea (CIESM) that aims at implementing a Mediterranean-wide port and port-proximate survey using standardized protocols to collect baseline data on alien species, particu-larly those which might be introduced by shipping. The Valletta harbours (Marsamxett Harbour and Grand Harbour) and Marsaxlokk Bay are the major harbours of the Maltese Islands. Information on fouling assem-blages within the Maltese harbours and harbour-like environments is very scarce. Practically, the only work carried out has been a preliminary study of fouling organisms in oyster cultures in three Maltese bays, including at Rinella within the Grand Harbour [1]. Methods Pinto Wharf in Grand Harbour, a fuel jetty and a buoy at Birzebbuga in Marsaxlokk Bay were sampled using the PORTAL standard methodology. Fouling biota was collected from three replicate 0.1 m 2 quadrats at each of three depths (0.5 m, 3 m, 7 m), on the vertical wall of the wharf or jetty at three different stations, while on the buoy three replicates were sampled at 0.5 m.