Port Baseline Biological Surveys and seaweed bioinvasions in port areas: What's the matter in the Adriatic Sea?

Abstract One of the objectives of the BALMAS project was to conduct Port Baseline Biological Surveys of native and non-indigenous benthic flora in 12 Adriatic ports. Samples of macroalgae growing on vertical artificial substrates were collected in spring and autumn 2014 and/or 2015. A total number of 248 taxa, 152 Rhodophyta, 62 Chlorophyta, and 34 Ochrophyta, were identified. Of these, 13 were non-indigenous seaweeds, mainly filamentous macroalgae, that were probably introduced through hull fouling. Some of these taxa had already been described in the study areas, others were recorded for the first time, a few were no longer detected at sites where they had previously been recorded (e.g. Sargassum muticum ). Some other NISS reported for the Adriatic Sea, were not collected at any sampling site (i.e. Caulerpa cylindracea , Codium fragile ). Possible reasons for the absence of these species are discussed.