Plankton diversity in Anthropocene: Shipping vs. aquaculture along the eastern Adriatic coast assessed through DNA metabarcoding.

Coastal ecosystems globally are exposed to the most pervasive anthropogenic activities, caused by a suite of human infrastructure and enterprises such as shipping ports, aquaculture facilities, fishing, and tourism. These anthropogenic activities may lead to changes in ecosystem biodiversity, followed by loss of ecosystem functioning and services. Shipping industry and aquaculture have also been recognized as the main vectors for introduction of marine non-indigenous species (NIS) worldwide. In this study, we used DNA metabarcoding-based methods to investigate plankton biodiversity under varying anthropogenic pressures (shipping and bivalve aquaculture) along the eastern Adriatic coast (the northernmost part of the Mediterranean Sea). Our comparative assessment revealed similar community structures among investigated coastal locations (Northern, Central and Southern Adriatic). When the whole plankton communities were considered, they did not differ significantly between port and aquaculture sites. However, the proportion of the unique zOTUs in the port samples was remarkably higher than that in aquaculture sites (40.5% vs 8.2%), indicating that port areas may receive higher abundance and species richness of NIS than aquaculture sites. Further important difference between the two types of anthropogenically impacted habitats was a high abundance of three notorious invaders - M. leidyi, M. gigas, and H. elegans in late summer at the aquaculture site in Northern Adriatic. Therefore, the plankton community of the area is under pressure not only from aquaculture activities, but also establishment of NIS. Port areas are probably under greater introduction pressure from NIS, but aquaculture sites may experience greater community changes due to their establishment.

Competitive feeding interactions between native Ostrea edulis and non-native Crassostrea gigas with implications of introducing C. gigas into commercial aquaculture in the eastern Adriatic Sea.

In order to detect the possible regulatory effect of non-native C. gigas on the native O. edulis, under aquaculture conditions, feeding interactions between them were investigated in a highly productive environment of Lim Bay (Adriatic Sea). The present study uses a multi-methodological approach, including stomach content, DNA barcoding and stable isotope analysis to elucidate the feeding ecology of two oyster species. The research confirmed a high overlap throughout the year in the feeding traits among native and non-native oyster species. Competition for food was not the only relationship that exists between the investigated species as the presence of O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. Findings are not in favour of introducing C. gigas to commercial aquaculture in any new areas in the Adriatic Sea and support the need to improve the existing O. edulis aquaculture and conserve its wild stocks.

Comparison of amnesic, paralytic and lipophilic toxins profiles in cockle (Acanthocardia tuberculata) and smooth clam (Callista chione) from the central Adriatic Sea (Croatia).

Searching for Amnesic (ASP), Paralytic (PSP) and Lipophilic (LT) toxins in seafood is of great importance for consumer protection. Studies are usually focused on the most aquacultured species, the mussel. But, there are a number of potentially commercially important shellfish species as rough cockle Acanthocardia tuberculata (Linnaeus, 1758) and smooth clam Callista chione (Linnaeus, 1758) which are common in the Croatian Adriatic Sea. Investigation of marine biotoxins accumulation in these two species of shellfish from the Adriatic Sea has not been conducted up to now. In order to detect the potential marine biotoxin profile of A. tuberculata and C. chione wild populations, samples were taken monthly during one-year survey from the estuarine area in the central Adriatic Sea. HPLC-FLD with pre-column oxidation and HPLC-UV-DAD methods were employed for PSP and ASP toxins determination, respectively, while LTs were determined by LC-MS/MS. This research had revealed the differences in the accumulation of ASP, PSP and LT toxins between the two studied species, as Acanthocardia tuberculata showed more diverse profile with higher concentrations of analysed toxins. Both investigated shellfish species had shown levels of these biotoxins under the legal limits set by the European Commission.