15N and 13C enrichment in Balanus perforatus:  tracers of municipal particulate waste in the Murter Sea (Central Adriatic, Croatia)

Tadej Doleneca,b, Sonja Lojenb,*, Matej Doleneca, Živana Lambašac, Meta Dobnikara, Nastja Rogana

a Department of Geology, Faculty of Natural Sciences and Engineering, 1000 Ljubljana, Slovenia,
b Department of Environmental Sciences, Jožef Stefan Institute, 1000 Ljubljana, Slovenia, sonja.lojen@ijs.si
c Šibenik-Knin County, 22000 Šibenik, Croatia

Stable isotopic compositions of nitrogen and carbon in barnacles Balanus perforatus from the Pirovac Bay (Central Adriatic), highly impacted by untreated municipal waste, and from unaffected sites from the southern part of the Kornati Islands were compared. The differences in δ13C and δ15N values observed in organisms from both areas suggest that this benthic invertebrate could be a potential biomonitor for sewage-derived nutrients in coastal seas. Both nitrogen and carbon were enriched in heavy isotopes in organisms collected in Pirovac Bay, as well as in those from the area around the fish farm at Vrgada Island. These point toward an increased input of 15N and 13C enriched anthropogenic and/or aquaculture derived nitrogen and carbon into the local marine ecosystem. It is suggested that benthic filter feeders, such as B. perforatus, could be useful sentinels for detecting anthropogenically-derived inputs of nutrients into the coastal marine ecosystems. However, to get a better insight into the transfer rates of anthropogenic C and N into the food web, more extended research on a larger population is needed, as well as a detailed investigation of seasonal variation of abundance and isotopic composition of particulate organic matter as their presumed food source. 

Keywords: Balanus perforatus; particulate organic matter; nitrogen, carbon; stable isotopes; sewage; aquaculture