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

Tadej Dolenec^a,b, Sonja Lojen^b,*, Matej Dolenec^a, Živana Lambaša^c, Meta Dobnikar^a, Nastja Rogan^a

Absrtract
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