Accumulation and persistance of fecal pollution in the coastal area of Rovinj

Fekalno onečišćenje važan je ekološki problem priobalnih područja koji utječe na ekosustav i ugrožava ljudsko zdravlje. Akumulacija i postojanost fekalnoga onečišćenja istraženi su u vodenom stupcu i sedimentu tri rovinjske uvale izložene različitim vrstama i količinama otpadnih voda. Razina fekalnog onečišćenja kvantificirana je pomoću bakterijskih indikatora i fekalnih sterola. Raspodjela otpadnih voda oko glavnog kanalizacijskog ispusta u uvali Cuvi ovisila je o udaljenosti od ispusta, volumenu ispuštenih voda, trenutnom strujanju i prisutnosti termokline. Bakterijski indikatori i fekalni steroli bili su značajno korelirani iako se njihov odnos mijenjao sezonski. Fekalna kontaminacija je registrirana u radiusu od 300 m oko ispusta. Sezonske promjene brojnosti heterotrofnih bakterija i produkcije bile su vrlo slične kao i na neonečišćenom području, uz blago povećanje brojnosti i brzine dijeljenja na ispustu. U uvali Valdibora izloženoj utjecaju ispusta tvornice za preradu ribe, unatoč deset puta manjem volumenu u odnosu na ispust u uvali Cuvi razine onečišćenja bile su usporedive. Brojnost heterotrofnih bakterija je bila najveća oko industrijskog ispusta, dok je brzina dijeljenja bakterijskih stanica bila izrazito niska. Granulometrijski sastav površinskih sedimenata (0-5 cm) bio je izmijenjen u odnosu na dublje sedimente (5-10 cm) u krugu od 300 m oko glavnog kanalizacijskog ispusta. U blizini ispusta koprostanol je najvećim dijelom bio vezan za frakciju vrlo sitnog pijeska. Otpadne vode iz tvornice za preradu ribe stvorile su izražene anoksične uvjete u sedimentu koji su pogodovali dijagenetskom procesu nastanka koprostanola. U sedimentima južne luke, izloženim ispuštanju sa brodova i jahti razina fekalnog onečišćenja je bila niska.Fecal contamination represents an important problem for coastal areas that affects the ecosystem and poses a threat to human health. The accumulation and persistence of fecal pollution was analyzed in the sediments and waters along the coast of Rovinj from 3 bays exposed to different types and amounts of sewage effluents. The level of sewage contamination was quantified using fecal indicator bacteria and fecal sterols. The distribution of waste waters around the main sewage outfall in Cuvi bay depended on the distance from the outfall, the volume discharged, the momentary currents and the presence of the thermocline. Fecal indicator bacteria and sterols were strongly correlated but their relation changed from season to season. Fecal contamination was detected in a radius of 300 m from the outfall. Seasonal changes of the abundance and production of heterotrophic bacteria were very similar in the contaminated and uncontaminated areas with a limited increase in the abundance and production close to the outfall. In the bay of Valdibora, influenced by a fish cannery effluent around 10 times smaller than the outfall in Cuvi bay the levels of contamination were comparable. The abundance of heterotrophic bacteria was the largest around the industrial outfall, while the specific rate of replication was very low. The grainsize composition of surface sediment (0-5cm) was altered in comparison to the less contaminated deeper sediment (5-10 cm) in a radius of 300 m around the main sewage outfall. At the sewage disposal site, coprostanol was predominantly associated with very fine sand. The fish cannery effluent, created highly anoxic conditions in the sediment that favored the diagenetic formation of coprostanol. The sediments from the southern harbor, exposed only to boat and yacht effluents displayed very low levels of fecal contamination