Spatio-temporal variations in the concentration of microbiological indicators of bathing water quality at three beaches in Kaštela bay

Onečišćenje mora ima štetne učinke na zdravlje ljudi, ekosustav i okoliš. Indikatorski mikroorganizmi poput bakterija Escherichia coli i crijevnih enterokoka služe kao "upozoravajuće svijetlo" koje ukazuje na onečišćenje fekalnog podrijetla te mogući rizik za zdravlje kupača. U ovom istraživanju određivana je kakvoća morske vode za kupanje na trima plažama u Kaštelanskom zaljevu: Gojača, Kamp i Torac. Mjerenja su provedena 3 puta dnevno (ujutro, prijepodne i poslijepodne) tijekom 7 dana u sezoni kupanja 2022. godine. Rezultati su pokazali prostorne i vremenske varijacije indikatora fekalnog onečišćenja. Osim problema uzrokovanog stanjem kanalizacijskog sustava na ovom području, razine indikatorskih mikroorganizama na identificiranim izvorima fekalnog onečišćenja u blizini ovih plaža ukazuju na značajno opterećenje fekalnim materijalom. Zbog raznih fizikalnih utjecaja poput Sunčevog zračenja, crijevni enterokoki su se pokazali kao bolji indikator kvalitete mora neovisno o vremenu uzorkovanja, dok je E. coli bila bolji pokazatelj tijekom istraživanja rano ujutro. Kada se sagleda godišnja ocjena, plaža Gojača imala je nezadovoljavajuću ocjenu, dok su plaže Kamp i Torac imale izvrsne ocjene, ali rezultati uzakuju na povremena kratkotrajna onečišćenja. To znači da su potrebni dodatni napori kako bi se locirali i uklonili izvori fekalnog onečišćenja na ovom području te donijele ispravne mjere za zaštitu zdravlja ljudi i očuvanje okoliša.Pollution of coastal marine environment has harmful effects on human health and the ecosystem. Indicator microorganisms such as Escherichia coli and intestinal enterococci serve as "warning signals" of potential marine pollution, especially of fecal origin and a possible risk bathers’ health. In this study, the quality of seawater for bathing was determined at three beaches in Kaštela Bay: Gojača, Kamp and Torac. Measurements were performed 3 times a day (morning, before noon, and afternoon) on 7 days during the bathing season in 2022. The results showed spatial and temporal variations. In addition to the problems with the sewage system in the area, the levels of indicator microorganisms at the identified sources of fecal pollution near these beaches indicate a significant load of fecal material. Due to various physical influences such as solar radiation, intestinal enterococci proved to be a better indicator of seawater quality for samples collected during the day, while E. coli samples were the most reliable indicator for early morning measurements. In the annual assessment, Gojača obtained unsatisfactory results, while Kamp and Torac obtained excellent ratings, but some measurements indicated short-term pollution. This means that additional efforts are needed to locate and eliminate sources of fecal pollution in the area and to implement appropriate measures to protect human health and preserve the environment