Abstract
This research was conducted between March 2016 and March 2017 as the first study on the water and mussel quality in the coastal area of Dubrovnik (Croatia). Bacteriological analyses were conducted simultaneously on wild mussels (Mytilus galloprovincialis) tissue and their ambient water. The total numbers of heterotrophic bacteria, total coliforms, faecal coliforms and faecal streptococci in the water were determined. Concentrations of Escherichia coli were measured in mussel. The investigated stations are located in coastal water, which is particularly influenced by climatic and anthropogenic factors interacting at the boundaries between the land and freshwater and seawater environments. Seasonal variables, such as rainfall and riverine network characteristics, determine the delivery of bacteria (including E.coli) to coastal water. Direct methods of assessing the density of heterotrophic bacteria at all sampling stations showed the characteristics of an oligotrophic area. The abundance of faecal coliform bacteria was in all cases higher within mussel tissue than in the surrounding water where levels were sometimes undetectable. Maximum E. coli concentrations in mussels and seawater were regularly recorded through the summer, with the exceptions of April 2016 and January 2017 at two stations following precipitation. Minimum faecal coliform concentrations were recorded in the winter.
Highlights
To investigate the ecology of coastal waters six microbiological parameters were used: the total number of heterotrophic bacteria, cultivated heterotrophic bacteria, total coliforms, faecal coliforms, faecal streptococci and concentrations of Escherichia coli measured in Mytilus galloprovincialis tissue
The significant correlation (p
Broj heterotrofnih bakterija u uzorcima morske vode: a) ukupni broj metodom epifluorescentne mikroskopije, b) broj kolonija metodom širenja razmaza heterotrophic bacteria obtained by direct method were within values of mL-1 (0.137-0.323 x mL-1), fairly low for coastal waters, which characterized it as oligotrophic (Figure 14 a) [19]
Summary
This research was conducted between March 2016 and March 2017 as the first study on the water and mussel quality in the coastal area of Dubrovnik (Croatia). Faecal indicator bacteria are a potential hazard to the health of swimmers and other consumers This is the first study conducted on the seawater and mussel quality of the Dubrovnik coastal area. To investigate the ecology of coastal waters six microbiological parameters were used: the total number of heterotrophic bacteria, cultivated heterotrophic bacteria, total coliforms, faecal coliforms, faecal streptococci and concentrations of Escherichia coli measured in Mytilus galloprovincialis tissue. This study was conducted in the highly stratified Ombla Estuary, near the city of Dubrovnik It is in a zone of karst source waters and is in contact with Adriatic seawater, combined with an increasing anthropogenic influence during the summer tourist season.
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