Winter and summer aspect of heterotrophic and coliform bacteria and some ecological characteristices of polluted seawater in the region of Rijeka in North Adriatic

Abstract

       In littoral region of bay of Rijeka in North Adriatic on 32 stations the number of heterotrophic and coliform bacteria in the end of winter and summer period are examined. Heterotrophic bacteria are cultivated on nutrient and seawater agar of respondent composition and for coliforms the most pro­bable number (MPN) in 1 liter of seawater are determined.

       For toxic activity of fenol and mineral oil on populations from superficial sealayers on 15 stations are also examined the quantity of this polluted matters.

       It is established that heterotrophic bacteria cultivated on nutrient agar better indicate the situation in polluted seawater as they cultivated on seawater agar. In the region of the strongest pollution around the cities and inhabitats it is established the highest number of bacteria that gradualy decrease towards neighbouring regions of less polluted seawater. Regular in the end of summer it was more heterotrophic bacteria than in the end of winter.

        The most probable number of coliforms in major examined stations was relative high. In seawater from harbours in the end of summer was allways amounted more than 2,400.000 in 1 liter of seawater. Only in harbour of Rijeka the number was the same as in the end of winter period. In very little stations of Croatian seaside (Hrvatsko primorje) and in eastern coast of Istria coliforms are not established. The lowest values were noted for the places of bath in Croa­tian seaside (except city of Crikvenica). In riviera of Opatija only as exception could estbalished low values.

       Only on 5 stations the quantity of fenol was under the tolerance of 10 micrograms in 1 liter of water, proposed of World health organisation. The highest quantities are measured in vicinity of biggest inhabitats, but also in places of bath in considerably quantity. That is ascribed to activity of rafineries in Rijeka and Kostrena. In bay of Bakar are measured a slight quantity of fenol, where are also measured the lowest quantity of mineral oils. In the other regions the quantity of mineral oils are considerable higher and regular amount about 1 to 5 mg/l.

       It is also pointed aut that polluted matters can be suitable for growth of bacteria and toxic matters, as fenol and mineral oils, in many places of exami­ned region are present in quantity destructive for bacteria.