Distribution of heterotrophic bacteria in the coastal and open middle Adriatic

Abstract

      Distribution of heterotrophic bacteria and their repro­ductive rate were studied in the coastal and open sea wa­ters of the middle Adriatic on a monthly basis from 1968 —1978. Horizontal distribution, annual and seasonal vari­ations were observed as affected by some abiotic factors: temperature, salinity and organic phosphate quantities. It was statistically established that organic phosphate quanti­ties mostly affected the distribution of heterotrophic bacte­ria. Their quantity is usually higher in the coastal area than in the open sea, predominantly for an order of mag­nitude. Annual maxima as a rule coincided in time with the ingression of the eastern Mediterranean water (in 1968 and 1976—1978). Seasonal oscillations showed summer max­imum. Generation time of heterotrophs ranged from 0.6—180 hrs in the Kaštela Bay and from 0.6—145 hrs in the open sea. In the majority of cases rate of heterotrophic bacteria reproduction was higher in the open sea where land effects are not felt and environmental conditions are considerably more stable (than in the coastal area).