Primary organic production, distribution and reproduction of the bacteria in the middle Adriatic euphotic zone

Abstract

       In this work are given the data about the primary organic production and distribution, and the bacteria reproduction in the region of the middle and north Adriatic, at the stations »Kaštelanski zaljev«, »Pelegrin«, »Vis«, »Gargano«, »Rovinj«, and »Lim«.

       The primary production determined with the radioactive C¹⁴ method for the entire column of the euphotic zone in the region under examination shows us that the production g C per m³ per day was the richest in June 1959, i. e. it was 0,40 g C/m³/day, while for the other months at all the stations it was more or less the same with very little fluctuation, and it was about 0,25 g C/m³/day. The average productivity for the above men­tioned three stations from February till August 1959 was 0,29 g C/m³/day.

      It has been generally shown that the productivity in the littoral waters, or in the waters under the direct influence of the mainland or other fresh waters (the Bay of Kaštela, and the north Adriatic) was higher than in the open Adriatic region.

       The vertical and horizontal distribution of the bacteria and the bacterial biomass in the euphotic zone of the region under study has shown its greatest richness in the middle layer of the euphotic zone, while with the increase of depth it decreased. The station »Kaštelanski zaljev« which is under the direct influence of mainland and fresh waters, during the examination from February to August 1959 had the richest bacterial flora.

       The bacteria reproduction showed that the biomass increase per sea water volume unit was from 0,70 to 1,53 mg per m³ of bacteria per hour. The greatest bacterial biomass increase was found at the station »Kaštelanski zaljev«. The general average bacterial biomass increase in the examined re­gion was 1,08 mg/m³ per hour or 25,68 mg/m³ per day.

       The relation between the bacteria, phosphate, and the primary pro­duction in the examined region as ecological factors mutually closely con­nected and conditioned has been discussed. The analysis of the relation of these factors has shown that the bacterial population and the phosphate quantities found in a determined sea water layer are in inverse ratio, and the same relation has been stated for the quantities of the found phosphate and the primary production mg C/m³/day.

       The quantity of the phosphate regeneration and of the primary pro- uction in the Adriatic, and in some other sea and ocean regions has been compared. It has been stated that the Adriatic can be numbered among some regions with lower productivity in regard to the oceanic productivity, but that some littoral regions with their productivity aproach some more abun­dant regions in other seas.