Ecological study of gas fields in the northern Adriatic. 12. Ecological features of the benthic community
Abstract
During the period from 1982 to 1985 and at the beginning of 1986 floristic and faunistic compositions and distributions of benthic communities of southwestern rocky coast of Istra (cape Proštine to Cape Kamenjak on Premantura peninsula) and of deeper mobile bottoms of open waters towards the IVANA field were studied. Benthic flora consisted of 245 species and intraspecific taxa of multicelular algae (Rhodophyta 146 taxa, Phaeophyta 57 taxa, Chlorophyta 42 taxa) and 2 species of sea grasses.
Benthic algal settlements on a greater coastal part are characterized by numerous species and infraspecific taxa (246) that inhabit solid (rocky and stone) bottoms. Other considerable surfaces of the deeper mobile (sediment) bottom in the open part of the studied area have almost no phytobenthic settlements at all, because only 15 species were determined there. At certain parts of the studied coast from Cape Proština (near Pula) to Cape Kamenjak, especially in shallow water phytobenthic settlements, progressive phases of degradation process were noticed due to the negative impact of the increased sea pollution.
Regarding quality and quantity zoobenthic settlements are well developed and cover 299 macrozoobenthic species from nine systematic groups. The distribution of these settlements at deeper mobile bottoms of the open part is characterized by high total and mean values, but shows considerable variations in relation to the mechanical structure of the sediment at certain parts of the studied area. It was noticed that at mostly silty bottoms, species from the Arthropoda group dominate by quantity and quality, while sandy bottoms are dominated by species from the Mollusca and Echinodermata groups.
Ichthyological (groundfish stock) settlements are well developed at mobile bottoms of the wider area of the IVANA and IKA fields which is well confirmed by the rather high total amounts of the quantity of the zoobenthos of 47 950 t, of which the edible part (fish, crustaceans, shellfish and cephalopoda), total 6 680 t and nonedible 41 270 t. From the point of view of fisheries and economy the wider area of gas fields, due to the abundancy and variability of edible resources, represents a significant part of the open Adriatic fishing grounds.
