ASSESSMENT OF DISTURBANCE IN MEDITERRANEAN LAGOONS - AN EVALUATION OFMETHODS

A number of methods were applied to assess disturbance in macrozoobent hic communities in three Mediterranean lagoons with different levels o f stress. Tsopeli, Ionian Sea, with no obvious source of stress, harbo urs a fauna typical of brackish-water lagoons. Vivari, Aegean Sea, als o without apparent source of disturbance, is characterised by a few ty pical lagoonal species and some species characteristic of perturbation . Gore lagoon, in the northern Adriatic, is much larger and more open to the sea. At the centre of the lagoon, where anoxia is known to occu r in the summer (''Goro polluted''), the fauna is dominated by species typical of disturbance and a few lagoonal species. A dredged area clo ser to the sea (''Goro dredged'') is totally dominated by species char acteristic of disturbance. The species diversity in all lagoons ranges from low to very low. According to the distribution of individuals in geometric abundance classes, all the lagoons are characterised as str essed. The distribution of individuals in geometric size classes shows dominance of larger specimens in the least disturbed Tsopeli and excl usively small sizes in the greatly disturbed dredged area of Gore. The abundance/biomass comparison curves characterise Tsopeli as undisturb ed, Vivari and Gore polluted stations as moderately disturbed and Gore dredged station as disturbed. The last two methods agree with the cha racterisation derived by examining the dominant species. It is conclud ed that methods based on size changes of the fauna are more sensitive than those based on relative abundance in assessing disturbance in coa stal brackish-water lagoons.