Assessment of disturbance in Mediterranean lagoons: An evaluation of methods.

A number of methods were applied to assess disturbance in macrozoobenthic communities in three Mediterranean lagoons with different levels of stress. Tsopeli, Ionian Sea, with no obvious source of stress, harbors a fauna typical of brackish-water lagoons. Vivari, Aegean Sea, also without apparent source of disturbance, is characterized by a few typical lagoonal species and some species characteristic of perturbation. Goro 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 occur in the summer ("Goro polluted"), the fauna is dominated by species typical of disturbance and a few lagoonal species. A dredged area closer to the sea ("Goro dredged") is totally dominated by species characteristic 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 are characterized as stressed. The distribution of individuals in geometric size classes shows dominance of larger specimens in the least disturbed Tsopeli and exclusively small sizes in the greatly disturbed dredged area of Goro. The abundance/biomass comparison curves characterize Tsopeli as undisturbed, Vivari and Goro polluted stations as moderately disturbed and Goro dredged station as disturbed. The last two methods agree with the characterization derived by examining the dominant species. It is concluded that methods based on size changes of the fauna are more sensitive than those based on relative abundance in assessing disturbance in coastal brackish-water lagoons.