Effects of industrial and urban pollution on the benthic macrofauna in the Bay of Muggia (industrial port of Trieste, Italy).

The benthic macrofauna of the Bay of Muggia and its evolution in time was analysed in order to assess the impact of man-made pollution in this port area. The north and NE zones are totally industrialised while the southern zone is mainly used for tourism and aquaculture. The most important anthropic impacts were stagnation and direct urban and industrial discharges, which operated until the beginning of the 1990s. Forty-four stations were sampled in 1981, 12 of which were monitored over time (1975, 1981 and 1994). From 172 taxa 11783 organisms were identified. Polychaetes were the richest group, followed by molluscs, crustaceans and echinoderms. The dominant species was Corbula gibba (39.5%) followed by Pectinaria koreni (9%). Uni- and multivariate analyses showed a declining pattern for the fauna along a gradient of environmental stress. The very high concentrations of heavy metals in the Bay's sediments, especially Pb, contrasted with the diversity and biological index values found, indicating that many species could survive these conditions. The enforcement of the Italian ecological laws regarding water pollution control benefited the local macrofauna and evidenced the resilience of the system. C. gibba constituted a good biological indicator of zones of high instability (especially sedimentary) and of intermediate levels of pollution.