Monitoring of marine macrobenthic communities at a dumping site: Are cause/effect relationships clear?

This paper reports and criticises a study carried out in the Thyrrhenian coastal zone to assess the impact of harbour dredged material on marine macrobenthic community. Unpolluted sediments dredged from Livorno harbour were dumped at sea 6 nautical miles NW of the city. Procedures and method ological approaches were according to Italian rules and regulations running in Italy in 1991. Fauna was collected dredging in 15 stations before and after dumping and data analysis included multivariate analysis (nMDS), structural parameters, ABC curves and biocoenotic approach. Before dumping communities were well structured (high diversity), unpolluted (ABC method), and with a "heterogeneous" biocoenotic composition. After dumping only "heterogeneous" communities showed modifications and were considered sensitive communities. No clear and univocal answer to the question "does dumping affect the benthos?" can be achieved by the methods suggested by regulations. The need for planning more consistent monitoring programs to identify disturbance from dumping which can really answer the question if impact exists is suggested.