Use of Faunal Indicators for Assessing the Impact of a Port Enlargement near Bilbao (Spain)

Abstract

In order to assess the effects of the execution of the ‘Port of Bilbao Enlargement Project’, epifauna living on hard substrata and environmental parameters were quantitatively investigated from 1994 to 1996. A programme of repeated non-destructive sampling at 8 stations was carried out during the construction period of a breakwater and the filling operations on the shoreline. A correlation analysis was used as a method to extract potential indicator species of particular environmental conditions measured in the field. We postulate that the remaining species (about 80% of the total species data set), insensitive to any of the investigated environmental factors, were unnecessary for the purposes of assessing the environmental impact caused by the port building works. Classification and ordination techniques were then conducted at two contrasting levels by using the full species data set and the selected faunal indicator data subset. All plots showed separation of sampling sites in 3 major groups, which were easily related to the perturbations caused by a siltation gradient from the estuary mouth. This suggests that the amount of effort required in the enumeration of all the organisms sampled may be dramatically reduced by identifying only faunal indicators of environmental discontinuities in the field. So far, the engineering works developed on the western side of the bay have not caused dramatic temporal changes in species composition, or at least they have not had an effect that was larger than the variations detected among the study sites due to siltation from the estuary mouth.