Preliminary results of biological monitoring using benthic macroinfauna of the discharge areas of Lisbon drainage basins in Tagus estuary after new developments in sanitation infrastructures

The present study focused on the use of benthic macroinfauna to assess the ecological quality status of two specific areas in the Tagus estuary (Portugal), after the improvement in the sanitation infrastructures discharging in those areas. The sampling campaigns were held in summer of 2009, 2010 and 2011 in a set of impact and control stations. Multivariate analysis was used to determine the evolution of spatial and temporal patterns in benthic macroinfauna assemblages' composition. The ecological status of these assemblages was assessed by means of taxa richness, Shannon-Wiener diversity index and AMBI and M-AMBI biotic indices. The results obtained in both study areas seemed to indicate a trend for an improvement in the ecological condition of their benthic macroinfauna assemblages over time, although a consistent pattern was not found in all the analyses performed. When benthic macroinfauna assemblages under analysis are considerably degraded, the multimetric index M-AMBI seems to be more adequate for conducting monitoring studies than the AMBI index. However, the continuation of this work is indispensable to ensure the validity of this conclusion.