Compliance of the macrophyte quality index (MaQI) with the WFD (2000/60/EC) and ecological status assessment in transitional areas: The Venice lagoon as study case

The macrophyte quality index (MaQI) for the assessment of the ecological status of transitional systems has been recently adopted by the Italian Law in agreement with the WFD (2000/60/EC) requirements and successfully intercalibrated in the framework of the WFD intercalibration exercise. In this paper the last structure of MaQI is presented and discussed. Its application takes into consideration 29 sites spread all over the Venice lagoon. Sampling campaigns were carried out in spring and autumn and monthly in four choked sites showing a high seasonal variance. The analysis of the macrophyte assemblages and several environmental parameters measuring anthropogenic pressures indicate that the worst ecological status mainly depends on the combination of high sediment re-suspension, water turbidity and nutrient availability. High water turbidity and the settlement of fine particles prevent the macrophyte attachment to the bottom and their growth also in the presence of nutrients. Under those conditions macrophytes are almost missing and opportunistic taxa, belonging to Gracilariaceae, Solieriaceae and Vaucheria submarina, are replacing Ulvaceae. (C) 2014 Elsevier Ltd. All rights reserved.