Defining sea grass ecological status in Ria Formosa under the european water framework directive

Marin, Patricia Garcia

http://hdl.handle.net/10400.1/713

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Authors

Marin, Patricia Garcia

Advisor(s)

Cabaço, Susana Isabel dos Santos

Newton, Alice

Abstract(s)

The Water Framework Directive (WFD) aims to achieve a good quality status of all the European water bodies by the year 2015. The Directive demands that the ecological status is quantified based primarily on biological indicators. Seagrasses are one of the biological quality elements (BQE) to be used in defining the ecological quality status (EQS) of transitional and coastal waters. This thesis focuses on the application of seagrasses as BQE to assess the ecological status of the Ria Formosa lagoon. The sites of Ponte and Ramalhete, already registered as part of the European list of inter-calibration sites for the WFD, were assessed. The metrics established by the Directive for this BQE, i.e. the taxonomic composition and the seagrass abundance (bed area extent and shoot density), were determined and compared with the reference conditions. The Ponte and Ramalhete sites had a mean score of Ecological Quality Ratio (EQR) of 0.90 and of 0.97, respectively (both scores correspond to high ecological status). The main difference resulted from the lost of one seagrass species in the Ponte site. As a result Ria Formosa was considered at high ecological status using the seagrass biological quality element. However the classification provided by seagrasses was slightly higher than the classification obtained by other studies considering other BQE (phytoplankton, nutrients). This study was the first attempt to establish the EQS of Ria Formosa using seagrass as a BQE. Further research is required to establish a more accurate and integrated EQS of the Ria Formosa lagoon.