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Mar Pollut Bull. 2015 Jul 15;96(1-2):197-209. doi: 10.1016/j.marpolbul.2015.05.029. Epub 2015 May 23.

Determining the footprint of sewage discharges in a coastal lagoon in South-Western Europe.

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University of Algarve, FCT - CIMA, Campus de Gambelas, 8005-139 Faro, Portugal. Electronic address:
University of Algarve, FCT - CIMA, Campus de Gambelas, 8005-139 Faro, Portugal.
CCMAR, University of Algarve, Campus of Gambelas, 8005-139 Faro, Portugal.


Ria Formosa is a highly productive lagoon in South-Western Europe, supporting 90% of Portuguese clam production. Decreases in shellfish production have been ascribed to deterioration of water quality due to sewage discharges. Nevertheless, a thorough study considering their impact on the whole lagoon system has been missing. This work determined the sewage footprint from the major sewage treatment plants (STP) regarding eutrophication and microbial contamination within a two-year monitoring program. This focused on salinity, oxygen, nutrients, chlorophyll-a and faecal coliforms. Areas closer to sewage discharges showed an evident impact with maximum effects detected at the major STP. However, globally, the Ria Formosa did not show clear eutrophication problems due to high tidal flushing. Ammonium, oxygen, chlorophyll-a and faecal coliforms, unlike the other parameters, showed no seasonality. Microbiological contamination was of great concern and public health issues could be avoided by settling shellfish beds at least 500 m away from discharge points.


Eutrophication; Faecal coliforms; Nutrients; Ria Formosa; Sewage discharges; TRIX index

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