Environmental chemical data and Carcinus maenas biochemical responses in a coastal eutrophic ecosystem (Obidos Lagoon, Portugal)

The status of Obidos Lagoon (Portugal) was assessed combining water quality, sediment quality, and oxidative stress responses in female shore crab Carcinus maenas. Two sites were surveyed in October 2005, one located in an impacted, confined inner branch (Barrosa) and another in the middle of the lagoon more influenced by the seawater input. Concentrations of ammonium and nitrate + nitrite were notably higher in Barrosa, although the differences in sediment metal contamination were minor. The availability of dissolved Mn, Cu, Ni, and Cd was higher in Barrosa, particularly in the morning, which suggests the influence of internal processes occurring near the sediment during the night. Female crabs captured at Barrosa exhibited alterations in hepatopancreas antioxidants, clearly indicating that the inner branch is a more polluted area. Crabs displayed increased activity of glutathione peroxidase, catalase, and glutathione S-transferase, as well as lipid peroxidative damage, whereas no differences were observed for total glutathione. Those significant responses were not accompanied by a significant elevation of metal levels in the hepatopancreas, suggesting that adverse effects may have been caused by the synergism of stressors.