Fatty acids profiles modifications in the bivalves Cerastoderma edule and Scrobicularia plana in response to copper sulphate

Abstract

At the past 30 years were recorded an intensive practice in the use of fertilizers and pesticides, mainly in the European Mediterranean region, that, in particular cases, exceeded the limits of regular legislations established by the European Union. The widespread use of these chemicals compounds and the pressure over agricultural fields near valuable ecologically coastal areas conducted to the implementation of monitoring plans to the recovering of aquatic ecosystems. Since the 80′s Mondego estuary (Figueira da Foz, Portugal) has been harassed by anthropogenic pressures, which triggered the implementation of mitigation monitoring programs at the last 18 years, allowing its recovery. Copper sulphate is used in industrial activities, but also it is much used in pesticides formulations, with application in agricultural activities, namely in rice farms to control pests. Studies reported that copper may affect biochemical processes, such lipid metabolism of some organisms, although specific changes in fatty acid (FA) profiles are still unknown. Nowadays, bivalve species are used in ecotoxicological bioassays due some particular characteristics, such as the wide distribution, ecological relevance, the capacity to filter and ingest large volumes of sediment particles and water and ease handling in the field and in the laboratory. Therefore, this work aims to determine toxic effects and changes in fatty acids profile composition of the two marine bivalve species Cerastoderma edule and Scrobicularia plana when exposed to copper sulphate, considering small (medium body size=1.97cm and 3.47cm, respectively) and big (medium body size=2.45cm and 4.20cm, respectively) size classes. In a first phase organisms were exposed under laboratorial conditions to copper sulphate to determine lethal concentration; at a second phase, it was compared the FA profile and the nutritive quality of both species and size classes at the field and in the lab. Our results state C. edule is more sensitive to copper sulphate (LC50=0.818 (0.595–0.987)mg/L; 1.129 (0.968–1.289)mg/L, to big and small organisms, respectively) than S. plana (LC50=2.563 (2.229–2.903)mg/L; 4.705 (3.540–12.292)mg/L, to big and small organisms, respectively). Furthermore the last one presents greater abundance and variety of FA and essential fatty acids (EFA), namely DHA and EPA, rates than C. edule. Still, big size class of both bivalve species is the most affected by the contaminant.