COPPER BIOGEOCHEMISTRY IN A BRAZILIAN MARINA

Marinas play an important role in global transportation and leisure activities since their operations can deteriorate the environmental quality of sediments and biota. Among the myriad of disturbances near marina activities, trace metal contamination has emerged as one of the most stressful. The intensive use of copper (Cu) compounds as an alternative biocide in antifouling paints (APs) has resulted in wide Cu contamination in the marine environment, especially near marinas and harbors. In response, this study investigated copper contamination history associated with antifouling paint uses in oysters and sediment core collected from Bracuhy marina (Southeast Brazil). The analysis targets trace elements (Cu) and Cu isotopes. Cu isotopic compositions were obtained by MC-ICP-MS after ion-exchange chromatographic separation and are expressed in δ65Cu notations values in relation to NIST SRM 976. Metal distribution in the sediment core demonstrates that Cu enrichment increased up to 15 times compared to the local background. This severe Cu contamination coincides with the onset of marina operations and can be attributed to the use of antifouling paints. The overall isotope composition for the sediment core shows a slight variability, from −0.40 to 1.29 ‰. The plot of δ65Cu values against 1/Cu for all dataset allowed us to identify natural (+0.04 ± 0.06 ‰) and anthropogenic (+0.59 ± 0.02 ‰) end-members. However, sample isotope systematics were not consistent with a conservative mixing binary source process. The results of Cu concentrations for oysters show distinct groups controlled by proximity to the source (marina). Cu contents for oysters collected in pristine regions away from the marina varied from 30 mg kg-1 to 100 mg kg-1, well below the values for oysters collected in the marina, whose concentrations were recorded between 1130 mg kg-1 and 1700 mg kg-1. The results obtained in the oyster transplant experiment from a pristine environment to the marina revealed significant enrichment in Cu, demonstrating high Cu bioavailability. At the end of three months, the exposure time of the transplanted oysters, oysters from an uncontaminated environment reached Cu concentrations similar to oysters collected at the marina. The temporal evolution of δ65Cu values in transplanted oysters had a little shift and evolved from values close to those in pristine regions (+0.09 ± 0.04 ‰ to 0.18 ± 0.02 ‰), values higher than native marina oysters (δ65Cu = -0.06 ± 0.03 ‰). Based on Cu isotope results, oyster isotopic signatures cannot identify changes related to anthropogenic Cu inputs bound to antifouling paints. This limitation can be overcome by combining different isotopic systems such as Zn and Pb.