Linking stable isotopes and biochemical responses in Balanus glandula under sewage influence.

In the present study, we analyzed the influence of untreated sewage exposure on carbon (δ13C) and nitrogen (δ15N) isotopic composition and several biochemical responses in the barnacle Balanus glandula. The main objective was to evaluate whether changes in stable isotopes signature do reflect biochemical sub-lethal effects in a sewage influence gradient. Stable isotopes analysis showed differences in isotope signatures between close sewage influence and distant sites, being δ13C signatures stronger than that of δ15N. Regarding biochemical effects, although organisms close to the effluent would be clearly exposed to contaminants (increased GST activity) the oxidative stress would not be too evident (peroxidases and ACAP not affected). The most affected physiological aspect was the digestive one, reflected in increased alkaline proteases and lipases activities. A clear relation between δ15N and GST activity was found, showing to δ15N as an indicator of potential exposure to chemical contaminants.

Comparative biomonitors of coastal trace metal contamination in tropical South America (N. Brazil).

Samples of 5 bivalve molluscs (Crassostrea rhizophorae, Mytella charruana, Anomalocardia brasiliana, Anadara ovalis, Phacoides pectinata), 2 barnacles (Fistulobalanus citerosum, Balanus amphitrite) and leaves of the mangrove tree Rhizophora mangle were collected from up to 11 sites in two estuaries in Natal, Brazil--the comparatively contaminated Potengi estuary and the comparatively uncontaminated Curimataú estuary. Specimens were analysed for the trace metals Zn, Cu, Cd, Fe, Mn and Ni, and a comparative assessment made of the power of the different species as trace metal biomonitors. Four of the 5 bivalves (not P. pectinata) take up metals from solution and suspended material (food source), while P. pectinata as a lucinid with symbiotic chemosynthetic bacteria takes up metals from dissolved sources only. The organisms with the strongest net accumulation of particular metals showed the greatest discrimination between trace metal bioavailabilities between sites. Barnacles (F. citerosum) showed the best discrimination, but oysters (C. rhizophorae) are particularly recommended as biomonitors given their strong accumulation patterns for many trace metals, their large size and their local abundance.