Understanding trophic transference role in mercury biomagnification and bioaccumulation in the Atlantic spotted dolphin (Stenella frontalis).

Mercury is a metal of toxicological importance that occurs naturally. However, its concentration can be affected by anthropogenic activities and has the potential to bioaccumulate and biomagnify in food webs. Thus, knowing how its concentration varies along the trophic levels allows us to understand its potential risks to the biota. The present study aimed to investigate mercury transfer through the Stenella frontalis food web in Ilha Grande Bay (IGB), Rio de Janeiro state, Brazil. Samples of muscle and liver of S. frontalis were obtained from carcasses (n = 8) found stranded in the IGB, and its potential prey species were collected in fishing landings in the same Bay (n = 145). Total mercury (THg) concentrations were determined by atomic absorption spectrometry, and the δ15N was determined by an isotope ratio mass spectrometer. To investigate how trophic transfer affects mercury contamination in biota, six linear models were applied between THg logarithmic concentrations and δ15N or trophic position (TP). The trophic magnification factor (TMF) was calculated from each model to estimate the trophic transfer. Mean THg concentration in S. frontalis was higher in the liver than in muscle, but no correlation was found with age and δ15N values. Instead, the hepatic and muscular THg concentrations positively correlated with the trophic position. In the summer, THg concentration, TP, and δ15N values in prey species varied significantly, as well as in the winter, except for THg concentration. All trophic transfer models were significant in both seasons, and the TMF >1. The present study showed that trophic transfer is an essential factor in mercury biomagnification in both seasons but is not the unique driver. Both δ15N and TP could explain mercury trophic transfer, but TP better integrates metabolic diversity and seasonality.

Mercury toxicology in Epinephelidae fishes: A multiple tissue approach in two groupers species from southwestern Atlantic (SE-Brazil).

Epinephelidae fishes are important to reef ecosystems, as well as for commercial fishing and cultural heritage. Additionally, most of these species are at some risk of extinction, as Epinephelus marginatus and Hyporthodus nigritus. This study aimed to determine total mercury (THg) concentrations and burden on eight tissues of E. marginatus and H. nigritus. A Cold Vapor/Atomic Absorption Spectrometer was used for the THg determination. THg concentrations and burden varied significantly between tissues in both species. The highest concentrations were determined in the liver, and the greatest burden was in muscle. The gonad concentrations were higher than the toxicological threshold. General trends of increase in THg concentrations and burden along growth were observed. Mercury is a threat for both species evaluated, raising this concern for other Epinephelidae species.