High Mercury Concentrations Reflect Trophic Ecology of Three Deep-Water Chondrichthyans

Abstract

The relative contributions of proximity to mercury sources and trophic ecology to realized axial muscle mercury concentrations were explored for three deep-water chondrichthyans (Etmopterus princeps, Centroscymnus coelolepis, and Hydrolagus affinis), two species of which are harvested for human consumption. Samples were taken at three North Atlantic Ocean locations: the Azores, the Charlie Gibbs Fracture Zone, and the Bear Seamount. Despite the long distances between anthropogenic sources and the sampling locations, all species from all locations had muscle mercury concentrations exceeding the United States human health screening value of 0.3 mg/kg wet weight. Proximity to anthropogenic sources was not an obvious determinant of these elevated concentrations. Generally, mercury concentrations appeared to increase with increased dependence on benthic versus pelagic food sources (as indicated by interspecies differences in δ(13)C), and with higher position in the trophic web (as indicated by differences in δ(15)N).

Trophic structure and biomagnification of mercury in an assemblage of deepwater chondrichthyans from southeastern Australia

“…Squaliforms primarily feed on mesopelagic and bathypelagic fishes and squids (Bulman et al 2002, Pethybridge et al 2011). High δ 15 N levels (TP) have been reported in other benthic feeding chimaeras (small-eyed rabbitfish Hydrolagus affinis) from the North Atlantic Ocean (Newman et al 2011) and linked to variable but typically high TP values reported in carnivorous gastropod (TP = 2.8 to 3.8) and polychaetes (TP = 3.4 to 4.3, Davenport & Bax 2002). Clearly diet and habitat (food web and species composition) structure are largely responsible for the differences in mercury biomagnification rates between holocephalans and elasmobranchs, and among-system differences in calculated TMF (Table 2); however, the full implications remain unknown.…”

“…As this phenomenon depends on the structure and complexity of the food web (Wang 2002), stable isotopes have been suitably coupled with contaminant analysis to delineate bioaccumulation patterns in marine food webs (Atwell et al 1998, Power et al 2002 and better understand the extent of biomagnification in top-order predators, including sharks (Fisk et al 2002, Domi et al 2005, Newman et al 2011. Mercury in its most toxic form, monomethylmercury (MeHg), continues to draw a great deal of scientific and policy interest (Selin 2011) largely due to its harmful health effect (Eisler 2006) and its long-ranging atmospheric transport and global distribution (Mason et al 1995).…”

Global versus local causes and health implications of high mercury concentrations in sharks from the east coast of South Africa

“…Given CH 3 Hg biomagnification through aquatic food webs, it is expected that sharks feeding at a higher trophic position will have higher CH 3 Hg concentrations than those feeding lower in the food web. To date, a small number of studies have reported positive correlations between CH 3 Hg concentrations and trophic position, or nitrogen stable isotope ratios (δ 15 N) as a proxy for trophic position, in sharks (Cai et al 2007;Cresson et al 2014;McMeans et al 2010;Newman et al 2011;Pethybridge et al 2012). Additionally, recent studies have found correlations between shark CH 3 Hg tissue values and foraging depth or other habitat-use metrics, including carbon stable isotope ratios (δ 13 C) as a proxy for resource use, e.g., inshore benthic versus offshore pelagic (Choy et al 2009;Cossa et al 2012;McMeans et al 2010).…”

Mercury in Cobia from Estuarine and Offshore Waters of the Southeastern United States: Fisheries Implications

“…Available mercury in benthic prey may be different from that in pelagic prey; it also could vary with mercury dynamics in specific habitats or regions (Newman et al. ; Driscoll et al. ; Sackett et al.…”

“…Stable isotope data and fatty acid signatures also suggest that Cobias are more closely linked to benthic food sources than is typical for other large, pelagic fishes (Cai et al 2007). Available mercury in benthic prey may be different from that in pelagic prey; it also could vary with mercury dynamics in specific habitats or regions (Newman et al 2011;Driscoll et al 2012;Sackett et al 2015). Foraging ecology, food web dynamics, factors related to the onset of maturity, and age-related factors all contribute to the extent of mercury bioaccumulation in Cobias.…”