Mercury (Hg) speciation in coral reef systems of remote Oceania: Implications for the artisanal fisheries of Tutuila, Samoa Islands

Abstract

We investigated Hg in muscle tissue of fish species from three trophic levels on fringing reefs of Tutuila (14°S, 171°W), plus water, sediment and turf alga. Accumulation of total Hg in the herbivore Acanthurus lineatus (Acanthuridae, lined surgeonfish, (n =40)) was negligible at 1.05 (±0.04) ngg -1 wet-weight, (~65% occurring as methyl Hg). The mid-level carnivore Parupeneus spp. (Mullidae, goatfishes (n =10)) had total Hg 29.8 (±4.5) ngg -1 wet-weight (~99% as methyl Hg). Neither A. lineatus or Parupeneus spp. showed a propensity to accumulate Hg based on body size. Both groups were assigned a status of "un-restricted" for monthly consumption limits for non-carcinogenic health endpoints for methyl Hg. The top-level carnivore Sphyraena qenie (Sphyraenidae, blackfin barracuda, n =3) had muscle tissue residues of 105, 650 and 741ngg -1 wetweight (100% methyl Hg, with increasing concentration with body mass, suggesting that S. qenie >15kg would have a recommendation of "no consumption".

Mercury Biomagnification Through a Coral Reef Ecosystem

“…Nonetheless, the biota from the Keys contained higher [Hg] than levels reported from a limited number of surveys of reef biota from other locations (Plessi et al 2001;Voegborlo and Akagi 2007;Chouvelon et al 2009;Morrison et al 2015). For example, [Hg] were higher in surgeonfish, goatfish and barracuda in the present study than similar species from fringe reefs in the remote Pacific near the American Samoan island of Tutuila (Morrison et al 2015; after adjusting their wet weight concentrations from CVAF as outlined above). Likewise, chubs (Kyphosidae) and groupers (Serranidae) in the present study had high [Hg] than fishes surveyed along the coast of New Caledonia, despite being near potential point sources (Chouvelon et al 2009).…”

“…First, like many other studies (e.g., 127 studies summarized in Lavoie et al 2013), we quantified biomagnification and TMS based on total-Hg rather than MeHg. As previously discussed, %MeHg is known to vary depending on tissue type, trophic level and [Hg] (Wiener et al 2003;Seixas et al 2013;Morrison et al 2015). Thus, this continued reliance on total-Hg as a proxy of MeHg introduced uncertainty and variance in the TMS.…”

“…Moverover, numerous adaptations and symbioses among autotrophs and mixotrophs lead to efficent recycling of nutrients that allows coral reefs to be some of the most biologically productive ecosystems while inhabiting waters that are generally low in nutirents (Odum and Odum 1955;Johannes et al 1972). Although a limited number of studies have surveyed Hg concentrations in coral reef biota (Strom et al 1992;Guzmán and Garcia 2002;Chouvelon et al 2009;Berry et al 2013;Morrison et al 2015), to our knowledge, SIA has not been applied to these systems to assess their efficiency (vulnerability) for biomagnification.…”

Mercury Biomagnification Through a Coral Reef Ecosystem

“…[Hg] (Wiener et al 2003;Seixas et al 2013;Morrison et al 2015). Thus, this continued reliance on total-Hg as a proxy of MeHg introduced uncertainty and variance in the TMS.…”

“…Although a limited number of studies have surveyed Hg concentrations in coral reef biota (Strom et al 1992;Guzmán and Garcia 2002;Chouvelon et al 2009;Berry et al 2013;Morrison et al 2015), to our knowledge, SIA has not been applied to these systems to assess their efficiency (vulnerability) for biomagnification.…”