Mercury bioaccumulation and biomagnification in Ozark stream ecosystems

Abstract

a b s t r a c tCrayfish (Orconectes spp.), Asian clam (Corbicula fluminea), northern hog sucker (hog sucker; Hypentelium nigricans), and smallmouth bass (smallmouth; Micropterus dolomieu) from streams in southeastern Missouri (USA) were analyzed for total mercury (HgT) and for stable isotopes of carbon (d S, and TP in hog suckers increased with total length (length) at some sites, indicating site-specific ontogenetic diet shifts. Changes with length were less evident in smallmouth. Length-adjusted HgT site means in both species were strongly correlated with HgT in crayfish (r 2 ¼ 0.97, Po0.01), but not with HgT in Corbicula (r 2 ¼ 0.02, P40.05). ANCOVA and regression models incorporating only TP and, for hog suckers, length, accurately and precisely predicted HgT concentrations in both fish species from all locations. Although low compared to many areas of the USA, HgT (and therefore methylmercury) concentrations in smallmouth and hog suckers are sufficiently high to represent a threat to human health and wildlife. Our data indicate that in Ozark streams, Hg concentrations in crayfish are at least partly determined by their diet, with concentrations in hog suckers, smallmouth, and possibly other higher-level consumers largely determined by concentrations in crayfish and other primary and secondary consumers, fish growth rates, and TP.

Using sulfur stable isotopes to assess mercury bioaccumulation and biomagnification in temperate lake food webs

“…In the lakes in the present study, most d 34 S measures of aqueous SO 4 2-(median 10.5‰), sediments (11.2‰), zooplankton (10.3‰), and all littoral invertebrate taxa (from 10.8‰ in Aeshnidae dragonflies to 12.0‰ in Limnephilidae caddis flies) were >10‰, a benchmark indicating dietary reliance on marine sources of S for birds (e.g., Ofukany et al [24] and Lavoie et al [46]). In fact, fish d 34 S values from our temperate systems were higher and more consistent with values from estuarine and marine fishes [26,28] than values in freshwater ecosystems in other parts of North America [12,14,25,27,44,45,47]. In the present study, the similarity of d 34 S composition in aquatic ecosystems in this region to estimates from marine systems may be related to their proximity to the coast.…”

“…Values of d 34 S in bulk sediments and aqueous SO 4 2from our study lakes fell within the range typical for precipitation SO 4 2- [43], and these d 34 S data were more positive than results from other freshwater food webs [12,14,25,27,44,45]. In the lakes in the present study, most d 34 S measures of aqueous SO 4 2-(median 10.5‰), sediments (11.2‰), zooplankton (10.3‰), and all littoral invertebrate taxa (from 10.8‰ in Aeshnidae dragonflies to 12.0‰ in Limnephilidae caddis flies) were >10‰, a benchmark indicating dietary reliance on marine sources of S for birds (e.g., Ofukany et al [24] and Lavoie et al [46]).…”

“…across sites but no relationship for Asian clams (Corbicula fluminea [44]) despite significant differences in d 34 S within both of these invertebrate groups across sites. Whereas there were no relationships within invertebrate taxa between log-MeHg concentrations and d 34 S in the present study (see section, Relationships between Hg concentrations and S isotopes), results from Ozark mountain streams (AR, USA) were mixed, with a positive relationship between THg and d 34 S values in crayfish (Orconectes spp.)…”

Methylmercury exposure during early Xenopus laevis development affects cell proliferation and death but not neural progenitor specification

“…Easily transported through the atmosphere due to its low boiling point, elemental mercury can be deposited far from its source where it rapidly enters the food chain through methylation by microorganisms into a highly bioavailable methylmercury (MeHg) form (Amyot et al 2005; Harris et al 2007; Schaefer et al 2011). Because of MeHg’s relatively long half-life in biological tissues, there is considerable biomagnification (Chumchal et al 2011; Horvat et al 2013), leading to elevated concentrations and increased toxicity in animals at higher trophic levels (Schmitt et al 2011; Spada et al 2012). On the biochemical level, toxicity is facilitated by the ability of MeHg to conjugate with the exposed thiol group of cysteine, leading to disruption of thiol and selenol rich enzyme activities (Carvalho et al 2008; Zemolin et al 2012) and providing MeHg active transport across the blood-brain and placental barriers through formation of a methionine mimic with free cysteine (Simmons-Willis et al 2002; Yin et al 2008).…”

Implementation of a Non-lethal Biopsy Punch Monitoring Program for Mercury in Smallmouth Bass, Micropterus dolomieu Lacepède, from the Eleven Point River, Missouri

“…Preliminary analyses indicated that the Hg:fish size relations differed between sites. Hg concentrations were therefore normalized for fish size with ANCOVA by adjusting to the grand mean TL (335 mm) using site-specific linear regressions (Schmitt et al 2011). Statistical significance testing was set at p \ 0.05 unless otherwise indicated.…”