Influences of prey- and predator-dependent processes on cadmium and methylmercury trophic transfer to mummichogs (Fundulus heteroclitus)

Abstract

Factors affecting CH3Hg and Cd trophic transfer from six invertebrates and a juvenile fish prey to mummichogs (Fundulus heteroclitus) were investigated using prey-dependent and predator-dependent approaches. Prey-specific trophic availability of metals to mummichogs was estimated using a subcellular partitioning approach (i.e., trophically available metals (TAM), as originally proposed by Wallace and Luoma (2003)). The proportions of CH3Hg partitioned to TAM (CH3Hg-TAM%) ranged from 39.7% to 82.7%, while the proportions of Cd partitioned to TAM (Cd-TAM%) ranged from 51.8% to 67.4%. CH3Hg-TAM% and Cd-TAM% were significantly correlated with the proportions of metals released from prey by in vitro solubilization with mummichog gut fluid (i.e., gut solubilizable metals (GSM)), CH3Hg-GSM% and Cd-GSM%, respectively. This relationship suggests that the majority of CH3Hg and Cd partitioned as TAM in prey were solubilized in the digestive tract of mummichogs. Mummichogs retained 52.7% to 73.7% of the ingested CH3Hg, which was comparable with prey-specific CH3Hg-TAM% and CH3Hg-GSM%. However, mummichogs retained only 3.2%-11.0% of ingested Cd, which was substantially lower than Cd-TAM% or Cd-GSM%. These results suggest that solubilizable, prey-associated CH 3 Hg was transported through the gut membrane of mummichogs, whereas the majority of preyassociated Cd was excluded and subsequently eliminated, regardless of its subcellular partitioning.Résumé : Nous avons étudié les facteurs qui affectent le transfert trophique de CH 3 Hg et de Cd de six proies invertébrées et d'un jeune poisson proie au choquemort (Fundulus heteroclitus) en utilisant des approches dépendantes des proies et dé-pendantes des prédateurs. Nous avons estimé la disponibilité trophique des métaux aux choquemorts spécifique à chaque proie à l'aide de la méthode de partitionnement subcellulaire (c'est-à-dire les métaux trophiquement disponibles (TAM), méthode proposée au départ par Wallace et Luoma (2003)). Les proportions du CH 3 Hg réparti en TAM (CH 3 Hg-TAM%) varient de 39,7 % à 82,7 %, alors que les portions du Cd partitionné (Cd-TAM%) varient de 51,8 % à 67,4 %. Il y a une corrélation significative entre CH 3 Hg-TAM% et Cd-TAM% et les proportions de métaux libérés des proies par une solubilisation in vitro avec du liquide provenant du tube digestif de choquemorts (c'est-à-dire, les métaux solubilisables dans le tube digestif (GSM)), respectivement CH 3 Hg-GSM% et Cd-GSM%. Cette relation laisse croire que la plus grande partie du CH 3 Hg et du Cd partitionnés en TAM chez les proies est solubilisée dans le tube digestif des choquemorts. Les choquemorts retiennent 52,7 % à 73,7 % du CH 3 Hg ingéré, ce qui se compare aux CH 3 Hg-TAM% et CH 3 Hg-GSM% spécifi-ques aux proies. Cependant, les choquemorts ne retiennent que 3,2 % à 11.0 % du Cd ingéré, ce qui est considérablement plus bas que les valeurs de Cd-TAM% et Cd-GSM%. Ces résultats indiquent que le CH3Hg solubilisable associé aux proies est transporté à travers la membrane du tube digestif des choquemort...

Relevance of intracellular partitioning of metals in prey to differential metal bioaccumulation among populations of mummichogs (Fundulus heteroclitus)

“…This differential Cd trophic availability from P. pugio among sites was clearly reflected in the Cd bioaccumulation in mummichogs at these sites. Although there have been several experimental studies on the effects of metal detoxification in prey from chronically polluted habitats on metal trophic transfer to predators (e.g., Nott and Nicolaidou, 1994;Wallace et al, 1998), it is still unclear if detoxification strategies used by predators simultaneously influence metal trophic transfer (Goto and Wallace, 2009). Through the chronic exposure to trace metals, both prey and predators living in metal-polluted habitats may independently develop detoxification strategies, resulting in differential metal bioaccumulation in predators.…”

“…Samplings of mummichogs and two of the most commonly consumed prey items of mummichogs in AK, decapods (Palaemonetes pugio) and polychaetes (Nereis acuminata) (Goto, 2009), were conducted during the summers (June-September) of 2001 and 2004. Large adult mummichogs (>70 mm TL) were collected using a seine net with polyester mesh or cylindrical minnow trap.…”

Biodynamic understanding of mercury accumulation in marine and freshwater fish

“…In fish, it has been well recognized that the AEs of metals are dependent on the food conditions such as the food density and food type (Ni et al 2000, Wang and Wong 2003, Zhang and Wang 2006. These external conditions may significantly affect the ingestion, digestion, solubilization (Leaner andMason 2002, Goto andWallace 2009), membrane transport (Mason et al 1996), and gut passage time (Xu and Wang 2002) and subsequently affect the dietary AEs. The AEs of Hg(II) are generally more variable than the AEs of MeHg.…”

“…proposed grouping organelles, HDP and HSP together and referred to them collectively as the trophically available metal (TAM) fraction. Goto and Wallace (2009) found that MeHg partitioned in the TAM fraction could be solubilized in the gut fluid of mummichogs (Fundulus heteroclitus). Dang and Wang (2010) quantified the AEs of Hg(II) and MeHg in a marine fish, the grunt Terapon jarbua, based on mercury subcellular partitioning in preys (brine shrimp, clams, mussels, scallops and fish) and purified subcellular fractions of prey tissues (from mussel digestive glands and fish muscle into insoluble fraction consisting of cellular debris, MRG and organelles, HSP and HDP).…”

Assimilation of Elements and Digestion in Grass Shrimp Pre-Exposed to Dietary Mercury

“…Assimilation of pollutants can be influenced by partitioning in food as well as consumer digestive physiology (Goto and Wallace 2009;Dang and Wang 2010). The effects of ingested pollutants on digestion may be related to mode of internal exposure.…”