Influences of prey- and predator-dependent processes on cadmium and methylmercury trophic transfer to mummichogs (Fundulus heteroclitus)
نویسندگان
چکیده
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 CH3Hg 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 CH3Hg 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 dépendantes 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 CH3Hg réparti en TAM (CH3Hg-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 CH3Hg-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 CH3Hg-GSM% et Cd-GSM%. Cette relation laisse croire que la plus grande partie du CH3Hg 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 CH3Hg ingéré, ce qui se compare aux CH3Hg-TAM% et CH3Hg-GSM% spécifiques 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 choquemorts, alors que la plus grande partie du Cd associé aux proies est exclue et ensuite éliminée, indépendamment de son partitionnement subcellulaire. [Traduit par la Rédaction]
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