[OANNES Foro] The influence of depth on mercury levels in pelagic fishes and their prey

[Raul Sanchez Scaglioni]

PNAS August 18, 2009 vol. 106 no. 33 13865-13869 
The influence of depth on mercury levels in pelagic fishes and their prey


C. Anela Choya,1, 
Brian N. Poppb, 
J. John Kanekoc and 
Jeffrey C. Drazena
- Author Affiliations


aDepartment of Oceanography, University of Hawaii, 1000 Pope Road, Honolulu, HI 96822; 

bDepartment of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822; and 

cPacMar Inc., 3615 Harding Avenue, Suite 409, Honolulu, HI 96816 

Abstract
Mercury distribution in the oceans is controlled by complex biogeochemical cycles, resulting in retention of trace amounts of this metal in plants and animals. Inter- and intra-specific variations in mercury levels of predatory pelagic fish have been previously linked to size, age, trophic position, physical and chemical environmental parameters, and location of capture; however, considerable variation remains unexplained. In this paper, we focus on differences in ecology, depth of occurrence, and total mercury levels in 9 species of commercially important pelagic fish (Thunnus obesus, T. albacares, Katsuwonus pelamis, Xiphias gladius, Lampris guttatus, Coryphaena hippurus, Taractichthys steindachneri, Tetrapturus audax, and Lepidocybium flavobrunneum) and in numerous representatives (fishes, squids, and crustaceans) of their lower trophic level prey sampled from the central North Pacific Ocean. Results indicate that total mercury levels of predatory
 pelagic fishes and their prey increase with median depth of occurrence in the water column and mimic concentrations of dissolved organic mercury in seawater. Stomach content analysis results from this study and others indicate a greater occurrence of higher-mercury containing deeper-water prey organisms in the diets of the deeper-ranging predators, X. gladius, T. obesus, and L. guttatus. While present in trace amounts, dissolved organic mercury increases with depth in the water column suggesting that the mesopelagic habitat is a major entry point for mercury into marine food webs. These data suggest that a major determinant of mercury levels in oceanic predators is their depth of forage. 

depth of forage
marine pelagic predators
North Pacific Ocean
mercury bioaccumulation
mesopelagic zone

Footnotes

1To whom correspondence should be addressed. E-mail: cachoy en hawaii.edu


      
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