Biomagnification Profiles of Trace Elements through the Food Web of an Integrated Shrimp Mangrove Farm in Ba Ria Vung Tau, South Vietnam

Problem statement: Ba Ria Vung Tau (BRVT), a Vietnamese province with one of the fastest growing economies in the country, faces significant environmental challenges, including increased contamination of rivers and estuaries with urban and industrial wastes. Approach: Concentrations of 23 trace elements and stable isotope ratios (δ¹³C and δ¹⁵N) were analyzed in suspended particulate matter, one species of peanut worm, one species of octopus, six species of crustaceans and 13 species of fish collected from an integrated shrimp mangrove farm in the BRVT. Results: Concentrations of Cu, Zn, Se, Mo, Ag, Cd, Sb and Bi in octopus, Mn, Sr and Ba in crustaceans and Hg in fish were the highest among organisms analyzed. Using δ¹⁵N values to identify trophic positions, we found that Zn, Se and Hg biomagnified through the food web. The slope for Hg (0.048) was remarkably lower than those reported for other aquatic food webs. In contrast, the concentrations of most trace elements followed reverse trends (i.e., decreasing concentrations with increasing trophic level). Trace element concentrations we measured in organisms were within safe levels for human consumption according to criteria established by the Ministry of Agriculture, Fisheries and Food (MAFF) in the UK. However, concentrations of Cu in black tiger shrimps and octopus and Zn in Commerson's glassy fish were higher than the MAFF guidelines. Conclusion: The results of this study highlight the usefulness of δ¹³C and δ¹⁵N as a tool not only for elucidating the trophic position of biota, but also for tracing contaminants within food webs.