RELEASE OF TRACE-METALS BY SEWAGE SLUDGE AND THE SUBSEQUENT UPTAKE BY MEMBERS OF A TURTLE GRASS MANGROVE ECOSYSTEM

This research was initiated to determine the rates of uptake, by a Thalassia testudinum Konig/mangrove ecosystem, over a 125-day period, of Cd, Cr, Cu, Ni, Pb, and Zn. The metals were leached from sewage sludge by flowing seawater (8.4 L min-1) and subsequently traversed the model system. The largest net uptake of metals occurred in the “fouling organisms” where Cd, Pb, and Zn uptake closely paralleled the net loss of metals from the sewage sludge. Thalassia leaves showed a net uptake for Cr, Pb, Ni, and Zn. The urchin Lytechinus variegatus (Lamarck), a grazer of Thalassia leaves, also demonstrated a net uptake of Cu, Cr, Pb, Zn, and Ni. The sea cucumber Holothuria mexicana (Ludwig) showed a net uptake of Cr, Cu, Pb, and Zn. Net uptake of metals was shown by the roots of the red mangrove Rhizophora mangle Linne. Because of insufficient sample mass, no consistent metal uptake was found for the clam Codakia orbicularis (Linne), oyster Crassostrea rhizophorae (Guilding), or the snail Nerita tessellata (Gmelin). The results indicate that the dumping of sewage sludge in coastal tropical waters can lead to the uptake and concentration of toxic trace metals by members of a turtle grass community. © 1979, American Chemical Society. All rights reserved.