EVALUATION OF BIOASSAYS TO MONITOR SURFACE MICROLAYER TOXICITY IN TROPICAL MARINE WATERS

Bioassays were developed, using embryos of: coral, Montastraea faveola ta; graysby, Epinephelus cruentatus; grouper, Epinephelus adscensionis x gruttatus (hybrid); queen conch, Strombus gigas; rock-boring urchin , Echinodemata lucunter; spotted seatrout, Cynoscion nebulosus; varieg ated urchin, Lytechinus variegatus; winged pearl oyster, Pteria colymb us; and yellowtail snapper, Ocyurus chrysurus. Relative sensitivities and precison of various species-endpoint combinations were evaluated u sing three reference toxicants: copper, sodium dodecyl sulfate, and Di brom(R). The 24-h P. colymbus embryo test had the best overall sensiti vity and exhibited a high degree of precision. However, oyster embryos were difficult to obtain and did not aggregate at the air-water inter face. Therefore, the P. colymbus embryo test was deemed unsuitable for use as a bioassay for monitoring sea-surface microlayer (SSML) toxici ty. Tests based on normal development of L. variegatus to the early pl uteus 3 stage and percent normal-live C. nebulosus larvae at 48 h were relatively sensitive and exhibited good replicability and repeatabili ty. The L. variegatus urchin embryo test was also found to be highly r eproducible. The results of this comparative study indicated that L. v ariegatus and C. nebulosus were suitable surrogates for coral-reef spe cies in toxicity assessments of the SSML.