PT13 Aquatic Ecotoxicology I
Exhibit Hall
8:00 AM - Tuesday
(PT207) Acute and chronic toxicity of brevetoxin to oysters and grass shrimp.
Walker, C1, Winstead, J1, Foss, S1, Kurtz, J1, Watts, J1, Scott, J1, Fisher, W1, 1 US EPA, Office of Research and Development, Gulf Ecology Division, Gulf Breeze, FL, USA
ABSTRACT- Brevetoxins (PbTx) produced by the Florida red tide dinoflagellate, Karenia brevis, are potent, acute acting neurotoxins that cause massive mortalities of marine fish, marine mammals, sea birds and other wildlife. Little is known about PbTx toxicity to molluscs and decapods and chronic exposures to such toxins, a more realistic and less visible phenomenon, has received little attention. To better understand the ecological effects of PbTx, a mollusc and a decapod were examined for changes in physiological and reproductive capacity related to acute and chronic PbTx exposures. Eastern oysters, Crassostrea virginica, were measured for height and length and the posterior valve of each was notched for measurement of new shell growth (NSG). Comparable size oysters were placed into control and experimental aquaria and maintained on flow-through raw seawater. Experimental aquaria were dosed with K. brevis (1×106 cells/oyster) twice a week for 14 weeks. Oysters were sampled at 7 and 14 wks, measured for NSG, opened and samples taken for histological analysis. Several target responses were examined, including disease occurrence, reproductive status, connective tissue condition and body weight. Analysis of variance showed NSG in K. brevis dosed oysters was significantly less than in control oysters at the end of 14 wks (P=.008) but no differences between other parameters measured. Adult grass shrimp, Palaemonetes pugio, exhibited unexpected mortality when exposed to K. brevis extracts during chronic effects studies. Acute toxicity studies were performed and LC-50's for adult and embryo/larvae were 46 and 42 ng total PbTx/mL, respectively. The results show that relatively low concentrations of K. brevis blooms can cause adverse effects in key estuarine species not previously recognized as affected.
Key words: oyster, brevetoxin, shrimp, LC-50