Short term and long-term effects of toxicants on larval red abalone, Haliotis rufescens

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Conroy, P. T. Short term and long-term effects of toxicants on larval red abalone, Haliotis rufescens.
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TitleShort term and long-term effects of toxicants on larval red abalone, Haliotis rufescens
AbstractExperiments were conducted to correlate a short-term 48-hour aquatic toxicity test endpoint of abnormal larval shell development with other, more clearly adverse effects. In similar experiments conducted with two different toxicants, zinc sulfate and Bleached Kraft Mill Effluent (BKME), red abalone (Haliotis rufescens) embryos were simultaneously added to identical dilution series and incubated for three different exposure periods: 48-hours, 48-hours followed by an 8-day recovery period, or a 10-day continuous exposure. Abnormal larval shell development was assessed in the 48-hour tests, and inhibition of metamorphosis was assessed in the exposure-recovery (ER) and long-term (LT)exposures. For the zinc experiments, the median effective concentration (ECso) values for the 48-hour exposure, the ER, and the LT exposures were 40, 32, and 29 ~g/L zinc, respectively. For the BKME experiments, the ECso values were 1.00%, 0.78%, and 0.67% effluent, respectively. Results indicate that toxicant concentrations causing abnormal larval shell development also inhibit metamorphosis, and that larvae exposed to toxicant concentrations which inhibit larval shell development do not recover to metamorphose when transferred to clean seawater. None of the successfully metamorphosed post larvae had deformed larval shells, indicating that shell deformity precludes survival past the planktonic stage. To determine if toxicant exposure delays metamorphosis, a 15-day continuous and exposure-recovery EKME experiment was conducted. No significant difference in post-larval shell lengths of successfully metamorphosed abalone could be attributed to either toxicant concentration or duration of exposure. Results indicate that exposure to a toxicant acts to inhibit rather than delay the initiation of metamorphosis.

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