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Title: The Effects of Dursban® Insecticide on Pocillopora damicomis (Cnidaria: Scleractinia) 
Author: Te, Franklyn Tan
Date: 1992-12
Publisher: University of Hawaii, Honolulu
Citation: Te, Franklyn Tan. The Effects of Dursban® Insecticide on Pocillopora damicomis (Cnidaria: Scleractinia). Honolulu: University of Hawaii, 1992.
Abstract: The effects of Dursban®, a chlorpyrifos-based pesticide, on reef-building
corals was investigated. Short-term (96 hours) static bioassays with renewal of
toxicant every 24 hours were conducted with Pocillopora damicomis colonies.
Two sets of experiments were conducted. The first examined the toxicity of the
commercial pesticide mixture made up of filtered seawater (0.45 µm) and the
manufacturer's recommended dose for the treatment of lawns and gardens
(0.91 mI/l). The second determined the toxicity of effluent seawater obtained
from a soil column 24 hours after it was treated with Dursban® mixture (0.91 mi/l)
at the manufacturer's recommended level of coverage (1.53 ml/12.6 cm2). In both
experiments, coral branches were exposed to logarithmic dilutions of the toxicant
mixture for up to four days. The 96 hour median lethal concentration (96 h LC50)
for the pesticide mixture was found to be 1.2 x 10-7% of the original solution while
the soil effluent mixture had a 96 hour LC50 of 7.0 x 10-8% of the effluent solution.
Gas chromatographic analysis of the pesticide stock solution showed that the
chlorpyrifos levels remained relatively stable for the duration of the experiment.
Pesticide levels were monitored in the experimental test water at each dilution
level prior to exposure of corals to determine actual pesticide concentration
although several of the lower dilutions yielded concentrations below the
analytical detection limit of 2 µg/l.
Data gathered from the bioassay tests revealed high sensitivity of the coral
Pocillopora damicomis to the two toxicant preparations. The soil effluent water
was appreciably more toxic to the coral than the straight pesticide mixture. This
was thought to reflect formation of more toxic breakdown products derived from
chlorpyrifos after application to the soil column. Other factors, like the
interactive effects between the chemical binders and dispersants within the
commercial formulation and the soil may have contributed to the increase in
toxicity of the soil effluent solution. Effluent water from pesticide-treated areas
may be more toxic to corals than previously suspected.
Pages/Duration: 47 pages
Rights: All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
LC Subject Headings: Coral reef biology -- Hawaii
Coral reef ecology--Hawaii

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