Alternate Title

Toxicity of Drilling-Mud Biocides to Developing Estuarine Macrobenthic Communities


The effects of various blocides, as used in drilling muds for exploratory drilling for oil offshore, were determined by comparing macrobenthic communities that developed from planktonic larvae in treated and untreated aquaria. Surflo®-B33 and Aldacide® were tested simultaneously. Harvest at seven weeks yielded 1,941 animals, representing 37 species of 6 phyla. The etfects of Surflo-B33 (25% dichlorophenol and other chlorophenals) on these communities were similar to those of pentachlorophenol (Tagatz et al, 1977; 1978), a biocide known to be toxic to many aquatic organisms (Rao, 1978). Significantly fewer (a=0.05) chordates, mollusks, and annelids occurred in 819 µg Surflo-B33/l (measured) than in the control; mollusks were most sensitive and also significantly fewer in aquaria receiving 41 µg/l. Average numbers of animals and species per aquarium did not significantly decrease in Aldacide (91% paraformaldehyde) at nominal concentrations of 15 and 300 µg/l. The high toxicity of the chlorophenols tested indicates that use of alternative biocides, possibly paraformaldehyde, should be considered for natural waters.