EFFECTS OF NO. 2 HEATING OIL 
ON FILTRATION RATE OF BLUE MUSSELS, 
MYTILUS EDULIS LINNE 
J. G. Gonzalez, D. Everich, J. Hyland, and B. D. Melzian 
U.S. Environmental Protection Agency 
Environmental Research Laboratory 
Narragansett, Rhode Island 02882 
ABSTRACT 
Reductions in gill filtration rates were observed for adult blue mussels, 
Mytilus edulis, that were exposed in a continuous flow-through dosing system, 
to three concentrations of the water-accommodated fraction of No. 2 fuel oil. 
The oil concentrations were measured routinely by infrared spectrometry, and 
averaged 0.019 ppm, 0.06 ppm, and 0.64 ppm throughout the exposure period. 
Filtering rates for healthy, unexposed mussels ranged from 7.2 to 30.9 ml/min, 
depending on ambient water conditions. In comparison to controls, filtering 
rates decreased as the oil concentration increased, with significant reductions 
occurring at all dose levels within 48 hours of exposure. Continued oil 
exposure up to two weeks produced progressively higher reductions in filtering 
rate. When returned to uncontaminated water for two weeks, the mussels 
resumed their normal feeding rates, revealing that the effect was reversible. 
Mussels collected from a small oil spill site exhibited similar responses. 
INTRODUCTION 
Bivalve mollusks are of considerable value to ecologists studying the effects 
of pollution; because many of the species are sedentary filter feeders, and are 
likely to accumulate contaminants from their surroundings. Mytilus edulis , the 
blue mussel, has become one of the most widely studied members of the group 
since it has a worldwide distribution; it is easy to maintain in the laboratory; 
and it is exploited commercially, particularly in European countries. Also, 
Mytilus , because of its intertidal existence, is particularly vulnerable to oil 
exposure. 
Several investigators have demonstrated a reduced feeding rate in mollusks 
exposed to environmental stress. Galtsoff et al (3) reported fifty percent 
reduction in gill ventilation rate of oysters exposed to an extract of crude oil. 
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