COMPARISON BETWEEN LAMPREY AMMOCOETES AND BIVALVE MOLLUSKS AS BIOMONITORS OF ORGANOCHLORINE CONTAMINANTS

Lamprey ammocoetes were determined to be as suitable as adult bivalve molluscs for monitoring persistent organochlorine contaminants in the freshwater environment. Ammocoetes of four lamprey species and adults of three bivalve mollusc species, collected from the same seven rivers of the St. Lawrence River basin in Quebec, were assayed for 21 organo chlorine pesticides and for polychlorinated biphenyl (PCB) congeners. All organochlorine compounds assayed were detected in one or more of t he 15 lamprey samples whereas Aldrin, beta-BHC, and PCB congeners 1, 3 , 12(13), 29, 54, 189, 191, and 199 were not detected in any of the ni ne bivalve samples. Nine pesticides (Aldrin, Dieldrin, gamma-BHC, alph a-Chlordane, gamma-Chlordane, o,p'-DDD, p,p'-DDD, p,p'-DDT, and alpha- Endosulfan) had higher concentrations in the lampreys. PCB congeners 1 67(185) and 209 had higher concentrations in bivalves. PCBs accounted for 96.6 - 99.4% of the organochlorine lipid burden in bivalves, but o nly 33.4 - 76.8% in lampreys. On average, ammocoetes had 44 times more lipids per body dry weight than did bivalves. The differences observe d in concentrations and types of organochlorine compounds found in the two taxa may be due to differences in the amounts (observed) and type s (postulated) of body lipids they each possess.