Chironomids from three rivers within the Niagara River Watershed were sampled and divided into two groups: those with ligulae and those with labial plates. The latter group of chironomids (i.e. the Chironomini and Tanytarsini) were classified as either normal (no deformities in their labial plates), slightly deformed (slight asymmetries due to teeth which were missing or chipped) or grossly deformed (those with extra teeth, fused teeth, crossed teeth or large gaps between their teeth). Among the 1,062 chironomids taken from the 15 sample sites, 699 possessed labial plates and 14% of these (97) displayed gross deformities in the structure of their labial plate. Most of the chironomids displaying gross deformities came from areas in the Niagara River watershed where sediments were contaminated with a number synthetic teratogens.

The highest frequency of chironomid labial plate deformities (47% gross deformities) occurred at the B.F. Goodrich Company’s discharge pipe. In 1986, 33 kg of vinyl chloride, (C2H3Cl), a known carcinogen, was released into the Welland River at this site. This substance is suspected of causing the high frequency of deformities observed at this site.

The second highest frequency of chironomids with gross labial plate deformities occurred in the heavily industrialized section of the Buffalo River, (Buffalo, New York). Thirty-five percent of the Chironomini and Tanytarsini at the five sampling sites in the Buffalo River displayed gross deformities as compared to 9% at the “control” site.

It was concluded that the frequency of chironomid labial plate deformities provides researchers with a useful index for evaluating sediments

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© CAWQ 1989
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