Rapid assessment of water quality, using the fingernail clam, Musculium transversum

Apparatus and methods were developed for testing the effects of water quality factors on the ciliary beating rate of clam gills. Musculium transversum was chosen as the test organism because it is a major food source for fish and waterfowl, and because it has died out in areas of the Illinois River where it was formerly abundant. Populations of this fingernail clam also declined recently in the Keokuk Pool, Mississippi River, an important feeding area for migratory waterfowl and commercially valuable species of fish. The ciliary beating response is extremely sensitive. For example, a zinc concentration of .00006 μg/l produced a statistically significant reduction in the ciliary beating rate of gills from large fingernail clams. Gills from small clams were much less sensitive, requiring .06-.6 μg/l zinc to produce the same response. Concentrations of potassium and un-ionized ammonia which inhibited the ciliary beating response of gills from small clams were quite close to the concentrations which reduced the survival or growth of intact clams during chronic bioassays. The threshold concentration of potassium for cilia inhibition of small clams lay between 39 and 390 mg/l. The maximum acceptable toxicant concentration (MATC) for long-term survival of fingernail clams lay between 195 and 275 mg/l potassium. Un-ionized ammonia concentrations of .08-. 09 mg/l inhibited the cilia of small clams, and the growth of the clams was reduced at concentrations between .20 and .34 mg/l NH₃-N. In addition to potassium and ammonia, the following factors were tested singly or in combination: light, temperature, dissolved oxygen, sodium nitrate, sodium sulfate, cyanide, lead, copper, zinc, suspensions of silica particles, suspensions of illite clay particles, and raw Illinois River water. Comparison of the levels of these water quality factors in the Illinois and Mississippi Rivers with the levels which had detrimental effects on the clam gills suggests that un-ionized ammonia and heavy metals may have affected fingernail clams in the Illinois River in the 1950's and in the Mississippi River in 1976-1977. These tentative conclusions should be validated using chronic bioassays in which fingernail clams are exposed to conditions simulating those in the Mississippi River in 1976-1977, and by deletion bioassays in which certain components are removed from raw Illinois River water and the survival, growth, and reproduction of clams in the treated water are measured. KEY WORDS: water pollution effects, bioassay, bioindicators, animal physiology, fingernail clams, Sphaerium transversum, Musculium transversum, Sphaeriidae, heavy metals, silt, heat, dissolved oxygen, cyanide, ammonia, . - potassium, suspended solids, suspended sediment, sodium nitrate, sodium sulfate, lead, copper, zinc, Keokuk Pool, Mississippi River, Illinois River, Asiatic clam, Corbicula manilensis, blue mussel, Mytilus edulis, Elliptio complanata.U.S. Department of the InteriorU.S. Geological SurveyOpe