Upper Midwest Environmental Sciences Center
The effects of ammonia on freshwater unionid mussels
Newton, T. J., 2003, The effects of ammonia on freshwater unionid mussels: Environmental Toxicology and Chemistry, v. 22, no. 11, p. 2543-2544.
Ammonia is a relatively toxic compound generated in water and sediments by heterotrophic bacteria and accumulates in sediments and pore water. Recent data suggest that unionid mussels are sensitive to un-ionized ammonia (NH3) relative to other organisms. Existing sediment exposure systems are not suitable for ammonia toxicity studies with juvenile unionids; thus, we modified a system to expose juveniles to ammonia that was continuously infuses into sediments. This system maintained consistent concentrations of ammonia in pore water up to 10 d. Juvenile Lampsilis cardium mussels were exposed to NH3 in pore water in replicate 96-h and 10-d sediment toxicity tests. The 96-h median lethal concentrations (LC50s) were 127 and 165 µg NH3-N/L, and the 10-d LC50s were 93 and 140 µg NH3-N/L. The median effective concentrations (EC50s) (based on the proportion affected, including dead and inactive mussels) were 73 and 119 µg NH3-N/L in the 96-h tests and 71 and 99 µg NH3-N/L in the 10-d tests. Growth rate was substantially reduced at concentrations between 31 and 76 µg NH3-N/L. The lethality results (when expressed as total ammonia) are about one-half the acute national water quality criteria for total ammonia, suggesting that existing criteria may not protect juvenile unionids.
Unionids, Ammonia, Toxicity, Juveniles, freshwater mussels