title: Effects of ammonia on periphytic communities.
abstract: Laboratory tests were conducted to evaluate the chronic effects of ammonia on periphytic communities. Species richness of the protozoan component of these communities was affected at un-ionized ammonia concentrations of </= 0.01 mg NH3 litre(-1). A biologically important concentration was defined as the concentration of ammonia affecting 20% of species and was estimated from a concentration-response regression as 0.011 mg litre(-1). A comparable value based on literature reports of chronic toxicity to fish and invertebrates was 0.0126 mg litre(-1). Other non-taxonomic responses were equally sensitive to ammonia. Biomass (ash-free dry weight) and algal biomass (in vivo fluorescence) were significantly reduced even at the lowest tested ammonia treatment, 0.01 mg litre(-1), but the abundance of bacteria was reduced only in the highest treatment group, 0.43 mg litre(-1). Net community metabolism was reduced in all ammonia treatments. Periphyton communities were affected at levels below the USEPA chronic criterion of 0.027 mg litre(-1) (temperature = 8.8 degrees C and pH = 8.1). Successional maturity or age of the periphytic community affected the amount of biomass and algal biomass, but did not modify sensitivity to ammonia.
authors.affiliation: University Center for Environmental and Hazardous Materials Studies and Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Niederlehner
authors.forename: J
authors.initials: J
authors.lastname: Cairns