Chronic toxicity of ammonia to New Zealand freshwater invetebrates a mesocosm study

• Published in: Archives of environmental contamination and toxicology 1999-01, Vol.37 (3), p.338-351
• Main Authors: Hickey, C W, Golding, LA, Martin, M L, Croker, G F
• Format: Article
• Language: English
• ISSN: 0090-4341

Macroinvertebrate communities were collected from a spring-fed stream and exposed to ammonia in a mesocosm study under flow-through conditions for 29 d. Concentrations of ammonia were approximately 2, 5 and 12 times greater than the U.S. EPA (1985) water quality guidelines for ammonia at pH 8.0 and 15C. Exposure resulted in no significant effect on taxa richness, number of taxa in the orders Ephemeroptera, Plecoptera and Trichoptera (EPT), or in the quantitative macroinvertebrate community index (QMCI). There was no drift response to ammonia exposures. Significant differences were observed for mean abundance of the numbers of EPT individuals, of which the mayflies Deleatidium sp. demonstrated significant reduction in abundance. The 29 d EC50 values for this species for total and unionized ammonia were 2.15 mg (nitrogen) per litre and 0.145 mg (ammonia-nitrogen) per litre. No observed effect concentration values were 0.95 mg (nitrogen) per litre and 0.066 mg (ammonia-nitrogen) per litre. The threshold effect concentration was 1.49 mg (nitrogen) per litre and 0.102 mg (ammonia-nitrogen) per litre. Comparison of this sensitivity data with updated U.S. EPA 1998 data suggested that use of the criteria for the latter would provide minimal protection for this species. There are 52 references.