The combined effects of chlorine and ammonia on litter breakdown in outdoor experimental streams

Abstract

The response of Potamogeton crispus L. breakdown to controlled doses of different levels of chlorine and chlorine + ammonia was investigated over two years in outdoor experimental streams. In 1985, downstream riffles of 2 streams were dosed (observed in-stream concentrations) at ca. 10 jug/L Total Residual Chlorine (TRC), one stream at 64 #g/L TRC and one stream at 230 ftg/L TRC. Two control streams were not dosed and the upstream riffles of each stream served as within stream controls. In 1986, the downstream riffle of one stream was dosed at 70 jtg/L TRC and a second stream was dosed at 200 tg/L TRC. Four streams were also dosed with 2.5 mg/L NH 3 -N: one stream with no chlorine, one stream with ca. 10 jig/L TRC, one with 56 pg/L TRC, and one with 150 ug/L TRC. A seventh stream was dosed for 2 h at 2000 jug/L TRC and 2.5 mg/L ammonia and then allowed to recover (recovery stream). Each year, litter decomposition (degree day k values) was measured during two 35 day trials (Jun-Jul and Aug-Sep). In 1985, when streams were dosed with chlorine alone, decomposition was significantly reduced with the high (230 yg/L TRC) chlorine dose. Downstream decomposition was 27 % (Jun-Jul) and 59% (Aug-Sep) of the upstream (control) rate. No other chlorine effects were found during this period. In Jun-Jul 1986, there was significantly lower decomposition in the downstream dosed sites of the 200 #g/L TRC alone stream, the 146 #g/L TRC + ammonia stream and the recovery stream; downstream decay rates were (respectively) 56%, 42% and 64% of the upstream control sites. No other up-down pairs were different in July 1986. In Aug-Sep, all three streams with chlorine + ammonia (6, 56 and 146 ktg/L TRC + 2,5 mg/L ammonia) and the 70 ,g/L TRC alone stream had significantly lower decomposition rates in the downstream dosed sites. For these streams, downstream decay rates ranged from 46 % (high chlorine + ammonia) to 73 % (low chlorine + ammonia) of the upstream control rates. No other up-down pairs were different during this trial. Up and downstream sites of the stream dosed with 2.5 mg/L ammonia alone were nearly identical for both trials (< 3 % difference). These results indicate that TRC at less than 250 g/L can significantly reduce litter decomposition and strongly suggest that addition of ammonia to chlorinated water can increase the toxic effect of chlorine. 70

Identification of predominant environmental factors structuring stream macroinvertebrate communities within a large agricultural catchment

“…Direct effects of these compounds on invertebrate communities are difficult to determine. However, ammonia may have direct and synergistic toxic effects in streams (Newman & Perry, 1989) and the toxicity of substrates with high organic composition, as observed at some of our sites, can alter invertebrate community composition (Ankley et al, 1992). Nitrogen and phosphorus compounds are more likely to influence communities through indirect pathways that affect ecosystem parameters such as primary productivity.…”

Differences in processing dynamics of fresh and dried leaf litter in a stream ecosystem

“…where m, is the mass remaining at time r, mo is the initial mass, and k is the decay coefficient, or fixing the intercept (mo) and fitting to the simplified model with only one coefficient to be estimated (Wieder & Lang, 1982;Chauvet, 1987;Newman & Perry. 1989).…”

“…While it is true that drying is convenient and the use of dried litter may be acceptable in investigations where leaf processing serves as a tool for assessing the effects of ecosystem disturbance or pollution (e.g. Mulholland et al, 1987;Newman & Perry, 1989;Benfield et al, 1991), leaf material in its natural state should be used in studies aimed at identifying fundamental principles of leaf processing, or in those concerned with integrating processing data in ecosystem mass balances both with respect to carbon (Cuffney, Wallace & Lugthart, 1990) and nutrients.…”