Use of leaf litter breakdown and macroinvertebrates to evaluate gradient of recovery in an acid mine impacted stream remediated with an active alkaline doser

Abstract

The spatial congruence of chemical and biological recovery along an 18-km acid mine impaired stream was examined to evaluate the efficacy of treatment with an alkaline doser. Two methods were used to evaluate biological recovery: the biological structure of the benthic macroinvertebrate community and several ecosystem processing measures (leaf litter breakdown, microbial respiration rates) along the gradient of improved water chemistry. We found that the doser successfully reduced the acidity and lowered dissolved metals (Al, Fe, and Mn), but downstream improvements were not linear. Water chemistry was more variable, and precipitated metals were elevated in a 3-5-km "mixing zone" immediately downstream of the doser, then stabilized into a "recovery zone" 10-18 km below the doser. Macroinvertebrate communities exhibited a longitudinal pattern of recovery, but it did not exactly match the water chemistry gradient Taxonomic richness (number of families) recovered about 6.5 km downstream of the doser, while total abundance and % EPT taxa recovery were incomplete except at the most downstream site, 18 km away. The functional measures of ecosystem processes (leaf litter breakdown, microbial respiration of conditioned leaves, and shredder biomass) closely matched the measures of community structure and also showed a more modest longitudinal trend of biological recovery than expected based on pH and alkalinity. The measures of microbial respiration had added diagnostic value and indicated that biological recovery downstream of the doser is limited by factors other than habitat and acidity/alkalinity, perhaps episodes of AMD and/or impaired energy/nutrient inputs. A better understanding of the factors that govern spatial and temporal variations in acid mine contaminants, especially episodic events, will improve our ability to predict biological recovery after remediation.

Organic Matter Decomposition and Ecosystem Metabolism as Tools to Assess the Functional Integrity of Streams and Rivers–A Systematic Review

“…Environmental changes most represented in bioassessment studies using organic matter decomposition were driven by agriculture/pasture (16 studies), forestry (14), industry/urbanization (11), and nutrient enrichment/eutrophication (11) (Figure 4a). Interestingly, three studies used organic matter decomposition to assess the effects of restoration practices on stream functioning ( [207,216,217]; Figure 4a). Environmental changes that were most represented in bioassessment studies using ecosystem metabolism were driven by agriculture/pasture (22 studies), industry/urbanization (12), organic pollution (7), hydromorphologic pressures (3), forestry (3), restoration (3), and mining (2) (Figure 4b).…”

“…For the remaining types of environmental changes, the effectiveness of organic matter decomposition and ecosystem metabolism as bioassessment tools varied between 50% and 82% (Figure 12). Particularly interestingly was the fact that both organic matter decomposition [207,216,217] and ecosystem metabolism [240][241][242] were effective in detecting the effects of restoration practices. Despite the low number of studies, this result suggests that these ecosystem functions may be useful indicators for the evaluation of restoration practices.…”

“…Despite the difficulties in incorporating indicators of stream functional integrity in large scale bioassessment programs, these can be particularly useful in bioassessment programs at smaller scales. Examples include the evaluation of the effects of stream restoration practices [66,207,216,[240][241][242] or of particular point source pollution (pesticide spill [253], wastewater treatment plant [110,254]).…”

Assessment of Impacts of Coal Mining in the Region of Sydney, Australia on the Aquatic Environment Using Macroinvertebrates and Chlorophyll as Indicators

“…Sulphur containing material in mine comes in contact with water, which naturally generates sulphuric acid, termed as acid mine drainage (AMD), which can dissolve harmful metals and metalloids from the surrounding rocks and increase the water contamination level [ 3 ]. Alkaline dozers are used to reduce the acidity and dissolved metals from the acid mine drainage, but the improvements were shown as non-linear [ 4 ].…”

Using macroinvertebrates to assess ecological integrity of streams remediated for acid mine drainage

“…FD is a key component of biodiversity that connects organism traits to ecological processes such as predation, herbivory, and detritivory. Responses of macroinvertebrate functional‐feeding groups to AMD remediation primarily have focused on specific guilds rather than an overall index of FD in the community (Carlisle & Clements ; Johnson et al ; however, see He et al ). Our hypothesis was that all metrics would indicate restoration improved macroinvertebrate communities below treatment, but estimates of the degree of recovery would differ depending on the measure used.…”