Acid Mine Drainage
Impact of mining activities on stream ecosystem functions
Decomposition and shredding are major a resource pathway for stream food webs. As part of a collaborative project, led by Jon Harding, research has focused on how leaf and wood breakdown by bacteria, fungi (Fig. 1) and invertebrates (Fig. 2) is influenced by stressors associated with mine drainage (Fig. 3). These stressors include low pH, elevated dissolved metal concentrations and precipitation of metal oxides on the stream bed.
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Figure 1. Fungal hyphae on the
surface of a |
Figure 2. The stonefly Austroperla cyrene coated |
Figure 3. Leaf litter and wood showing signs
of breakdown after inundation in a West Coast stream.
Litter breakdown was most strongly influenced by abundance of metal oxide precipitates (Fig. 4), rather than pH or the concentration of dissolved Al and Fe. An increase in metal oxides was highly correlated with decreased microbial respiration (largely fungi). Although the density and diversity of shredders in both impacted and natural reference streams was low, shredder abundance was lower in the most impacted streams (Barnden & Harding 2005, pdf, 580kb). Thus, reduced breakdown rates in AMD impacted streams are driven by decreased processing by shredders and microbes.
Figure 4. Marked decline in leaf breakdown rates
with
the
increased precipitation of metal oxides.
People involved in this project
University of Canterbury
Jon Harding
Justin Kitto (Completed MSc Student)
Annabel Barnden (Completed MSc Student)
Missouri University of Science & Technology
Dev Niyogi
University of Maine
Kevin Simon
Publications
Barnden 2005 Ecology of streams affected by iron precipitates and iron flocculants. MSc thesis, University of Canterbury (pdf, 1.6mb).
Barnden & Harding 2005
Shredders and leaf breakdown in streams polluted by coal mining in the South Island, New Zealand. New Zealand Natural Sciences 30:35-48 (pdf, 580kb).