Acid Mine Drainage

Ecosystem processes in streams under anthropogenic stress

Both natural and anthropogenic stresses affect almost all aquatic ecosystems.  A "stress," such as mine drainage or agriculture, can pose several distinct stressors (having a negative influence), or in some cases subsidies (having a positive influence), to streams. Dev Niyogi's (Missouri University of Science & Technology) research centres on the effects of stress on ecosystem processes, including primary production and litter decomposition, in streams.

Dev is most interested in how the effects of stress on ecosystem processes are mediated by the biological communities that perform those processes. The biomass, diversity, and specific taxa of communities can all affect the rates of ecosystem processes in stressed systems.

In New Zealand, Dev works with Jon Harding and FERG students on the effects of acid mine drainage (AMD) on streams along the West Coast of the South Island. AMD poses three main stressors on stream biota: acidity, dissolved metals, and metal hydroxide precipitates. Different stream communities have varying responses to these stressors. Remediation of mine drainage must focus on all the stressors in downstream systems.

A recent project on the effects of mine drainage on litter breakdown found that breakdown was related to effects on shredding invertebrates and microbes, mainly aquatic fungi (Fig. 1). Shredders were uncommon in most streams, including pristine reference streams. Fungi were abundant and active in many streams (Fig. 2), including some that were very acidic (pH < 3).

Figure 1. Beech detritus and wood sticks used to assess organic matter breakdown in streams.	Figure 2. Scanning electron microscope image of fungal hyphae that have colonised a beech leaf in a Westland stream.

People involved in this project

University of Canterbury
Jon Harding
Kristy Hogsden (PhD stduent)
Justin Kitto (Completed MSc Student)

Missouri University of Science & Technology
Dev Niyogi

University of Maine
Kevin Simon