Diatom communities across a gradient of acid mine drainage on the West Coast, South Island, New Zealand (2012)
Type of ContentTheses / Dissertations
Thesis DisciplineEnvironmental Sciences
Degree NameMaster of Science
PublisherUniversity of Canterbury. Biological Sciences
Acid mine drainage (AMD) is a major environmental issue worldwide. On the West Coast of the South Island, New Zealand, numerous catchments receive AMD, with significant negative impacts on in-stream flora and fauna. Diatoms are commonly regarded as powerful biological indicators and may be found in high abundance in AMD-contaminated streams; however, relatively little work has been done on diatoms in mining environments in New Zealand. Initially, I conducted a survey of epiphytic diatom communities in 39 streams ranging from non-impacted reference streams to those severely impacted by AMD. Streams were assigned to one of four classes along an AMD gradient: circum-neutral reference, naturally acidic reference, moderately impacted, and severely impacted. There was a wide range in diatom taxonomic richness in reference and moderately impacted streams (8 – 33 taxa). Taxonomic richness was greatly reduced in severely impacted streams (1 – 5 taxa) at a threshold of pH 3.4 and was dominated by Pinnularia cf. acidophila (69 – 100% relative abundance). Community composition differed between circum-neutral reference, moderately, and severely impacted streams; however, naturally acidic and moderately impacted streams had similar diatom communities primarily composed of acid-tolerant Eunotia and Frustulia species. This indicated that diatoms are strongly structured by pH and able to tolerate moderate conductivity and metal concentrations without a corresponding shift in community composition. Survey data were then used to develop two diatom-based indices for streams impacted by AMD: a single Biotic Index and a Multimetric Index. While neither index was able to distinguish naturally acidic from moderately impacted streams, both indices successfully categorised streams as circum-neutral reference, moderately or severely impacted by AMD. These indices may be useful in assessing AMD impact on circum-neutral streams or in identifying when a stream has crossed a threshold from moderately to severely impacted by AMD. Diatoms would be especially useful as bioindicators of AMD if they respond rapidly to a change in mine discharge. To test this, mature algal biofilms were reciprocally transferred between circum-neutral reference streams and streams of varying degrees of AMD over a period of 13 days. Diatom mortality increased rapidly in the reciprocal transfer between reference and severely impacted streams. Reference communities resembled the ambient diatom community of severely impacted streams 13 days post-transfer. However, in the reverse transfer, a change in community composition was slow to occur. Diatoms respond faster to an increase in pollution than to pollution amelioration. Overall, results indicated that diatom communities may be a useful tool for monitoring the presence and magnitude of AMD in New Zealand streams.
Keywordsacid mine drainage (AMD); diatoms; natural acidity; periphyton; biotic index; multimetric index
RightsCopyright Kate Schowe
Showing items related by title, author, creator and subject.
The ecology of algal assemblages across a gradient of acid mine drainage stress on the West Coast, South Island, New Zealand Bray, Jonathan Peter (University of Canterbury. Biological Sciences, 2007)Physicochemical factors, algal diversity, taxonomic composition and standing crop were investigated across a broad gradient of AMD stress in streams and rivers. 52 sites were surveyed in the vicinity of Greymouth, Reefton, ...
Variation in the effects of disturbance along a soil drainage gradient for a lowland temperate rainforest, South Westland, New Zealand Rogers, Howard Michael (University of Canterbury. Forestry, 1995)Variation in the effects of disturbance across three differently aged glacial terraces in a terrace rimu (Dacrydium cupressinum) forest were investigated. Disturbance histories were reconstructed and associated patterns ...
Harbrow, Michael Andrew (University of Canterbury. School of Biological Sciences, 2001)Macroinvertebrate assemblages, physico-chemical factors, epilithic algal biomass and leaf decomposition were examined in streams draining the Charming Creek and Stockton-Millerton coalfields north of Westport, South Island. ...