CSIRO PUBLISHING Marine and Freshwater Research, 2008, 59, 1084–1091 www.publish.csiro.au/journals/mfr Periphyton communities in New Zealand streams impacted by acid mine drainage Jonathan P. Bray A , Paul A. Broady A , Dev K. Niyogi A and Jon S. Harding A,B A School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. B Corresponding author. Email: jon.harding@canterbury.ac.nz Abstract. Discharges from historic and current coal mines frequently generate waters low in pH (<3), high in heavy metals (e.g. Fe, Al) and cover streambeds in metal precipitates. The present study investigated periphyton communities at 52 stream sites on theWest Coast, South Island, New Zealand, representing a range of impacts from acid mine drainage (AMD).Taxonomic richness was negatively related to acidity and metal oxides and biomass was negatively correlated with metal oxides, but positively related to acidity. Streams with low pH (<3.5) had low periphyton richness (14 taxa across all sites) and were dominated by Klebsormidium acidophilum, Navicula cincta and Euglena mutabilis. As pH increased, so did taxonomic richness while community dominance decreased and community composition became more variable. Canonical correspondence analyses of algal assemblages revealed patterns influenced by pH. These findings indicate that streams affected by AMD possess a predictable assemblage composition of algal species that can tolerate the extreme water chemistry and substrate conditions. The predictability of algal communities declines with decreasing stress, as other abiotic and biotic factors become increasingly more important. Additional keywords: algal diversity, benthic algae, metal oxides, metals, pH. Introduction Periphyton assemblages can be spatially complex and temporally variable depending on a wide range of environmental and biolog- ical factors (Biggs and Kilroy 2004; Peterson 2007). In streams, light (DeNicola et al. 1992), nutrients (Biggs and Close 1989), temperature (DeNicola 1996), current velocity (Biggs and Close 1989), physical disturbance (Biggs and Close 1989), substrate type (Murdock and Dodds 2007), competition (Stevenson et al. 1991) and invertebrate grazing (Peterson et al. 2001) can all influence periphyton assemblages. However, in systems receiv- ing acid mine drainage (AMD), the chemical characteristics of the receiving waters are of overriding importance and can strongly affect algal diversity and community structure (Verb and Vis 2000, 2001, 2005; Niyogi et al. 2002). Acid mine drainage is often characterised by high acidity, high concentrations of dissolved metals (e.g. Fe, Al, Zn), and metal oxide deposition (Younger et al. 2002; Harding 2005). Metal oxides commonly precipitate from solution when acidic waters mix with waters of higher pH such that the solubility of the metals is exceeded. Highly turbid waters containing coal fines and suspended sediment can also be a major issue in active mine sites (Younger et al. 2002; Harding 2005). Algal communities respond to these environmental stressors and may be structured by a combination of pH (Kinross et al. 1993), heavy metal contamination (Soldo and Behra 2000) and metal oxide deposition (Niyogi et al. 1999). Niyogi et al. (2002) found that even low levels of oxide deposition could decrease algal diversity, biomass and function. Similarly,Anthony (1999) found algal biomass was low in AMD-affected streams on the West Coast of the South Island, New Zealand, and suggested that metal oxides may have prevented attachment of algae or that precipitate deposition onto algal cells may have inhibited photo- synthesis. Other authors have found increased algal biomass at low pH, but usually where metal oxide deposition was low or absent (Mulholland et al. 1986; Stokes 1986; Niyogi et al. 1999). Many algal studies in AMD systems have concentrated on the most severely affected systems (e.g. Brake et al. 2001; Sabater et al. 2003), or have focussed on ecosystem function- ing and biomass (Niyogi et al. 2002) rather than diversity and composition. Several studies have focussed on diatoms. For example, DeNicola (2000) produced a comprehensive review of diatoms in acidic habitats, such as sulfur ponds and AMD- impacted systems. He identified 124 taxa in habitats of pH ≤3.5 from 28 different studies. Species of Eunotia, Pinnu- laria, Achnanthes, Nitzschia, Cymbella, Fragilaria and Synedra have all been reported from AMD systems (DeNicola 2000; Hill et al. 2000; Verb and Vis 2000; Sabater et al. 2003). The euglenophyte Euglena mutabilis has also been commonly found at highly acidic sites (Verb and Vis 2000; Sabater et al. 2003). However, green algae (chlorophytes and streptophytes) often dominate algal communities in acidic waterways, and tolerant species of genera such as Klebsormidium, Microspora, Mougeo- tia, Ulothrix, Stigeoclonium, Zygnema and Microthamnion have been recorded in severely affected streams (Niyogi et al. 2002; Sabater et al. 2003; Verb and Vis 2005; Novis 2006; Novis and Harding 2007). Periphyton assemblages in AMD streams in New Zealand have received little attention (Anthony 1999; Novis and Harding 2007). However, Winterbourn et al. (2000) identified © CSIRO 2008 10.1071/MF08146 1323-1650/08/121084