Jon S. Harding

Effects of contrasting land use on physico‐chemical conditions and benthic assemblages of streams in a Canterbury (South Island, New Zealand) river system

Abstract Physico‐chemical conditions and benthic invertebrate assemblages in streams draining catchments dominated by different land use activities were investigated near Hanmer Springs, South Island. Four streams in pastoral, scrubland, exotic pine plantation forest (primarily Pinus spp.), and native beech forest (Nothofagus spp.) catchments were sampled in four seasons. Alkalinity, pH, and calcium concentrations were highest among scrubland streams, whereas iron and potassium concentrations were highest in pastoral streams. Both taxonomic richness and invertebrate biomass were greatest in the beech forest streams where most species of Ephe‐meroptera, Plecoptera, Coleoptera, and Diptera were found. Forest streams were dominated by the mayflies Deleatidium and Coloburiscus humeralls, the stonefly Stenoperla prasina, and the caddisfly Olinga feredayi. The facultative shredder Austroperla cyrene was also abundant in pine forest streams. However, mayfly, stonefly and caddisfly taxa were poorly represented in...

Consequences of acid mine drainage for the structure and function of benthic stream communities: a review

Abstract.  Streams affected by acid mine drainage (AMD) are highly stressed ecosystems and occur worldwide. These streams typically have low pH, high concentrations of dissolved metals, and substrata coated with metal hydroxide precipitates. This combination of chemical and physical stressors creates a challenging environment for aquatic biota. We provide a synthesis of the effects of AMD on stream food webs to provide a holistic perspective of these highly stressed ecosystems. First, we reviewed the effects of AMD on the structure and function of algal, microbial, invertebrate, and fish communities. Then, we used this published information to propose generalized food webs and identify areas for future research. In general, AMD-affected streams have depauperate communities that are dominated by a few tolerant species, and ecosystem processes (e.g., decomposition) are often impaired. Biota respond differently to the individual stressors (e.g., pH compared to precipitates), which may complicate remediation efforts that focus primarily on neutralizing acidity and removing metals from mine discharges. Food webs in these streams are substantially altered because basal resources are less productive or inaccessible, microbial processing of organic matter is slow, many grazers and shredders are absent, and fish are replaced by invertebrates as top predators. Structurally, declines in species diversity and the loss of fish shorten and simplify food webs by decreasing the number of interactions among species. Functionally, most energy pathways are weakened by disrupted trophic links, and this problem should to be a key target of restoration efforts. We think research that focuses on species interactions in a foodweb context is needed to provide a better understanding of community organization and functioning in these highly stressed ecosystems.

Habitat loss drives threshold response of benthic invertebrate communities to deposited sediment in agricultural streams

Agricultural land uses can impact stream ecosystems by reducing suitable habitat, altering flows, and increasing inputs of diffuse pollutants including fine inorganic sediment (< 2 mm). These changes have been linked to altered community composition and declines in biodiversity. Determining the mechanisms driving stream biotic responses, particularly threshold impacts, has, however, proved elusive. To investigate a sediment threshold response by benthic invertebrates, an intensive survey of 30 agricultural streams was conducted along gradients of deposited sediment and dissolved nutrients. Partial redundancy analysis showed that invertebrate community composition changed significantly along the gradient of deposited fine sediment, whereas the effect of dissolved nitrate was weak. Pollution-sensitive invertebrates (%EPT, Ephemeroptera, Plecoptera, Trichoptera) demonstrated a strong nonlinear response to sediment, and change-point analysis indicated marked declines beyond a threshold of -20% fine sediment covering the streambed. Structural equation modeling indicated that decreased habitat availability (i.e., coarse substrate and associated interstices) was the key driver affecting pollution-sensitive invertebrates, with degraded riparian condition controlling resources through direct (e.g., inputs) and indirect (e.g., flow-mediated) effects on deposited sediment. The identification of specific effects thresholds and the underlying mechanisms (e.g., loss of habitat) driving these changes will assist managers in setting sediment criteria and standards to better guide stream monitoring and rehabilitation.

Biofilm Bacterial Community Structure in Streams Affected by Acid Mine Drainage

ABSTRACT We examined the bacterial communities of epilithic biofilms in 17 streams which represented a gradient ranging from relatively pristine streams to streams highly impacted by acid mine drainage (AMD). A combination of automated ribosomal intergenic spacer analysis with multivariate analysis and ordination provided a sensitive, high-throughput method to monitor the impact of AMD on stream bacterial communities. Significant differences in community structure were detected among neutral to alkaline (pH 6.7 to 8.3), acidic (pH 3.9 to 5.7), and very acidic (pH 2.8 to 3.5) streams. DNA sequence analysis revealed that the acidic streams were generally dominated by bacteria related to the iron-oxidizing genus Gallionella, while the organisms in very acidic streams were less diverse and included a high proportion of acidophilic eukaryotes, including taxa related to the algal genera Navicula and Klebsormidium. Despite the presence of high concentrations of dissolved metals (e.g., Al and Zn) and deposits of iron hydroxide in some of the streams studied, pH was the most important determinant of the observed differences in bacterial community variability. These findings confirm that any restoration activities in such systems must focus on dealing with pH as the first priority.

Stream biomonitoring using macroinvertebrates around the globe: a comparison of large-scale programs

Water quality agencies and scientists are increasingly adopting standardized sampling methodologies because of the challenges associated with interpreting data derived from dissimilar protocols. Here, we compare 13 protocols for monitoring streams from different regions and countries around the globe. Despite the spatially diverse range of countries assessed, many aspects of bioassessment structure and protocols were similar, thereby providing evidence of key characteristics that might be incorporated in a global sampling methodology. Similarities were found regarding sampler type, mesh size, sampling period, subsampling methods, and taxonomic resolution. Consistent field and laboratory methods are essential for merging data sets collected by multiple institutions to enable large-scale comparisons. We discuss the similarities and differences among protocols and present current trends and future recommendations for monitoring programs, especially for regions where large-scale protocols do not yet exist. We summarize the current state in one of these regions, Latin America, and comment on the possible development path for these techniques in this region. We conclude that several aspects of stream biomonitoring need additional performance evaluation (accuracy, precision, discriminatory power, relative costs), particularly when comparing targeted habitat (only the commonest habitat type) versus site-wide sampling (multiple habitat types), appropriate levels of sampling and processing effort, and standardized indicators to resolve dissimilarities among biomonitoring methods. Global issues such as climate change are creating an environment where there is an increasing need to have universally consistent data collection, processing and storage to enable large-scale trend analysis. Biomonitoring programs following standardized methods could aid international data sharing and interpretation.

Historic deforestation and the fate of endemic invertebrate species in streams

Abstract Deforestation is a global phenomenon threatening the biodiversity of many unique forested ecosystems. The volcanic calderas of Banks Peninsula, New Zealand, experienced widespread deforestation from 1860 to 1900 when >98% of the indigenous forest was removed. Streams on the Peninsula possess several regionally‐endemic species. The objective of this study was to assess the effect of historic deforestation on stream faunas by surveying the distribution of endemic and other benthic invertebrate species in relation to remnant and regenerating indigenous forest fragments. Twenty‐seven sites, in nine catchments were surveyed. Three catchments were dominated by forest, three by farmland, and three were predominantly farmland with forested headwaters. Taxonomic richness was significantly greater in forested streams than agricultural streams, particularly for Ephemeroptera, Plecoptera, and Trichoptera taxa. Distributions of the regionally‐endemic hydrobiosid caddisflies Costachorema peninsulae and Edpercivalia banksiensis were restricted to forest fragments. Two other endemics, the stonefly Zelandobius wardi and the caddisfly Hydrobiosis styx, were rarely collected but seemed to be restricted to headwater sites in forest. In contrast, the blepharicerid Neocurupira chiltoni was widely distributed in streams, regardless of land cover, and in relative abundances unrelated to site location within the catchment. Evidence from Banks Peninsula streams suggests that throughout New Zealand a number of species unknown to science may have been lost because of past deforestation, and that remnant forested habitats may be vital to the conservation and preservation of regionally endemic species.

Anthropogenic and natural sources of acidity and metals and their influence on the structure of stream food webs

We compared food web structure in 20 streams with either anthropogenic or natural sources of acidity and metals or circumneutral water chemistry in New Zealand. Community and diet analysis indicated that mining streams receiving anthropogenic inputs of acidic and metal-rich drainage had much simpler food webs (fewer species, shorter food chains, less links) than those in naturally acidic, naturally high metal, and circumneutral streams. Food webs of naturally high metal streams were structurally similar to those in mining streams, lacking fish predators and having few species. Whereas, webs in naturally acidic streams differed very little from those in circumneutral streams due to strong similarities in community composition and diets of secondary and top consumers. The combined negative effects of acidity and metals on stream food webs are clear. However, elevated metal concentrations, regardless of source, appear to play a more important role than acidity in driving food web structure.

Distribution and dispersal of adult stream insects in a heterogeneous montane environment

The distribution and dispersal of adult mayflies, stoneflies and caddisflies were investigated in an approximately 5 ha area of montane forest and grassland-scrub in the South Island, New Zealand. Low-flying insects were collected in 28 Malaise traps set along stream channels, in dry valleys and on hillsides for 8 weeks in late summer. Adult assemblages differed in forest and grassland and along valleys depending on distance from streams that were their probable sources. Stoneflies and mayflies occurred predominantly in forest and were taken mainly above the stream or very close to it. In contrast, caddisfly species exhibited a wide range of distribution patterns with some restricted to forest and others being found in both forest and grassland up to 300 m from the nearest likely source. Many females of several species that were taken well away from their natal stream (e. g., Pycnocentria evecta and Aoteapsyche colonica), were not fully developed, reproductively, suggesting they were dispersing inland to mature, whereas others packed with eggs (e. g., most Hydrobiosis parumbripennis) were more likely to be searching for oviposition sites. Many more male and female caddisflies were trapped in valleys than on hillsides, even where surface-water was absent, suggesting that valleys provide important corridors for dispersal, at least of low-flying individuals.

Response of a new zealand mayfly (Deleatidium spp.) to acid mine drainage: Implications for mine remediation

Investigating the toxicity of acid mine drainage (AMD) on benthic communities in receiving waters can be highly challenging because of the difficulty in unraveling the effects of acidity, dissolved metals, and precipitates. Furthermore, the survival of different species may vary depending on any natural adaptation they may have acquired to low pH, metals, or sedimentation. We investigated the effect of different pHs and AMD on the survival of a common New Zealand leptophlebiid mayfly (Deleatidium spp.) in 96-h laboratory trials. Our results indicate that the primary driver of toxicity in AMD was pH, although some mortality could be attributable to the presence of dissolved heavy metals at low pH (<or=3.6). Mayflies sourced from three naturally acidic streams (pH approximately 5.7-6.5) had a distinctly higher tolerance to AMD and low pH (3.5-4.0) compared to mayflies sourced from three circumneutral streams (pH approximately 7.0-7.4). This indicates that the chemistry of the natal stream strongly influences the sensitivity of mayflies to AMD, which, in turn, could have consequences for the successful remediation of a given AMD-impacted stream. Furthermore, the water chemistry of unimpacted streams that could be sources of potential recolonists might provide ecologically relevant water-quality targets for remediation of AMD-damaged streams. Understanding the variable tolerances of common lotic benthic taxa can provide ecologically relevant water-quality criteria for mine remediation.

Periphyton communities in New Zealand streams impacted by acid mine drainage

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 the West 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.