Selection of the Mayfly Rithrogena hageni as an Indicator of Metal Pollution in the Upper Arkansas River

Ecological Applications

Carlisle

Lazorchak

et al. 2000

342

231

The development of field sampling designs that employ multiple reference and polluted sites has been proposed as an alternative to the traditional upstream vs. downstream approach used in most biomonitoring studies. Spatially extensive monitoring programs can characterize ecological conditions within an ecoregion and provide the necessary background information to evaluate future changes in water quality. We measured physicochemical characteristics, heavy‐metal concentrations, and benthic macroinvertebrate community structure at 95 sites in the Southern Rocky Mountain ecoregion in Colorado, USA. Most sites (82%) were selected using a systematic, randomized sampling design. Each site was placed into one of four metal categories (background, low, medium, and high metals), based on the cumulative criterion unit (CCU), which we defined as the ratio of the instream metal concentration to the U.S. Environmental Protection Agency criterion concentration, summed for all metals measured. A CCU of 1.0 represents a conservative estimate of the total metal concentration that, when exceeded, is likely to cause harm to aquatic organisms. Although the CCU was less than 2.0 at most (66.3%) of the sites, values exceeded 10.0 at 13 highly polluted stations. Differences among metal categories were highly significant for most measures of macroinvertebrate abundance and all measures of species richness. We observed the greatest effects on several species of heptageniid mayflies (Ephemeroptera: Heptageniidae), which were highly sensitive to heavy metals and were reduced by >75% at moderately polluted stations. The influence of taxonomic aggregation on responses to metals was also greatest for mayflies. In general, total abundance of mayflies and abundance of heptageniids were better indicators of metal pollution than abundance of dominant mayfly taxa. We used stepwise multiple‐regression analyses to investigate the relationship between benthic community measures and physicochemical characteristics at the 78 randomly selected sites. Heavy‐metal concentration was the most important predictor of benthic community structure at these sites. Because of the ubiquitous distribution of heavy‐metal pollution in the Southern Rocky Mountain ecoregion, we conclude that potential effects of heavy metals should be considered when investigating large‐scale spatial patterns of benthic macroinvertebrate communities in Colorado's mountain streams.

Section: Discussionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 99%

Heavy Metals Structure Benthic Communities in Colorado Mountain Streams

Ecological Applications

Carlisle

Lazorchak

et al. 2000

342

231

“…In particular, mayfly abundance varied predictably along a gradient of metal pollution. Mayflies are generally more sensitive to metals than other aquatic insect taxa, and heptageniid mayflies have been suggested as indicators of metal pollution (Nelson & Roline, 1993, 1996; Clements, 1994). In the present study, Heptageniidae were very rare in the Animas River and greatly reduced (>50%) in experimental exposure chambers.…”

Section: Discussionmentioning

confidence: 99%

Assessing the influence of water and substratum quality on benthic macroinvertebrate communities in a metal‐polluted stream: an experimental approach

Courtney

2002

Freshwater Biology

SUMMARY 1. Field and laboratory experiments were conducted to assess the relative influence of water quality and substratum quality on benthic macroinvertebrate communities in the Animas River, a metal‐polluted stream in south‐western Colorado (U.S.A.). 2. A community‐level in situ toxicity test measured direct effects of Animas River water on benthic invertebrates collected from a reference stream (Elk Creek). The effects of metal‐contaminated biofilm were examined by comparing macroinvertebrate colonisation of clean and contaminated substrata placed in Elk Creek. A feeding experiment with the mayfly Baetis tricaudatus Dodds (Ephemeroptera: Baetidae) examined metal bioaccumulation and effects of metal‐contaminated biofilm on growth and survival. 3. Animas River water was acutely toxic to most taxa, with greatest effects observed on mayflies (Heptageniidae, Ephemerellidae) and stoneflies (Taeniopterygidae and Capniidae). 4. Although Animas River biofilm was characterised by high concentrations of metals and low algal biomass, most taxa colonised substratum from the reference stream and the Animas River equally. The exceptions were Ephemerellidae, Taeniopterygidae and Simuliidae, which were less abundant on Animas River substratum. Mayflies grazing Animas River biofilm accumulated significantly more metals and showed reduced growth compared with organisms feeding on Elk Creek biofilm. 5. Results of our experiments demonstrated that effects of heavy metals on benthic community structure in the Animas River were complex, and that responses to metals in water and contaminated substratum were species‐specific. Predicting recovery of benthic communities following remediation requires an understanding of these species‐specific responses.

“…Although R. hageni was common in the AR, its abundance was lower than in the PR on all sampling occasions. It is likely that reduced abundance of R. hageni in the AR resulted from heavy metal pollution Roline 1993, Nelson andRoline 1996).…”

Section: Tolerance To Metalsmentioning

confidence: 99%

Metal Tolerance and Predator–prey Interactions in Benthic Macroinvertebrate Stream Communities

Ecological Applications

1999

Predicting responses of benthic communities to contaminants requires an understanding of both direct and indirect effects. I examined the influence of previous exposure to heavy metals on metal tolerance and susceptibility of benthic communities to stonefly predation in experimental streams and field cages. Benthic communities obtained from a reference stream, the Cache la Poudre River (PR), and a metal‐polluted stream, the Arkansas River (AR), in Colorado were exposed to a mixture of Cd, Cu, and Zn at ∼2× the U.S. EPA chronic criterion level (2.2 μg Cd/L, 24 μg Cu/L, and 220 μg Zn/L) for 10 d in stream microcosms. Effects of metals on survival were significantly greater on mayflies (Ephemeroptera) from the unpolluted PR than from the metal‐polluted AR. Metal exposure also significantly increased drift of Rhithrogena hageni, the dominant mayfly in the unpolluted stream but had no effect on invertebrates from the AR. In a second experiment, communities from the two locations were exposed to predatory stoneflies (Claassenia sabulosa) in stream microcosms. Stonefly predation significantly reduced total macroinvertebrate abundance, number of taxa, and abundance of Baetis tricaudatus (Ephemeroptera) and R. hageni. Mayflies from the metal‐polluted AR were also more susceptible to stonefly predation, but these results were probably influenced by differences in initial prey density. Results of caging experiments conducted at PR and AR field sites were consistent with results of laboratory experiments and showed that stonefly predation significantly reduced abundance of B. tricaudatus and R. hageni; however, effects of predation in the AR were relatively weak because of high prey immigration. Results of these experiments suggest that abiotic factors influence the outcome of species interactions in metal‐polluted streams. Ecosystems disturbed by contaminants, particularly those polluted for relatively long periods of time, provide excellent opportunities to study these interactions.