PM02 Metals in the Environment: Aquatic Biological Perspectives
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM060) Impacts of acid mine drainage-associated aluminum on invertebrate oxygen consumption in circumneutral pH waters.
Soucek, D1, 1 Illinois Natural History Survey, Champaign, IL, USA
ABSTRACT- Field assessments in the North Fork Powell River, Virginia, indicated that while the common stonefly, Acroneuria sp. (Plecoptera, Perlidae), comprised approximately three percent of benthic macroinvertebrate samples collected from upstream reaches, they were virtually non-existent in neutral waters (pH = 7.8) downstream of an acid mine drainage (AMD) impacted tributary. Analysis of chemical concentrations in water, sediment, and invertebrates suggested that the factor most strongly associated with variation in perlid stonefly populations from site to site was total aluminum (Al) concentration in the water column, rather than bioaccumulation of other metals. Al toxicity to invertebrates under slightly acidic conditions is generally attributed to ionoregulatory impairment. However, when an acidic tributary enters a much larger, neutral receiving stream, a variety of Al polymers and/or precipitates can be produced from the dissolved ion. As these species form, they may bind to or simply cover the bodies of invertebrates, potentially creating a physical barrier that causes a reduction in surface area available to absorb dissolved oxygen from the water. I hypothesized that these large-gilled perlid stoneflies with high oxygen requirements may be more susceptible than other invertebrates to potential respiratory effects from Al in circum-neutral waters, accounting for their absence below the AMD impacted tributary. Therefore, my objective was to determine if a pulse of Al in the process of precipitating/polymerizing at pH >7.0 can cause invertebrates to consume less oxygen than those in waters without Al. In three experiments with Daphnia magna, Al significantly reduced oxygen consumption relative to controls, with organisms exposed to 500 and 1000 ppb total Al consuming only 61 and 38 percent, respectively, of that consumed in controls. A similar trend was observed with the perlids Acroneuria abnormis, and Perlesta lagoi at lower concentrations; however, at higher Al concentrations, oxygen consumption was similar to that in controls.
Key words: Oxygen, Aluminum, Perlidae