Water Resources Research Act Program

Details for Project ID 2013TN101B

Chemical and Morphological Analyses of Trout Otoliths as a Measure of Aluminum Exposure in Streams Impacted by Acid Deposition in the Great Smoky Mountains National Park

Institute: Tennessee
Year Established: 2013 Start Date: 2013-03-01 End Date: 2014-02-28
Total Federal Funds: $10,000 Total Non-Federal Funds: $24,900

Principal Investigators: Michelle Connolly, John Schwartz

Abstract: Acid deposition is a global issue, which greatly affects fish populations throughout the Northern Hemisphere. In the Southeastern United States stream acidification is thought to be responsible for the extirpation of brook trout (Salvelinus fontinalis) from many headwater streams in the Great Smoky Mountains National Park (GRSM). The management of fishery resources and particularly populations of native brook trout is a high priority for conservation efforts within the Park. Streams within the GRSM are particularly susceptible to the effects of acid deposition due to the low buffering capacity associated with the geology in this region. Our archival datasets indicate that aqueous aluminum (Al) is prevalent at high elevations in the Park, where acid deposition has led to increased trace metal exposure, especially under stormflow conditions. Yet until recently it was unclear whether these Al levels were bio-accumulating in fish. In 2011, members of our research team were the first to show that trace aluminum could be detected in GRSM fish (rainbow trout otoliths and gill arches). Otoliths have long been used as an environmental archive as they continuously incorporate inorganic material (including trace metals) into their calcified matrix. However, relatively little is known about aluminum (Al) uptake in freshwater fish, especially among streams impacted by acid deposition. Notably, our 2011 study was conducted within Walker Camp Prong (WCP), a GRSM stream that is impacted by acid deposition but is also buffered by unusual calcium (Ca) levels due to the salting of nearby roads. Here we propose extending our research efforts to four GRSM streams that are not buffered by anthropogenic Ca input, in order to determine whether the age-specific Al/Ca trends observed among fish from Walker Camp Prong are applicable to other regions and species (brook trout) in the Park. As our research team has previously shown that an abnormal form of calcium carbonate calcification is present in a subset of fish in the Park, trout otoliths will be excised and photographed prior to trace metal analysis in order to map differences in bone morphology (vateritic otolith formation) within and across sites. This morphological survey will contribute to our understanding of abnormal otolith formation in the Park and will help determine whether these morphological differences are linked to Al-rich environments. In addition, this work will provide insight into species-specific tolerance to acid deposition among brook trout and rainbow trout, which will help delineate the upper limit their range in acidic environments. Following morphological analyses, otoliths will be chemically analyzed. Trace Al and Ca levels will be quantified among sagittal otoliths using established Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) methods. These data will be compared to archival aqueous datasets (1993-present), which have been collected by Dr. Schwartz group (co-PI on this project) in order to develop predictive regression models of the biological impacts of acid deposition in the Park. These regression analyses will also be used to provide information on stream conditions where long-term chemical analysis data are not available and will thus contribute to ongoing management and prioritization strategies in the Park.