Pollutants in Lotic Ecosystems III
Presiding: R M Thompson, Biodiversity Research Centre, University of British Columbia; D Olsen, University of Vermont
NB52A-01 10:30h
Do Headwater Streams Recover From Longwall Mining Impacts in Northern West Virginia, USA?
This study measured longwall mining impacts on headwater streams and addressed the question: do streams recover? Two years of field research compared 8 longwall mined streams with 3 unmined and 3 room-and-pillar mined streams. Analysis of Variance was used to compare average physical, chemical, and biological dimensions and to determine if spatial recovery occurred along the course of headwater stream gradients. Regression analysis was used to assess temporal recovery. Significant physical and chemical differences in average longwall mined versus reference streams included 31% less stream width, 0.8oC lower temperature, 100 umhos greater conductivity, 11% lower dissolved oxygen, and 64 ppm greater alkalinity. Physical and chemical attributes of longwall mined streams did not recover to reference conditions either spatially or temporally. Macroinvertebrate communities in longwall mined streams had 44% lower abundance, 47% lower diversity, and 51% fewer semivoltine taxa compared to reference streams. No water was present at 18% of samples from longwall mined streams, and an additional 17% of samples failed to support a minimum viable community. Regional omnipresence for 57 of 60 taxa decreased in longwall mined streams, whereas 3 taxa increased. Diversity, longevity, and ubiquity of benthic communities failed to exhibit convincing evidence of spatial or temporal recovery.
NB52A-02 10:45h
Accumulation and Growth Responses in Corbicula fluminea Along a Longitudinal Gradient of Metal Exposure
In a previous study, we investigated the concentrations of arsenic, selenium, cadmium, and mercury associated with different land uses in a large river system using an indicator species Corbicula fluminea (Asiatic clam). We found that Corbicula fluminea collected from sites downstream of discharges from coal-fired power plants (CFPP) had significantly higher tissue concentrations of selenium and cadmium than all other land use types. In order to quantify the bioavailability of metals associated with CFPP discharges in a lotic system, we designed a three month experiment in which clams were deployed in cages at four sites along a 3.5 km reach of stream at the Savannah River Site. We assessed metal accumulation in the clam tissue and shell growth over the entire reach. After 84 days, clams at the upstream, most contaminated site had the highest growth rate and highest mean concentrations of arsenic (7.85 ppm), selenium (17.05 ppm), and cadmium (7.28 ppm). Tissue concentrations decreased rapidly over the first 400 m rather than gradually along the entire reach.
NB52A-03 11:00h
Proteogenomic studies of natural microbial biofilms
Acid mine drainage (AMD) forms when rocks rich in pyrite, FeS2, are oxidized upon exposure to air and water. Iron-oxidizing microorganisms accelerate pyrite dissolution by generating ferric iron, an especially effective sulfide oxidant. We have used cultivation-independent methods to study the gene (Tyson et al., 2004) and protein (Ram et al., in review) complements of microbial biofilms from an AMD environment in Richmond, CA. The genomes of the biofilm organisms indicated potential proteins and other small molecules that each organism type can produce. We then used this genome data in combination with 2D LC-MS/MS mass spectrometry to identify proteins within extracellular/periplasmic, soluble, and membrane fractions of the biofilm. This method enabled us to infer the most abundant proteins in each fraction and their general location. In particular, it led us to identify an extracellular/periplasmic cytochrome central to iron oxidation and acid mine drainage, as well as to analyze hypothetical proteins (proteins predicted from the genome with no significant homology to known proteins), some of which are likely to be adaptations by the biofilm organisms for thriving in this unique metal-rich acidic environment.
NB52A-04 11:15h
Phytoavailability of Arsenic in pesticide-Applied Soils: Effect of Chemical Remediation
Arsenic (As) occurs naturally in rocks and soils and in the water in contact with them. Arsenic contamination is also caused by a variety of anthropogenic activities such as the use of arsenical pesticides, mining, and other industrial processes. In humans, chronic exposure to As has been found to cause a number of cancers, peripheral nerve damage, and skin hyper-pigmentation. In plants, As causes growth inhibition, chlorosis, defoliation, and water-deficiency stress. The main objective of the present study was to evaluate the efficacy of water treatment residuals (WTRs) in reducing the phytoavailability of As in soils. WTRs are the by-products from drinking water purification plants and contain sediments, organic material from the raw water, Al/Fe oxides and activated C. They are amorphous and have an affinity for oxyanions (e.g., arsenate and arsenite), due to the high positive surface charge they generally possess. A greenhouse study was performed using two different types of soils, chosen on the basis of their potential differences with respect to reactivity and phytoavailability of As: Immokalee series (bleached sand with low pH) and Orelia series (sandy loam with high percentage of Ca; Mg and high pH). Rice (Oryza sativa var. M202) was used as the test crop to study the effect of WTR amendment on the plant availability of As. The soils were amended with two arsenical pesticides; sodium arsenate and dimethylarsenic acid (DMA) at two rates: 675 and 1500 mg/kg of As, representing the high end of As contamination, simulating Superfund site conditions. Rice plants were grown with and without WTRs for a period of 6 months. Growth parameters (germination percentage, plant biomass, root and shoot length) as well as As accumulation in plant tissues were studied. Soils were analyzed to determine the levels of plant available As in WTR-treated and untreated soils. Results obtained indicate that WTR-amendment of sodium arsenate contaminated soils resulted in considerable decrease in the levels of phytoavailabe As, and hence, increased seed germination and plant growth. In contrast, in soils contaminated with DMA, seed germination and plant growth was inhibited, with no significant effect of WTR.
NB52A-05 11:30h
A Mass-balance Approach to Assessing Arsenic Transport Through the Hyporheic Zone of a Mine-influenced Mountain Stream
We are investigating the biogeochemical controls on the transport of arsenic through the hyporheic zone (i.e., zone of interaction between surface and groundwater) in a montane headwater stream in Southwest Virginia. At the site, arsenopyrite was mined from 1903 to 1919 and waste piles of roasted ore remain adjacent to the stream. Arsenic concentrations in the stream are heavily influenced by the location of the waste piles and increase exponentially with distance downstream ranging from 0.002 to over 5 mg/L. More than 90% of stream water arsenic occurs as arsenate (i.e., As(V)). We are characterizing spatial and temporal variation in arsenic fluxes using a mass-balance approach. Dilution gauging and continuous discharge measurements from flumes are being used to quantify groundwater inputs. Vertical hydraulic gradients indicate that the stream is gaining. Groundwater arsenic concentrations paired with groundwater discharge measurements are used to determine the gross groundwater load (concentration*discharge). By closing the mass-balance equation, net groundwater inputs can be compared to measured gross groundwater inputs to determine if the hyporheic zone is retaining or releasing arsenic to the stream. Employing this mass-balance approach will allow us to determine the importance of this groundwater-surface water interface in the transport of trace elements.
NB52A-06 11:45h
Influence of Multiple Disturbances on Ecosystem Structure and Function of a Headwater Stream
Many studies in lotic systems have focused on pulse disturbances such as floods, while others have centered on press disturbances like chronic pollution. This research explores the combined effects of press and pulse disturbances on ecosystem structure and function in a headwater stream adjacent to an abandoned arsenic mine. Influences of floods were compared between an upstream (reference) reach and a `disturbed' reach adjacent to the arsenic mine. Average base flow discharge was 1.2 L/s. Floods were categorized as events with discharge more than 3x base flow. Arsenic in stream water was < 10 ppb in the reference reach and increased to 1000 ppb at the bottom of the mine-influenced reach. Phosphorus solute injections, ecosystem metabolism, and standing crop estimates of organic matter were determined monthly from April to December 2004 and ranged from 4 to 44 days post-flood event. We used regression analysis to explore relationships between type and intensity of disturbance and response variables such as spiraling metrics, standing crops, and ecosystem metabolism.