Extracellular Enzyme Activity of Plant Litter-Associated Microorganisms Depends on Dissolved Inorganic Nutrient Availability
Plant litter-associated microbial decomposers (primarily fungi) are important intermediaries in carbon and energy flow in streams. Since they can obtain nitrogen (N) and phosphorus (P) from both the substrate and the water column, changes in dissolved inorganic nutrient availability (e.g. due to human impacts) may affect the activity of extracellular enzymes involved in N, P and carbon (C) acquisition from organic substrates. We measured the activity of phosphatase, chitinase, leucine aminopeptidase and beta-glucosidase associated with decomposing plant litter differing in C quality and N and P content (maple and rhododendron leaf litter, wood veneers) in streamside channels with manipulated concentrations of dissolved inorganic N, P, and N:P ratios. Artificial fluorogenic substrates have been used for all assays. Phosphatase activity per unit of fungal biomass showed a strong negative correlation with dissolved P concentration for all substrates (R2=0.73-0.81, p<0.014) supporting our hypothesis that production of P-mining enzymes is suppressed when inorganic P is available. However, we did not find any significant relationship between the activity of N-acquiring enzymes (chitinase + leucine aminopeptidase) per unit of fungal biomass and inorganic N concentration. Beta-glucosidase activity was driven mostly by dissolved N, but not P, availability. Thus, dissolved nutrient concentrations modulate microbially driven plant litter decomposition, nutrient immobilization and transfer to higher trophic levels.
Dept of Biology, Coastal Carolina University, Conway, SC
P124 • Charlie R. Wiggins, Aundrea N. Duncan, Amber N. Blocker, Dr. Gretchen K. Bielmyer, Dr. Matthew N. Waters
The Impact of Urbanization on Water Quality in Four Rivers With Varying Degrees of Anthropogenic Disturbance
A study was conducted to determine the impact of urbanization on four streams of varying orders and surrounded by varying degrees of urbanization. Several water quality parameters were measured at three different sites along each stream over time including: alkalinity, hardness, chloride, pH, carbon dioxide (CO2), dissolved oxygen (DO), temperature, ammonia, nitrate, and nitrite. So far, we have observed differences in water quality between the sites, as a consequence of rainfall and river depth, and due to changing seasons. For example, hardness and alkalinity differed among sites. Increased rainfall resulted in elevated CO2 and decreased pH in all four of the streams, particularly in the more shallow areas. Additionally, decreased temperature and nutrient concentrations were correlated with increased DO. Due to urbanization, many factors, such as rainwater, runoff from homes and farms, and increased organic debris, may contribute to increased nutrient concentrations, which can increase phytoplankton growth and decrease oxygen levels; thus impacting community structure. The biological diversity of each sampling site is also being calculated using Shannon-Weiner and Simpson’s Index of Diversity and will be correlated to the water quality parameters and surrounding land use at each site.
Biology Dept, Valdosta State University, Valdosta, GA
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P125 • Elyse Russing, L. M. Siefferman, M. D. Madritch, Michael Gangloff
Influence of Small Dams on Leaf Decomposition and Invertebrate Communities in Western North Carolina Streams
Stream restoration increasingly targets restoring hydrological connectivity via dam removal but dam impacts on stream ecosystem function remain poorly understood. We used a field experiment to examine impacts of small impoundments on leaf decomposition in 2 western North Carolina streams. We placed sugar maple leaf packs at three sites associated with 1 intact, 1 breached and 1 relict dams. Leaf packs were removed at 4-week intervals between October 2012 and January 2013 and we quantified water chemistry and mass lost. In addition, we quantified invertebrate abundance, species richness and diversity. Preliminary data suggests that leaf decomposition rates are paradoxically higher in impoundments despite the fact that these habitats harbor reduced invertebrate abundance and richness relative to up and downstream, free-flowing reaches. These findings suggest that microbial or physical decomposition may be driving detritus processing in reaches downstream of small dams, possibly as a response to dam-induced physical habitat and water chemistry changes. On-going work will attempt to disentangle the microbial and invertebrate components of this pattern and assess broader-scale effects of impoundments on stream energy pathways.
Dept of Biology, Appalachian State University, Boone, NC
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P126 • Catherine, W. Bennett, Karen, K. Bernd
Characterizing the Effects of Electronic Cigarettes: The Development of a Vaping Study
Electronic cigarettes (e-cigarettes) have emerged as an alternative to traditional tobacco cigarettes. With commercial production and increased use of e-cigarettes, regulatory agencies, including the WHO and FDA, are seeking data regarding their safety. Studies have been conducted to determine the chemical composition of e-cigarettes, but studies have not been performed to look at the effects of e-cigarette vapor on alveolar cells. In this study, methods were developed to expose alveolar cells (L2 cells) grown in culture to e-cigarette vapor. L2 cells were exposed to e-cigarette vapor for 2 seconds per minute for 30 minutes, and the neutral red dye (NRD) cytotoxicity assay was performed to determine cell viability. Data underscores the importance of parallel (rather than sequential) exposure and processing of vapor-treated and untreated cells. Preliminary data suggests small differences in viability with e-cigarette vapor leading to no difference in cell number. Further experimentation is necessary to increase the sample size and apply analysis for statistical significance.
Dept of Biology, Davidson College, Davidson, NC
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P127 • Amber Brown
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