State Water Resources Research Institute Program

Project ID: 2008MD171B
Title: Microbial nitrogen sequestration in detrital-based streams of the Chesapeake Bay watershed under stress from road-salt runoff.
Project Type: Research
Start Date: 7/01/2008
End Date: 6/30/2009
Congressional District: MD 7th
Focus Categories: Non Point Pollution, Ecology, Nutrients
Keywords: road salt deicer, runoff, streams, invertebrates, nitrogen sequestration
Principal Investigator: Swan, Christopher (University of Maryland, Baltimore County)
Federal Funds: $ 29,857
Non-Federal Matching Funds: $ 59,715
Abstract: Headwater streams are known to be sensitive to landscape disturbances, as they comprise the majority of stream miles in a watershed. These habitats are hotspots of important processes related to water quality, especially rates of organic matter decomposition and nutrient cycling. Therefore, any disturbance disrupting the ecological interactions involved in such processes is likely to be especially pronounced in these small streams, as they are in intimate contact with the landscape. Road-salt runoff has been recently identified as one such stressor and, since inputs of road-salt are expected to increase as road density increases, the subsequent effects on stream ecosystems important to understand . To date, work in my lab and others has revealed important consequences for both carbon and nitrogen dynamics as mediated by microbial communities and the invertebrates that consume them. Food webs in small forested streams rely on the annual input of leaf litter from streamside forests as a major source of energy, and the microbial community breaking down this material can serve as a sink for nitrogen from the water column. Evidence in the literature has shown that the organic matter-microbial-invertebrate pathway is one means by which excess nitrogen might be sequestered from the water column vs. being transported downstream. Given the negative effect of salt stress on carbon mineralization documented for stream microbial communities by my lab, I expect salt to also alter rates of nitrogen sequestration. As a result, road salt runoff might alter the natural ability of headwater streams to ameliorate excess nutrient delivery to larger, downstream waterbodies (e.g., the Chesapeake Bay). I propose a multi-factorial study to learn how these ecological interactions (i.e., organic matter-microbial-invertebrate) react to a gradient of salt stress currently imposed on freshwater ecosystems in the region, and how this changes the capacity for the stream community to remove nitrogen from streams.

Progress/Completion Report, PDF

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