Variation in organic matter production, storage and processing associated with sand accumulation in the Salmon Trout River, Michigan

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Conference Proceeding

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Sediment deposition changes the physical characteristics of river beds, which can alter microbial community abundance, organic matter delivery and processing, and metabolism. We conducted a comparative study of organic matter production and processing in two reaches with exposed rock substrates, and two with sand accumulations in the Salmon Trout River, a tributary of Lake Superior where watershed disturbances have lead to 3-fold increases in benthic fine sediments in the past decade. Ecosystem metabolism measured Jul–Sept in light-dark chambers revealed that net ecosystem production was negative on sand, but was typically positive on rocks. Ecosystem respiration was 1.5x greater on sand vs. rock, and was correlated with larger standing stock of fine and coarse benthic organic matter in sand habitats. Biofilm chlorophyll a was 2-3x greater on rock substrates, but ash-free dry mass was 4x greater on sand substrates. Together, these results suggest that sand accumulation alters organic matter processing in this river from net production during the summer to net consumption and storage of organic matter, perhaps due to increased burial and decreased primary production in sand sediments.

Publication Title

North American Benthological Society 2011 Annual Meeting