Spatial and temporal measurements of N, P, and C uptake in small Lake Superior tributaries

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Conference Proceeding

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In-stream biogeochemical uptake and transformation can alter the timing and form of nutrients exported to downstream ecosystems, but spatial and temporal nutrient contributions from small streams to large lakes have been generally ignored. We measured uptake of ammonium (NH4), soluble reactive phosphate (SRP), and dissolved organic carbon (DOC) in Lake Superior tributaries to determine whether nutrients may be modified or retained before being exported, and to identify how uptake may be related to in-stream and watershed characteristics. Nutrient uptake velocities were correlated with discharge and background NH4, but not DOC, SRP, biofilm chlorophyll a or ash-free dry mass, temperature, canopy cover, or wetland area in watersheds. From our study sites elements must travel 370-23,000 m before reaching Lake Superior, and our results show that on average, NH4 traveled 141-2000 m, SRP 435-3330 m, and DOC 333-2500 m before being taken up. We also modeled C and N exported from three streams using a maximum-likelihood estimation model, and ultimately will use stream size and watershed characteristics to scale these estimates up to account for contributions of all small Lake Superior tributaries.

Publisher's Statement

Conference Homepage: http://www.sgmeet.com/jasm2014/viewabstract.asp?AbstractID=14396

Publication Title

Joint Aquatic Sciences Meeting 2014