Aquatic Sciences Meeting, Albuquerque 2001

SS33 Human Impacts and Activities on Riverine Ecosystems (Science and Society Connections)

Date: Thursday, February 15, 2001, Time: 10:15:00 AM

Location: Galisteo

Hopkinson, C, S, Marine Biological Laboratory, Woods Hole, USA, chopkins@mbl.edu

Claessens, l, , Marine Biological Laboratory, Woods Hole, USA, lclaesse@mbl.edu

Rastetter, E, , Marine Biological Laboratory, Woods Hole, Canada, erastett@mbl.edu

Vallino, J, , Marine Biological Laboratory, Woods Hole, Canada, jvallino@mbl.edu

Williams, M, , Marine Biological Laboratory, Woods Hole, Canada, mikewilliams@mbl.edu

LAND USE EFFECTS ON NITROGEN LOADING BUDGETS FOR THE IPSWICH RIVER WATERSHED

There have been major land use changes in the Ipswich River Watershed over the past century: abandonment of agricultural land, reforestation, and finally urbanization. We have been defining stream water nutrient concentration signatures as they vary with land cover and catchment size. For first order catchments, we find a strong positive relation between urban and agricultural land use and NO3 concentration. There is no relation between DON, DOP, DOC, NH4 or PO4 and land use composition. The exception is for DON, which correlates with percent forested land during the fall. Because of the strong relation between nitrate and land use, organic nutrients are the dominant form of N and P in forested catchment streams and inorganics dominate urban and agricultural streams. Watershed export of nutrients does not reflect the sum of inputs, rather we observe substantial inorganic N loss in 1st and 2nd order streams, and nitrification in 3rd and 4th order regions. Nutrient mass balance indicates that of about 500-1000 Mt N input to the watershed annually, about 64-82% is retained on land and 8-16% is retained in the river.

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Aquatic Sciences Meeting, Albuquerque 2001

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