Hopkinson, C. S.. Marine Biological Laboratory, chopkins@lupine.mbl.edu
Claessens, L. S.. Marine Biological Laboratory, luclaes@lupine.mbl.edu
Rastetter, E. Marine Biological Laboratory, erastett@lupine.mbl.edu
Vallino, J. J.. Marine Biological Laboratory, jvallino@lupine.mbl.edu

We are studying and modeling patterns of land use change, nutrient and water export from land, riverine processing and retention of nutrients, and the overall mass balance for nutrients in the Ipswich River Watershed to evaluate temporal patterns of coupling to the coastal zone. There have been major changes in land cover and land use since European settlement. For example agricultural land has decreased over 70% and urban land now comprises about 30% of the total cover. Stream water nutrient concentrations vary across land cover, being low in forested areas and high in urban and agricultural areas. Whereas organic nutrients are the dominant form of N and P in forested watersheds, inorganics dominate urban and agricultural areas. Nutrient mass balance indicates that of about 500-1000 Mt N input to the river annually, only about 10-20% is exported to the estuary. Downstream transects of nutrient concentration and mass balance indicate large sinks in relatively slow moving wetland dominated 2nd and 3rd order reaches. Experimental nutrient/tracer additions of inorganic N do not demonstrate similar uptake dynamics however. It appears that N retention is tightly coupled with the availability of inorganic P, which varies by source and along the length of the river.
Day: Wednesday, Feb. 3
Time: 09:15 - 09:30am
Location: Sweeney Center
Code: CS59WE0915S