Steve Kahl

Inferring regional patterns and responses in nitrogen and mercury biogeochemistry using two sets of gauged paired-watersheds

Principal Investigator:		Co-Investigators:
	Steve Kahl Senator George J. Mitchell Center for Environmental & Watershed Research 102 Norman Smith Hall University of Maine Orono, ME Phone: (207) 581-3244 FAX: (207) 581-2725 e-mail: Kahl@maine.edu	Ivan Fernandez, University of Maine Stephen Norton, University of Maine Bruce Wiersma, University of Maine George Jacobson, University of Maine David Manski, Acadia National Park Terry Haines, USGS-BRD Lindsey Rustad, USDA-Forest Service Charles Roman, USGS-BRD Robert Lent, USGS-WRD
	Park: Acadia National Park

Project Summary:

This project is part of long-term ecological research using two gauged-watersheds to be imple-mented at Acadia National Park through collaborative funding by USGS and this proposal to EPA. The focus of this request is atmospheric deposition of nitrogen (N) and mercury (Hg), and their ecological consequences. Both elements are of major concern, both regionally and to the Park Service at Acadia. This location offers the advantages of a) co-funding for cost-effectiveness; b) a natural experimental design for the two watersheds because of a major forest fire in part of the Park in 1947; c) parallel design with the acidic deposition experiment on paired-watersheds at the nearby Bear Brook Watershed, Maine (BBWM); and d) prior research at Acadia and BBWM that supply background data, and provide the basis for ecosystem indicators to be applied at Acadia. Our objectives will address N cycling and saturation, and Hg input and bioavailability, in paired watersheds with different forest types. We will use the natural landscape contrasts provided by fire to compare patterns and processes in N and Hg sequestration and mobility. Nitrogen loading to estuaries will be addressed by periodic sampling of estuary tributaries as "satellite" locations, whose N loading will be extrapolated from occasional sampling by using the more intensively monitored main watersheds as index sites.

Our approach will involve using input/output measurements at the watershed scale to define the unknowns of Hg inputs to landscapes, determine locations and processes of Hg speciation, resolve the status of N retention, and estimate N loading to selected estuaries that have prior background data. We will determine the relative input of Hg and methyl-Hg from wet deposition, throughfall and litterfall. The expected results will provide new information for Acadia and for the New England region on the ecological consequences of high N deposition at Acadia, and the loading of N to estuaries in the region. We lack an explanation of the high accumulation rates of Hg in sediment and peat cores compared to wet-only deposition, and have not explained why Acadia has some of the highest Hg concentrations in biota in the world. The general repres-entativeness of Acadia forests for the New England region, combined with the fire history to be included in our experimental design (fire also being "typical" of the historical New England landscape), offers the opportunity to understand some key issues for Acadia, while providing insight into these issues at the regional scale.