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Scientific Investigations Report 2012–5166

Prepared in cooperation with the National Park Service

Ambient and potential denitrification rates in marsh soils of Northeast Creek and Bass Harbor Marsh watersheds, Mount Desert Island, Maine

By Thomas G. Huntington, Charles W. Culbertson, and John H. Duff

Thumbnail of and link to report PDF (6.93 MB)Abstract

Nutrient enrichment from atmospheric deposition, agricultural activities, wildlife, and domestic sources is a concern at Acadia National Park on Mount Desert Island, Maine, because of the potential problems of degradation of water quality and eutrophication in estuaries. Degradation of water quality has been observed at Bass Harbor Marsh estuary in the park but only minimally in Northeast Creek estuary. Previous studies at Acadia National Park have estimated nutrient inputs to estuaries from atmospheric deposition and surface-water runoff, and have identified shallow groundwater as an additional potential source of nutrients. Previous studies at Acadia National Park have assumed that a certain fraction of the nitrogen input was removed through microbial denitrification, but rates of denitrification (natural or maximum potential) in marsh soils have not been determined. The U.S. Geological Survey, in cooperation with Acadia National Park, measured in-place denitrification rates in marsh soils in Northeast Creek and in Bass Harbor Marsh watersheds during summer 2008 and summer 2009. Denitrification was measured under ambient conditions as well as after additions of inorganic nitrogen and glucose.

In-place denitrification rates under ambient conditions were similar to those reported for other coastal wetlands, although they were generally lower than those reported for salt marshes having high ambient concentrations of nitrate (NO3). Denitrification rates generally increased by at least an order of magnitude following NO3 additions, with or without glucose (as the carbohydrate) additions, compared with the ambient treatments that received no nutrient additions. The treatment that added both glucose and NO3 resulted in a variety of denitrification responses when compared with the addition of NO3 alone. In most cases, the addition of glucose to a given rate of NO3 addition resulted in higher rates of denitrification. These variable responses indicate that the amount of labile carbohydrates can limit denitrification even if NO3 is present. For most sites in both watersheds, the maximum denitrification rates ranged from of 150 to 900 micromoles of nitrous oxide per square meter per hour. These rates were equivalent to the release of 37 to 221 grams of nitrogen per square meter per year. Weak positive correlations were observed for soil temperature and for measured ammonium concentration in groundwater. Weak negative correlations were observed between denitrification rate and water level and specific conductance.

The rates of denitrification in Bass Harbor Marsh and Northeast Creek under ambient conditions, both of which were relatively low, indicate that NO3 availability is low in both systems. It is evident from the addition of combined treatments of NO3 and glucose that these marsh soils are capable of comparatively high rates of denitrification, therefore, estuarine eutrophication is not a result of nitrogen inputs to marsh soils that are in excess of the denitrification capacity in these systems. If terrestrial inputs to the estuary are the cause of the observed eutrophic condition in Bass Harbor Marsh, then these inputs to the estuary must bypass the marsh in channelized surface flow, or perhaps they circumvent the marsh in shallow groundwater seepage along subsurface pathways that enter the estuary directly.

First posted November 15, 2012

For additional information contact:
Director
U.S. Geological Survey
Maine Water Science Center
196 Whitten Road
Augusta, ME 04330
(207) 622–8201
http://me.water.usgs.gov/

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Suggested citation:

Huntington, T.G., Culbertson, C.W., and Duff, J.H., 2012, Ambient and potential denitrification rates in marsh soils of Northeast Creek and Bass Harbor Marsh watersheds, Mount Desert Island, Maine: U.S. Geological Survey Scientific Investigations Report 2012–5166, 40 p., available only at http://pubs.usgs.gov/sir/2012/5166/.



Contents

Abstract

Introduction

Field Denitrification Methods

Laboratory Denitrification Methods

Laboratory N2O Analytical Methods and Computation of N2O Release Rate

Field Methods for Water Quality Sampling and Measurements

Laboratory Methods for Water Quality Analysis

Ancillary Data

Laboratory Denitrification Experiments to Determine N2 to N2O Ratios

Laboratory Denitrification Experiments to Determine Response to Nitrate and Glucose Additions

Field Measurements of Denitrification Under Ambient Conditions

Field Measurements of Denitrification Following Nitrate and Glucose Addition Treatments

Field Denitrification Rate in Relation to Environmental Variables

Tributary Water Quality

Denitrification Potential of Marsh Soils at Acadia National Park

Conclusions

Acknowledgments

References Cited


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