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Scientific Investigations Report 2014-5033

Quantifying Benthic Nitrogen Fluxes in Puget Sound, Washington—A Review of Available Data

By Richard W. Sheibley and Anthony J. Paulson

Thumbnail of and link to report PDF (6.4 MB)Abstract

Understanding benthic fluxes is important for understanding the fate of materials that settle to the Puget Sound, Washington, seafloor, as well as the impact these fluxes have on the chemical composition and biogeochemical cycles of marine waters. Existing approaches used to measure benthic nitrogen flux in Puget Sound and elsewhere were reviewed and summarized, and factors for considering each approach were evaluated. Factors for selecting an appropriate approach for gathering information about benthic flux include: availability of resources, objectives of projects, and determination of which processes each approach measures. An extensive search of literature was undertaken to summarize known benthic nitrogen fluxes in Puget Sound. A total of 138 individual flux chamber measurements and 38 sets of diffusive fluxes were compiled for this study. Of the diffusive fluxes, 35 new datasets were located, and new flux calculations are presented in this report. About 65 new diffusive flux calculations are provided across all nitrogen species (nitrate, NO3-; nitrite, NO2-; ammonium, NH4+). Data analysis of this newly compiled benthic flux dataset showed that fluxes beneath deep (greater than 50 meters) water tended to be lower than those beneath shallow (less than 50 meters) water. Additionally, variability in flux at the shallow depths was greater, possibly indicating a more dynamic interaction between the benthic and pelagic environments. The overall range of bottom temperatures from studies in the Puget Sound area were small (5–16 degrees Celsius), and only NH4+ flux showed any pattern with temperature. For NH4+, flux values and variability increased at greater than about 12 degrees Celsius. Collection of additional study site metadata about environmental factors (bottom temperature, depth, sediment porosity, sediment type, and sediment organic matter) will help with development of a broader regional understanding benthic nitrogen flux in the Puget Sound.

First posted March 13, 2014

For additional information, contact:
Director, Washington Water Science Center
U.S. Geological Survey
934 Broadway, Suite 300
Tacoma, Washington 98402
http://wa.water.usgs.gov

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Suggested citation:

Sheibley, R.W., and Paulson, A.J., 2014, Quantifying benthic nitrogen fluxes in Puget Sound, Washington—A review of available data: U.S. Geological Survey Scientific Investigations Report 2014-5033, 44 p., http://dx.doi.org/10.3133/sir20145033.

ISSN 2328-0328 (online)



Contents

Abstract

Introduction

Factors Influencing Benthic Nitrogen Flux

Methods for Measuring Benthic Nitrogen Fluxes

Benthic Nitrogen Fluxes in Puget Sound

Incorporating Benthic Fluxes into Marine Water Quality Models

Future Approaches and Areas of Research for Characterizing Benthic Fluxes in Critical Areas of Puget Sound

Conclusions

Acknowledgments

References Cited

Appendix A. Detailed Site and Location Information from All Compiled Flux Measurements

Appendix B. Summary of Compiled Benthic Flux Data for Nitrogen for All Individual Chamber Measurements

Appendix C. Summary of All Compiled Porewater Concentration Gradients

Appendix D. Compilation of All Orthophosphate Benthic Flux Data


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