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The University of Massachusetts Amherst

Long-term record of Atmospheric N deposition interact with climate to influence estuarine impacts


Atmospheric deposition can be an important contribution to nitrogen loading in coastal regions. Atmospheric loading is suggested to have declined due to pollution control efforts, however the degree and impact of this has not been quantified on Cape Cod. Additionally, it is predicted that climate change, especially with respect to rain events and durations, may interact with atmospheric conditions to affect estuarine productivity.  This project analyzed a long-time series of atmospheric N deposition and climate to determine trends and the associated impacts to estuarine systems. 

We have compiled the data and examinied the trends. Results have shown significant decreases in NO3 deposition in the NE US, similar to those observed in other regions such as central Europe. If decreases in N deposition have had demonstrable effects on the recovery of estuarine areas and reduced eutrophication, it will allow managers to focus a more useful targeting of management on other sources of nitrogen (fertilizer use and wastewater disposal).  

Our results have confirmed an unprecedented decrease in nitrate deposition over the entire North American continent, particularly marked in the Northeast US and Southeast Canada. The decrease is linked to a parallel reduction in vehicle and stationary source emissions, but it also responds to the own climatic characteristics of the regions where the most marked decreases are observed as most of the deposition in these places is originated in upwind industrial regions. Results from the analyses of field samplings in Cape Cod estuaries revealed that, despite the increase in nitrogen inputs from septic systems, the reduction in atmospheric pollution has caused that the trophic status of the estuaries has not change, as confirmed by the nutrient and chlorophyll concentrations as well as macro algal biomasses.


  • Reductions in atmospheric oxidized nitrogen deposition over North America: The relative role of emission controls and climatic patterns. The Ecosystems Center 2016 Seminar Series. Woods Hole, MA.
  • Skelton, S., Valiela, I., Lloret, J., Owens, C., Elmstrom, E., 2015 MBL Undergraduate Research Symposium. The impact of nitrogen loading in Waquoit Bay, MA on estuarine food webs constructed by stable isotope analysis.  Aug 19-20.
  • Owens, C., Valiela, I., Lloret, J., Elmstrom, E., Skelton, S., 2015 MBL Undergraduate Research Symposium. Effects of changing nitrogen loads on vegetation patterns in Waquoit Bay, 1990-2014. Aug 19-20.


  • Maps for wet atmospheric deposition of N have been produced for US, Canada and Europe.  Trend analyses have also been mapped in both North America and Europe.