Nitrogen is among the most abundant elements on Earth. It comprises 78 percent of the Earth's atmosphere and is essential for all life forms. Since it is so abundant and important, one might wonder, "What is the problem with a little more nitrogen?" The issue is that most of the global nitrogen exists in its elemental gaseous form that is biologically unavailable to all organisms except those that can fix nitrogen (convert it from N2 to NH4), which include some bacteria, algae, and flowering plants (such as legumes that have nitrogen-fixing bacteria in their roots). Most natural ecosystems, especially marine aquatic systems, have evolved under the constraint of a shortage of biologically available nitrogen (though other nutrients, such as phosphorus, may also be limiting in some ecosystems).

Humans have dramatically altered the global nitrogen cycle through industrial nitrogen fixation for fertilizer production, nitrogen fixation by internal combustion engines, and agricultural practices that rely on fertilization and favor nitrogen-fixing crops (peas and beans). Humans also mobilize large amounts of stored nitrogen through land clearing, wetland draining, and combustion of biomass and fossil fuel. Humans have more than doubled the amount of organic nitrogen available to Earth's ecosystems, forcing ecosystems to adjust to a tremendous excess of nutrients. Some coastal waters have seen a 10-fold anthropogenic increase in nitrogen flux over the last few decades.

Nitrogen enters the Gulf of Maine from a variety of sources, including continental slope water, atmospheric deposition, watershed export, point sources (such as wastewater treatment plants and industry), urban runoff, septic systems, agricultural runoff, aquaculture operations, and marinas and boating. Some of the biological consequences of nitrogen pollution on marine environments include:

• Increased primary production
• Increased oxygen demand and hypoxia
• Changes in benthic community structure due to anoxia and hypoxia
• Changes in plankton community structure
• Changes in marine food webs
• Loss of biological diversity
• Blooms of harmful and nuisance algae
• Degradation of seagrass and macroalgal beds
• Increases in diseases and pathogens.

Whereas increased primary production is desirable under many circumstances, too much nitrogen can cause primary production to become too high or increase too rapidly, causing ecosystem imbalances that lead to environmental problems. These changes may cause a variety of biological, economic, and social consequences, and detract from our utilization and enjoyment of the coastal region and marine resources.

Though isolated examples of such effects have been observed in the Gulf of Maine, in general the Gulf of Maine has not experienced the severe eutrophication problems that have been observed elsewhere in North America. Scientists have proposed that the coastal hydrology, geology, and climate of the Gulf of Maine region may make its coastal areas less susceptible to eutrophication. However, human population in the region is growing rapidly and new demands are being placed on the region's land and water resources. Now is the time for scientists, managers, and public to take a proactive approach to the problem through research, monitoring, and management.

The Gulf of Maine Council on the Marine Environment is actively involved in activities that address nitrogen pollution in the Gulf of Maine. The Council co-sponsored a nitrogen workshop in 2001 [download workshop report (pdf)] that framed the basic issues of managing nitrogen impacts in the Gulf, and continues to work collaboratively with other agencies and organizations to develop and implement research, monitoring, and management programs in the region. Nitrogen is one of three priority contaminants in the Council's Action Plan 2001-2006, and some of the planned activities include:

• Increase public awareness of the problem
• Promote science-based management by providing scientific information and training on nitrogen issues to coastal decision-makers
• Use the results and recommendations of a 2001 nitrogen workshop to address nutrient assessment, monitoring and prediction, nutrient control strategies, and policy, regulatory, and implementation issues
• Strengthen existing stewardship programs by identifying funding sources, providing training opportunities, and enhancing networking
• Formulate a set of nutrient-related environmental health indicators that describe current conditions, threats, and management challenges facing Gulf resources.