Sources of Nitrogen to Estuaries

Terrestrial-Atmospheric 1. Natural biological fixation (pre-agriculture) 110 90-130 90-170 

Fixation due to planting of nitrogen-fixing plants 3. Total biological fixation (1+2 above) 150 43  

Watershed-estuary system Watershed type Agriculture runoff Non-point source Urban forest runoff Upland human sewage Atmospheric deposition Total 

Watershed types are based on the primary sources of N to each estuary. Watersheds dominated by urban N sources (e.g., point, septic, and non-point source runoff) were classified as urban, watersheds dominated by agricultural N sources (e.g., fertilization, fixation, and manure) were classified as agriculture, and watersheds dominated by atmospheric N deposition were classified as atmospheric. Effluent from sewage treatment plants in the Barnegat Bay watershed is discharged offshore sewage inputs to the Barnegat Bay estuary are from septic systems in the watershed. Modified from Castro et al. (2003). 

Shinnecock Bay, New York Waquoit Bay, Massachusetts Chesapeake Bay, mesohaline Chesapeake Bay, mesohaline Chesapeake Bay, mesohaline Chesapeake Bay, mouth Apalachicola Bay Delaware Estuary Elba Estuary 

---