Nitrogen external nutrient source

External nutrient supply is defined as the supply of dissolved nutrient that is biologically available for shelf plankton. The sources of these nutrients are from the river and upwelled offshore waters, nitrogen fixation regenerated terrestrial organic niatter, and absorbed material. The flux of P from desorption is considered part of this external supply, whereas the recycling of estuarine biogenic material (via microbial degradation or dissolution) is not. 

The inputs of nitrogen to wetlands include biological N2 fixation, and point and nonpoint loads from external sources (Eigure 8.2). Examples include atmospheric nitrogen deposition, agricultural and urban runoff, application of fertilizers to rice paddies, stormwater runoff carrying nutrients and... 

---