Photo by Scott Taylor 



Understanding the estuary also means understanding the people who use it 



A 



molecule of one nutrient may stay in 

 the estuary for years. 



Perhaps a molecule of nitrogen arrives in the estuary. 

 There, it finds itself taken up by marsh grass, or maybe by 

 algae or seaweed. When the grass dies, the nitrogen is 

 released and deposits itself in the sediments where it's 

 covered up by more sediment. 



Months may go by before something, perhaps a shrimp, 

 disturbs the sediments, sending the molecule back into the 

 water column. Then the process begins all over again. 



Estuaries are nutrient traps, says Sea Grant researcher 

 Hans Paerl. "There is a net loss but it can be years before 

 nutrients are released from the estuary." 



The sediments in an estuary tend to adsorb (the nutrients 

 attach to the sediments) nutrients and the circulation pat- 

 terns of the estuary make it easy for them to stay there. A 



particle might be carried toward the sea by the freshwater 

 flow at the surface and then returned upstream by the tidal 

 currents below, says Sea Grant researcher Charles Peterson. 



That explains why estuaries have a much higher concen- 

 tration of nutrients than the sea or than the fresh waters 

 draining into the estuaries, says Peterson. Nutrients 

 stimulate plant growth, resulting in the high productivity 

 for the estuary. According to some estimates, an acre of a 

 North Carolina estuary is more productive than an acre of 

 farmland producing rice, corn or hay. 



A farmer may work year after year, cultivating, fertiliz- 

 ing and irrigating his soil. Without all the nurturing, the 

 nutrients would eventually be used up. Not so with an es- 

 tuary. Paerl says the continuous inflow of fresh water 

 provides the estuary with all the nutrients it needs. 



"Most of those nutrients come from the freshwater en- 

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