J * r o m sound to sea 



king up 



Estuary 



x several billion gallons of salt 

 water with a like amount of fresh water. 

 Add tons of decaying salt marsh grass, 

 weeds and wood particles. Whisk in 

 pounds of tiny floating plants and season 

 with stands of marsh grass and sub- 

 merged seagrass beds. Fold in a medley 

 of critters — zooplankton, benthic 

 worms, shrimp, oysters, clams, crabs and 

 fish. Pour into a shallow 

 basin rimmed with barrier 

 islands. 



What do you have? 



An estuary. 



For most people, the 

 word estuary is nebulous. 

 Is it the marsh? The 

 sound? The bay? Creeks 

 and river mouths? 



Quite simply, it's all 

 of the above. An estuary 

 is where fresh water and 

 salt water mix it up. 

 Estuaries receive fresh 

 water and sediment from 

 upland rivers and tidal 

 doses of salt water from 

 the ocean through the 

 inlets. Then currents, 

 winds and tides stir the 

 fresh and salt water into a 

 brackish soup that teems 

 with life. 



North Carolina has been blessed 

 with an abundance of estuaries. Some 

 have names that are well-known — 

 Pamlico and Albemarle sounds; others 

 ring familiar only to the ears of fishermen 

 and long-time natives — Rose Bay, Back 

 Sound and South Creek. 



But together, North Carolina estuar- 

 ies comprise the third largest estuarine 

 system in the United States, trailing only 

 Louisiana and Alaska. Tar Heel residents 

 can proudly claim 2.3 million acres of 

 estuaries. And from this expanse of fertile 

 water comes 90 percent of the state's 

 commercially and recreationally impor- 

 tant species of fish and shellfish. 



Some important species, such as 

 clams, oysters and crabs, spend their 



entire lives in the estuary. Others, such as 

 shrimp, spot, croaker and menhaden, 

 spend only their juvenile stages in the 

 estuary's shallow fringes and fingers. 

 These areas, considered primary nurseries 

 by resource managers, offer juvenile fish 

 protection from predation by larger fish 

 and an ample supply of food to eat. 



Fringing the estuary are meadows of 





i i ir f 











salt marsh cordgrass and needlerush that 

 are bathed by lunar and wind-driven tidal 

 influxes of brackish water. Called 

 marshes, these areas stand alongside rain 

 forests and coral reefs as nature's most 

 productive ecosystems. 



The biomass of marshes, fertilized 

 by nutrients from rivers, can be as high as 

 5 to 10 tons of organic matter per acre per 

 year. Compare this to a wheat field that 

 produces 1 ton per acre per year or the 

 open ocean or desert where production is 

 less than 0.5 ton per year. 



Nutrients, washed from the land, are 

 swept downstream via rivers and streams 

 to the marshes. There, they are trapped by 

 the ebb and flow of the tide. And more 

 nutrients are added by the yearly cycle of 



growth and dieback of salt marsh 

 grasses. As the grass dies and withers 

 into the estuary, bacteria attack the plant 

 matter, breaking the tissue into detritus, a 

 primary food source for the estuarine 

 food chain. 



The detritus feeds tiny creatures 

 such as zooplankton, benthic worms and 

 juvenile fish. In turn, these creatures 



provide breakfast, lunch 

 and dinner for an array of 

 other wildlife — fish, 

 shellfish and birds — 

 higher up the food chain. 



The tides that bathe 

 these marshes transport 

 the nurturing doses of 

 marsh soup to other 

 estuarine habitats — 

 seagrass beds and mud 

 and sand flats. Fields of 

 seagrass carpet the 

 bottom of North 

 Carolina's estuaries, 

 providing yet another 

 source of food, habitat 

 and protective cover for 

 inhabitants. 



Although sand and 

 mud flats offer no protec- 

 tion, their substrates 

 provide homes for a 

 variety of estuarine 

 dwellers — oysters, clams, whelks, 

 flounder, crabs and worms. 



Today, scientists understand more 

 about the function and value of estuaries 

 than ever before. But there is more to 

 learn and an urgency to learn it. Devel- 

 opment of nearby beaches and adjacent 

 and upriver lands is affecting our 

 estuaries. 



Already, scientists are seeing 

 changes in water quality, nutrient loads, 

 circulation patterns and valuable habitats 

 such as seagrass beds. The rush is on for 

 scientists to learn more about this pro- 

 ductive and complex ecosystem so that 

 resource managers can have the informa- 

 tion they need to sustain it for the future. 



Kathv Hart 



COASTWATCH 21 



