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                                           Estuarine Habitats

To survive in any habitat an organism must be adapted to the conditions existing there. In shoreline
habitats the chief environmental factors include climate, water level, salinity, oxygen level, carbon
dioxide level, water and air temperatures, and substrate. Any variations in these factors can have a
profound influence on the plants and animals living in the shoreline communities.

Water level exerts a strong influence on the shoreline habitats. As the tide changes the water level
alternately exposes and submerges areas of the shoreline. Habitats along the shoreline are divided into
zones based on tidal changes while elevation and slope of the land determine how far the zones extend
into a habitat.


Forest types in the coastal plain include upland and lowland hardwood forests, mixed hardwood and
pine forests, natural pine forests and pine plantations. The coastal plain contains nearly half of the
forests in North Carolina. These forests are in danger of being logged faster than they can grow because
of the growing demand for lumber and wood chips and urban sprawl. More trees are being cut, thus
narrowing the gap between new growth and logging. Along the water's edge, forests are a mixture of
evergreens and deciduous trees. Their hardy root systems take up large amounts of nitrogen and
phosphorus that would otherwise pollute estuarine waters.


Freshwater wetlands recharge groundwater and act as natural filters, trapping pollutants before they
enter the waters. Wetlands cover 4.7 million acres of North Carolina -- 17 percent of the state. Of those
wetlands, 95 percent are in the eastern part of the state. Estimates are that between 35 percent and 55
percent of the state's original wetlands have been lost or significantly degraded during the last 200
years. More than 70 percent of species listed as endangered, threatened or of special concern in North
Carolina depend on wetlands for survival.


Eight major rivers flow through North Carolina emptying into coastal estuaries. The headwaters of these
rivers once began in forests and wetland bogs. Rivers contain vital freshwater that mixes with the sea to
create productive estuaries. They also provide food and habitat for fish to spawn and grow. Today, all
the state's rivers are polluted to some extent. The pollution comes in many forms: storm water runoff
from cities, suburbs, agricultural farms and hog operations, sewage, industrial discharges, and air
pollution from factories and cars. Recent estimates are that nitrogen loads into the Neuse River have
increased 60 percent to 70 percent during the past century. The 5,000 dams that have been built along
North Carolina's rivers, tributaries, and streams block fish from reaching their nursery grounds.

Estuarine shorelines encompass the zone between the upland areas and the waters that flood the
marshes. These lands are the last line of defense against water-borne pollutants. A forested shoreline
can remove as much as half of the nutrients and bacteria in runoff before it reaches estuarine waters.
Experts believe that hurricanes and other natural processes alter the growth patterns of shorelines
keeping them in a constant state of change. Common species in these areas include loblolly pine, red
maple, sweet gum, swamp tupelo, and live oak. The understory usually contains red bay and wax myrtle.

Primary nursery areas are shallow estuarine waters with the highest abundance and diversity of juvenile
fish. These waters are home and spawning grounds to economically important fish and shellfish. They
also offer food and protection to the young of many species. Only four percent of North Carolina's 2.1
million acres of estuary are designated as primary nursery area. These areas are essential to helping
produce almost half of the fish commercially harvested on the east coast of the United States.


Salt marshes are found along 4,500 miles of shoreline along the state's coastal sounds, creeks and rivers.
They filter the water, protect the land from erosion, and provide food and shelter to countless
creatures. Salt marshes that fringe open waters tend to be much more productive than those further
from the water's edge and less influenced by tides. As sea level rises, salt marshes maintain themselves
by migrating landward. Waterfront property owners build bulkheads along an estimated 16 miles of
shoreline each year, killing this valuable habitat.


Beaches are generally regarded as flat sea shores, but are often a part of a complex dune and ridge
system along an ocean shore. They can be sandy or rocky. Particularly popular for recreation, short term
high densities of people can have serious effects on nesting animals and vegetation of beach systems.
Pollution (particularly bacteria from sewage and human waste) and other results of large human
populations have resulted in an increasing number of beach closures in the U.S. and other countries.
These pathogens can cause a wide variety of diseases that threaten the public health.


Open waters encompass the mouths of coastal rivers and the sounds that lie between the barrier islands
and the mainland. North Carolina has approximately 2,032,875 acres of estuarine open water. The
salinity is about 35 parts salt per thousand parts of water (ppt) along the outer coast and drops to zero
ppt up the tributary tidal creeks and rivers. Estuarine water can become layered, with deeper waters
being saltier than surface waters. Nutrients are relatively scarce in clean estuaries because they are
taken up rapidly by plant life. In normally productive coastal waters too much nitrogen will cause
harmful algae blooms and low oxygen conditions. Nutrients find their way into estuaries from overland
storm water runoff, sewage, and rainfall. Scientists suggest that 30-50 percent of nitrogen input into
estuaries comes from rain, and much of this comes from sources only 60-100 miles away.

Shellfish beds are areas in tidal creeks, rivers and near-shore estuarine waters where shellfish such as
oysters and clams live. Nearly 5,900 oysters can grow in an area of one square yard. One of them can
purify almost 1.5 gallons of water an hour because they extract nutrients with their gills as they feed. In
1996, about 95 percent of the oysters and clams caught in North Carolina came from the waters
between Cedar Island and the South Carolina border. Within the state, 363,733 acres of waters are
permanently closed to shellfishing because of pollution. Most of the remaining high quality shellfishing
areas in the state are also contaminated when only two inches of rainfall occurs within a 24-hour period.

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