Estuaries


An estuary is a coastal area where fresh water from rivers and streams
mixes with salt water from the ocean. Many bays, sounds, and lagoons along
coasts are estuaries. Portions of rivers and streams connected to estuaries are
also considered part of the estuary. The land area from which fresh water
drains into the estuary is its watershed. Estuaries come in all shapes and sizes,
each unique to their location and climate. Bays, sounds, marshes, swamps,
inlets, and sloughs are all examples of estuaries.
An estuary is a fascinating place from the largest landscape features to
the smallest microscopic organisms. When viewing an estuary from the air on is
practically amazed by dramatic river bends as freshwater finds its way back to
the sea. The vast expanse of marsh grasses or mudflats extend into calm waters
that then follow the curve of an expansive barrier beach. Wherever there are
estuaries, there is a unique beauty. As rivers meet the sea, both ocean and
land contribute to an ecosystem of specialized plants and animals.
At high tide, seawater changes estuaries, submerging the plants and
flooding creeks, marshes, panes, mudflats or mangroves, until what once was land
is now water. Throughout the tides, the days and the years, an estuary is
cradled between outreaching headlands and is buttressed on its vulnerable
seaward side by fingers of sand or mud.
Estuaries transform with the tides, the incoming waters seemingly
bringing back to life organisms that have sought shelter from their temporary
exposure to the non-aquatic world. As the tides decline, organisms return to
their protective postures, receding into sediments and adjusting to changing
temperatures.
The community of life found on the land and in the water includes
mammals, birds, fish, reptiles, shellfish, and plants all interacting within
complex food webs. Flocks of shore birds stilt through the shallows, lunging
long bills at their abundant prey of fish, worms, crabs or clams. Within the
sediments, whether mud, sand or rocks, live billions of microscopic bacteria, a
lower level of the food web based largely on decaying plants.
Estuaries are tidally-influenced ecological systems where rivers meet
the sea and fresh water mixes with salt water. Estuaries provide habitat;tens
of thousands of birds, mammals, fish, and other wildlife depend on estuaries.
They provide marine organisms, most commercially valuable fish species included,
depend on estuaries at some point during their development. Where productivity
is concerned, a healthy, untended estuary produces from four to ten times the
weight of organic matter produced by a cultivated corn field of the same size.
Estuaries provide water filtration;water draining off the uplands carries a load
of sediments and nutrients. As water flows through salt marsh peat and the
dense mesh of marsh grass blades, much of the sediment and nutrient load is
filtered out. This filtration process creates cleaner and clearer water.
Estuaries also provide flood control. Porous, resilient salt marsh soils and
grasses absorb flood waters and diffuse storm surges. Salt marsh dominated
estuaries provide natural buffers between the land and the ocean. They protect
upland organisms as well as billions of dollars of human real estate.
Estuaries are crucial transition zones between land and water that
provide an environment for lessons in biology, geology, chemistry, physics,
history, and social issues. Estuaries are significant to both marine life and
people. They are critical for the survival of fish, birds, and other wildlife
because they provide safe spawning grounds and nurseries. Marshes and other
vegetation in the estuaries protect marine life and water quality by filtering
sediment and pollution. They also provide barriers against damaging storm waves
and floods.
Estuaries also have economic, recreational, and aesthetic value. People
love water sports and visit estuaries to boat, fish, swim, and just enjoy their
beauty. As a result, the economy of many coastal areas is based primarily on
the natural beauty and bounty of their estuaries. Estuaries often have ports
serving shipping, transportation, and industry. Healthy estuaries support
profitable, commercial fisheries. In fact, almost 31 percent of the Gross
National Product (GNP) is produced in coastal counties. This relationship
between plants, animals, and humans makes up and estuary\'s ecosystem. When its
components are in balance, plant and animal life flourishes.
Humans have long been attracted to estuaries. Indian mittens consisting
of shellfish and fish bones are reminders of how ancient cultures lived. Since
Colonial times we have used estuaries and their connecting network of rivers for
transporting agricultural goods for manufacturing and trade. Not only do
commercially important fish and shellfish spawn, nurse, or feed in estuaries,
estuaries also feed our hears and minds. Scientists and even poets and painters
are inspired by the beauty and diversity found in an