Where Rivers Meet The Sea

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Where Rivers Meet The Sea
By Kelsea and Ramona
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What is an Estuary?
An estuary is a partially enclosed body of water
where saltwater from the sea mixes with
freshwater from rivers, streams and creeks. These
areas of transition between the land and the sea
are tidally driven, like the sea, but sheltered
from the full force of ocean wind and waves, more
like a river. Estuaries are generally enclosed in
part by the coastline, marshes and wetlands the
seaward border may be barrier islands, reefs and
sand or mud flats.
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Its not what you thinkit is?
An estuary is an ecotone or a rather complex
buffer zone. Sharing some characteristics of
both types of aquatic ecosystems, but identical
to neither. Every estuary is unique each
individual ecosystem has different components
that complete the estuarine habitat.
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Locations
Some examples of estuaries are The Chesapeake
Bay, San Francisco Bay, Boston Harbor, Tampa Bay
and Puget Sound. There are also wetlands in the
Great Lakes with estuarine-like functions.
An estuary may be enclosed by marshes and barrier
islands, while another estuarys borders are the
coastline and reefs. Bodies of water that may be
estuaries are bays, harbors,sounds, and inlets.
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Climate

• The water in estuaries, and especially that
  overlying the tidal flats, is relatively thin, so
  it follows the variations in temperature of the
  atmosphere more closely than does the water of
  the open ocean. The water is much colder in
  winter,and warmer in summer than the sea.

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Natural Resources
The chemical components of fresh water can vary
greatly, whereas salt water is fairly uniform.
Consequently, variations in the chemistry of
river water produce considerable differences in
estuarine nutrient cycles. In general the most
important compounds for estuarine life that are
supplied by fresh water are silicon, iron,
nitrogen, and phosphorus. Estuaries provide
some of the most productive habitats on earth
because of the accumulation of nutrients along
with adequate light conditions that fuel the
production of phytoplankton, the tiny,
single-celled algae that drift into the water.
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Plant Life

• Mangroves
• Seagrass
• Seaweed
• Eelgrass
• Saltmarshes
• Reeds

• Saltwort
• Lyngbyers Sedge
• Saltgrass

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Why do plants flourish in estuaries?

• The mixing of fresh water and salt water is an
  important feature of estuaries. The fresh water
  is less dense than seawater and therefore flows
  above it . The flow of some large rivers is so
  immense that a wedge shaped bottom layer of salt
  water, called a salt wedge , is pushed up the
  estuary along the river bottom by the force of
  the outgoing fresh water above it. This wedge of
  salt water can penetrate several kilometers from
  the rivers mouth, carrying with it nutrients for
  the estuarys plant life from the ocean.

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Mangroves

• Mangrove forests consist of diverse,
  salt-tolerant trees and other plant species which
  thrive in inter-tidal zones of sheltered tropical
  shores, and estuaries. Mangrove trees have
  specially adapted aerial and salt-filtering roots
  and salt-excreting leaves that enable them to
  occupy the saline wetlands where other plant life
  cannot survive.

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Animal Life

• Birds
• Belted Kingfisher
• Black Duck
• Black Turnstone
• Western Grebe
• Geese
• Herons
• Egrets

• Fish
• Bonefish
• Chum Salmon
• Milkfish
• Mudskipper
• Pink Salmon
• Catfish

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• Invertebrates
• Horseshoe Crab
• Mosquitos
• Water Boatman

• Mammals
• Dolphin
• Porpoise
• Manatee

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Manatee
Large, seal-like body that tapers to a powerful
flat tail. Two agile forelimbs with three to four
toenails on each, which act like arms to help the
manatee maneuver in shallow water, grasp and move
food toward their mouths, and act like flippers
during swimming.Most of the time is spent eating
vegetation. Manatees are found in coastal
waterways, estuaries, saltwater bays, rivers and
canals, particularly where seagrass beds are
located. Manatees are completely herbivorous and
can eat 10-15 of their body weight daily. In
captivity they are fed lettuce and other greens.
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Dolphin's
Several freshwater species inhabit river
estuaries in Asia and South America. The small,
graceful tucuxi, dolphin has been sighted more
than 2000km up the Amazon River. The tucuxi, is
the smallest dolphin, it is less than 1.2m long
the largest, the bottlenose dolphin, reaches a
length of 3m.
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Porpoise
The most frequently seen and most wide-ranging of
the porpoises is the common, or harbor, porpoise,
which inhabits cool and cold waters of the
northern hemisphere, especially around tidal
estuaries and inlets of large rivers. Unlike
dolphins, these porpoises are rarely seen in the
open ocean and do not play in the bow waves or
wakes of ships.
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Are They Permanent?
Many fish species do not reside in estuaries
permanently, but use them as nursery areas. The
adult fish spawn off shore and the young enter
the calm, food-rich estuaries to develop until
mature enough to breed, at which time they
migrate back to the sea. About 80 fish species
have adapted their life cycle to the extent that
they are entirely or partially dependent on
estuaries. For example salmon and seahorses
participate in this.
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Diversity

• The animal life in estuaries varies greatly.
  Tropical estuaries are generally more diverse
  than their temperate counterparts. High
  productivity and habitat complexity can lead to
  considerable wildlife diversity and, in some
  case, to huge concentrations of animals as well.

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Food Web

• The foundation of the estuarine food web is
  plankton. These microscopic animals are more
  diverse and essential to food webs and community
  structure than are vertebrates. Zooplankton feed
  on phytoplankton and are, in turn , eaten by fish
  and other animals. Dead plankton make up an
  important element of the organic bottom layer of
  estuaries.
• Benthic (bottom-dwelling) fauna such as
  barnacles, bryozoans, sponges, mussels, and
  hydroids live on the rich estuary floor. Fish,
  crabs and shrimp take advantage of the large
  numbers of invertebrates found in estuaries. This
  extremely high productivity makes the estuary an
  attractive nursery habitat for many crustacean
  and fish species and such an attractive fishing
  ground for humans.

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Food Web
The primary producers are phytoplankton seaweeds,
mangroves, eelgrasses, and reeds. Estuaries are
also important feeding grounds for a variety of
birds, which occupy different trophic levels
within the food web. These include plant eaters
such as red-knobbed coot. Invertebrate feeders
such as greenshank,sanderlings and curlew
sandpipers. Fisheaters such as kingfishers,
terns, cormorants, fish eagles, pelicans, and
herons.
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Human Population Density
The economy of many coastal areas is based
primarily on the natural beauty and bounty of
estuaries. When those natural resources are
imperiled, so too are the livelihoods of the many
people who live and work there. 110 million
Americans around half the U.S. population now
live in coastal areas, including the shores of
estuaries. Coastal counties are growing three
times faster than counties else where in the
nation.
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Why are estuaries important?

Estuaries are important for many reasons.
Estuaries are among the most biologically
productive ecosystems on the planet. More than
two thirds of the fish and shellfish we eat,
spend some part of their lives in estuaries.
These ecosystems also provide many other
important ecological functions they provide
protection from flooding, and other important
functions. Estuaries also have economic
importance . These dynamic bodies of water
provide us with an important source of food, but
are also a popular tourist destination . And
millions of people visit the nations estuaries
each year to boat, swim , bird watch and fish.
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Importance of Estuaries
Estuaries are critical for the survival of many
species. Tens of thousands of birds, mammals,
fish, and other wildlife depend on estuarine
habitats as places to live, feed, and reproduce.
Estuaries provide ideal spots for migratory
birds to rest and refuel during their journeys.
And many species of fish and shellfish rely on
the sheltered waters of estuaries as protected
places to spawn, giving them the nickname
nurseries of the sea. Hundreds of marine
organisms, including most commercially valuable
fish species, depend on estuaries at some point
during their development.
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Ecological Problms facing Estuaries
Since the early 18oos , sprawling urbanization,
ever more sophisticated technology, and pollution
from industries have taken a heavy toll on
estuarine ecology. Canals, oil rigs, dredging,
drainage, and increased watershed erosion have
led to radical physical changes in most
estuaries. When sewage and other organic wastes,
along with certain inorganic substances, are
discharged into rivers and estuaries, the result
is nutrient enrichment, which leads to excessive
algae growth and eventually to oxygen depletion.
Warm water that is discharged into estuaries from
thermal plants can exacerbate this situation.
Factories have discharged mercury, DDT, and PCBs
into estuaries. In addition, other factors, such
as loss of habitat, overfishing, and the
introduction of exotic species such as the coypu,
have caused changes in the animal and plant
communities of estuaries. Also as more people
flock to the shore, we are upsetting the natural
balance of estuaries and threatening their
health. We endanger our estuaries by polluting
the water and building on the lands surrounding
them.
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Why we need to protect estuaries?
Because of the fragile balance of these
productive estuarine environments may be easily
destroyed by human activities. Changes in water
quality, by dredging and construction, to the
multiple components of estuaries can result in
harmful changes in the ecosystem.
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Predation
Humans are one of the main predators. Humans eat
almost every kind of fish found in estuaries.
That is one example of predation. Also birds eat
different kinds of fish and shell fish. Dolphins
and porpoises are also considered predators.
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Plant-Herbivore Interactions
There is a selection of plant types found in
estuaries, but there are few true herbivores to
consume them. One of these true herbivores is the
manatee.
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Competition
In estuaries there is a lot of competition for
different organisms. There is competition between
invertebrates that eat phytoplankton and
zooplankton. Then there is competition between
fish, amphibians and birds which eat the
invertebrates. Then there is competition between
birds,larger birds, and mammals, including
humans. They eat the smaller fish, smaller birds,
and amphibians. Without bacteria, though an
estuary would not be able to survive.
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Symbiotic Relationships
An example of a symbiotic relationship would have
to be detritus and all animals of an estuary.
Detritus is a nutritious layer of bacteria. This
bacteria is very important, because many species
of animals feed on it. Without this bacteria no
animal could survive in an estuary.
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Bibliography
www.sacoast.uwc.ac.za www.epa.gov www.
marine-ed.org www.education.noaa.gov www.estuaryli
ve.com www.encarta.com www.homesafe.com www.inlet.
geol.sc.edu www.inforain.org www.cws-scf.ec.gc.ca
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