Download Lawson_Estuaries PP

Estuaries
By Dan Lawson
What is an estuary?

An estuary is a coastal body of water
which is openly connecting a freshwater
stream with a saltwater environment such
as the ocean.
Location

Estuaries are found all
over the world in coastal
areas. They can also be
called bays, lagoons,
harbors, or sounds. They
are only true estuaries,
however, when there is
both salt and fresh water
present.
Types of Estuaries





Drowned River ValleysMany estuaries of this type were
formed between 15,000-6,000
years ago.
They were formed when the end
of the last glaciation period
caused sea level to rise 100130m.
Drowned river valleys are typically
wide and shallow, rarely
exceeding 30m in depth.
Examples include Chesapeake Bay
(the largest estuary in the United
States) and Delaware Bay.
Chesapeake Bay from Satellite
Types of Estuaries



Lagoon-TypeSemi isolated from the ocean
by barrier islands, which are
narrow strips of land that only
allow water to flow through
small inlets.
A good example is Pamlico
Sound, the largest lagoon on
the US east coast. Located in
North Carolina, it is separated
from the Atlantic by the Outer
Banks.
Types of Estuaries





Fjord Type –
Found in valleys that are
deeply eroded from
glacial activity.
Very narrow and deep
Can exceed 300m in
depth
Examples include Alaskan
coast, Puget Sound
region of Washington,
areas in Norway, and
New Zealand.
Organisms Found in Estuaries


Estuaries are among the most heavily populated
areas in the world, with almost 60% of species
being found in estuaries and coastal areas. In
order to survive in the water found in an
estuary, organisms must be euryhaline (able to
adapt to a wide range of salinity)
Some examples of organisms found in estuaries
are eels, horseshoe crabs, oysters, seahorses,
blue crabs, bull sharks, salmon, striped bass,
and sturgeon.
Threats to Estuaries



Estuaries are threatened by both human and
non-human environmental impacts.
Some of the main natural threats include
sediment deposition which can clog feeding and
breathing holes of certain species. Sediment also
works to fill in estuaries, decreasing space for
organisms to live.
Another problem is rapidly changing salinity
levels, which create a harsh environment for
organisms in the estuary.
Threats to Estuaries






Human Impacts –
Of the 32 largest cities in the world, 22 are located on estuaries.
Pollution from upstream travels down the river and affects the
estuary environment.
Bioaccumulation can occur which is when pollutants such as
Mercury or pesticides build up in the tissues of marine animals,
making them unsafe for consumption.
Another threat to estuary life is overfishing. The Chesapeake Bay
oyster population used to be huge, but has almost been wiped out
due to overfishing. This greatly reduces the ability of oysters to help
filter the water.
It has been said that the oysters used to filter excess nutrients from
all of the water in the estuary in 3-4 days. Now the process takes
almost a year.
In Conclusion




Estuaries are a vital part of the ecosystem. The
huge amount of organisms living in this
environment are essential to the well being of
other environments such as the ocean and
rivers.
Estuaries are essential to anadromous animals
that travel up stream to spawn.
They also act as the filters of the water
travelling downstream towards the ocean.
Without estuaries, many species of plants and
animals would not be able to survive.