Oceans and Coastal Zones

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Oceans and Coastal Zones
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The Ocean Ecosystem

• Approximately 97 of the worlds surface water is
  salt water
• circulates through the ocean in currents, tides,
  and wave systems
• southern Hemisphere is dominated by oceans
• northern Hemisphere is dominated by land masses

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Regions of the Ocean

• The ocean ecosystem consists of a number of
  separate but interrelated ecosystems, each with
  their own physical and biological
  characteristics
• continental shelves
• continental slope
• ocean floor

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Where are the Oceans?

• While the ocean can be considered one enormous
  ecosystem -- it is not a uniform environment
• Better to perceive the ocean as a set of as set
  of interconnected ecosystems.
• Four main basins can be distinguished
• Pacific
• Atlantic
• Indian
• Arctic

Map of the worlds oceans, with red dots
corresponding to dead zones
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Major US drainages
The Mississippi River Watershed is highlighted in
yellow.
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Major US drainages
Ohio River
Sub-watersheds of the Mississippi River
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Select Watersheds in Indiana and Illinois
White River Watershed
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Ocean Circulation

• This difference between the hemispheres is
  important in determining the distribution of
  weather and climate patterns around the world.

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What factors drive ocean circulation?

• Temperature
• Salinity
• Atmospheric Circulation

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Ocean Environments
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The Coastal Zone
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Importance of the Coastal Zone

• majority of the Earths population lives within
  100 km of the coast
• means that a large portion of the Earths
  population is at risk from large storms generated
  over the ocean
• Also means that the ocean, and particularly the
  continental shelves, are susceptible to human
  impact

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Health of the Oceans

• The health of the world's ocean is imperiled
• The symptoms can be seen everywhere
• increasing occurrences of toxic algal blooms
• declining fish populations
• widespread bleaching of coral reefs
• continuing losses of wetlands

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• Perhaps more troubling still are less visible
  problems, such as pollutants that pour into the
  seas from rivers and streams and runoff from
  urban and agricultural areas.

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Coastal Processes
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• Coastal zone represents the transition zone
  between land and sea, as such it is dynamic,
  constantly changing environment.
• Coastal zones encompass a wide variety of
  environments
• mangroves swamps
• estuaries
• salt marshes
• beaches
• coral reefs

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Mangrove Swamps
Mangroves are a tropical tree that grows in
shallow salt and brackish water. The trunks are
above high tide, held up by sturdy roots. The
root systems host a diverse ecology where many
young fish and young invertebrates grow.
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Estuaries

• A partially enclosed body of water formed where
  freshwater from rivers and streams flows into the
  ocean, mixing with the salty sea water.
• Often known as bays, lagoons, harbors, inlets, or
  sounds.
• Estuarine environments are among the most
  productive on Earth.
• http//earth1.epa.gov/nep/sheds.htm

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Secondary coasts reefs
Coral Reefs
Reefs only form in warm, tropical seas, but in
those environments they form important
shorelines. These images are of atolls in the
western Pacific Ocean.
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Coastal Erosion

• Erosion and its effects are often seasonal
• Summer
• waves low, long wavelength
• sand is transported shoreward, settles out
• beach sands, sea cliffs protected by low energy
  of system

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Coastal Erosion

• Winter
• waves higher, shorter wavelength
• sand eroded from beaches, kept in suspension and
  transported offshore
• beach reduced, may be completely removed
• waves attack sea cliffs
• Significant changes can occur to the beach during
  short intense periods (storms) followed by longer
  periods of little change

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Factors affecting erosion

• oceanic conditions
• resistance of coastal materials
• alteration of normal drainage
• growth of vegetation
• vibration and load effects above cliff

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Rates of Coastal Retreat

• California coast
• rate depends on nature of coastal materials
• resistant rocks 0 - 1 cm/yr
• nonresistant rocks 30 cm/yr
• at Ano Nuevo near San Francisco, average rate of
  retreat over the past 300 years is estimated at
  2.7 m/yr

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Stabilization and Control of Coastlines

• rip-rap
• large blocks of resistant rock, etc., placed at
  the base of cliff to absorb wave energy
• rip-rap must be continuous or waves will erode
  cliff around, and ultimately behind the rip-rap
• commonly utilized by individual property owners
• can be expensive

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Stabilization and Control of Coastlines

• seawalls
• concrete structures built along coast, same
  principle as rip-rap
• usually significant erosion just seaward of the
  wall due to reflected wave energy -- seawall may
  topple over if erosion is allowed to continue

Galveston seawall
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Stabilization and Control of Coastlines

• groins, jetties
• built perpendicular to coastline to stabilize or
  built a beach by trapping sediment being
  transported by longshore current
• major problem is erosion down the coastline

Pacific Palisades , California
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Stabilization and Control of Coastlines

• breakwater
• structures built offshore to protect the
  coastline from approaching waves

Terrebonne Parish, Louisiana
Wessex Coast, Southern England
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• The health of the world's ocean is imperiled
• The symptoms can be seen everywhere
• increasing occurrences of toxic algal blooms
• declining fish populations
• widespread bleaching of coral reefs
• continuing losses of wetlands

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• Perhaps more troubling still are less visible
  problems, such as pollutants that pour into the
  seas from rivers and streams and runoff from
  urban and agricultural areas.