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MAY 2011
Oceanography – Ch.# 11.
The Coastal Ocean.
The coastal ocean is a most important asset because:
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Most of the world’s fishery is harvested from above the continental shelves (within
320 Km of the shoreline.
Estuary and wetlands environments are among the most productive ecosystems
Resources (Oil and Gas), Recreation, shipping, and employment are located in
coastal waters.
Chemical, physical and biological processes occur in this environment
Undergoing increasing stress as a consequence of development and exploitation,
and waste disposal.
11 – 1. Laws governing the Ocean ownership.
Initially based on the assumption that resources in the ocean were inexhaustible.
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National domain over the sea to a distance of 3 Nautical miles (1692) – Territorial
sea. Subsequently changed to the distance a cannon can be fired – 12 miles.
UN (1958) Domain extended over the continental shelf. But there are Interpretation
problems.
3rd. – (1973 – 82) adopted by all but 3 countries. The objection was: It made mining
on the deep sea floor unprofitable. Deep ocean mineral resources are regulated by
the Int’l Seabed Authority (UN). And disputes are handled by a UN Tribunal
EEZ was extended to 350 nautical miles (648 km) from shore. US size is increased by
11.5 Million Sqkm. The Shelf is defined geologically, if it extends beyond 200
nautical miles.
All ships have a right to free passage across the continental shelves.
11 – 2. Characteristics of Coastal waters
Strongly influenced by processes that occur on land.
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Salinity. A halocline develops from runoff, except where shallow (mixing occurs), and
it is then an Isohaline. Offshore winds can increase salinity. Evaporation occurs when
the wind moves from landward to seaward.
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Temperature. In low latitudes, surface waters do not mix thoroughly. Sfc temp can
exceed 110 Deg F. In high latitudes, sea ice may form .
Coastal Geostrophic Currents, the circular path around a gyre. Wind and runoff can
be the cause. Wind blows, water piles up and gravity pulls the water into the open
ocean. Coriolis effect is also present. (the Davidson Current)
11 – 3. Types of Coastal waters
Estuaries: partially enclosed fresh water dilutes the salty water. Rising sea level resulted from
melting glaciers.
Types : * Coastal plains, drowned River valleys
 Fjords, glaciated valleys
 Bar built estuaries, separated by barrier bars from the ocean
 Tectonic estuaries
Water mixing in estuaries due to less dense, fresh water.
Vertically mixed in low volume, shallow valleys.
Slightly stratified in deeper estuaries. Two layers recognized, separated by a zone of
mixing.
Highly stratified in a deep estuary
Salt water wedge in a deep high volume estuary.
Estuaries and Human activity. These are important breeding grounds and nurseries (Columbia
River- dikes built; Chesapeake Bay formed by the drowning of the Susquehanna River, is highly
stratified, experiences large seasonal changes, and has developed anoxic areas.
Coastal wetlands – protected from the open oceans.
Types * Salt marshes , extend to 65 Deg N or S Lat.
 Mangrove Swamps, intermittently submerged by ocean water, extend to 30 Deg N
or S Lat.
 Lagoons
 Marginal seas.
11 – 4. What Issues Coastal Wetlands face?
Salt marshes are nurseries for commercially important fishes in the SE US. (Flounder and Blue
fin feed in these marshes during winter months and the area is also used for protection.
Oyster, Clams and Scallops inhabit. Coastlines are very productive.
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Mangroves are nurseries for shrimp, prawn and shell fish. Clean up pollution before it reaches
the ocean, by removing inorganic compounds, and metals from ground water and sfc water.
Stores water from flooding and protect coastline from erosion. Serious loss of wetlands which
was originally 87 MHectares is now 43 Mh. EPA now controls wetlands. Rise in MSL is expected
to exacerbate the loss.
Lagoons – located landward of barrier islands. There are three zones within the lagoon.
 Fresh water near the head of the lagoon.
 Transitional or brackish water in the middle
 Salt water near the mouth.
The water may become hypersaline due to high evaporation.
Marginal Seas are semi – isolated water bodies, a result of tectonic activity. Example: the
Mediterranean is a remnant of the Tethys Sea. It is a series of small seas connected by narrow
necks overlying oceanic crust. The water that is lost by evaporation, is replenished through the
Strait of Gibraltar. It flows along the north coast of Africa, sinks in the eastern area and returns
to the Atlantic through the Strait, denser and cooler.
Wetlands are typically saturated most of the time. They can border either fresh water or
marine coastal marine environments. The types of wetlands are:
 Salt marshes. Generally restricted to between 30 and 65 Deg. Latitude
 Mangrove swamps
11 – 5. What is Pollution.
Marine pollution is any harmful substance. It must be introduced by man. A standard lab
bioassay is used by the EPA. If the pollutant exceeds that which causes 50% mortality among
test’s organisms.
Waste disposal in the ocean. Diluting pollutants often renders them less harmful.
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11 – 6. Main types of Marine Pollutants
Petroleum. Accidents (Exxon Valdez); Deliberate (Persian Gulf); Drilling . Althoughit is
biodegradable, spills can cause death to many marine organisms because HC contains many
other elements. Natural Oil seeps make up 47% of oil in the ocean.
Petroleum products – contain toxic components.
Cleaning Oil Spills. Initially any oil floats. Volatile components evaporate. The more viscous
matter forms into tar balls and sink.
 Absorbent materials are used. Collected oil is dispersed elsewhere and in strong
winds mousse forms (a mixture of water and oil).
 Microorganisms - bioremediation
 Ignited – MV New Carissa.
Double walled tankers are used in an effort to prevent spills during transport.
Sewage sludge. Exposed to chlorine, contains human waste, oil , zinc, copper, lead, Silver,
mercury, and pesticides. These latter substances bioaccumulate (and biomagnification). Others
are persistent and still others are tied to diseases.
New York disposes its waste at sea.
Plastics make up the majority of debris in the marine environment. A few plastics are
photodegradable.
DDT and PCBs
Now present in every environment. Its extreme effectiveness and persistence as a toxin in the
environment eventually resulted in a hosts of problems.
Mercury and Minamata Disease
When these elements enter the ecosystem, mercury forms an organic compound that is
generally toxic to all living things. Mercury poisioning causes a degenerative neurological
disorder.
Non Point source Pollution and Trash
Also called poison source.