Script :- Marine Environment

7/28/2019 Script :- Marine Environment

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MARINE ENVIRONMENT

Contents

Marine environment

Oceans &seas

Division of the Marine Environment

Sea state Douglas Sea Scale

Beaufort scale


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MARINE ENVIRONMENT- INTRODUCTION

The word "marine" comes from the Latin word "mar" or "mare,"meaning sea or ocean. Today, the term marine environment would refer to bodies

of salt water and any plants, animals and other objects that exist in the body of

water

Marine environments are diverse and can change rapidly depending on

tidewaters and currents. They include many unique animals and plants, such as

corals and bi-valves, and many unique habitats, such as underwater volcanoes.

Marine ecosystems are most often crossing national borders, and research and

management of local and regional seas need substantial international co-ordination.

Oceans cover about 71% of the Earth's surface, and because of their depth they

contain about 300 times the habitable volume of the terrestrial habitats on Earth.

Marine protected area

Marine protected areas, like any protected area, are regions in which human

activity has been placed under some restrictions in the interest of conserving the

natural environment, its surrounding waters and the occupant ecosystems, and anycultural or historical resources that may require preservation or management.

Marine protected areas' boundaries will include some area of ocean, even

if it is only a small fraction of the total area of the territory.Natural or historic marine resources are protected by local, state, territorial, native,

regional, or national authorities and may differ substantially from nation to nation.This variation includes different limitations on development, fishing practices,

fishing seasons and catch limits, moorings, bans on removing or disrupting marinelife of any kind.

Marine habitats

Marine habitats can be divided into coastal and open ocean

habitats. Coastal habitats are found in the area that extends from the shoreline to


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the edge of the continental shelf. Most marine life is found in coastal habitats, even

though the shelf area occupies only seven percent of the total ocean area. Openocean habitats are found in the deep ocean beyond the edge of the continentalshelf.

CORAL REEFS

Coral reefs are underwater structures made from calcium carbonatesecreted by corals. Coral reefs are colonies of tiny animals found in marine waters

that contain few nutrients. Most coral reefs are built from stony corals, which inturn consist of polyps that cluster in groups. The polyps are like tiny sea anemones,

to which they are closely related. Unlike sea anemones, coral polyps secrete hardcarbonate exoskeletons which support and protect their bodies. Reefs grow best in

warm, shallow, clear, sunny and agitated waters.


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MANGROVE

Mangroves are various types of trees up to medium height and shrubs

that grow in saline coastal sediment habitats in the tropics and subtropics mainlybetween latitudes 25 N and 25 S. It Found in warmer, tropical areas.Inlets andbays are covered by mangrove trees.Mangrove swamps protect the shore from

erosion.Mangrove swamps act like giant sponges and absorb the impact of stormsand high waters.

wetland

A wetland is a land area that is saturated with water, either permanently or

seasonally, such that it takes on the characteristics of a distinct ecosystem.Primarily, the factor that distinguishes wetlands from other land forms or water

bodies is the characteristic vegetation that is adapted to its unique soil conditions


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OCEANS &SEAS

OCEANS

An ocean is a massive body of salt water, encircling a planet, that contains large,

continuous body of salt water. Ocean covers nearly 71% of the Earth's surface and

is divided into major oceans and smaller seas. They are considered to be ancient

formations in the morphology of the earth and are mainly separated from eachother by the continents.

The three principal oceans, the Pacific, Atlantic, and Indian, are largely delimited

by land and submarine topographic boundaries.

The word "sea" is often used interchangeably with "ocean", but strictly speaking a

sea is a body of saline water (possibly a division of the World Ocean) partly orfully enclosed by land.

Physical properties

The total mass of the hydrosphere is about 1,400,000,000,000,000,000 metric tons

(1.51018 short tons) or 1.41021 kg, which is about 0.023 percent of the Earth's

total mass.

Less than 3 percent is fresh water; the rest is saltwater, mostly in the ocean.

The area of the World Ocean is 361 million square kilometers (139 million squaremiles), and its volume is approximately 1.3 billion cubic kilometers (310 million

cu mi).

Sea

The sea is the connected body of salt water that covers 70 percent of the Earth's

surface.

The sea is important in the earth's climate, in providing food and oxygen, in its

enormous diversity of life, and for navigation.The study of the sea is called oceanography.

Seawater is characteristically salty, containing as its main salt sodium chloride but

also chlorides of potassium and magnesium.

The temperature of the sea is dependent on the amount of solar radiation falling on

the surface.


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Sea water has a freezing point of about 1.8 C (28.8 F).

Sea water is slightly alkaline and during historic times has had a pH of about 8.2.

There is no sharp distinction of seas from oceans, though generally seas are

smaller, and are often partly (as Marginal seas) or wholly (as inland seas) bordered

by land. Similarly, seas are generally larger than lakes.The law of the sea states that the entire ocean is "sea

The differences between ocean and seas are: Seas are smaller than oceans and are

usually located where the land and ocean meet. Typically, seas are partially

enclosed by land.

The following table lists the world's oceans and seas, according to area and

average depth, including the Pacific Ocean, Atlantic Ocean, Indian Ocean,

Southern Ocean, Mediterranean Sea, Arctic Ocean, Caribbean Sea, and BeringSea.

Name

Area

Average

depth

Greatest

known

depthPlace of

greatest known

depthsq. mi. sq. km ft. m ft. m

Pacific Ocean 60,060,700 155,557,000 13,215 4,028 36,198 11,033 Mariana Trench

Atlantic Ocean 29,637,900 76,762,000 12,880 3,926 30,246 9,219 Puerto Rico

Trench

Indian Ocean 26,469,500 68,556,000 13,002 3,963 24,460 7,455 Sunda Trench

SouthernOcean

1

7,848,300 20,327,000 13,10016,400

4,0005,000

23,736 7,235 South SandwichTrench

Arctic Ocean 5,427,000 14,056,000 3,953 1,205 18,456 5,625 7745'N;175W

MediterraneanSea

2

1,144,800 2,965,800 4,688 1,429 15,197 4,632 Off CapeMatapan,

Greece

Caribbean Sea 1,049,500 2,718,200 8,685 2,647 22,788 6,946 Off Cayman

IslandsSouth ChinaSea

895,400 2,319,000 5,419 1,652 16,456 5,016 West of Luzon

Bering Sea 884,900 2,291,900 5,075 1,547 15,659 4,773 Off BuldirIsland

Gulf of Mexico 615,000 1,592,800 4,874 1,486 12,425 3,787 Sigsbee Deep

Okhotsk Sea 613,800 1,589,700 2,749 838 12,001 3,658 14610'E;


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4650'N

East China Sea 482,300 1,249,200 617 188 9,126 2,782 2516'N; 125E

Hudson Bay 475,800 1,232,300 420 128 600 183 Near entrance

Japan Sea 389,100 1,007,800 4,429 1,350 12,276 3,742 Central Basin

Andaman Sea 308,000 797,700 2,854 870 12,392 3,777 Off Car NicobarIsland

North Sea 222,100 575,200 308 94 2,165 660 Skagerrak

Red Sea 169,100 438,000 1,611 491 7,254 2,211 Off Port Sudan

Baltic Sea 163,000 422,200 180 55 1,380 421 Off Gotland


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Division of the Marine Environment

The marine ecosystem is the largest aquatic system on the planet. Its size andcomplexity make it difficult to deal with as a whole. As a result, it isconvenient to

divide it into more manageable arbitrary subdivisions

Open ocean can be subdivided vertically and horizontally.

The entire area of the open water is the pelagic realm; pelagicorganisms are thosethat live in the open sea away from the bottom. This is in contrast to the benthic

realm, which is a general term referring to organisms and zones of the sea bottom.

Horizontally Division - , the Pelagic Realm

This can be divided into two zones.

- The neritic zone - encompasses the water mass that overlies the

continental shelves.


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The oceanic zone includes all other open waters

Vertical Division, the pelagic realm

This can be further subdivided. Two schemes are possible.- The first is based on light penetration. The photic or euphotic zone is that

part of the pelagic realm that is lighted.

- Generally, the lower boundary is between 100 and 200m.

- A synonym for this zone is the epipelagic zone. Because it is the zone of

primary production in the ocean, it is of major importance.

-

The permanently dark water mass below the photic zone is the aphoticzone. Some scientists prefer to recognize a transition zone between the

photic and aphotic called the disphotic zone.

The pelagic part of the aphotic zone can be subdivided into

zones that succeed each other vertically.

- The mesopelagic is the uppermost of the aphotic areas. Its lowerboundary in the tropics is the 10oC isotherm, which ranges from 700 to

1000m, depending on the area.

- Next is the bathypelagic, lying between 10 and 4oC, or in depth between700 and 1000m and between 2000 and 4000m.

-Overlying the plains of the major ocean basins is the abyssal pelagic,which has its lower boundary at about 6000m.

- Hadal pelagic - The open water of the deep oceanic trenches between

6000 and 10,000m is called the hadal pelagic.


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Corresponding to the last three pelagic zones are three bottom or

benthic zones.

- The bathyal zone is that area of bottom encompassing the continental

slope and down to about 4000m.

- The abyssal zone includes the broad abyssal plains of the ocean basins

between 4000 and 6000m.

- The hadal is the benthic zone of the trenches between 6000 and 10,000m.

- The benthic zone underlying the neritic pelagic zone on the continental

shelf is termed the sublittoral or shelf zone.

SEA STATE CONDITIONS

Sea state

In oceanography, a sea state is the general condition of the free surface on a

large body of water with respect to wind waves and swell at a certain location and

moment. A sea state is characterized by statistics, including the wave height,

period, and power spectrum. The sea state varies with time, as the wind conditions

or swell conditions change. The sea state can either be assessed by an experienced

observer, like a trained mariner, or through instruments like weather buoys, wave

radar or remote sensing satellites.

Sea conditions are identified by two geographical sectors; East and West. In

deep water, sea state is determined by the mean wind speed, the fetch (the distanceover which it blows), and the duration of the wind over the open water. A sea state

is generally described by significant wave height, which is the average height of

the one-third highest waves.


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The following variables are made available within the Sea State

Condition service:

Significant wave height

Mean wave period

Wind 10 meters

In order to determine sea state:

Use the sea state photo guide and descriptions.

Use binoculars to make an accurate assessment.

Look into the wind to record the greatest sea state observed within the

observation area.

Discount coastal surf.

Record your final assessment one minute before shore watch start time.

Make a discrete decision on the sea state, i.e. 0, 1, 2, 3 or 4, and avoid using

a range of sea states i.e. 2 to 3.

Douglas Sea Scale

The Douglas Sea Scale is a scale which measures the height of the

waves and also measures the swell of the sea.The Douglas Sea Scale,

also called the International Sea and Swell Scale, was devised in the

1920s by Captain H.P. Douglas.

State of the sea (wind sea)

Degree Height (m) Description

0 no wave Calm (Glassy)


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1 0 - 0.10 Calm (Rippled)

2 0.10 - 0.50 Smooth

3 0.50 - 1.25 Slight

4 1.25 - 2.50 Moderate

5 2.50 - 4.00 Rough

6 4.00 - 6.00 Very Rough

7 6.00 - 9.00 High

8 9.00 - 14.00 Very High

9 14.00+ Phenomenal

Swell

Degrees Description

0 No Swell

1 Very Low (short and low wave)

2 Low (long and low wave)

3 Light (short and moderate wave)

4 Moderate (average and moderate wave)

5 Moderate rough (long and moderate wave)

6 Rough (short and heavy wave)

7 High (average and heavy wave)

8 Very high (long and heavy wave)

9 Confused (wavelength and height indefinable)


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Wave length

Short wave 100 m -

Average wave 100200 mLong wave 201 m +

Wave height

Low wave 2 m -

Moderate wave 24 m

High wave 4.01 m +

Beaufort scale

The Beaufort scale is an empirical measure that relates wind speed toobserved conditions at sea or on land. Its full name is the Beaufort wind force

scale, although it is a measure of wind speed and not of "force" in the scientific

sense of the word. There are 0-12 sea state conditions according to beaufort

scale.

Modern scale

Beaufo

rt

numbe

r

Descriptio

n

Wind

speed

Wav

e

heigh

t

Sea

conditionsLand conditions Sea state photo

Associated

Warning

Flag

0 Calm

iron oxide

Step 2 iron oxide + water --> hydrated iron oxide (rust)

Corrosion is the atmospheric oxidation of metals. That means thatoxygen combines with the metal and forms a new layer. This layer can be good or

bad. By far the most important form of corrosion is the rusting of iron and steel.
http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Rustinghttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Rustinghttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Metal


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Rusting is a process of oxidation in which iron combines with waterand oxygen to form rust, the reddish-brown crust that forms on the surface of the

iron. Because iron is so widely used, e.g., in building construction and in tools, its

protection against rusting is important. Rusting can be prevented by excluding airand water from the iron surface, e.g., by painting, oiling, or greasing, or by plating

the iron with a protective coating of another metal. Many alloys of iron areresistant to corrosion. Stainless steels are alloys of iron with such metals as

chromium and nickel; they do not corrode because the added metals help form ahard, adherent oxide coating that resists further attack.

Corrosion in marine Environments

Seawater systems are used by many industries such as shipping, offshore oil

and gas production, power plants and coastal industrial plants. The main use of

seawater is for cooling purposes but it is also used for fire fighting, oil field water

injection and for desalination plants. The corrosion problems in these systems have

been well studied over many years, but despite published information on materials

behavior in seawater, failures still occur.

Galvanic corrosion is the most frequent cause of unexpected

corrosion failures in seawater. It has caused failures of ship fittings and deckhouse

structures, fasteners, hull plating, propellers, shafts, valves, condensers, and piping.

In sea atmospheres, galvanic corrosion causes failures of roofing, gutters, and car

trim. The reason that galvanic corrosion causes so many failures is that it can occur

any time that two different metals are in electrical contact in seawater. Since most

structures and devices are made of more than one kind of metal, this diversity of

materials is common and frequently overlooked in corrosion prevention activities.

(reference)


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Types of Corrosion

Uniform Corrosion

Galvanic Corrosion

Crevice corrosion

Pitting corrosion

Intergranular corrosion

Selective corrosion (dealloying)

Graphitic corrosion

THE CONSEQUENCES OF CORROSION

Reduction of metal thickness leading to loss of mechanical strength and

structural failure or breakdown. When the metal is lost in localised zones soas to give a cracklike structure, very considerable weakening may result

from quite a small amount of metal loss.

Hazards or injuries to people arising from structural failure or breakdown

(e.g. bridges, cars, aircraft).

Loss of time in availability of profile-making industrial equipment.

Reduced value of goods due to deterioration of appearance.

Contamination of fluids in vessels and pipes (e.g. beer goes cloudy when

small quantities of heavy metals are released by corrosion).

Perforation of vessels and pipes allowing escape of their contents and

possible harm to the surroundings. For example a leaky domestic radiatorcan cause expensive damage to carpets and decorations, while corrosive sea

water may enter the boilers of a power station if the condenser tubesperforate.

Loss of technically important surface properties of a metallic component.

These could include frictional and bearing properties, ease of fluid flow over

a pipe surface, electrical conductivity of contacts, surface reflectivity or heattransfer across a surface.


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Mechanical damage to valves, pumps, etc, or blockage of pipes by solid

corrosion products.

Added complexity and expense of equipment which needs to be designed to

withstand a certain amount of corrosion, and to allow corroded components

to be conveniently replaced.

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