 Oceanography is the science that studies the oceans along with marine organisms and ecosystem dynamics, ocean currents and waves, plate tectonics and the geology of the sea floor, and the chemical substances and physical properties of the world oceans.

2.  Oceanography is the
science that studies the
oceans along with
marine organisms and
ecosystem dynamics,
ocean currents and
waves, plate tectonics
and the geology of the
sea floor, and the
chemical substances and
physical properties of
the world oceans.

3.  study the composition of
seawater, its processes and
cycles, and the chemical
interaction of seawater with the
atmosphere and sea floor.
 analyze seawater components,
the effects of pollutants, and the
impacts of chemical processes
on marine organisms.
 use chemistry to understand
how ocean currents move
seawater around the globe and
how the ocean affects climate or
to identify potentially beneficial
ocean resources such as natural
products that can be used as
medicines.

4. The surface of the planet is approximately 71%
water and contains (5) five oceans: Arctic,
Atlantic, Indian, Pacific and Southern.

5. By Size Greatest Depths
 Pacific - 155,557,000
sq km
 Atlantic - 76,762,000
sq km
 Indian - 68,556,000 sq
km
 Southern - 20,327,000
sq km
 Arctic - 14,056,000 sq
km
 Mariana Trench, Pacific
35,827 ft
 Puerto Rico
Trench, Atlantic 30,246
ft
 Java Trench, Indian
24,460 ft
 Arctic Basin, Arctic
18,456 ft
 Southern Ocean, 23,737
ft

6.  Surface Area of the Planet (510,066,000
sq km)
 Land Area on the Planet (148,647,000
sq km) 29.1%
 Ocean Area (335,258,000 sq km)
 Total Water Area (361,419,000 sq km)
70.9%
 Type of Water (97% salt), (3% fresh)

7.  The Ring of Fire
coincides with the edges
of one of the Pacific
Plate which is world's
main tectonic plates. It
contains over 450
volcanoes and is home
to approximately 75%
of the world's active
volcanoes.
 Nearly 90% of the
world's earthquakes
occur along the Ring of
Fire; most recently, the
devastating quakes in
Chile, Japan and New
Zealand.

8.  Water covers 71% of the surface of the
earth. This fact is combined with the
great depth of many of the oceans
(average depth 3700 m / 12140 ft.)
provides a living space estimated to
200 times larger than all the land
ecosystem. Aquatic ecosystem can be
divided into fresh water systems (rivers
and lakes) and marine systems (salt
water).

9.  Aquatic ecosystems are better able to support life than the
terrestrial ecosystem.
 Because of the constancy of the water environment when
compared to the land environment the diversity of life in the vast
aquatic ecosystem is relatively small.
 Water, is a major natural resource. Water is the basis of life, it
supports life, and countless species live in it for all or part of their
lives. Freshwater biomes supply us with our drinking water and
water for crop irrigation.
 The world's oceans have an even greater effect on global climate
than forests do. Water has a high capacity for heat, and because the
Earth is mostly covered with water, the temperature of the
atmosphere is kept fairly constant and able to support life.
 The oceans contain several billion photosynthetic plankton, which
account for most of the photosynthesis occurring on Earth.
Without these, there might not be enough oxygen to support such
a large world population and complex animal life.

10. A watery environment was almost certainly the original source of
all life on this planet.
 Water provides a protective shield around plants and animals,
preventing the drying out of cells, providing buoyancy
transporting food to the organism and carrying waste products
away.
 Water also makes fertilization much easier than on land,
preventing the developing young from becoming dry, maintaining
an even temperature, filtering out harmful ultraviolet light from
the sun, and dispersing the young after birth.
 One of the most remarkable properties of water is its dissolving
power. Chemical compounds can be dissolved, transported and
precipitated out with virtually no chemical alteration due to
neutrality of rainwater (pH about 6.5 just slightly acid). In some
places, acid rain has increased the acidity of water, with harmful
consequences for the organisms living in it.

11. Marine Freshwater

12.  Water has several unusual properties that combine to minimize
temperature changes, thus the range of variation is smaller and
changes more slowly in water than in air.
 It has the largest specific heat, the largest heat of evaporation. At
ordinary temperature, it conducts heat better than any common
liquid except mercury. The special properties of water arise
from the structure of water molecules. Water is the only natural
substance that expands when it freezes. The density of ice is less
than of water, and it floats. Because of this peculiarity when the
temperature of the air falls far enough, a layer of ice forms on
the surface of a body of water and floats there.
 It serves as the barrier that reduces the rate of heat flow from the
liquid water from the atmosphere. As freezing continues, the
increasing thickness of the ice between the atmosphere and the
water slows down freezing greatly. A layer of ice only feet thick
protects the rest of the water from freezing, so that aquatic plants
and animals can carry on their life processes below the ice.

13.  The most important factor which depends principally
upon the amount of sodium chloride dissolved in it,
along with the small amount of bromides, carbonates
and sulfates of the elements sodium, potassium,
calcium and magnesium.
 Salinity is lowest typically 30 parts per thousands (ppt)
near the estuaries of large rivers where the addition of
fresh-water dilutes the concentration of salts. High
salinity (70ppt) is recorded where rainfall is low and
evaporation is high in the Red Sea. The amount is
salinity divides aquatic ecosystems into two main
groups: the fresh water ecosystems and the marine
ecosystems.

15.  Evaporation against
precipitation:
The relative amount of
evaporation or precipitation
in an area causes variations
in ocean salinity. If there is
more evaporation than
precipitation, then the
salinity increases;
considering the fact that salts
are not evaporated into the
atmosphere along with
water. If there is more
precipitation than
evaporation then the salinity
decreases

16. When large rivers meet
the oceans, they change
the salinity of
water. Large rivers have
more impacts on the sea
water salinity as
compared to the smaller
rivers and streams. The
runoff from the smaller
streams and rivers is
quickly mixed with
ocean water by the
currents and has little
effect on salinity and in
other hand, large rivers
e.g. Nile, Amazon,
Ganges, etc considerably
affect the salinity due to
its little or no salt
content.

17.  Out of 3% freshwater
available on earth, 67%
is stored in glaciers,
icebergs and ice caps.
Large icebergs that are
made up of frozen fresh
water and without any
salts can decrease the
salinity of the ocean
water upon melting in
the ocean water.
Glaciers are the largest moving objects on
earth. They are massive rivers of ice that
form in areas where more snow falls each
winter than melts each summer.

18.  As per the information by NASA Science
(‘highest concentrations (which is about 37
practical salinity units) of salt water are
present in the mid-Atlantic Ocean and
lower-Atlantic off the coast of Brazil, the
Mediterranean Sea and the Red Sea. Lower
concentrations are found near the Arctic
and Antarctic and the coastal regions of
East Asia and western North America’.

19.  Salinity affects seawater density, which in
turn governs ocean circulation and climate.
We know that the wind drives upper ocean
currents, however ocean current can also
flow deep below the surface. These deep-
ocean currents are driven by differences in
the sea water density. As sea water density is
controlled by temperature and salinity, these
factors make the oceans very dynamic in
nature.

20.  thermohaline circulation (THC) (thermo– temperature
and haline – salt content)
 refers to a part of the large-scale ocean current circulation that
is driven by global density gradients created by surface heat and
salinity of the sea water

21.  the principal mechanism by which
the oceans store and transport heat.
Since salinity is a key ingredient in
the global thermohaline circulation,
its measured value helps to discover
how its variation induces change in
global ocean circulation.

22.  Oxygen is a vital component of all aquatic ecosystems.
Most oxygen is found on the surface of the water bodies
especially in turbulent streams or when waves break.
 The amount of dissolved oxygen in water can be
severely altered due to human activity. In particular,
the dumping of untreated sewage and industrial waste
directly into the seas and rivers has caused a huge
increased in demand for oxygen by the organism that
feeds on the effluents. Organic debris, phosphates from
soap powder and ammonia from agricultural sources
and sewage all provide rich food supply for bacteria
and scavenger organisms. They feed rapidly on this
effluent, growing and reproducing much more quickly
that in unpolluted waters. The increase in numbers
consumes most or evens all of the dissolved oxygen and
this in turn asphyxiates other aquatic life forms.

23.  It depends upon the quantity of suspended materials
and floating organisms in the water. Usually some 50%
of red, orange and yellow light is absorbed in the top
2m (61/2 ft.) of water and by 20m (65 ft.) only small
amount of blue green light remain to give its typical
color.
 The rapid removal of sunlight makes all aquatic
ecosystems that are more than several meters deep into
dark relatively cold environments.
 Even at the equator the temperature of deeper water
does not exceeds 4 degree Celsius (39 degrees
Fahrenheit).

24. 1. Secchi disc
2. By measuring the intensity
of submarine daylight at
different depths by
means of photoelectric
cells.
Both methods are limited to
comparatively small depths,
where the residual daylight
has a measurable intensity. In
addition, the results, if no
color filters are used, are
affected by the changes in
spectral composition which
daylight undergoes with
increasing depth.