The sea covers over 70% of the Earth's surface. It is very deep in some areas, with ocean bottoms over 6 miles below the surface. The sea is dominated by tides, currents, and waves. It is generally salty, containing dissolved salts and nutrients essential for marine life. Temperature varies greatly between polar and tropical waters, and the sea is stratified into different zones based on depth and temperature. Estuaries, mangroves, and coral reefs are important marine ecosystems. Coral reefs face threats from human activities like pollution, dynamite fishing, and tourism that can drive corals to extinction if not addressed.

2. SEA FEATURES
1. The sea is big; it covers more than 70% of the earth’s
surface.
2. The sea is deep ; in some areas the ocean bottom lies
more than 6 miles (10km) below the surface.
3. The sea is continues; not separated as land and freshwater
habitats.
4. The sea is in continuous circulation.
5. The sea is dominated by waves of many kinds and
produced tides produced by the pull of moons and the sun.

3. 6. The sea is salty . The salinity of the open sea is fairly
constant. Sea water contains biogenic ions. Biogenic salt
are dissolved salt vital life.
7. The concentration of dissolve nutrients is low and
constitute and important limiting factors in determining
the size of marine population.
8. The ocean and some groups of organism that live in it
older than the ocean floor which is constantly being
altered And renewed by tectonic and sedimentary
processes.

4. temperature
The range of temperature is far away in land,
although the range of variation in temperature over
the ocean is considerably arctic water at negative
degrees Celsius are much colder than the tropical
water.

5. zonation
In many places around the continents the land
gradually slopes under water to a depth of about
600ft. (180m). This submerged land called the
continental shelf. In some areas, the continental shelf
extends hundreds of miles or kilometers.

6. zonation
The shallow water zone is the zone between high and
low tides. The oceanic zone is the zone of the open
ocean beyond continental shelf.
The deepest portion of the sea is called abyssal.

7. stratification
The upper layer of ocean water exhibits stratification
of temperature. Depth below 300m are usually
thermally stable. In high and low latitudes,
temperature remain fairly constant throughout the
year. In middle latitude, temperatures varies with
season and is associated with climate changes. In
summer, the surface water become warmer and
lighter forming a temporary seasonal thermocline.

8. Estuarine ecology
Is an area where freshwater flows into the sea. It is
zone between freshwater and marine biomes.
Estuary act as the nursery for the young of many
marine fishes and shellfish used by human for
foods.
Salinity the distribution of life in the estuary.

9. Mangroves and coral reefs
Mangroves are among the few emergent land plant that
tolerates the salinity of the open sea.
Red mangroves have an extinctive disposition of mud,
silt, and provide surfaces for attachment on marine
organism.
Mangroves are not only important in extending coast
and building island, but also in protecting coast from
excessive erosion whish otherwise produced pierce
tropical storm.

10. Mangroves and coral reefs
Coral reefs are widely distributed in shallow waters
of warm seas.
There are three kinds of coral reef fringing which
grows along the rocky shores of island s continents,
and atolls, horsed shaped surrounding lagoons.
Such lagoons are about 40 m deep are usually
connected to the open sea by breaking in the reefs.

11. Mangroves and coral reefs
Coral reefs are complex ecosystem involving close
relationship between coral and algae.
At night coral polyps feed, extending their tentacles
to capture zooplanktons from the water and thus
securing phosphorus and other elements needed by
the coral land its symbiotic algae.
During the day, the algae absorb sunlight and carry
on the photosynthesis and directly transfer organic
materials to coral tissues .

12. Other uses of corals
The Spaniards have use coral reef resources for
building churches and houses.
Highway builders have use coral stone in paving
streets and road.
Coral reef s serves as tools and even in laboratories
in science.

13. Threats coral reefs
These benefits from coral reef may not last long if
our ways continue as they are. Natural causes such
as typhoons, el Niño, and predation can already
greatly reduce the coral reefs. But with continued
careless activities of man, coral reef may be on the
verge of extinction.
Some of these activities like extraction of corals for
sale to tourist in shops, dynamite fishing, etc.

14. Ways to prevent the extinction of corals:
Do not collect corals when you go to the beach.
Do not buy fancy jewelry or accessories made from
corals.
When going scuba diving, do not step or touch the
coral animals, no matter how attractive they look.
Do not throw waste into the seas or beach when
you go out swimming.

15. Ways to prevent the extinction of corals:
Watch out pollution culprits like factories , ships,
construction, etc. Report them to your local office
of the DENR.
Participate in education campaign that some
NGO’s government may be doing on the way to
save coral reefs,
Report to the local DENR any knowledge you have
on illegal ways of fishing like muro – ami, use of
small meshed nets etc.

16. Ways to prevent the extinction of corals:
Write to the newspaper , TV, or radio station, etc.
about these violation or if you see an activity which
destroy the natural resources in general.