Revision of the previous class (05:11 PM) 

Factors influencing salinity (05:23 PM)

• a)Temperature: The higher temperature will result in Higher salinity
• b)Wind speed: Higher wind speed causes a higher rate of evaporation resulting in higher salinity.
• c)Ocean Currents: Help distribute salinity from one region to another.
• Regions for Higher salinity
• Also, Refer World map as drawn in the class.
• Sub-Tropical Regions: Due to the Higher rate of Evaporation. Examples: Mediterranean sea, Red sea, Persian Gulf, and Sub-tropical regions of the Atlantic and Pacific oceans.
• Regions with below-average salinity: North sea, Baltic sea, Berring sea, Arctic Ocean, Southern Ocean
• Regions with Exceptionally High salinity: Lake van, Dead sea, and Great salt lake.

Oceanic Deposits (05:37 PM)

• Terrigenous Deposit: Deposits are derived from the land and found in oceans which is why also known as Lithigeneous. Example: Sand, Gravel, Mud, silt.
• Biogeneous Deposits: Shells, Corals, Ooze(These are the deposits derived from calcareous and silicious shells and skeletal remains of marine microorganisms. Biogeneous deposits are also called organic deposits.
• Hydrogenous Deposits: Example: Salt, Polymetallic nodules.
• Cosmogenous Deposits: Meteorites debris.

Coral Reefs (05:47 PM)

• Coral Reefs are masses of limestone and dolomite accumulated by a lime-secreting organism called coral polyps.
• They are developed due to the symbiotic relationship between coral polyps and zooxanthellae algae.
• The coral reef provides habitat to nearly 31 phyla of Animals leading to Rich biodiversity, Therefore they are also called rainforests of oceans.
• Conditions
• a)Temperature: 20 degrees celsius, Not beyond 30 degrees North and south latitude.
• b)Depth: Maximum depth between 200-250 feet below sea level.
• c)Sediment-free water: Therefore coral reefs are not found near deltas.
• d)Salinity: Average of 35 parts per thousand.
• e)A platform on which the corals can build reefs i.e Continental shelves.
• Corals are not found in the western margins of the continents due to cold ocean currents.

Distribution (06:15 PM) 

• Atlantic Ocean: Around the Caribbean sea, Mexico, and the surrounding regions.
• Indian Ocean: Red sea, Persian gulf, western and Northern Indian ocean, A&N islands, Lakshwadeep, Gulf of Mannar, Gulf of Kutchh, Maharashtra Coast, and Goa Karnataka coast.
• Southeast Asia and Pacific: Covering Coral Triangle from Indonesia, Malaysia, Philippines, and Australia(Great Barrier Reef), The islands of the pacific ocean.
• Types of Coral Reefs (06:24 PM) 
• Fringing Reefs
• 
• A narrow and discontinuous patch of coral reef located near the coast. Example coral reef of the Caribbean sea.
• Barrier Reef 
• 
• A wide and continuous coral reef located far from the coast and is separated by a lagoon, Example: Great Barrier Reef.
• Atoll Reef
• 
• A circular Coral reef developed around a sea mount or Gyot or island. Ex: Lakshwadeep, Maldives, and islands of the pacific ocean.

Coral Bleaching (06:34 PM)

• Corals receive their colouration from zooxanthellae.
• Coral Bleaching refers to the loss of colour of corals due to the stress-induced expulsion of symbiotic algae.
• The reasons behind coral bleaching are:
• Changes in water temperature, salinity, Increased sedimentation, Increased pollution, and Ocean acidification.Increased incidence of cyclones, Storms, and Elnino.
• Examples of Coral Bleaching: Between 2014 to 2017, Due to El Nino the Great Barrier Reef was bleached by nearly 50%.
• In 1997-98 the Northern Indian ocean lost the majority of coral reefs.

Oceanic circulation (07:18 PM)

• Surface/Ocean Current 
• An ocean current is the general movement of the ocean's surface water in a definite direction over long distances.
• Types of ocean currents:
• a)Warm Ocean current: Moves from Equator to pole
• b)Cold ocean current: Moves from poles to the Equator.
• Factors affecting ocean currents
• Winds: The steady blowing of winds drag the surface water in its direction and brings about the surface flow and sets the water currents in motion.
• The shape of the Coastline and Topography: Modify the ocean currents' direction.
• Differences in temperature, salinity, and density: Cause the water to move and reduce variations such differences guide the movement of ocean currents.
• Coriolis force: It causes ocean currents to deflect right in the Northern hemisphere and left in the southern hemisphere.

Ocean Currents of the world (07:45 PM)

• Currents of the Atlantic Ocean
• Under Trade winds influence 
• a)North Equatorial current
• b) South Equatorial current 
• c)Counter Equatorial current which goes along the Equator in the west-to-east direction.
• d)Florida current: Anteles +Gulf current, Along the coast of Florida.
• e)Gulf stream: Towards the Northeast direction, USA coast.
• f)North Atlantic Drift: Gulf stream takes a total right turn once it crosses Newfoundland under the influence of westerlies and Coriolis force.
• g)Norweigian current: Along the coast of Norway
• h)The canary current: A cold current, Along the canary islands, flowing southwards.
• Two cold ocean currents Labrador and the East Greenland current. Labrador joint Gulf stream and East Greenland joins North Atlantic Drift.
• Seaweed in the Gyre grows which is known as sargasso that is what the sea is known as Sargasso sea.

The Topic for the next class: El Nino