To Study Daily Current Affairs, Click here. To Download Budget Highlights. Click here.



Which of the following is the correct description of tidal bores?

  1. Gravitational bulge of the water surface of the ocean
  2. Steep wall of water created by incoming high tides in constricted estuaries of coastal rivers.
  3. Rise in sea level as high tide comes in along the coast
  4. Fall of seawater and its movement away from the coast

Which of the given factors are known to modify ocean currents:

  1. Configuration of coast line
  2. Anthropogenic activity
  3. Bottom Reliefs
  4. Variation caused due to seasons
  5. 1, 2 and 4
  6. 2, 3 and 4
  7. 1, 2 and 3
  8. 1, 2, 3 and 4

Assertion : Counter equatorial current moves eastward

Reason: The excess water piled up by equatorial currents flows downslope due to gravity

  1. Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.
  2. Both Assertion and Reason are correct but Reason is not the correct explanation of the


  1. Assertion is correct, Reason is wrong
  2. Assertion is wrong, Reason is correct


Water Mass

A body of water with a common formation history, for example, convection caused by surface cooling, having its origin in a particular region of the ocean. Water masses are identified by their temperature, salinity, and other properties such as nutrients or oxygen content.




Ekman Transport

  • The wind blows across the ocean and moves its waters as a result of its frictional drag on the surface. Ripples or waves cause the surface roughness necessary for the wind to couple with surface waters. A wind blowing steadily over deep water for 12 hrs at an average speed of about 100 cm per sec would produce a 2 cm per sec current (about 2% of the wind speed).
  • However, because Earth rotates, the shallow layer of surface water set in motion by the wind is deflected to the right of the wind direction in the Northern Hemisphere and to the left of the wind direction in the Southern Hemisphere.


Ekman Spiral


Ekman Spiral

  • The Ekman spiral indicates that each moving layer is deflected to the right of the overlying layer’s movement; hence, the direction of water movement changes with increasing depth. In an ideal case, a steady wind blowing across an ocean of unlimited depth and extent causes surface waters to move at an angle of 45 degrees to the right of the wind in the Northern Hemisphere. Each successive layer moves more toward the right and at a slower speed. At a depth of about 100 to 150 m (330 to 500 ft), the Ekman spiral has gone through less than half a turn. Yet water moves so slowly (about 4% of the surface current) in a direction opposite that of the wind that this depth is considered to be the lower limit of the wind’s influence on ocean movement.
  • In the Northern Hemisphere, the Ekman spiral predicts net water movement through a depth of about 100 to 150 m at 90 degrees to the wind direction .The resulting flow is at 90 degrees to the right of the wind direction. In the Southern Hemisphere, the net water movement is 90 degrees to the left of the wind direction. This net transport of water due to coupling between wind and surface waters is known as Ekman transport.




When the wind blows parallel to a coastline, surface waters are pushed offshore and water is drawn from below to replace the water that has been pushed away. The upward movement of this deep, colder water is called upwelling.

The deeper water that rises to the surface during upwelling is rich in nutrients. These nutrients “fertilize” surface waters, encouraging the growth of plant life, including phytoplankton. These phytoplankton serve as the ultimate energy base in the ocean for large animal populations higher in the food chain, providing food for fish, marine mammals, seabirds, and other critters.

Regions of Upwelling



 What are Coral Reefs?

Coral reefs are large underwater structures composed of the skeletons of colonial marine invertebrates called coral. The coral species that build reefs are known as hermatypic, or “hard,” corals because they extract calcium carbonate from seawater to create a hard, durable exoskeleton that protects their soft, sac-like bodies. Other species of corals that are not involved in reef building are known as “soft” corals.

Each individual coral is referred to as a polyp. Coral polyps live on the calcium carbonate exoskeletons of their ancestors, adding their own exoskeleton to the existing coral structure. As the centuries pass, the coral reef gradually grows, one tiny exoskeleton at a time, until they become massive features of the marine environment.


Conditions for the Growth of Coral Polyps

  • Mean annual range of temperature is narrow 20-21 degrees Celsius
  • Water should be clean and sediment ree
  • No freshwater
  • Narrow range of salinity between 27-30 ppt
  • Ocean currents and waves are favourable for food supply
  • Extensive submarine platforms are required
  • Human economic activities should be at a minimum


Distribution of Coral Reefs



Distribution of Corals

  • Estimated to cover 284,300 sq km of the ocean surface
  • 1% are in the Indo-Pacific region
  • 3% in South East Asia
  • 8% in Pacific including Australia
  • 6% Atlantic and Caribbean

Coral reefs are believed by many to have the highest biodiversity of any ecosystem on the planet—even more than a tropical rainforest. Occupying less than one percent of the ocean floor, coral reefs are home to more than twenty-five percent of marine life.

Types of Coral Reefs


Darwin’s Theory of Subsidence



Coral Bleaching

Coral bleaching occurs when coral polyps expel algae that live inside their tissues. Normally, coral polyps live in a symbiotic relationship with these algae, which are crucial for the health of the coral and the reef.

According to Clive Wilkinson of the Global Coral Reef Monitoring Network coral bleaching has occurred at a large scale off the coasts of West Asia, East Africa, South, Southeast and East Asia, East Pacific and the Caribbean and the Atlantic Ocean in 1998. More than 70% mortality was observed off the coasts of Kenya, Maldives, Andaman and Lakshadweep.


Mass Bleaching Events

  • 1998 2010
  • 2014-17

The coral-bleaching event of 2014–2017 was unusual not just for its long duration, experts say, but also because it wasn’t entirely due to El Niño. Though an El Niño was anticipated in 2014, it didn’t really materialize until March 2015, yet bleaching-level heat stress was already well underway by that time. A strong El Niño arrived in 2016, and heat stress occurred at 51 percent of the world’s coral reefs into early 2017, when a La Niña was in place. More than 75 percent of Earth’s tropical reefs experienced bleachinglevel heat stress between 2014 and 2017, and at nearly 30 percent of reefs, it reached mortality level.

Causes of Coral Bleaching

  • Natural – diseases, change in sea level due to emergence or submergence etc.
  • Man made – pollution, global warming, oil spills

Impact of Coral Bleaching

  • On corals
  • On humans
  • On biodiversity

Civil Services PYQ

Consider the following statements:

  1. Most of the world’s coral reefs are in tropical waters.
  2. More than one- third of the world’s coral reefs are located in the territories of Australia, Indonesia and Philippines.
  3. Coral reefs host far more number of animal phyla than those hosted by tropical rainforests.Which of the statements given above is /are correct ? (a) 1 and 2 only
  • 3 only
  • 1 and 3 only
  • 1, 2 and 3


Marine Biological Resources (MBR)

  • Food Resources – animal resources, plant resources
  • Non-Food Resources – corals

MBR can also be classified as:

  1. Plankton communities – phytoplankton, zooplankton
  2. Nekton Communities – Pelagic fishes, demersal fishes
  3. Benthos Communities – Epibenthic, inflora and infauna



Marine Mineral Resources

On the basis of Nature

  • Metallic minerals
  • Fuel Minerals (petroleum, natural gas)
  • Construction materials (gravels, sands etc.)

Polymetallic Nodules

  • Polymetallic nodules, also called manganese nodules, are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core.
  • Nodules vary in size from tiny particles visible only under a microscope to large pellets more than 20 centimetres (8 in) across. However, most nodules are between 3 and 10 cm (1 and 4 in) in diameter, about the size of hen’s eggs or potatoes. Their surface textures vary from smooth to rough.
  • Nodules lie on the seabed sediment, often partly or completely buried. They vary greatly in abundance, in some cases touching one another and covering more than 70% of the sea floor. They are found both in shallow seas and in deeper oceans.
  • They contain approximately 24% manganese, compared to 35 to 55% manganese in land ore bodies, so they do not offer solid economics as a manganese source, but they also contain iron (14%), copper (>1%), nickel(>1%), and cobalt (0.25%).

Deposits of PMN

Sizeable deposits have been found in four areas:

  • Penrhyn Basin near within the Cook Islands.
  • North central Pacific Ocean in a region called the Clarion Clipperton Zone (CCZ) roughly midway between Hawaii and Clipperton Islands.
  • Peru Basin in the southeast Pacific,
  • Southern tropical Indian Ocean in a region termed the Indian Ocean Nodule Field (IONF) roughly 500 km SE of Diego Garcia Island.


Ferromanganese Crusts

Cobalt-rich ferromanganese crusts occur at shallower depths of <400 to about > 5000 meters in areas of significant volcanic activity.

The crusts grow on hard-rock substrates of volcanic origin by the precipitation of metals dissolved in seawater in areas of seamounts, ridges, plateaus and where prevailing currents prevent deposition of unconsolidated sediments and occupy large areas on top of these topography highs.

Polymetallic Sulphides

  • PMS are formed by precipitation of metals leached by hydrothermal fluid as it interacts with the cooler ambient seawater at or beneath the seafloor at hydrothermal vent sites.
  • PMS are typically composed of iron pyrite but contain varying proportions of pyrrhotite, pyrite/marcasite, sphalerite/wurtzite, chalcopyrite, bornite, isocubanite, and galena.
  • Copper and zinc are the most likely metals to be recovered, but some deposits exhibit significant gold (0–20ppm) and silver (0–1200 ppm) grades as well.
  • Submarine massive polymetallic sulphide bodies are principally found along the earth’s major tectonic belts.

Marine Energy Resources

  • Conventional Energy – Oil and gas ● Non- Conventional Energy:
  1. Tidal Energy
  2. Wave Energy
  3. Ocean Thermal Energy Conversion (OTEC)
  4. Offshore wind and solar energy
  5. Ocean Current Energy
  6. Biomass Energy
Maritime Zones



Internal Waters


Internal waters are all the waters that fall landward of the baseline, such as lakes, rivers, and tidewaters. States have the same sovereign jurisdiction over internal waters as they do over other territory. There is no right of innocent passage through internal waters.

Territorial Sea

Territorial seas are the most straightforward zone. Much like internal waters, coastal States have sovereignty and jurisdiction over the territorial sea. These rights extend not only on the surface but also to the seabed and subsoil, as well as vertically to airspace. The vast majority of States have established territorial seas at the 12 nautical mile limit, but a handful have established shorter thresholds.

While territorial seas are subject to the exclusive jurisdiction of the coastal States, the coastal States’ rights are limited by the passage rights of other States, including innocent passage through the territorial sea and transit passage through international straits. This is the primary distinction between internal waters and territorial seas.

Contiguous Zone

States may also establish a contiguous zone from the outer edge of the territorial seas to a maximum of 24 nautical miles from the baseline. This zone exists to bolster a State’s law enforcement capacity and prevent criminals from fleeing the territorial sea.

Within the contiguous zone, a State has the right to both prevent and punish infringement of fiscal, immigration, sanitary, and customs laws within its territory and territorial sea. Unlike the territorial sea, the contiguous zone only gives jurisdiction to a State on the ocean’s surface and floor. It does not provide air and space rights.

Exclusive Economic Zone

States may claim an EEZ that extends 200 nautical miles from the baseline. In this zone, a coastal State has the exclusive right to exploit or conserve any resources found within the water, on the seafloor, or under the seafloor’s subsoil.

These resources encompass both living resources, such as fish, and non-living resources, such as oil and natural gas.4 States also have exclusive rights to engage in offshore energy generation from the waves, currents, and wind within their EEZ. Article 56 of UNCLOS also allows States to establish and use artificial islands, installations and structures, conduct marine scientific research, and protect and preserve the marine environment through Marine Protected Areas.

Continental Shelf

The UNCLOS allows a State to conduct economic activities for a distance of 200 nautical miles from the baseline, or the continental margin where it extends beyond 200 nautical miles.

To prevent abuse of the continental shelf provisions, the UNCLOS established the Commission on the Limits of the Continental Shelf (CLCS). The CLCS uses scientists to evaluate States’ claims about the extent of their continental shelves and whether they conform to the Convention’s standards.


Practice Question


Consider the following statements:

  1. The contiguous zone extends 12 nm from the outer limits of the territorial sea.
  2. It is regarded as the sovereign territory of the State.
  3. All disputes regarding the extent of the contiguous zone are settled in the International Court of Justice only.

Which of the given statements is/are incorrect:

  1. 1 only
  2. 2 and 3
  3. 2 only
  4. 1 and 3

UN Convention on the Law of the Seas

  • International Tribunal for the Law of the Seas (ITLOS)
  • International Seabed Authority (ISA)
  • Commission on the Limits of the Continental Shelf (CLCS)


ITLOS is the specialized international judicial body for the settlement of disputes concerning the interpretation or application of UNCLOS, and for the rendering of advisory opinions. It is based out of Hamburg, Germany.

The Tribunal is open to States parties to UNCLOS, other States, as well as other entities, such as international organizations and natural or legal persons in any case expressly provided for in Part XI of the Convention – relating to exploration and exploitation of the international seabed “Area” – or in any case submitted pursuantto any other agreement conferring jurisdiction on the Tribunal that is accepted by all the parties to that case.

International Seabed Authority (ISA)

International Seabed Authority (ISA), international organization established in 1994 to regulate mining and related activities in the international seabed beyond national jurisdiction, an area that includes most of the world’s oceans.

The ISA is headquartered in Kingston, Jamaica, and has more than 150 state members.


Practice Question


Which of the following bodies have been formed under the UN Convention on the Laws of the Seas? 1.     International Seabed Authority

  1. Permanent Court of Arbitration
  2. Commission on the Limits of the Continental Shelf
  3. 1 and 2
  4. 1 and 3
  5. 2 and 3
  6. 1, 2 and 3


International Whaling Commission (IWC)


It is an international body set up under International Convention for the Regulation of Whaling (ICRW).

  • ICRW governs the commercial, scientific, and aboriginal subsistence whaling practices of fifty-nine member nations. It was signed in Washington, D.C., United States, in 1946.
  • Headquarters — Impington, near Cambridge, England.
  • In 1986, it adopted a moratorium on commercial whaling. This ban still continues.

Whale Sanctuary

In 1994, it created the Southern Ocean Whale Sanctuary surrounding the continent of Antarctica. Here, the IWC has banned all types of commercial whaling.

Only two such sanctuaries have been designated by IWC till date. Another is Indian Ocean Whale Sanctuary by the tiny island nation of the Seychelles.


Questions for the Day


  • Discuss the mechanism that leads to upwelling. What is the importance of upwelling? (150 words)
  • Enumerate the various energy sources available in the marine environment and discuss any two non-conventional sources. (250 words) What are maritime zones? (150 words)