Oceanography

Question 1

Coral reefs: intro?

Answer 1

Coral reefs are cemented and compacted deposits of skeletons (corallites) of corals (or polyps, are marine organisms of Cnidaria phylum) found in tropical and sub-tropical oceans and seas

Question 2

coral reefs: morphology?

Answer 2

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1. coral ridge or algal ridge: highest point; bears the brunt of sea waves; only the encrusting corals, corals with zooxanthelle algae, can withstand the waves due to their skeletons
2 buttress zone: on seaward side of coral ridge; has undulating features- spikes, ridges and furrows that helps in withstanding waves; colonized by brain corals and branching corals
3. reef face: the steep fall on the face of the ridge beyond buttress zone; beyond 80m depth, no corals found; above that, habitated by fan corals, branching corals, platy corals etc.
4. On the landward side of algal ridge, a lagoon can be formed. On the landward vicinity of algal ridge, back reef can form. Some organically formed mounds may project above the water surface of the lagoon, These are called patch reefs. The flat ‘tabletop’ on the landward side of ridge is called reef terrace

Question 3

Fringing Reef?

Answer 3

1. Coral reefs developed along the continental margins or along the islands are called fringing reefs
2. The seaward slope is steep and vertical while the landward slope is gentle. The upper surface is uneven and corrugated.
3. If a fringing reef grows directly from the shoreline, then the reef flat extends to the beach and there is no backreef. In other cases (e.g., most of the Bahamas), fringing reefs may grow hundreds of yards from shore and contain extensive backreef areas within which it contains food and water, examples are Philippines, Indonesia, Timor-Leste, the western coast of Australia, the Caribbean, East Africa, and Red Sea
4. Though fringing reefs are usually attached to the coastal land but some times there is gap between them and land and thus lagoon is formed between the fringing reef and the land. Such lagoon is called boat channel. Fringing reef is distinguished from the other main types, barrier reefs and atolls, in that it has either an entirely shallow backreef zone (lagoon) or none at al
5. Coral reefs are generally long but narrow in width.
6. Sometimes it is hard to tell the difference between fringing reefs and another type of reef called a barrier reef. One of the ways that these two types of reefs are separated is based on the depth of the lagoon in the back reef. Barrier reefs have at least some deep portions; fringing reefs do not. Another major difference is that barrier reefs tend to be much farther away from shore than fringing reefs
7. The largest fringing coral reef in the world is the Ningaloo Reef, stretching to around 260 km (160 mi) along the coastline of Western Australia

Question 4

Barrier Reef?

Answer 4

1. The largest coral reefs off the coastal platforms but parallel to them are called barrier reefs. Barrier reefs are the largest, most extensive, highest and widest reefs of all types of coral reefs.
2. There is extensive but shallow lagoon between the coastal land and barrier reef. They resemble the later stages of a fringing reef with its lagoon but differ from the latter mainly in size and origin. Their lagoons can be several kilometres wide and 30 to 70 metres deep.
3. Barrier reefs are seldom found as continuous chains rather they are broken at many places and thus the lagoons have contact with the open seas and oceans through tidal inlets. Some times, tidal inlets are so wide that ships enter the lagoons through them.
4. Some times, the base of barrier reefs exceeds the required depth for the develop ment of coral polyps i.e. 300 feet (91m). Thus, the existence of barrier reefs at such greater depth (beyond the permissible depth of 60-77 m) poses the problem of their formation. It may be argued that barrier reefs might have been formed at suitable depth but at much later date there might have been subsidence. Formation takes considerably longer than for a fringing reef, thus barrier reefs are much rarer.
5. The best known and largest example of a barrier reef is the Australian Great Barrier Reef.Other major examples are the Belize Barrier Reef and the New Caledonian Barrier Reef.

Question 5

Atoll?

Answer 5

1. A ring of narrow growing corals of horse shoe shape and crowned with palm trees is called atoll. It is generally found around an island or in elliptical form on a submarine platform.
2. There is a lagoon in the middle of coral ring. The depth of lagoon ranges between 80-100 m
3. Atolls are divided into 3 types. e.g. (i) true atoll characterized by circular reef enclosing a shallow lagoon but without island, (ii) island atoll having an island in the central part of the lagoon enclosed by circular reef, and (iii) coral island or atoll island does not have island in the beginning but later on island is formed due to erosion and deposition by marine waves.
4. Of the 440 atolls found in the world, most are in pacific nd Indian Ocean. Atolls are found in Antilles Sea, Red Sea, China Sea, Australian Sea, Indonesian Sea . Funfutti Atoll of Ellice Island is a famous atoll. The enclosed lagoon is 12.8 km wide and 19.2 km long. Atolls are found in the Indian Ocean, for example, in the Maldives, the Chagos Islands, the Seychelles and around Cocos Island. The entire Maldives consist of 26 atolls.

Question 6

Great Barrier Reef?

Answer 6

1. World’s largest coral reef system, composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres (1,400 mi) over an area of approximately 344,400 square kilometres. The Great Barrier Reef can be seen from outer space and is the world’s biggest single structure made by living organisms
2. The reef is located in the Coral Sea, off the coast of Queensland, Australia, separated from the coast by a channel 100 miles wide in places and over 200 feet deep
3. According to a study published in October 2012 by the Proceedings of the National Academy of Sciences, the reef has lost more than half its coral cover since 1985, a finding reaffirmed by a 2020 study which found over half of the reef’s coral cover to have been lost between 1995 and 2017, with the effects of a widespread 2020 bleaching event not yet quantified
   In March 2017, the journal Nature published a paper showing that huge sections of an 800-kilometre (500 mi) stretch in the northern part of the reef had died in the course of 2016 due to high water temperatures, an event that the authors put down to the effects of global climate change. The percentage of baby corals being born on the Great Barrier Reef dropped drastically in 2018 and scientists are describing it as the early stage of a “huge natural selection event unfolding”. Many of the mature breeding adults died in the bleaching events of 2016–17 leading to low coral birth rates. The types of corals that reproduced also changed
4. Another key threat faced by the Great Barrier Reef is pollution and declining water quality. The rivers of north-eastern Australia pollute the Reef during tropical flood events. Farming practices damage the reef due to overgrazing, increased run-off of agricultural sediments, nutrients and chemicals including fertilisers, herbicides and pesticides representing a major health risk for the coral and biodiversity of the reefs
5. Other threats faced by Great Barrier Reef:
   -> loss of coastal wetland, which act as a natural filter for toxins and help deposit sediment
   -> Eutrophication: The crown-of-thorns starfish preys on coral polyps. Their numbers increase due to increased phytoplankton due to eutrophication
   -> Sediment runoff
   -> pollution from mining: Mining company Queensland Nickel discharged nitrate-laden water into the Great Barrier Reef in 2009 and 2011
   -> overfishing: unsustainable overfishing of keystone species, such as the giant Triton, can disrupt food chains vital to reef life
   -> shipping: There have been over 1,600 known shipwrecks in the Great Barrier Reef region
   -> shark culling: government of Queensland has a “shark control” program (shark culling) that deliberately kills sharks throughout Queensland, including in the Great Barrier Reef. Environmentalists and scientists say that this program harms the marine ecosystem
6. Protection efforts:
   -> selected as a World Heritage Site in 1981. A large part of the reef is protected by the Great Barrier Reef Marine Park, which helps to limit the impact of human use, such as fishing and tourism
   -> In March 2015, the Australian and Queensland’s governments formed a plan for the protection and preservation of the reef’s universal heritage until 2050. This 35 years plan, titled “Reef 2050 Plan” is a document proposing possible measures for the long-term management of the pollution, climate change and other issues that threaten the life span and value of this global heritage.

Question 7

Origin Theories of Coral reefs: Subsidence Theory of Darwin: intro?

Answer 7

Charles Darwin postulated his subsidence theory first in 1837 and modified it in the year 1842 during his Voyage on the ‘Beagle’.
Darwin postulated his theory in order to solve the riddle of this contradiction i.e., confinement of coral polyps to shallow depth but their occurrence, in prac­tice, at greater depth.

Question 8

Origin Theories of Coral reefs: Subsidence Theory of Darwin: axioms/assumptions?

Answer 8

According to him the land or island involved in the origin and growth of coral reefs is seldom stationary rather it undergoes gradual sub­sidence.

According to him fringing reefs, barrier reefs and atolls are successive stages of the development of coral reefs.

Darwin did not invoke sudden and rapid subsidence of land rather he conceived gradual and slower rate of land subsidence than the rate of upward growth of corals so that they could never find them­selves in deeper waters.

Question 9

Origin Theories of Coral reefs: Subsidence Theory of Darwin: fringing reef stage?

Answer 9

First of all coral polyps flock together along a suitable submarine platform and grow upward and ultimately reach sea­-level and fringing reef is formed. Thus, fringing reef is formed in stable condition of the land. After this, the land is subjected to subsidence because of tectonic forces and thus coral polyps also reach greater depth where they may not survive.

Question 10

Origin Theories of Coral reefs: Subsidence Theory of Darwin: barrier Reef stage?

Answer 10

To avoid dying out at greater depths, they grow upward and outward at much faster rate so that they can get food for their survival. The growth of polyps is retarded near the shore of the land but it is very phenomenal and vigorous at the outer edge of the land. Consequently, a lagoon is formed between the coast and fringing reef and barrier reef is formed

Question 11

Origin Theories of Coral reefs: Subsidence Theory of Darwin: atoll stage?

Answer 11

There is further subsidence of the land and the island is completely submerged under water and a ring of coral reef in the form of atoll is formed.

It may be noted that the depth of lagoon does not increase inspite of gradual subsidence of the land because there is continuous sedimentation in the la­goon.

Question 12

Origin Theories of Coral reefs: Subsidence Theory of Darwin: evidences in support?

Answer 12

1. The shallowness of lagoons indicates gradual subsidence of land. If the land is taken to be stable, the lagoon would be filled due to deposition of sediments.
2. The absence of cliffs along the coral islands vali­dates the idea of subsidence of land because cliffs are found along only those coral islands which are station­ary.
3. The coasts and the islands of the Pacific Ocean having raised beaches (indicative of emergence of land) are devoid of barrier and atoll reefs.
4. The islands having atolls are characterized by very steep slopes. It may be mentioned that very steep slopes are found only along the upper parts of the islands. This fact also denotes subsidence of the land.
5. The thickness of coral reefs increases downward. This feature reveals the fact that coral reefs are formed along the subsiding base of submarine platforms.
6. The Deep Sea Drilling Project sought evidence of volcanic cores beneath coral reefs (to explain the subsidence of the islands) and found it. First, in 1952 at the Einwetok Atoll in the Marshall islands, and again, in 1960 at the Midway Atoll, teams found volcanic rock strongly supporting Darwin’s theory that coral reefs form around submerging islands.

Question 13

Origin Theories of Coral reefs: Subsidence Theory of Darwin:criticism?

Answer 13

1. The fringing reefs, barrier reefs and atolls are not 3 successive stages of the develop ment of coral reefs because there are such examples also which show that fringing and barrier reefs grow together simultane ously along the same islands, example: Narai Island of Fiji.
2. If the subsidence theory is accepted, most of the islands of the Pacific Ocean would be leftovers from a vast land that was submerged. There are no geological evidences to support submergence of such a large land in Pacific ocean.
3. The geological evidences show that the atolls were formed on submarine platforms of shallow water depth.
4. There are also some evidences of the existence of coral reefs associated with the emerg­ing islands.
5. Lagoons with depths of 40-45m and many km wide cannot be explained on the basis of subsidence
6. Scientists like Agassiz and Semper have argued that corals have developed in places where there is no evidence of subsidence. eg. corals of Timor sea (off the NW coast of Australia)

Question 14

Origin Theories of Coral reefs: Subsidence Theory of Darwin: conclusion?

Answer 14

Today, Darwin’s theory is universally accepted as a means of explaining these reef formations

While many of the Pacific reefs form around islands as Darwin’s theory describes, this is not the case in the Caribbean where there are few atolls. Here, other reef types like patch and bank are also exhibited and form separately than Darwin’s theory describes.

Question 15

Daly’s glacial Control Theory: intro?

Answer 15

The Glacial Control Theory was propounded by Daly in 1915
on the basis of the study of the coral reefs of the Hawaiian
islands.

This is also a type of stand still theory in which the change in
the sea level and has been considered as the basis for the
development of coral reefs

Question 16

Daly’s glacial Control Theory: axioms?

Answer 16

1. According to this theory, three types of coral reefs are related
   to three different topography , i.e. the fringing reef is
   associated with the coast, the barrier reef with the submarine platforms and plateaus & the atolls are associated
   with islands.
2. The change in sea level, during Pleistocene glaciation, is related to the change in
   temperature and in turn influences the development and destruction of coral polyps and
   attempted to explain the origin of coral reefs in the context of
   glaciation.

Question 17

Daly’s glacial Control Theory: theory?

Answer 17

1. At the time of the Pleistocene glaciation, the sea level had
   gone down by 100–150 m and many pre-existing coral reefs
   came above the sea level.
2. The lowering of the sea level also led to the formation of
   platforms and steps created by the work of ocean waves along
   the continental shelves and the islands. Horizontal ledges and terraces are formed by erosional waves
3. After the Pleistocene glaciation, when the sea level began to rise, coral polyps started developing on these different types of platforms.
4. Fringing reefs were formed on the narrow wave-cut platforms
   along the new continental shelves.
5. When the coral polyps developed on the broad wave-eroded platforms situated away from the coast, it led to the
   formation or barrier reefs with deeper and broader lagoons.
6. Thick horse-shoe shaped reefs or atolls having steep slopes
   developed on the platforms situated along the islands
7. According to Daly, lagoons of uniform depth were formed
   between the reefs and the land because of uniform lowering
   of sea level due to glaciation during Pleistocene ice age.

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Question 18

Daly’s glacial Control Theory: pros?

Answer 18

If this theory is considered the basis, then the coral reefs of
high latitudinal regions are explained

The thickness of the coral reef is confirmed by this theory.

This theory gives a scientific explanation of the depth of the
lagoon and the coral reefs. The discovery that lagoons have a relatively consistent depth of 150-270 feet, the approximate sea level during the last ice age, supported the glacial activity theory

Question 19

Daly’s glacial Control Theory: criticism?

Answer 19

1. According to this theory, the depth of all the lagoons of atolls
   & barrier reefs should be uniform, but actual observations do not validate this concept. According to W.M. Davis the depth of different lagoons varies considerably. Not only this, the
   depth even varies within a lagoon.
2. The coasts might have been cliffed due to wave erosion during the phase of the lowering of sea level during Pleistocene Ice Age. Thus, the cliffs formed during the glacial period should
   also be present now but they are seldom found.
3. Debris or mud are found on the surface of the platform which
   is not favourable for the growth of coral polyps
4. Although this theory explains the thickness of the coral reef,
   but the thickest coral reef of Bikini Island is not explained by it.
5. New technology and advanced resources have allowed scientists to more accurately estimate Pleistocene water temperature and ocean floor topography. It has become more apparent that the process of erosion and growth proposed by Daly may not have been possible in such a short span of time. it would have taken 0.5-1 million years to level a reef 1 kilometer wide if the erosion was constant, which is much longer than any individual low sea level period
6. Pleistocene Ocean Temperature Recent measurements of the fluctuations during the glacial periods of the Pleiostocene Epoch estimate the ocean temperature to have dropped 3°C in the Pacific Ocean, about 4-5°C in the Indian Ocean, and 6-8°C in the Atlantic. Subtracting these from the winter temperatures in the reef seas, only the very outer margins would have dropped significantly enough to hinder coral growth. It is likely that corals continued to grow in the tropical waters during the glacial periods
7. The Glacial Activity Theory describes the formation of flat, level terraces later colonized by corals. Modern science has produced better images of the topography of these structures with echo-sound technology, and surprisingly, these structures do not resemble what Daly described. Instead, they are highly irregular.

Question 20

Daly’s glacial Control Theory: conclusion?

Answer 20

The most important characteristic of this theory is that climate
change has been linked to the development of coral reefs,
which is a reality.

the two theories (Darwin’s and Daly’s) do not directly contradict each other. Where Darwin’s theory explains reef structure, Daly’s focuses on surface morphology. Daly’s is also an explanation of reef response to shifts in the environment. His ideas about water temperature are applicable to issues like global warming.

Question 21

stand still theory of Murray: intro?

Answer 21

Murray propounded his theory of the formation of coral reefs in the year 1880 on the basis of the information received during the Challenger expedition (1872-76)

Question 22

stand still theory of Murray: axioms?

Answer 22

According to Murray, the development of different types of
coral structure is based on the topography of shallow ocean
and the effect of lagoon water.

According to this theory, for the development of coral reefs
it is necessary to have sub-marine platforms whose depth
should not exceed 54-55 m. The suitable depth is obtained by two processes. If the sub-marine platforms are higher than this, they are degraded by erosion & solution action and if they are
located below this depth, they are subjected to sub-marine
pelagic deposition and attain the required depth.

Question 23

stand still theory of Murray: theory?

Answer 23

Coral polyps develop on such platforms in large colonies and together these colonies form the coral reef.

Initially the reef develops in the form of fringing reef and its
lagoon is shallow.

The coral polyps on the outer edge of the platform grows
relatively quickly.

After some time, the coral reef extends beyond a depth of 54–
55 m, and after attaining this boundary, small pieces of coral
are broken down and deposited on the base of coral reefs.
Thus, without the subsidence of land the coral reef extends
into the deep ocean.

The coral polyps living on this pile of debris makes its development outward. On the other hand the coral polyps of the inner part of the reef dies due to lack of food.

The fresh water of the river flows into the lagoon of the fringing reef. The water of the lagoon slowly begins to dissolve the limedominated structure of the reef. When solution action begins in the lagoon, the lagoon begins
to deepen and the internal gradient of the coral structure
intensifies. In such a situation a barrier reef is developed.

When the solution action becomes more intense, the depth of the lagoon further increases and the internal gradient of the coral structure becomes even more intense. This type of feature is called an atoll.

Regarding the construction of the atolls, Murray said that they were built independently due to the circular growth of coral polyps at the top of sub-marine platforms and hills that are located at suitable depths. In this situation also, the coral polyps on the outer edge of the reef develop at a rapid pace and soon reach the surface to form the ring-shaped coral reef or atoll within which a lagoon is formed. Dead coral on the side of the lagoon dissolves
continuously in the water, which causes the lagoon to expand, but the outward development of the coral reef continues which increases the size of the atoll i.e. its thickness and width.

Question 24

stand still theory of Murray: criticisms?

Answer 24

According to this theory, for the construction of coral reefs,
innumerable sub-marine platforms & peaks should exist at
a depth of 54-55 m, which is not possible.

According to this theory, the surface of the lagoon is the
result of solubility and the maximum depth of the coral reef
can be 54–55 m and the depth of the lagoon will not exceed 54–55 m. This assumption does not apply in most circumstances.

Firstly, the soluble capacity of saline water of the sea is low.

Second, there is evidence of deposition instead of soluble
chemical action at the bottom of the lagoon and Third, the depth of many lagoons is 100 m or more.

It seems impossible to have both erosion and deposition processes at the same depth.

Question 25

stand still theory of Murray: conclusion?

Answer 25

On the basis of these facts, this theory has been
almost rejected and at present it has only theoretical
and historical recognition

Question 26

Coral reef restoration?

Answer 26

1. In the past coral restoration has been done as a response to a singular, destructive event like a ship running aground.
2. Coral nurseries:
   
   • Coral “farmers” nurture small, found pieces of coral on underwater structures until they can be replanted on existing reefs, stimulating recovery of these ecosystems.
   • in the low stress environment of a nursery, conservationists can grow corals much faster, giving the reefs a fighting chance.
   • more crucially, conservationists can manage the diversity of the coral population in nurseries. Some corals are able to withstand or recover from stresses better than others.
   • Nursery-grown corals can be used not only to help reefs damaged by groundings, storms or pollution but those harmed by changing ocean conditions as well.
3. scientists have discovered that “microfragments” sawed off these corals act a bit like wounded skin, growing extremely quickly—some 10 times faster than larger cuttings. Grown side by side in lab aquariums, polyps from the same colony will fuse, reducing the time needed to reach reproductive size. Raised this way, some species that typically take a decade or more to mature have begun spawning in just a few years.
4. corals selected are often selected for disease (eg. stony coral tissue loss) as well as heat tolerance. Effort is also dedicated to develop heat resistant algae and pairing them up with receptive corals
5. some scientists scoop up slicks of eggs and sperm released by corals that have survived bleaching and proven their heat tolerance amassing them in mesh enclosures near the ocean surface which promotes fertilization and larval formation; those offspring can then be drizzled over damaged reefs.
6. in some instances corals already are doing the job themselves: Scientists working on world’s largest atoll—Kiritimati in the central Pacific—discovered corals that were recovering from bleaching during a heat wave. They did it by taking in naturally heat-tolerant algae.
7. Meanwhile, as global temperatures trend up, some scientists have taken to prepping—stashing hard corals in “living biobanks” to conserve as much diversity as possible.

Question 27

What are Biorocks?

Answer 27

1. aka Mineral accretion technology, It is the substance formed by electro accumulation of minerals dissolved in seawater on steel structures that are lowered onto the sea bed and are connected to a power source, in this case solar panels that float on the surface.
2. The technology works by passing a small amount of electrical current through electrodes in the water. When a positively charged anode and negatively charged cathode are placed on the sea floor, with an electric current flowing between them, calcium ions combine with carbonate ions and adhere to the structure (cathode).
3. This results in calcium carbonate formation. Coral larvae adhere to the CaCO3 and grow quickly.
4. Fragments of broken corals are tied to the biorock structure, where they are able to grow at least four to six times faster than their actual growth as they need not spend their energy in building their own calcium carbonate skeletons.
5. Zoological Survey of India (ZSI), with help from Gujarat’s forest department, is attempting for the first time a process to restore coral reefs using biorock in gulf of Kachh

Question 28

Nine critical climate systems of the world that are close to tipping point: Coral reefs?

Answer 28

Scientists believe that many of the reef systems around the world have already breached their points of no return and saving them would be next to impossible.

Greatest threats: climate change, overfishing, introduction of invasive species, changes in land use and pollution

Despite covering only 0.1 per cent of the ocean floor around 100 countries, coral reefs host 37 per cent of all marine fish species along with other marine animals. Further they provide livelihood to 500 million people and provide ecosystem services which would be difficult to account for. For instance, they provide protection to coastal areas from waves generated during storms.

2016-2017 bleaching event in the Great Barrier Reef, which is the largest coral reef system in the world off the northeastern coast of Australia, killed 50 per cent of the corals. It happened after record breaking temperatures in 2016, which was the hottest year ever recorded, along with a strong El Niño event

Question 29

Global Coral Reef Monitoring Network (GCRMN) report on coral reefs?

Answer 29

• The value of goods and services provided by coral reefs is estimated to be $2.7 trillion per year. This includes $36 billion in coral reef tourism.
• Corals occupy less than one per cent of the ocean floor but over one billion people benefit directly from the reefs.

1. In the last decade, the world lost about 14 per cent of its coral reefs.
2. Threats: Ocean-acidification, warmer sea temperatures and local stressors such as overfishing, pollution, unsustainable tourism and poor coastal management.
3. Impact of global warming: Coral reefs across the world are under relentless stress from warming caused by climate change. Coral bleaching events caused by rise in elevated sea surface temperatures (SST) were responsible for coral loss.
4. Loss of hard coral cover: There has been a steady decrease in hard coral cover in the last four decades since 1978 when the world lost nine per cent of its corals. The decrease is disconcerting because live hard coral cover is an indicator of coral reef health.
5. Algal bloom: Algal bloom on coral ridges are a sign of stress on the structures. Since 2010, the amount of algae on the world’s coral reefs has increased by about 20 per cent.

Question 30

Coral Triangle?

Answer 30

The Coral Triangle (CT) is a roughly triangular area in the tropical waters around Indonesia, Malaysia, Papua New Guinea, the Philippines, the Solomon Islands and Timor-Leste. This area contains at least 500 species of reef-building corals in each ecoregion

The Coral Triangle is located between the Pacific and Indian oceans and encompasses portions of two biogeographic regions: the Indonesian-Philippines Region, and the Far Southwestern Pacific Region.

Known as the “Amazon of the seas”, it covers 5.7 million square kilometres of ocean waters. It contains more than 76% of the world’s shallow-water reef-building coral species, 37% of its reef fish species, 50% of its razor clam species, six out of seven of the world’s sea turtle species, and the world’s largest mangrove forest.

In 2014, the Asian Development Bank (ADB) reported that the gross domestic product of the marine ecosystem in the Coral Triangle is roughly $1.2 trillion per year and provides food to over 120 million people.

Question 31

The only coral reef area in the region to have been declared a UNESCO World Heritage Site?

Answer 31

is in Tubbataha Reef Natural Park in the Philippines (a part of Coral Triangle)

Question 32

What are Stylophora Pistillata?

Answer 32

A recent study has suggested that coral structures may withstand climate change owing to their impressive process of forming rock-hard skeletons.

The Study:

• It studied Stylophora pistillata, a common stony coral in the Indo-Pacific revealing that coral structures consist of a biomineral containing a highly organized organic mix of proteins that resembles human bones.
• It highlighted that several proteins are organized spatially – a process that’s critical to forming a rock-hard coral skeleton.
• The study highlighted that corals have survived global climate change over millions of years by the process called Biomineralization.
  • Biomineralization is the study of processes that lead to the formation of hierarchically structured organic–inorganic materials generated by living organisms, such as shells, bone and teeth.

Question 33

Corals: write up: about? benefits?

Answer 33

• Corals are made up of genetically identical organisms called polyps. These polyps have microscopic algae called zooxanthellae living within their tissues.
  • The corals and algae have a mutualistic relationship.
  • The coral provides the zooxanthellae with the compounds necessary for photosynthesis. In return, the zooxanthellae supply the coral with organic products of photosynthesis, like carbohydrates, which are utilized by the coral polyps for the synthesis of their calcium carbonate skeletons.
  • In addition to providing corals with essential nutrients, zooxanthellae are responsible for the unique and beautiful colors of corals.
• They are also called the “rainforests of the seas”.
• There are two types of corals:
  • Hard, shallow-water corals—the kind that builds reefs.
  • Soft corals and deepwater corals that live in dark cold waters.
• Benefits of Coral:
  • Habitat: Corals are home to over 1 million diverse aquatic species, including thousands of fish species. they occupy only 0.1 per cent of the global sea surfaces. But more than 25 per cent of marine biodiversity is supported by them
  • Income:
    
    • Coral reefs and related ecosystems have a global estimated value of ‘$2.7 trillion per year, or 2.2% of all global ecosystem service values’, this includes tourism and food.
    • loss and degradation of coral reefs can affect the livelihood of about 4.5 million people in SE Asia and the Indian Ocean.
    • In Bangladesh, the coral reefs of St. Martin’s Island contribute $33.6 million per year to the local economy.
    • It has been assessed that one square kilometre of coral reef produces 20-35 mega tonnes of fishes sufficient to feed about 600 people annually.
    • They are used in jewellery and as curios. The internal skeleton polished with colours is used in jewellery. Sea grasses that provide food for dugongs and dolphins are harboured by coral reefs. Coral blocks are used for buildings and road construction. The lime supplied by corals is used in cement industries.
• Coastal Protection: Coral reefs reduce shoreline erosion by absorbing energy from the waves. They can protect coastal housing, agricultural land, and beaches.
• Medicine: Reefs are home to species that have the potential for treatments for some of the world’s most prevalent and dangerous illnesses and diseases.
• Degradation and loss of coral reefs can affect about 4.5 million people in southeast Asia and the Indian Ocean, acc to IPCC sixth assessment report
• UN-IPBES Report on Species Extinction identified a range of risks, from the disappearance of insects vital for pollinating food crops, to the destruction of coral reefs that support fish populations that sustain coastal communities, or the loss of medicinal plants.

Question 34

initiatives to protect corals: global? Indian?

Answer 34

• A number of global initiatives are being taken to address the issues, like:
  • International Coral Reef Initiative
  • Global Coral Reef Monitoring Network (GCRMN) is an operational network of ICRI (International Coral Reef Initiative)with the primary task of reporting on the condition of the world’s coral reefs.
  • Global Coral Reef Alliance (GCRA)
  • The Global Coral Reef R&D Accelerator Platform
  • Aichi Target 10 which concerns reducing pressures on coral reefs and other vulnerable ecosystems impacted by climate change or ocean acidification
• INdia:
  • Integrated Coastal and Marine Area Management launched in 1998 aims at integrating the management of coastal and Marine areas has prepared model plans for the Gulf of Kutch.
  • India has also created mechanisms such as the National Coastal Zone Management Authority (NCZMA) and State Coastal Zone Management Authority for the protection of coastal and marine areas.
  • Ministry of Environment and Forests (MoEF), India has included studies on coral reef under the Coastal Zone Studies (CZS).
  • Corals are included in Schedule-I list of the Wild Life Protection Act, 1972: Ministry of Environment and Forest vide its notification dated 11 July 2001 has included all the hard coral in the Schedule List of WLPA of 1972
  • Environment Protection Act, 1986 (EPA): It confers exclusive jurisdiction to the Central Government to preserve and protect the marine environment and to prevent and control marine pollution.
  • Coastal Regulation Zone Notification (CRZ) 1991 under the EPA: It is the only law that explicitly outlaws coral mining in India.
  • Marine Protected Areas (MPAs): to preserve the certain areas of the nation’s waters, including some areas with coral reefs.

Question 35

Glowing Glowing Gone campaign?

Answer 35

by UNEP and Ocean Agency

is a creative awareness campaign that draws attention to coral fluorescence due to CC

a ‘glowing’ coral is a last line of defence before coral dies and bleaches

Question 36

Great barrier Reef: about?

Answer 36

The Great Barrier Reef Marine Park, which spreads across a length of over 2,300 km and is roughly the size of Italy, is home to about 3,000 coral reefs, 600 continental islands, 1,625 type of fish, 133 varieties of shark and rays and 600 types of soft and hard corals.
It is a world heritage site.

Question 37

Global Coral Reef Monitoring Network (GCRMN) report on status of coral reefs across the world: findings?

Answer 37

released in 2021, first report of its kind in 13 yrs.

1. In the last decade, the world lost about 14 per cent of its coral reefs.
2. Threats: Ocean-acidification, warmer sea temperatures and local stressors such as overfishing, pollution, unsustainable tourism and poor coastal management.
3. Impact of global warming: Coral reefs across the world are under relentless stress from warming caused by climate change. Coral bleaching events caused by rise in elevated sea surface temperatures (SST) were responsible for coral loss.
4. Loss of hard coral cover: There has been a steady decrease in hard coral cover in the last four decades since 1978 when the world lost nine per cent of its corals. The decrease is disconcerting because live hard coral cover is an indicator of coral reef health.
5. Algal bloom: Algal bloom on coral ridges are a sign of stress on the structures. Since 2010, the amount of algae on the world’s coral reefs has increased by about 20 per cent.
6. The survival of corals is likely to drop below 50 per cent if sea surface temperatures increase by one degree.
7. All of the world’s reefs will bleach by the end of the century unless the world acts together to reduce carbon emissions
8. if proper conservation and management measures are not taken, all coral reefs of the Indo-Malayan regionmay disappear in the next 40 years.

Question 38

Corals: Threats: Natural?

Answer 38

1. Cyclones and Tsunamis
2. Coral Diseases: also affected by coral diseases such as black band and white band due infectious microorganisms introduced by the human population that live on the coastal regions.
3. Acanthaster planci, also known as Crown-of-Thorns Star fish, eats corals during night. They may destroy the entire coral reefs if found in huge numbers.

Question 39

Corals: threats: Anthropogenic?

Answer 39

1. Global Warming and CLimate Chnage
2. Ocean Acidification
3. Pollution
4. Overfishing and Destructive Fishing practices
5. Development Activities

Question 40

Corals: threats: Anthropogenic: Global Warming and Climate Change? aka CORAL BLEACHING

Answer 40

• When the ocean water becomes too warm, the corals bleach as the symbiotic algae (Zooxanthallae) leave them. A brief bleaching event doesn’t necessarily kill coral—but prolonged, severe bleaching can lead to disease and starvation.
• Historically, global-scale coral bleaching has been associated with El Niño events, which generally raise global temperatures. The first mass coral bleaching was observed during the strong El Niño in 1983, and the first truly global event coincided with the strong El Niño of 1998. The world’s tropical reefs were stressed again during a moderate-strength 2010 El Niño.
• The first study to track thermal stress to corals at a global scale found that the percentage of global reefs that were impacted by bleached stress tripled over the 28-year period from 1985 to 2012. In the 1980s and ‘90s, it was rare for there to be more than ten events in any given year. From the millennium onwards, it was rare that there would be less than ten. We also see large spikes in particular years: 1983, 1987, 1998, 2010, and 2016. Most of these events were triggered by the so-called El Niño climate cycle
• In the 1980s, most bleaching events were reserved for El Niño years. We see examples of this in the 1983 and 1987 spikes. Bleaching was rare in moderate or La Niña years. This was particularly pronounced when we look at severe bleaching events- There was almost no severe bleaching in the absence of El Niño.This is no longer the case. Over these decades we’ve seen more and more events in moderate ENSO years, and even in La Niña years, the ‘cold phase’ of the cycle. This applies to the total number of bleaching events, but also the severe ones. Coral bleaching is no longer a rare El Niño occurrence; it happens every year, regardless.
• What’s new and concerning is prolonged and repeated bleaching episodes that they don’t have time to recover from. Nearly one-third of major coral reef clusters had eight or more episodes since 1980. That’s one every few years. Overall, the estimated return time of severe bleaching events has declined from once every 27 years in the 1980s to once every 5.9 years in 2016. That’s a 4.6-fold reduction.
• 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. The 36-month heatwave and global bleaching event were exceptional in a variety of ways. For many reefs, this was the first time on record that they had experienced bleaching in two consecutive years. Many reefs—including those in Guam, American Samoa, and Hawaii—experienced their worst bleaching ever documented. In theNorthern Line Islands in the South Pacific, upwards of 98 percent of the coral at some reefs were killed. Reefs in the northern part of Australia’s Great Barrier Reefthat had never bleached before lost nearly 30 percent of their shallow water corals in 2016, while reefs a bit farther south lost another 22 percent in 2017. All told, more than 75 percent of Earth’s tropical reefs experienced bleaching-level heat stress between 2014 and 2017, and at nearly 30 percent of reefs, it reached mortality level.

Question 41

Corals: threats: Anthropogenic: Ocean Acidification?

Answer 41

ocean acidification particularly impedes the thickening process—decreasing the skeletons’ density and leaving them more vulnerable to breaking.

Acc to a study, The impact will be especially strong in the Indo-Pacific region, with up to 20 percent reductions in the densities of coral skeletons by 2100 in parts of the Coral Triangle

Question 42

Corals: threats: Anthropogenic: Pollution?

Answer 42

1. Sewage and industrial Waste
2. Oil spills: eg. Wakashio spill off the coast of Mauritius, was near Marine Protected Area renowned for its remarkable corals including more than 1000 yr old brain coral (Lobophyllia), the largest brain coral in IO
3. increase in virulents in water

Question 43

Corals: threats: Anthropogenic: Overfishing and Destructive Fishing practices?

Answer 43

• Overfishing of certain species on or adjacent to coral reefs can affect the reef’s ecological balance and biodiversity. For example, overfishing of herbivorous fish can lead to high levels of algal growth.
• Destructive fishing methods: Fishing with dynamite, cyanide, bottom trawling and Muro Ami (banging on the reef with sticks) can damage entire reefs and is unsustainable.

Question 44

Corals: threats: Anthropogenic: Developmental Activities?

Answer 44

1. coastal development
2. increased sedimentation: Sedimentation is on the rise due to degradation of estuaries, salt marshes and mangrove forests. It reaches the marine ecosystem, including coral reefs, and causes suffocation to coral reefs.
3. Tourism and recreational activities: get damaged due to the fishing and tourist boats anchored on them.

Question 45

warm water and cold water corals?

Answer 45

There are two main types of corals: shallow, warm-water corals; and cold, deep-water corals. The obvious difference between the two is that warm-water corals live close to the sea surface – usually in coastal waters – whereas cold-water reefs can extend to depths of 3,000 meters below the surface

Warm and cold-water reefs therefore function in very different ways. Corals use calcium carbonate in ocean waters to build a hard exoskeleton. But the key to their success is how they get their energy. Warm-water corals contain microscopic algae called zooxanthellae in a symbiotic relationship. The algae photosynthesize for them, providing corals with most of their energy.⁶ These corals wouldn’t be able to survive without them. They can only do this by living close to the surface where light is abundant.

Once we reach 200 meters below the surface – which is where most cold-water corals live – there is so little light that photosynthesis is not possible. Cold-water corals don’t have these symbiotic algae, and get their energy from feeding on particles on the ocean floor instead.

Question 46

Coral Degradation does not always mean decline of coral cover?

Answer 46

We often rely on metrics such as coral cover or coral mortality as a marker of reef health. But this does not always give us an accurate comparison of reef health. As we saw discussed earlier, corals have always gone through periods of coral decline and recovery. Simply having low coral cover does not necessarily indicate poor reef health if it is on the path to recovery. A reef with 20% coral cover that is restoring quickly is arguably in a better state than a reef with 60% cover that is seeing year-on-year declines.

Many researchers have stressed that it’s not necessarily the absolute level of coral cover that matters for reef health, but where the reef lies between two states of equilibrium. Corals are often described in terms of a phase-shift. In one phase, a reef is resilient to pressures such as bleaching, storms, or disease; when these events occur they feel the short-term impacts but can quickly recover. This is the ‘coral-dominated state’.

But there is another phase: one triggered by a non-linear response. Reefs can be pushed too far and ‘flip’ into an ‘algae-dominated’ state. This is a state where the ecosystems have fundamentally changed from one dominated by coral to one of macroalgae. This new state of equilibrium is difficult to recover from. A reef in this state is an unhealthy one.

eg. Carribean Reefs. In the Caribbean we find reefs of algae, not of coral: 40% is covered by macroalgae versus only 15% of coral. It hasn’t always been this way: in the 1970s, macroalgae covered only 2% of Caribbean reefs. A 20-fold increase. Contrast that with the Great Barrier Reef where less than 5% of cover was algae, and 25% was coral. Its reefs are still very much in the ‘coral-dominated’ phase. This means they are resilient to pressures and can bounce back.