Coral Bleaching : Why it matters?


Cotext: Things aren’t looking too good for coral reefs. They’re suffering from bleaching, overfishing and are being cooked by warming oceans. But why does it matter?

What are Coral reefs?

  • Corals are nothing but calcareous rocks, formed from the skeletons of minute sea animals, called polyps.
  • The polyps extract calcium salts from seawater to form hard skeletons which protect their soft bodies. These skeletons give rise to corals.
  • The corals live in colonies fastened to the rocky seafloor. New generations develop on skeletons of dead polyps. The tubular skeletons grow upwards and outwards as a cemented calcareous rocky mass collectively called corals.
  • The shallow rock created by these depositions is called a reef. These reefs, later on, evolve into islands.
  • The corals Occur in different forms and colors, depending upon the nature of salts or constituents they are made of.
  • The progressive development of corals appears over the sea surface in different forms over a period of time. Small marine plants (algae) also deposit calcium carbonate, thus contributing to coral growth.

Ideal conditions for coral growth

  • Tropical waters-between 30°N and 30°S latitudes.
  • 45 m to 55 m depth below sea surface, where abundant sunlight available.
  • Temperature of water – around 20°C.
  • Adequate supply of oxygen plankton.
  • Fresh water and highly saline water are harmful.

Distribution of Coral Reefs

  • Between 30° north and 30° south latitudes.
  • The Indonesian/Philippines archipelago has the world’s greatest concentration of reefs and the greatest coral diversity.
  • World’s major coral reef regions are Caribbean/ western Atlantic, Great Barrier Reef of Australia, Pacific ocean, Indian Ocean, Arabian Gulf, Red Sea etc.

Causes of Coral Bleaching

  • As coral reef bleaching is a general response to stress. It is therefore difficult to unequivocally identify the causes for bleaching events.
  • Coral species live within a relatively narrow temperature margin and therefore, low and high sea temperatures can induce coral bleaching. Bleaching events occur during sudden temperature drops accompanying intense upwelling episodes, seasonal cold-air outbreaks etc.
  • Bleaching during the summer months, during seasonal temperature and irradiance maxima often occurs disproportionately in shallow-living corals and on the exposed summits of colonies.
  • Sudden exposure of reef flat corals to the atmosphere during events such as extreme low tides, ENSO-related sea level drops or tectonic uplift can potentially induce bleaching.
  • Rapid dilution of reef waters from storm-generated precipitation and runoff has been demonstrated to cause coral reef bleaching.
  • Other causes includes the increase in the concentration of inorganic Nutrients, sedimentation, oxygen starvation caused by an increase in zooplankton levels as a result of overfishing, ocean acidification, changes in salinity, sea level change due to global warming, cyanide fishing etc.

What are reefs good for?

  • Flood protection – Some 200 million people around the world depend on reefs to protect their coastal communities from storm surges and waves.
  • Coral reefs act like low-crested breakwaters and absorb 97% of wave energy. This substantially reduces coastal flooding and erosion.
  • Reefs lose just 1 meter in height, $5 billion in property and economic damage is at risk.
  • Coral reefs cover less than 0.5% of the earth’s surface, but they are home to about 25% of all marine species. Kind of like the rainforests of the sea.
  • With biodiversity, more is better. It provides planetary resilience, a vast resource of potential scientific discoveries, and is the result of millions of years of evolution. Biodiversity underpins a healthy planet and social well-being.

Why does that matter?

  • A huge number of modern medicine’s drugs are derived from natural sources. And so far, most of those have come from land organisms.
  • But given 80% of life is under water, researchers are increasingly looking to marine organisms to satisfy the need for novel chemicals and enzymes to build the pharmaceuticals of tomorrow.
  • The anticancer agent Ara-C, included on the World Health Organization’s List of Essential Medicines, is found in sea sponges on a Caribbean reef.
  • Sea hare: A very generous name for some gastropods that look more like dodgy quesadillas. But what they lack in good looks, they make up for with the presence of Dolastatin 10, which is being tested as a treatment for breast and liver cancers, tumors, and leukemia.
  • One promising molecule, eleutherobin, that is believed to slow  cancer cell growth is found in a common species of soft coral. Scientists have been able to use its genetic code to figure out how they might soon be able to manufacture the chemical in large quantities. Another success story from nature’s medicine cabinet is trabectedin, found in the sea squirt Ecteinascidia turbinata, and used in chemotherapy.

Anything else?

  • Humans eat about 150 million tons of seafood a year and these fish have to breed somewhere.
  • Coral reefs provide shelter and function as nursery grounds for some pretty commercially important fish, like grouper and snapper, as well as invertebrates like the lobster.
  • Some studies put the value of coral reef fisheries at $6.8 billion a year globally. About one billion people source their food or income directly from reefs. In countries like the Maldives, it provides people with 77% of their dietary animal protein. If managed well, reefs can continue providing this important source of food.

And if they’re not managed well?

Potential food shortages could be the consequence. Especially when combined with failing crops from climate change. A study of reef damage in Kenya revealed drastic declines in key fish catches after a combination of factors in 1998 warmed the ocean by between 1-2 degrees Celsius.

That’s not to mention the possibility of increased mass migration, as people try and avoid famine and flooding.

Protection of Reefs:

local restoration efforts by transplanting coral, the establishment of marine protection areas which work like national parks, and stopping run-off from agricultural and effluence.

But these efforts might all be in vain if humanity doesn’t get a hold on climate change, which presents the biggest singular threat to the future of coral reefs.

Source: Indian Express

Read more: Problems with Compensatory Afforestation in India