1) How do the corals form?
Corals are categorized under the class Anthozoa under the phylum
Cnidaria of the animal kingdom. They are marine invertebrates. Typically, they
are found in clean and clear tropical shallow waters. The single organism of
coral is called polyps.
In the reproduction, the gametes of polyps are fused, and its
free-swimming larva called Planula is produced. When Planula reaches a rock
surface or continental self, it starts to grow as clusters, and often form
colonies.
2) The symbiotic relationship between corals and
Zooxanthellae
Corals and Zooxanthellae exhibit a mutualistic relationship with each
other. Zooxanthellae are photosynthetic algae that inhabit in the cells of the
corals. It carries out photosynthesis and provides oxygen and other essential
substances like carbohydrates and proteins for the hosting of the coral’s
cells. In return, corals supply algae with the shelter and essential nutrients
for photosynthesis.
Zooxanthellae is a photosynthetic organism. It requires sunlight as an
input for their process. But sediments in the seawater reduces light
penetration into underneath layers of the ocean. So, coral reefs are only found
in the areas with high light penetration due to its relationship with
Zooxanthellae.
Furthermore, corals appear in
various colors due to pigmentation results from the Zooxanthellae inhabiting
their body cells. Corals are growing in tropical and subtropical oceans because
coral needs the light throughout the year for the continuation of the
photosynthesis of Zooxanthellae.
3) Why are corals important to the world?
Even though corals occupy less than 1% of the marine environment, coral
reefs are the most diverse ecosystem in the marine environment. It provides
diverse habitats and breeding grounds for numerous species of fishes,
crustaceans, and other animals. It safeguards the coastal zone from the Tsunami,
and storms by baking down the wave action of the sea. Thereby, coral reefs
prevent damage to coastal ecosystems, properties, and life of people in the
coastal zone.
Apart from the environmental value, coral reefs act as the major
contributor to the local economy. More than 500 million people entirely or
partially depend on the coral reefs for their food resources or livelihood. The
majority of the fishery industry entirely depends upon the coral reefs as
commercial fish species use the coral ecosystem as their spawning system. Coral
ecosystems are functioned as major tourist attractions are all over the world
due to its high species diversity.
In order to protect from predators, fish, and other marine organisms,
inhabitants in the coral ecosystem are adapted according to their environment.
This adaptation gives beautiful color patterns that increase the demand for
such species in the marine aquatic trade.
4) What is the “coral bleaching”?
Coral bleaching is a white color appearance in coral due to the loss of Zooxanthellae.
When the corals expose to stress conditions like high temperature and
pollution, they lose the Zooxanthellae. It results left alone the skeleton and
loss of colors due to the loss of pigmentation of the corals.
5) What are the causes of coral bleaching?
The high temperature in the oceans results from the high solar
intensity, direct discharge of warm water into the ocean, and anthropogenic
climate change. It causes the formation of oxygen radicles from the oxygen
expelling from the photosynthesis. These oxygen radicles negatively affect both
corals, and its symbiotic photosynthesis algae, Zooxanthellae.
Enhanced climate change has increased the frequency and intensity of
natural disasters. Frequent floods in uplands areas bring lots of sediments into
the ocean. And also, sea-level rise resulting from glaciers meting increases
the sediments around the coral reefs.
Sedimentation often interferes with light penetration, and Zooxanthellae
is also get affected.
Harmful chemical substances such as oxybenzone in personal care products
like sunscreens, body lotions, and shampoo, which are released into the ocean
by the swimmers and wastewater discharges, act as endocrine substances and they
cause detrimental effects for the corals in the juvenile stages. And also,
these substances increase the occurrence of viral infections in Zooxanthellae.
Consequently, Palau has become the first country to ban sunscreen
containing harmful chemicals that are toxic to corals and other marine life.
Discharge of nutrient-rich polluted water causes eutrophication and
algal blooms in the ocean at its later stage. The growth of algae at the
surface of the water body reduces light penetration. As a result, Zooxanthellae
finds difficulty in photosynthesis due to less availability of light. This
stress condition causes expelling Zooxanthellae out of corals cells.
6) Can corals recover back?
Only a few species of corals can survive after the loss of its symbiotic
Zooxanthellae. Most of them can survive only a few days. If Zooxanthellae
return soon into the effected corals, corals can recover and flourish again.
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