General Overview of Coral Significance and Endangerment
- Jessica Zhang
- Mar 12, 2024
- 3 min read
Corals are often mistaken for exotically vibrant plants, but they are actually animals!
Corals are made up of tiny living organisms called polyps. Polyps form hardened limestone exteriors – calicles – around their soft sac-like bodies and build off of each other, forming a colony of millions of miniscule creatures that act as a single organism.
Over hundreds of thousands of years, these colonies are conjoined, which create the extravagant structures that we see today. Aside from their visual beauty, coral reefs play a diverse role in our ecosystem. They serve as crucial defenders of coastlines, protecting them from storms and erosion, as well as providing job opportunities and recreational spaces. Additionally, coral reefs act as essential sources of sustenance for over half a billion people, supporting the livelihoods of coastal communities and the fishing industry, and in aiding medical research as well.
These underwater ecosystems sustain 25% of ocean life, underscoring their significance in the preservation of marine biodiversity. Corals provide shelter, food, reproduction sites, and havens, for various organisms, particularly fish, demonstrating the complex interdependence within these dynamic underwater ecosystems.
Zooxanthellae
Corals are naturally translucent. However, they get their array of colors from their symbiotic relationship with zooxanthellae, or a type of algae, that live in their tissue. (Similar to fruits, the pigment of the zooxanthellae’s chlorophyll determines the host organism's natural color). These algae take in sunlight through their chlorophyll to produce sugar for energy. A portion of this generated energy is then passed on to the polyps. In return, coral polyps supply the algae with carbon dioxide and a protected habitat. Beyond algae, polyps utilize their stinging tentacles to catch unsuspecting micro-organisms – zooplankton – as well, but zooxanthellae are still their primary source of energy.
However, when corals are threatened by pollution or other environmentally stressful factors, they either expel the algae or the algae leaves the polyps tissues, exposing the coral’s naturally white exterior. This process is called coral bleaching. By losing their primary source of food, corals are left vulnerable and more susceptible to diseases, thus endangering their survival.
Summarized Life Cycle of Coral
Energy Investment: Fully developed corals invest energy in the creation of reproductive cells through the process of meiosis.
Gamete Release: When the environment is suitable, corals release egg and sperm cells into the water.
External Fertilization: A fertilized zygote (egg) is formed externally in the water.
Miotic (Cell) Division: The zygote undergoes mitosis, a type of cell division, generating multiple cells and initiating embryo development.
Transformation to Planula: The developing embryo undergoes a transformation, becoming a planula larva, which is essentially coral plankton.
Settlement and Development: Using its cilia (tail) for propulsion, the planula drifts until it locates a suitable solid surface to attach itself to. Lastly it begins forming its hard exoskeleton. When multiple polyps attach to each other, coral is formed.
Then Versus Now
Scientists are still trying to figure out where these corals came from in evolution. Fossils show that corals appeared in the Middle Triassic period, and they were more diverse than expected. Molecular biology supports the idea that these corals might have come from soft-bodied ancestors that survived mass extinction. Most living coral reefs are less than 10,000 years old, but corals have been found in fossil reefs as old as 500 million years.
Scientists are applying various methods to conserve corals such as Replantation: Lab-grown coral replanted into aquatic ecosystems (this method is successful but could potentially reduce genetic diversity), and Genetic Engineering: Artificially crossbreeding species to create breeds with a wider range of tolerance (there is a risk of creating an invasive species with this method).
What Can You Do?
To support coral reef conservation, you can:
Scuba dive responsibly, avoiding coral and coral reefs
Choose reef-friendly sun protection to avoid releasing harmful ingredients in the waters
Dispose of trash properly, especially plastic
Participate in community cleanups.
Consider environmentally friendly transportation to reduce fossil fuel emission.
Spread awareness by sharing information with your community!
Work Consulted
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"The Evolution of Modern Corals and Their Early History." Science Direct,
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"Life Cycle." Khaled Bin Sultan Living Oceans Foundation,
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"7 Bold Ways Scientists Are Saving the Coral Reefs." The Hill, thehill.com/
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#:~:text=Scientists%20hope%20they%20can%20help%20increase%20resilience%20among,In
surance%20...%207%207.%20Fight%20climate%20change%20. Accessed 3 Dec. 2023.
"What Is Coral Bleaching?" National Ocean Service, oceanservice.noaa.gov/facts/
coral_bleach.html#:~:text=When%20the%20symbiotic%20relationship%20becomes,is%20mo
re%20susceptible%20to%20disease. Accessed 3 Dec. 2023.
"What You Can Do to Help Protect Coral Reefs." United States Environmental
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what-you-can-do-help-protect-coral-reefs. Accessed 3 Dec. 2023.
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