Corals Are Beautiful Creatures
No, they are not plants or rocks
When I mention the word animals, most people I talk to tend to think of elephants, lions, dolphins, or even more obscure ones such as ants or spiders; not many would think of the immobile and seemingly mundane cnidarians known as coral. Many people only know coral from reefs such as the Great Barrier Reef in Australia; some people might think of them as plants, but some of the people that I talk to even believe that corals are simply colourful rocks! However, did you know that corals are actually living animals? Corals are classified under the phylum Cnidaria, which makes them relatives of the more famous jellyfish.
While corals are a hot topic for conservation, they are generally overlooked and under appreciated by the general public. Hence, in this essay, in commemoration of World Reef Awareness Day (which falls on 1st June), I will shed some light on the secretive lives of coral and highlight the critical and urgent need to conserve and protect these valuable creatures.
What is a coral
Like its cousins, such as the Portuguese man of war (Physalia physalis), corals are made up of multiple tiny individual organisms called polyps. These polyps are interconnected and work together to form large colonies of coral. Each polyp in a coral colony consists of a mouth surrounded by tentacles, which capture food for the coral and defend against predators.
What makes a coral an animal
When you first look at a coral, there may be evidence that points to it being a plant, the most notable of which is its inability to move freely from place to place. However, that is where the similarities between plants and coral end. Unlike plants, corals are unable to photosynthesise food through sunlight and have to feed on other organisms. Coral generally feeds on small fishes and microscopic life forms such as zooplankton. Like jellyfish, the polyps of the coral use stinging cells lined along their tentacles called nematocysts to paralyse and capture their prey.
Coral also reproduces via gametes, something that is unique to the kingdom Animalia. Most corals are hermaphrodites, meaning they have both male and female reproductive organs and release both eggs and sperm. Coral within the same reefs will often synchronise their spawn timings, resulting in a spectacular event known as coral spawning. During coral spawning, the water around the reef is filled with clouds of colourful eggs and sperm, creating a mesmerising display. These events, similar to the nuptial flights of insects, drastically increase the chances of fertilisation. After fertilisation, the embryo develops into microscopic larvae, which float in the ocean currents for several days or weeks before settling onto a suitable substrate to form a new coral colony. On top of all these physical characteristics, scientists have also discovered that coral cells have thin cell membranes similar to other animal cells.
I thought corals photosynthesise?
Corals do not photosynthesise; they are animals that cannot do so. However, they do share a symbiotic relationship with a type of algae known as zooxanthellae. The zooxanthellae algae live inside the coral polyps and benefit from the carbon dioxide and waste expelled from the coral. Zooxanthellae are plants and thus are able to photosynthesise; therefore, by housing within the coral, the coral will be able to reap the products of the photosynthesising algae, which include glucose and amino acids.
Importance of Coral Reefs
Corals form reefs that are vital ecosystems for marine life. Coral reefs provide shelter, food, breeding grounds and even nurseries for over a million species of aquatic creatures. An estimated 25% of all marine species are reliant on coral reefs at some point in their lives. Fishes such as the clown fish and the Moray eel are just two iconic examples that depend heavily on coral reefs. Due to the high biodiversity that relies on coral reefs, the health of coral reefs indirectly impacts commercial fisheries and the seafood that we eat.
Reefs also serve as tourism hotspots, with countries such as Australia using their reef systems to attract visitors and generate revenue. According to the World Wildlife Fund (WWF), approximately 2.19 million people visit the Great Barrier Reef annually, generating about $5.89 billion in tourism revenue for the Australian economy.
In addition to the economy, coral reefs also serve as natural barriers, protecting coastlines from waves, storms and floods. The National Oceanic and Atmospheric Administration estimates that coral reefs buffer 97% of energy from waves, thus providing $9 billion in flood reduction services annually in the United States alone. With how reliant humans are on coral reefs, it is clear why preserving reefs should be a priority. However, coral reefs around the world are under immense threat.
Coral Bleaching
Coral reefs face a multitude of threats that have caused them to decline rapidly in recent decades. One of the leading causes of coral deaths is global warming and climate change. Corals thrive between the temperatures of 64 to 84 degrees Fahrenheit (18 to 29 degrees Celsius). They can be stressed out if the water gets too hot. Corals also require an approximate pH level of 8.1; however, as the amount of carbon dioxide in the atmosphere increases, more carbon dioxide dissolves into the ocean, making it more acidic. This ocean acidification will further stress the corals, causing a phenomenon known as coral bleaching. When corals become stressed due to unfavourable water conditions, they will expel their symbiotic algae, causing the coral to turn extremely white, hence the term ‘bleaching’.
When a coral undergoes bleaching, it is not dead yet but becomes highly vulnerable. Reefs can recover from bleaching; however, such a process can take a very long time, and the water conditions must be perfect. Otherwise, the corals will begin to die off slowly. If coral reefs were to die off, it would severely impact the millions of species that rely on them, which will, in turn, cause businesses that indirectly depend on reef systems, such as tourism and fisheries, to collapse. Coral reefs dying off will also lead to a domino effect that disrupts entire marine ecosystems and causes many species to go extinct.
Conservation of coral reefs
Thankfully, many organisations and governments around the world have recognised the importance of coral reefs and have taken steps to conserve and protect them. While Governments and Organisations such as the WWF try to find ways to reduce global greenhouse gas emissions and mitigate the effects of climate change, smaller local organisations such as the National Oceanic Atmospheric Administration (NOAA) in the United States have embarked on projects such as coral restoration. Coral restoration refers to the growing of coral in labs and nurseries before planting them on degraded reefs to help the reef recover and regenerate. Some countries have also banned practices that are detrimental to coral reefs, such as the use of cyanide or dynamite fishing, and restricted access to certain reef areas. So, what can you do to help preserve coral reefs?
One of the most important things you can do is to reduce your carbon footprint by using less energy and limiting the use of fossil fuels. You can also donate to organisations such as the Great Barrier Reef Foundation or the Ocean Conservancy to help support their cause. When visiting countries that house reefs, you can help support and fund local organisations that work to conserve them by paying for guided tours or snorkelling sessions. Avoid buying coral or coral-based souvenirs, as these can encourage the illegal harvesting of corals. Every individual has a role to play in preserving one of the most beautiful and vital ecosystems on our planet.
Overall, corals are amazing animals that are building blocks for one of the most beautiful and biodiverse ecosystems that support millions of species in the ocean. Not only do they generate revenue for us through tourism, but the fish and seafood that we consume are reliant on the well-being of coral reefs. Preserving coral reefs should be a priority for humans to ensure a healthy marine ecosystem for generations to come.
