Saving Corals
White cemeteries to Vibrant kaleidoscopes
Moonlit Euphoria
It’s the fifth day after the full moon in November. At the Great Barrier Reef, moonlight streams silver all across the ocean surface sprawling an area roughly in size as the entirety of Italy. The entire scene is lit up with the halo of the pearly white moon. This cold spring night awaits to witness a unique phenomenon. Underneath the water surface, nebulous white dots surrounded by ethereal clouds rise. They are coral gametes. As the eggs start going up, it looks almost like an eerie inverted underwater snowstorm. As thousands and thousands of colonies release their gametes synchronously once a year, the event is playfully dubbed as the ‘Annual Sex Festival’.
Warm ocean waters suddenly teem with trillions of eggs and sperm that swirl in the currents and merge to form new life, a profligate frenzy that can leave the ocean’s surface awash in pink flotsam. These fuzzy spawners are affected by the tiniest of shifts in water temperature and bright light.
What exactly are corals?
Are they animals? Are the plants? Or are they inanimate rock structures?
We’ll start with polyps, the building blocks of corals.
Coral polyps are tiny pinhead size, soft-bodied organisms related to sea anemones and jellyfish. Each polyp has a mouth surrounded by tentacles, and a stomach. Millions of polyps fuse and combine to form one single organization known as a coral. It all starts from a single zygote which turns into a floating larva searching for the right spot on the seafloor to latch onto. Once settled down, it converts into a developing polyp which further divides asexually via fragmentation or budding, into several genetically identical clone polyps which ultimately combine to form a single mature coral. Thus, corals can reproduce sexually as well as asexually.
Now, these corals have been guided by evolution to have a symbiotic relationship with specific species of microalgae known as zooxanthellae. Having a symbiotic relationship or symbiosis, put in simple terms means that the coral and the microalgae sign a mutually beneficial contract stating that the microalgae will photosynthesize and provide essential nutrients such as sugars, amino acids, and oxygen to the coral. In turn, the coral will provide the microalgae with the required raw materials for photosynthesis such as carbon dioxide, which is a byproduct of the coral’s cellular respiration. Not stopping there, the contract also requires the microalgae to help the coral in removing its waste. In return the coral has to accept the zooxanthellae as tenants in its tissues and that too with a dense population of several million per square inch, providing safety in the form of an effective shelter. Because of this intimate relationship, corals respond to the environment just as plants do. Nighttime is when the polyps come into action. They come out of their skeleton and search for food, like floating particles of zooplankton and critters. Their long, stinging tentacles come in handy as they harpoon in their prey.
Just 25 years ago, researchers believed that coral housed just one variety of symbiotic algae. Now, they have identified hundreds. And they are just beginning to examine the role played by the coral’s microbiome, the menagerie of bacteria that inhabit a coral polyp which could be a possible first step toward creating bacterial cocktails that could help their coral hosts by absorbing molecules released during heat stress. We still have a lot of ground to cover in terms of coral research.
What we do know is that corals are extremely sophisticated creatures but rather in a quiet, down to earth manner. They scourge for calcium carbonate in their surrounding water and manifest extraordinarily intricate, tall, exquisite, ornate and massive structures as their skeleton, which can even be seen from space! They’re the architects of the reef megacities housing in quite a warming manner, the marine fauna which we all know to be an enormous and widespread cosmopolitan crowd, in their limitless edifices. They’re like the rainforests of the oceanic ecosystems.
How exactly do corals sense moonlight?
Do they see it visually? Or do they detect it somehow by the movement of tides? The answer lies in a 2007 study which confirmed that corals can tell when the full moon arrives with the help of an ancient gene that allows them to sense how much moonlight is hitting the water.
How long do corals live?
Even though one in a million coral larvae lives in every 25 to 100 years, because of the ginormous amount of spawning the odds are well placed in the corals’ favor. And if they grow on to become massive corals, they can live for 800 years to several centuries. There’s no stopping to the life of a coral given the right environmental conditions. They’re just like jellyfish in that aspect.
Where are coral reefs generally found and how do they form?
Corals require clear water so that sunlight can reach their algal cells for photosynthesis. For this very reason, they are generally found only in waters with small amounts of suspended material or water of low turbidity and low productivity.
Reefs form in one of three ways:
- First, they can be directly attached to the shore, as a ‘fringing’ reef.
- Second, they can be separated from the shore by a channel as a ‘barrier’ just like the world’s most famous reef, the Great Barrier Reef.
- And, third, they can be entirely separate from land in a ring shape or circle known as an ‘atoll’ which has a lagoon in its middle. They can form their islands.
Selfless Corals
Coral reefs are biodiversity hotspots of great ecological, economic, and aesthetic importance. Nearly 500 million people worldwide depend on them for their livelihoods. Along with contributing to a 6 Billion dollars tourism industry in Australia alone and employing over 70 thousand people there, coral reefs break storm waves, surges, erosion and hurricane damage. Many of today’s islands exist because of their protection. They nurture a riot of marine species and fish stocks that feed millions of people. Covering only 0.0025 per cent of the ocean floor, they generate half of Earth’s oxygen and absorb nearly a third of the carbon dioxide generated from fossil fuels. Also, biomedical compounds found in corals serve as potential cancer cures.
White Cemeteries
Now let’s talk about coral bleaching:
I’m sure many of us have encountered the term ‘coral bleaching’ time and again. Coral’s most remarkable characteristic — being an animal that is part plant — is also its Achilles heel in a hotter world. Normally, coral polyps live in harmony with their algal partners, which help feed the polyps and give corals their bright colours. But during heat waves, the relationship sours and the contract is broken. Overheated polyps perceive the algae as an irritant and eject them like unwanted squatters. The coral is left bleached, bone-white and starving. If the heat persists, and the coral still hasn’t taken in new algae, it can die. The relentless rise of global temperatures is imperiling coral reefs around the world.
Climate change has reduced coral cover, and surviving corals are under increasing pressure as water temperatures rise and the frequency and severity of coral bleaching events increase. In the last 30 years, humanity had to witness the harrowing loss of around 50 per cent of the world’s corals. Half of the great barrier reef corals have been destroyed by the heat waves from 2016–2018.
The years 1992, 2002 and 2014–2018 are recorded to having witnessed major mass bleaching events.
A thorough prognosis reveals the following problems:
- Fertilizer and surface runoff.
- Water pollution.
- Coastal development.
- Overfishing and harvesting.
- Destructive tourism.
- Global warming.
- Climate change.
Coral conservation has traditionally focused on minimizing damage from invasive starfish and the first five aforementioned issues. Global warming and climate change are relatively new challenges faced.
In the past decade, heat waves have turned vast swaths of the reef from multihued oases to algae-coated deserts. Reef-building corals show few signs of adapting to the rapid change. If global temperatures rise by 2°C, the Intergovernmental Panel on Climate Change has concluded, reefs, as we know them, will be virtually gone worldwide. Today, the planet is on course to crack 3°C by 2100. Then there is the added threat of ocean acidification. The sea’s absorption of carbon dioxide lowers the pH of seawater, making it corrosive to the calcium carbonate shells that corals and many other marine creatures build.
Silver Linings
In such dire circumstances, it’s heartening to know that there are still glimmers of hope. We finally found ingenious ways to redeem our past mistakes. Armored with scientific creativity and an unparalleled display of mind and skills, we have finally found ways to tackle even this behemoth of an issue and ameliorate our present condition.
Today, four major promising lines of research exist:
- One involves cross-breeding corals to create heat-tolerant varieties, either by mixing strains within a species or by crossing two species that would not normally interbreed.
- A second enlists genetic engineering techniques to tweak coral or algae.
- A third tries to rapidly evolve handier strains of coral and algae by rearing them for generations in overheated lab conditions, something known as ‘assisted evolution’.
- A fourth approach, the newest, seeks to manipulate the coral’s microbiome.
CRISPR To The Rescue
In attempts to understand corals’ responses to stress and other aspects of their biology, numerous genomic and transcriptomic studies have been performed, generating a variety of hypotheses about the roles of particular genes and molecular pathways. Breaking genes to reveal the effects on the organism is a concept that’s been the focal point of decades of molecular biology.
The powerful gene-editing tool CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat)-Cas9(CRISPR associated protein-9) has taken the scientific world by storm. It gives researchers unique power and precision in making tweaks to practically any gene in a plant or animal and coral reefs have become its next beneficiary.
Phillip Cleves, PhD, a postdoctoral scholar at Stanford, is a geneticist whose efforts to delineate gene function in animals resides squarely within the marine invertebrate realm — namely, corals. Cleves is the lead author of the study which was first published on April 25, 2018, in the Proceedings of the National Academy of Sciences. Cleves and his team used CRISPR to edit three genes in corals growing in Australia’s Great Barrier Reef. Two of the genes were responsible for the reef’s coloring — coding for red and green fluorescent proteins — and one was involved in regulating how new coral settles and grows in a reef.
As for the methodology, Phil Cleves, in his lab, hunched over a microscope, works on a row of newly created coral embryos lined up in a small petri dish. Using a joystick, he guides the glass tip of a needle, less than a micron(one millionth of a meter), across until it punctures an embryo’s outer membrane and delivers new genetic material.
Once Cleves has punctured an embryo, a puff of air injects a droplet filled with the RNA and enzyme molecules that snip the DNA. Gene manipulation is done at a very early in the coral’s life cycle just after fertilization of egg and sperm when the coral is just one cell as it ensures that the genetic change was as widespread in the resulting coral’s genome as possible. The researchers will later expose those knockout embryos to different temperatures; if embryos that have had certain DNA sequences removed die at higher rates, the researchers could be a step closer to identifying key resilience genes.
Some researchers want to try to dim the sun over reefs by spreading a thin sun shield over the water or by spraying saltwater into clouds so that they reflect more sunlight. Others are looking at controlling coral spawn and steering it to reefs most in need. Some envision creating an entire aquaculture system — essentially coral farms — to raise handier strains, which could then be transplanted to ailing reefs.
Valid Trepidations
Genetically engineering corals to make them better able to withstand heat and resist bleaching is among the brightest of possibilities. But we can’t help but concede that the idea will face resistance, like all proposals to release modified organisms into the environment. But that doesn’t necessarily mean it should be shelved. Genetic engineering sure frightens people but in the coming 10 to 15 years our current plight is projected to deteriorate at an alarming rate and the only viable alternative left inevitably will be synthetic biology and its tools.
Considering the Great Barrier Reef and introducing a new coral in the largest organization of corals on the scale needed to make a dent on a network of 2900 reefs is a daunting challenge indeed. Even in its damaged state, the Great Barrier Reef still contains hundreds of millions of corals — enough to swamp the genetic impact of new coral species.
Then there’s the issue of double-crossing (in the generic, not genetic sense). Could some kind of ‘super coral’ as some researchers have dubbed them, run amok and create havoc among delicate coral ecosystems?
All Drains Lead To The Ocean
This is just a start. A beta version of an elaborate plan to save our planet. We can wait for everyone to open their eyes and then take the matter seriously or start working towards the problem actively ourselves. That’s what countless coral researchers and scientists did to achieve this current feat. Once a dreamlike kaleidoscope of life, color and movement now turned into a white cemetery.
Even though synthetic biology may be able to curb the issue now, the root of the problem persists. Climate change. We don’t usually notice the subtle changes which coral degradation or any other biodiversity losses bring on our planet. They seem benign at the surface. But our planet has a blue heart. It’s like our body temperature increasing two degrees or so. It doesn’t seem like much. But in the long term, each and every organ pays the price and we as the immune cells would have just brought about an irreversible autoimmune fatality. Denial has worsened the impact to the extent that short namesake measures will just serve as euthanasia for the domino of ecosystems lined up at the cost of short-term gains. We’re far from the stage of being prophylactic. We don’t run around looking for a mop when we see a running tap overflowing; we close the tap first.
