Coral reefs suffer from plastic pollution, bleaching, and increased ocean acidification. How can science and tech mitigate our devastating impacts on our oceans, helping to repair ecosystems, restore biodiversity, and create a hopeful future for our reefs?
Coral reefs are among the most breathtakingly beautiful and biodiverse ecosystems on our planet, supporting over a quarter of all marine species. They provide both humans and the natural world with a myriad of goods and services, such as nitrogen fixation, raw materials for medicines, employment opportunities, as well as an annual generation of $36 billion in global revenue for the tourism industry. They also support half a billion people around the world.
Unfortunately, the culmination of plastic pollution, increasing temperatures, overfishing, and ocean acidification has led to the severe destruction of these precious ecosystems. Such ecological catastrophes are tremendously difficult to reverse — even if global warming were to have ceased in 2017, scientists would still expect over 90 percent of coral reefs to die by 2050. However, as this harrowing ecosystem collapse occurs, the science and tech sectors are driving efforts, both on national and global scales, to reduce the drastic rates of coral reef death. Such intervention and research could be the key towards maintaining and rebuilding the coral reef ecosystems we so heavily rely upon.
However, as this harrowing ecosystem collapse occurs, the science and tech sectors are driving efforts, both on national and global scales, to reduce the drastic rates of coral reef death.
Currently, with one garbage truck’s worth of plastic entering our oceans every minute, it is indisputable that plastic consequentially causes marine life to suffer. Plastic which enters the ocean usually accumulates in one of the five major ocean gyres (systems of circulating ocean currents), often having deleterious consequences for marine life as the plastics can take hundreds of years to degrade. Coral reefs are particularly susceptible to the damage, as pathogenic bacteria responsible for a host of coral diseases can colonise and heavily accumulate on plastic, infecting the corals upon contact with them. These devastating diseases, known as “white syndromes,” cause parts of the coral to die, leaving white bands of dead tissue in their wake. This damage is also exacerbated by the fact that the plastic can block light and oxygen, which is needed by coral reefs to survive.
In addition to this problem, as with many marine organisms, corals can’t differentiate between microplastics (tiny plastic particles) and nutritious food. As a result, microplastics are consumed at the same rate as edible sustenance, which proves very damaging as the corals are not able to expel the plastic pieces once ingested. Such overexposure to plastic can cause corals to slowly die from starvation, which is a consequence of plastic build-up within the digestive system that hinders the corals from receiving necessary nourishment.
Removing plastic waste from our oceans is therefore a vital step towards healing our coral reefs. One organisation that has pioneered such efforts is The Ocean Cleanup, which impressively aims to remove 90% of ocean plastic by 2040. Their strategy involves a two-fold approach: first, minimising the amount of plastic entering our oceans, and second, deploying fleets of cleaning systems into each of the five ocean gyres to collect the plastic waste circling these currents. The accumulated rubbish is subsequently removed from the oceans and recycled to produce sustainable products.
The technologies engineered by The Ocean Cleanup are simple, yet highly effective. Their passive, floating systems concentrate and collect rubbish using a net which extends downwards from a buoyant barrier at the water’s surface. These systems are carried by the wind, waves, and currents, following the same trajectory as the plastic debris circling each gyre. Additionally, an anchor is used to slow down the system, so that it can effectively capture and retain the plastic waste, which usually floats at higher speeds.
One organisation that has pioneered such efforts is The Ocean Cleanup, which impressively aims to remove 90% of ocean plastic by 2040.
This operation proves efficient for multiple reasons. First, the systems are able to capture plastics ranging from millimetres to tens of metres in size. Second, the carbon emissions produced during this process — mainly from fuel usage — are often compensated for by the purchase of carbon credits, which support further environmental projects. The final reason is that these cleaning systems are highly effective at sequestering only plastics from the oceans. Extensive visual and acoustic monitoring carried out by scientific experts have indicated that these systems do not substantially interfere with marine life, and neither marine animals nor protected species have been observed to become entangled in the nets.
Such cleaning operations clearly prove crucial for supporting coral reefs. However, plastic is not the only threat to these fragile aquatic ecosystems. Ocean acidification and increasing water temperatures are two additional processes that have profound effects on the biogeochemical cycles of the ocean, and they are responsible for much of the coral reef destruction observable today. Both processes are the direct result of harmful anthropogenic activity.
Increasing water temperatures cause corals to experience stress– as a result, they expel the photosynthesising algae whom they have a symbiotic relationship with. The corals thus turn white in a process known as “coral bleaching.” If temperatures remain high, the corals eventually begin to starve since the algae is no longer present to provide around 90 percent of the corals’ energy. Upon death, the corals turn brown, and they cease being able to support a multitude of marine species, which depend on the corals for their food source and survival.
In addition to absorbing the excess heat caused by global warming, the ocean has also taken up around 25 percent of all the extra CO2 emitted by humans into the atmosphere since the Industrial Revolution. This has resulted in a 0.1 unit drop in seawater pH, which corresponds to a 30 percent increase in ocean acidity. In turn, this increase diminishes the abundance of carbonate ions present in the water. This proves detrimental for calcifying organisms, such as oysters, calcareous phytoplankton, and corals, which rely upon carbonate ions to build and maintain their shells or coral skeletons. Specifically, as carbonate ion concentrations in the ocean decrease, corals start to grow at a significantly slower rate, they become more brittle, and they also erode faster than they accrete.
Multiple scientific solutions are being developed to help improve the resistance of corals to increasing temperatures and ocean acidification.
Multiple scientific solutions are being developed to help improve the resistance of corals to increasing temperatures and ocean acidification. For example, one research group previously collected coral fragments that had experienced a heatwave and survived. These fragments were subsequently grown on mesh platforms that were located in sandy lagoons close to the reefs for a few months. When the corals had matured enough, they were transplanted back to the reef matrix, undergoing propagation. It is hoped that such interventions speed up reef recovery, since the natural process of coral reproduction often occurs too slowly for the reefs to survive a series of successive bleaching events.
A different restoration method uses a similar procedure, however, in this case corals that have already adapted to thrive in hot, acidic conditions (such as mangroves or hydrothermal vents) are used as the research subject. Specifically, interest lies in transplanting either the entire corals, their genes (which provide them with resistance to hot and acidic conditions), or their heat-resistant symbiotic algae into more vulnerable coral reefs. These vulnerable reefs — which are contrastingly damaged by such acidification and increasing temperatures — will benefit hugely from such restoration methods, as the more resistant corals will improve the ecosystem’s stability. While it is certain that human activity will not cease to threaten coral reefs until their environment has been restored to endurable conditions, such efforts may help to significantly mitigate any further damage caused until we reverse our devastating impacts on our oceans.
…people across the globe, including those involved in the science and tech industries, are slowly waking up to the destruction humanity has caused.
In conclusion, coral reef ecosystems are suffering immense levels of stress from the environmental damage caused by anthropogenic activity. With plastic pollution and ocean acidification only following an increasing trajectory, and with bleaching events expected to occur once a year by 2050, the picture-perfect, utopian vision we have for our coral reefs will be far from the reality. However, people across the globe, including those involved in the science and tech industries, are slowly waking up to the destruction humanity has caused. Many of them are determined to face the facts of climate change, to improve our ways of life, and to repair our ecosystems. New ideas and programmes for restoring biodiversity are becoming increasingly explored and implemented, and progress is steadily being made towards reducing our environmental impact. As a result, providing that we work with nature rather than against it, it is possible to envision a hopeful and optimistic future for our coral reefs.
Art by Nadja Vitorovic
UnEarth Magazine 
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