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Scitech | Stayin’ alive

The Great Barrier Reef isn't completely dead yet

On October 11, an article entitled “Obituary: Great Barrier Reef (25 Million BC-2016)” went viral, defying expectations for scientific articles. Although its overnight popularity was a great step for science journalism, the sensationalist article also spread misinformation, making it seem as though the Great Barrier reef had already died, and cannot be revived. In reality, while almost a quarter (22 per cent as of July, to be exact) of the Great Barrier Reef has died due to coral bleaching – which is the expulsion of marine algae from coral tissue, which leaves coral completely white (hence the name) – that still leaves 78 per cent which amounts to about 270,000 square miles still alive. Given this mass, the Great Barrier Reef can continue to be the only living structure visible from space. While this coral might not be healthy, it is salvageable if changes are made.

What is coral?

When you think of coral, you probably think of an interestingly shaped rock, right? Wrong. Coral is actually a marine animal in the phylum Cnidaria, which also includes jellyfish. Much like jellyfish, corals start their lives as minuscule organisms called polyps; as they develop, the polyps secrete calcium carbon ate, a mineral compound also composing the shells of sea snails, oysters and mussels. This mineral layer acts as a protective exoskeleton, as well as bonding the individual polyps together, ultimately forming what we know as coral. As more and more corals, often as different types, connect skeletons, they form large units that are referred to as coral reefs, the most famous of which is the Great Barrier Reef.

The Great Barrier Reef is unique both for its size and biodiversity. Larger than the size of Italy, it is composed of 2,900 individual reefs and 900 islands. Thirty species of whales, dolphins, and porpoises, over 1,500 fish species, seventeen species of sea snake, six species of sea turtles, and countless more organisms consider the Great Barrier Reef as their home – many of these species are endangered, and some are endemic to these reefs.

The reefs and climate change

When we think of climate change, we rarely think of the oceanic wildlife. We think of polar bears, the melting ice caps, and rising sea levels, but not what’s going on underneath the sea. However, there are two major outcomes of climate change that are devastating for marine life: increases in oceanic acidity, and increases in water temperature.

The process of ocean acidification begins with the accumulation of atmospheric carbon dioxide, which then dissolves into seawater. This leads to the formation of carbonic acid, which lowers the pH levels of the oceans, making them less hospitable for marine life. The increase of sea temperatures indirectly has a similar effect on coral through what is called ‘coral bleaching.’ Both of these outcomes are devastating for coral reefs. More acidic seawater will wear down existing corals, as well as slowing down new growth; increased temperature results in coral bleaching. The marine algae and coral have a symbiotic relationship – the coral provides the algae with a safe home, and the algae provides up to ninety per cent of the coral’s energy, which the coral then uses to grow and reproduce. When a coral is stripped of this algae, it starves and ceases to be able to grow and reproduce, further contributing to the reef’s decay.

In recent years, the health of the Great Barrier Reef has been steadily declining. Since the Industrial Revolution, ocean pH has dropped from 8.2 to 8.1 – while this might seem like a minute change over hundreds of years, the pH acidity scale is logarithmic, so this variation actually represents a thirty per cent increase in acidity. This March, Australia’s National Coral Bleaching Task force reported the most severe bleaching on record: 93 per cent of all coral reefs were affected – even the hardiest species had turned completely white. While the state of the Great Barrier Reef is disconcerting, anything but total death is reversible, and some corals are particularly resilient. If the temperatures which cause coral bleaching revert to their normal levels, algae can return to their coral homes, and corals will feed, grow, and regain their normal colour. They will experience stunted growth and increased susceptibility to disease for a time, but they will not necessarily die.

More acidic seawater will wear down existing corals, as well as slowing down new growth; increased temperature results in coral bleaching.

Ocean acidity is also not a sure mark of death. Some coral can use bicarbonate rather than carbonate ions to create their exoskeleton; as bicarbonate concentration increases as oceans acidify, this substitution can then serve as a buffer to the weakening effect of acidification on coral exoskeletons. Some coral are also adapted to a wider range of pH’s, while some can even survive without a skeleton and restore their exoskeleton once a comfortable pH is reached.

The Great Barrier Reef ’s future

Although it is not likely that the pH of the ocean will rise back to what it used to be, or that the average temperature of the Earth will decrease, if these factors are kept from worsening further as much as possible and additional stressors such as pollution and overfishing are mitigated, the Great Barrier Reef will survive. Ocean acidification can be lessened by decreasing atmospheric carbon dioxide levels, something we can all contribute to by having a smaller carbon footprint. Driving less, using a more fuel-efficient vehicle, taking the bus, biking, or walking are all great ways to do this, as are using eco-friendly fluorescent light bulbs, unplugging your devices when they’re not in use, and buying local products. While the effects of climate change are severe and often irreversible, it is important to realize that changing our habits in order to be more environmentally friendly can have an impact; it’s not too late for the Great Barrier Reef, so we shouldn’t give up quite yet.


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