Australia’s Great Barrier Reef, one of the most diverse ecosystems on the planet, is currently facing its sixth mass bleaching event. A symptom of climate change, mass bleaching events signal that the coral is in distress, holding implications for ocean ecosystems as well as the communities that rely on them.
What is Coral Bleaching?
Coral bleaching occurs when corals are under distress, most commonly in response to rising ocean temperatures. According to the Great Barrier Reef Foundation, when the corals are stressed, they expel the algae that live inside them: zooxanthellae. Zooxanthellae are essential to the thriving of corals, contributing to food production, waste removal and, most noticeably, giving them their iconic range of hues. Therefore, the transformation of coral reefs from vibrant wonderlands to white graveyards suggests that more is at stake than appearances.
While corals are relatively sensitive, with ocean temperature increases of just one degree Celsius for four weeks being able to trigger bleaching, they are not so quick to die. It is only after eight or more weeks of high temperatures that coral may begin to perish, suggesting that despite the fear surrounding the Great Barrier Reef’s latest bleaching event, many of the corals could pull through.
What’s Happening to the Great Barrier Reef?
Last week the Reef Authority and the Australian Institute of Marine Science confirmed a mass bleaching event on the Great Barrier Reef after conducting several aerial surveys. There are four management areas of the Reef, all of which contained bleaching. The bleaching patterns observed were highly consistent with areas of heat stress over the summer; however, with Australia entering autumn, it would typically be expected that ocean temperatures would have fallen in recent weeks an expectation that in an unfortunate turn of events for the Reef, appears unfounded.
In an April 1 update from the Great Barrier Reef Marine Park Authority, it was reported that temperatures across the Reef had stabilized at a lower, more conductive point than was observed in the early weeks of March. However, even with this improvement, the Reef is still experiencing critical effects of heat stress. It is a time of great uncertainty for the Reef much of the corals’ health depends heavily on localized weather patterns in the upcoming weeks.
As of right now, data is being analyzed to determine the true extent of the damage; however, preliminary observations suggest that the majority of reefs surveyed showed signs of bleaching. The areas that have experienced the greatest heat stress have also shown early mortality.
Why Should We Care?
Coral reefs, often referred to as the “rainforests of the sea,” are essential to the health of ocean ecosystems and, in turn, all communities that even remotely rely on the ocean as a means of food, work or otherwise. According to the National Oceanic and Atmospheric Administration, 25 percent of fish in the ocean rely on reefs in some capacity. Whether that be for shelter or reproduction, a place to find food or a place to rear their young many ocean ecosystems would simply collapse without the aid of coral reefs. Perhaps more pertinent to the everyday person is the extent to which humans rely on reefs. Reefs provide us with an abundance of help, from providing recreation to protecting coastlines from storms and erosion. Economically and environmentally, humankind relies on the health of the ocean to keep us alive.
So, What Can We Do?
Climate change is the primary contributor to coral bleaching events, meaning that protecting Earth’s coral reefs must primarily be done through combatting climate change. The Great Barrier Reef Foundation outlines two methods of reef protection: reducing emissions and helping coral reefs adapt.
In order to reduce emissions enough to save the reefs, immediate and drastic actions must be enacted globally to reduce greenhouse gas emissions. In the meantime, facilitating and strengthening ecosystems that absorb carbon dioxide for example, wetlands can begin to reduce levels of greenhouse gases in the atmosphere.
Scientists are currently working on interventions that will aid coral reefs in surviving through rising ocean temperatures. For example, using reefs that flourish in naturally cooler water as a refuge for corals experiencing bleaching or breeding heat-resistant corals that could be integrated into existing reefs.
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