In a recent episode of the BBC’s Blue Planet II, a number of various species were shown interacting in some of the healthiest reefs in the oceans. The episode emphasised that the reefs were under threat from rising ocean temperatures – a critical interference with the corals’ symbiotic relationship with the algae living within them that keep them alive; this interference causes the corals to expel the algae in a process called bleaching.
Bleaching leads to the death of coral colonies that build up the reefs. Ocean warming events linked to climate change have become more frequent in recent years, affecting reefs across the globe. Yet these warming events are predicted to become even more frequent in the future. Corals reproduce through spawning en masse to form polyps which will settle away from the parent corals to form new reefs.
Most coral reefs are already damaged by both warmer seas and human interaction through pollution, chemical run-off, and destructive methods of fishing such as deep-sea trawling. It is estimated that around 75% of the world’s coral reefs currently threatened and more than 30% have already been destroyed in the past 30 years, with 75% being predicted to die by 2050. Only 27% of reefs are found in marine protected areas, with the majority of those being away from human populations – thus already at a lower risk of damage from human factors.
What Can Be Done?
Corals that grow too close together will crowd each other out and eventually die; to avoid this, some are taken in a process called coral farming or gardening. Coral farming involves collecting parts of living corals from reefs, giving the remaining ones more room to grow safely, and the uprooted ones a chance to grow somewhere new. Each coral is then safely divided into multiple parts called fingers which will all continue to grow, and attached onto concrete discs where they are raised in an aquatic nursery for a year or two where they are broken down again (each finger can multiply into at least 50 in two years) and replanted into the reef.
This process takes some time: a couple of years are needed to grow the corals on the farm, and then another year for the replanted coral fingers to grow and bloom on the reef. It has been a success in small-scale but takes too long for it to be a viable method of conservation for larger reefs.
There is, however, a faster method of coral farming. Using land-based farms and a process called micro-fragmentation, results have shown growth rates 50 times greater than those of aquatic-based coral farms. Each coral is separated into small pieces before growing – as opposed to individual fingers – thus producing corals more resilient to changes in oceanic conditions, making it a more viable conservation method.
Despite this, the main causes of bleaching, such as greenhouse gas emissions, need to be addressed before any conservation work becomes a long-term solution rather than a short-term fix. As shown in Blue Planet II, coral reefs are amazing ecosystems in danger – there is time to save them if we act quickly.