A publication recently released in Science (BBC article) focuses on the prevalence of plastic in coral reefs. Over three years, researchers surveyed over 150 reefs across Indonesia, Australia, Thailand, and Myanmar. The worst plastic pollution was seen in Indonesia, and Australia showed the most promising results. Plastic was found distributed over one-third of the surveyed reefs. By blocking out light and decreasing available oxygen, plastic can cause a 20X increase in a reef’s risk of disease. Researchers estimated that 11 billion pieces of plastic waste were on the monitored reefs and expect that figure to rise to 15.7 billion by 2025.
I thought that this article was rather good timing as I had just finished summarizing the Chasing Coral documentary. If you have never seen the documentary, it is on Netflix and worth a watch. The film focuses on the increasing phenomenon of coral bleaching rather than plastic pollution, so I enjoyed being able to add some up-to-date, helpful information about another top threat to coral reef health. Below are the main highlights from Chasing Coral if you are not able to watch the full hour and a half documentary.
One primary issue facing marine conservationists is that most people do not see what’s actually IN the ocean. On the surface, we just see beautiful waves and (hopefully) well-maintained beaches. Hence, researchers decided to produce Chasing Coral, a documentary depicting real-time coral bleaching, in an attempt to engage and educate the public on this very real threat that has diminished the world’s corals by 50% in the past 30 years.
Corals are animals comprised of a multitude of polyps and come in all shapes and sizes. Millions of polys can occur on a single coral! Microalgae live inside coral tissues as part of a symbiotic relationship. The microalgae photosynthesize during the day, providing the coral with nourishment, and the coral provides shelter for the algae. During the night, the coral’s tentacles obtain food to help sustain the animal. Corals are important nurseries for fish, and it is suggested that 25% of all marine life relies on coral reefs. Over a billion people rely on coral reefs for their livelihood, and many drugs, including cancer-fighting ones, are created from marine sources. Moreover, reefs also play an important role in protecting land from large weather surges and cyclones.
Coral bleaching is directly related to climate change, and corals can begin to bleach if water temperatures increase by 2oC. (If you are thinking, 2 degrees?! That’s nothing! Just remember how much a slight difference in your own body temperature affects your health.) Approximately 93% of heat trapped by greenhouses gases, like carbon dioxide, is transferred to the ocean. If the ocean did not absorb this heat, the average land temperature would be closer to 122F rather than 58F! Corals bleach as a stress response to increased water temperatures. Similar to how humans purge when sick, corals purge as well. However, they purge their microalgae, leaving behind the characteristic white skeleton. Subsequently, the corals then begin to starve. Bleaching is reversible, but it is extremely difficult to achieve. (NOAA page on bleaching with pictures.)
- Bleached Fire Coral
To convey the magnitude of coral bleaching, the film team designed time-lapse cameras but end up having to do individual dives daily on several reefs to achieve the desired photographs. Among other locations, the team surveyed in Hawaii, Bermuda, Australia, and the Bahamas. The majority of footage shown ends up being from multiple locations around the Great Barrier Reef. The corals in New Caledonia actually started fluorescing in bright blue, green, and purple colors. These vivid colors were actually caused by the corals trying to produce a type of chemical sunscreen to protect against the heat! In total, the film shows two years of shocking time-lapse videos/photographs depicting coral bleaching. Soft corals also exhibit rapid tissue necrosis and literally rot and disintegrate. The average projections show that the majority of corals will be dead in 30 years because they will begin to bleach every year due to global warming and be unable to recover. The first recorded mass bleaching event was in the early 1980s. Bleaching on a global scale was documented between 1997 and 1998, with the second global scale mass bleaching in 2010. In 2016, almost 30% of the Great Barrier Reef died.
Overall, the film displayed some amazing footage, both good and bad. I am really excited that they made this documentary, and it seems to be doing a good job of raising awareness about coral reef health and their importance for maintaining a healthy ocean. I would highly recommend watching the film, but if you can’t, I hope you learned something new from my post. You can also visit chasingcoral.com to learn more about what you can do to help protect reefs around the globe. From the article I mentioned initially, it seems like recycling and reducing plastic waste would be a good place to start!
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