While we have been immersed in news of the global COVID pandemic the Great Barrier Reef has experienced a major bleaching event for the third time in five years. The reef experienced the hottest water temperatures on record since people started keeping reef temperature records in 1900. The Guardian has a short summary article that is worth a read.
For those of you who are asking, what is bleaching? Why is it bad? Here is a little primer on corals and bleaching. Corals are a tiny colonial animal. They are related to anemones and jellyfishes, so they have tiny tentacles with stinging cells. That’s not really the important part.
Corals have soft bodies made of two tissue layers. Microscopic algae (single-celled organisms) called Zooxanthellae live inside the cells of the inner layer. The Zooxanthellae are photosynthetic and provide corals with most of the energy they require for living. They are also responsible for giving corals their colors (all those photosynthetic pigments). The rest of the nutritional needs of the coral are met by capturing plankton with their tentacles. While the corals themselves are soft-bodied, they do make what is referred to as a skeleton. This is a hard base of calcium carbonate that the coral sits anchored in. This must be continuously maintained and built up. The coral expends energy to do this.
Corals are like Goldilocks (reference to Goldilocks and the Three Bears children’s story...do people read this to their kids anymore? Am I dating myself?). They have very specific environmental needs. We’ll use temperature as an example. The corals need water that is not too cold, not too warm, but just right. If the water gets too warm (hello global warming!) the Zooxanthellae malfunction and stress the coral out. The coral then kick the Zooxanthellae out of their cells. When the Zooxanthellae are gone, the corals lose their color and appear white, hence the term “coral bleaching.” Here’s a great animation about bleaching if you want to know more details. The corals can live for a little while without their Zooxanthellae because they can still capture plankton with their tentacles and live off of stored energy. But eventually they can’t survive without all the energy the Zooxanthellae provide, so they die.
Why should people care about corals dying? Coral reefs provide shelter and food for thousands of other species of marine organisms, most of which are not found in other ecosystems and many of which may produce compounds that could be used medicinally. This abundant wildlife supports ecotourism in many parts of the tropics and subtropics; reefs are estimated to generate $1 million per kilometer. Coral reefs also provide food for people (nearly 1 billion people are estimated to rely on reef ecosystems for food) and are important buffers to storm wave energy that could damage coastlines.
There is some hope that corals will become more resistant to bleaching. There are some kinds of Zooxanthellae that can tolerate higher temperatures than others. These Zooxanthellae have been found to become more common on reefs after bleaching has occurred (see Baker et al and Stat & Gates). This suggests that corals can switch to a more advantageous type of Zooxanthellae. Some researchers have even experimented with “planting” corals on reefs that have the resistant Zooxanthellae living in them. But even those heat-resistant Zooxanthellae have their limits with experimentally demonstrated high bleaching levels above 33°C. This recent heat wave on the Great Barrier reef saw temperatures of 31°C. What will the sea surface temperatures be in 10 years? By 2050? If even the most thermally tolerant corals and their zooxanthellae are subjected to temperatures over 33°C, reefs are likely to become a relic of the past and with them all the benefits that we get from the reef biodiversity.
So, what can we do about it? You know the drill! Look back at my old posts for a myriad of personal actions you can take to reduce greenhouse gas emissions and advocate for legislative change. Most importantly, you can vote in November. We need a sea change in the government of this country. Clearly the current administration needs to go, as they have been systematically dismantling all environmental regulations in this country and consistently denying that climate change is happening (here’s a link to that climate change deregulation tracker again, just for fun. Clearly we also need to get people who understand the seriousness of the climate crisis in control of Congress. Generally, that means you should vote for Democrats and not for Republicans. It’s funny how things have changed in the past 40-something years. It was under the Republican Nixon administration that all the great environmental legislation of the 1970s was passed. George H.W. Bush even campaigned on the promise to protect Americans from the threat of climate change in 1988 (of course, the tune changed during his administration, but there was a point when he acknowledged the dangers). Now the Democrats are the party of climate change action. If Democrats control both the House and the Senate, we could get some climate change legislation passed. So, vote Democrat whenever possible. And yes, no politician is perfect, but we need some that will at least do no more damage than has already been done (that’s the low bar) and ideally some that will start to make significant progress to reduce greenhouse gas emissions (that’s the high bar...let’s shoot high).
Commentary on environmental news/issues plus thoughts and stories about my journey to lower my environmental footprint and raise my voice.
-Another vegan environmentalist