What’s on your bucket list?
? See the Niagara Falls
? Watch the Northern Lights
? Cruise up the Amazon River
It’s hard to imagine that there will be any change to these extraordinary sights in a hundred or even a thousand years, but one such place may be gone before you are.
The Great Barrier reef which flanks the North East coast of Australia is our planet’s largest coral reef system and is the biggest single structure made by living organisms. While that makes it a marvel it is also what makes it mortal.
Because the survival of living structures is dependent on their surroundings they are vulnerable to changes in factors like temperature, food supply, salinity, predation and acidity.
With warming waters and acidifying oceans it is no wonder that the world’s coral reefs are suffering. Since 1950, 19% of the coral reefs have been lost and a further 35% are threatened or in critical condition. However warming and acidification are disproportionate and so is the loss. Areas like the Caribbean have lost 80% of their reefs and face considerably more warming and a decrease in pH by the end of this century.
Hard coral reefs are made up of small colonial Anthozoans which convert carbon dioxide in the water into calcium carbonate skeletons. Many corals have a symbiotic relationship with zooxanthellae which give the corals their colour. The coral skeleton provides protection and anchorage to microscopic unicellular algae which, in return, photosynthesise providing the coral with nutrition. This mutualism results in the most marvellous and diverse ecosystems which provide a home to anemones, starfish, shrimp and many other species.
The sad thing is that this mutualism is mortal and becomes disrupted when either partner is adversely affected. Unfortunately, reefs are under attack from both sides. In my post, The Sea Butterfly Effect, I explained how the increase in atmospheric CO2 causes the oceans to become more acidic and how it decreases the availability of carbonate ions which shelled marine organisms need to form their skeletons. With the increase in anthropogenically produced CO2 we have surpassed the levels of acidity that corals flourish at, making it harder for them to lay down new skeleton. On the other side, the increase in warming is affecting the zooxanthellae which do not survive temperatures warmer than 29°C. Rising sea levels are also increasing the depths of the reefs allowing less light to penetrate making it harder for the algae to photosynthesise. Pollution and increases in suspended sediment also decrease the light that reaches the reefs.
You know how when white light hits a prism it splits into the colours of the rainbow, well the complete opposite is happening to our reefs. The combination of acidification, warming, sea level rise and pollution results in the phenomenon known as coral bleaching. Under stress conditions the coral expel the zooxanthellae and then starve.
Ultimately, it is human development along with overfishing that is causing the startlingly fast loss of this unique habitat. In reading some comments around the issue I found one sarcastic Sam who says “Never mind, we can use our old motor tyres for a home for the fish. They’re just as beautiful.” and while most people are disgusted by how much humans are impacting the planet, critism doesn’t help a stitch.
It is now, at the 11th hour, where a team of scientists have decided to see what they can do to ‘throw threatened reefs a lifeline’. Palumbi, a marine biologist at Stanford University in California along with other coral researchers around the world have become interested in a reef which thrives in temperatures which would kill most corals. Off the coast of the South Pacific island, American Samoa, the lagoon hosts antler-like branching corals and huge mound corals.
What Palumbi and his team aim to do is harness the Samoan reefs’ ability to survive these harsh conditions and use it to create a hardy coral that has a chance of surviving the warming oceans. Starting this month, they aim to plant “the smartest future reef” they can imagine.
To determine which corals would make good transplant candidates they placed samples from a cool and a hot pool into controlled tanks and exposed them to temperatures of nearly 3°C above normal for four days. After this time all of the corals were bleached, but those that came from the hotter pools survived longer and had a higher expression of thermal-tolerance genes known to make heat-shock proteins and antioxidant enzymes.
Palumbi suggests that it is the genetic fitness and acclimatisation of the corals from the hotter pool allow them to better survive the environmental conditions. These heat-tolerant individuals also seem to survive transplants better. They plan to use experiments like these to find the fastest-growing and most heat-resistant corals for their smart reef. They will compare the growth of their smart reef to the growth of a second reef constructed from corals picked at random and see which survives better over the next few years.
The important things is that stress resistance developed through acclimatisation needs to be able to be passed on to offspring otherwise it will not be of use to future generations of coral. Another team based at the University of Hawaii have found that adult cauliflower corals (Pocillopora damicornis ), exposed to stress during brooding, produce larvae that are more resilient to high temperatures and low pH. This trans-generational protection is hypothesised to be due to epigenetic changes effecting gene expression. This team aim to cross-breed corals that have survived bleaching and then track the resilience of the offspring.
While for this type of smart-reef to work it is important to find a hardy coral, it is essential that the symbiotic algae are also stress tolerant. Fortunately the algae are shorter lived and therefore faster evolving than the coral host and other studies have already shown that they can pass on thermal tolerance to their offspring.
So far the research suggests that producing a smart-reef is possible, but is it a good idea? Their work will involve manipulating natural systems and essentially result in ‘human-assisted evolution’. We know that selective-breeding programmes can lead to genetic bottlenecks: the genetic variation is narrowed resulting in a decreased ability of the population to adapt to further changes. We also know that enhancing some traits can often come at the expense of other traits, such that heat-resistant corals may be less resistant to disease. We don’t know yet whether these trade-offs are worthwhile.
While some are completely against the idea of manipulating systems, sometimes it could be the only thing preventing the loss of an entire ecosystem.
Not only are coral reefs a beautiful sight, but some 500 million people depend on them in some way for food and income.
How do you feel about altering ecosystems and their ability to adapt to changing conditions? Are these designer reefs genuine? Or fake?
Want to know more about the state of reefs? This video gives an interesting, but sad perspective on their decline.
Mascarelli, A. (2014) Climate change adaptation: Designer reefs. Nature. 508:444-446.