Genuine Fake

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.

Great-Barrier-Reef

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.

coralatrisk

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.

GreatBarrierReefcolourful

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.

coral-bleaching

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.

Samoan reefs

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.

Collecting Samples For StudyTo 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?

Worlds-coral-reefs-at-risk

Want to know more about the state of reefs? This video gives an interesting, but sad perspective on their decline.

Coral reefs & climate change (full version) from Earth Touch on Vimeo.

Inspired by:
Mascarelli, A. (2014) Climate change adaptation: Designer reefs. Nature. 508:444-446.

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The Sea Butterfly Effect

Imagine for a minute that the air in which you live is a thicker, fluid medium growing gradually more and more acidic as another species much larger than yourself pumps gas into it. Now imagine it dissolving away your skeleton leaving you defenceless to predators.

Web

Apart from the fact that you wouldn’t be able to breathe, it may seem a little extreme, but this is what is happening to the exo-skeletons of the ocean’s tiny butterfly snails; pteropods.

sea butterfly 2

Pteropods are free-swimming marine gastropods, most less than 1cm long,  which have developed wing-like flaps instead of a muscular foot which they beat to stay afloat. They are a type of zooplankton and make up a hugely important part of the base of the ocean’s food-web. They are prey to krill, small fish and even shellfish.

With the rise in atmospheric CO2,the oceans have absorbed an estimated one third of human carbon emissions. The oceans act as a carbon sink, slowing the effect of global warming, which is great for us terrestrial beings, but poses multiple threats to marine life.

CO2 gas from the atmosphere reacts with water molecules to make carbonic acid (CO2 + H2O = H2CO3) this is why the ocean is ‘souring’ and becoming more acidic.

This poses the first problem to the pteropods as it causes the dissolution of their shells. The second problem is that the carbonic acid partly dissociates to make bicarbonate (H2CO3 = H+ + HCO3). This dissociation decreases the availability of carbonate ions that the pteropods use with calcium to lay down new shell.

The declining pH of the water not only affects the sea butterflies, but all the shelled marine organisms and has costly knock-on effects for marine food-webs and the rest of the ocean.

Ocean FoodWeb

In this “Sea” Butterfly Effect, changes in the abundance of these small and seemingly inconsequential critters could result in large-scale trophic shifts or ‘algal blooms’. There will be less food for their predators and they will no longer be controlling the phytoplankton populations.

A group of scientists recently discovered that the shells of Limacina helcina, a species of pteropod, are dissolving and have proposed that they be used as an indicator of declining habitat suitability due to ocean acidification. As Kintisch (2014) put it, ‘Sea Butterflies are a canary for ocean acidification’. They could be our early warning system, like canaries in a coal-mine.

The study measured aragonite, a relatively soluble form of calcium carbonate that organisms use to form their shells. Rising levels of CO2, combined with the increase in sea-ice melt, decrease the saturation of aragonite meaning that less is available to lay down new shell material. They looked at the proportion of shells that were damaged and related it to the saturation of aragonite in the water. They found that the less aragonite was available the more individuals’ shells were damaged.

Damage related to undersaturation

This next picture shows how a shell (A)  is damaged after being in acidic conditions for six days (B).

pteropod before and after exposure to acidification

The study focused on the pteropod-rich California Current ecosystem, an area known to be an acidification hotspot. Winds drive coastal upwelling which brings colder, naturally more acidic water to the surface. The organisms which live there are well adapted to the conditions and that was why the researchers did not expect to see a high degree of damage.

Previously, it has been shown that this damage makes pteropods more vulnerable to infection and predators and can make it harder for them to maintain buoyancy and metabolic activity. Some snails have been able to patch themselves up from the inside, but the decrease in carbonate ion availability will make this harder to do.

Further research into the resilience of these pteropods is imperative for the economy of local fisheries. The Californian fish stocks as well as stocks all over the world rely on stable pteropod populations and the things that eat them as a food source. If pteropods can’t adapt then these fisheries are at the risk of collapse.

Using pteropods as ‘canaries’ may be more important in the polar regions as CO2 is more readily absorbed in colder waters. It is also important in coastal areas as these appear to be breeding grounds due to the high numbers of juveniles found.

The impacts that they have observed will form a baseline with which to compare the effects of further ocean acidification. There is much uncertainty around what impacts changes in sea butterfly populations will have on their ecosystems. Much will depend on the resilience of the pteropods themselves; whether their predators can switch prey and whether other zooplankton which don’t have shells can fill the niche. Whatever the ramifications, these sea butterflies and their response to the rising CO2 will put the effect in motion.

For a very short-and-sweet video on the importance of pteropods take a look at this video.

This post was inspired by an article in Science (paywall).

Kintisch, E. (2014) ‘Sea Butterflies’ are a Canary for Ocean Acidification. Commenting on:

Bednarsek, N. et al. (2014) Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem. Proceedings of the Royal Society B. 281:2-8.