Ocean Acidification and the Impact on Coral Structures

There is little knowledge on the effects of acidification in the ocean and how that impacts the physiology of coral reefs. Corals build their structures towards the sunlight and thicken them in order to add more strength underneath them. New research is being done in order to understand how acidity in the ocean can cause these skeletal coral structures to be weaker than normal and be more vulnerable to breaking. With this research, scientists are able to predict where corals may become more or less impacted. Overall coral reefs endure multiple stresses, which include rising sea levels, changing nutrient regimes and warming sea temperatures. Ocean acidification is much harder to detect and predict due to the slow and gradual negative affects it deals with these corals. That’s why understanding these effects are crucial in possibly saving these rich biodiverse ecosystems.

Ocean acidification occurs through the absorption of CO2 from the earth’s atmosphere. About 30% of the CO2 emitted into the atmosphere by humans is absorbed into the ocean. This lowers the pH of the surface water levels and in turn, affects the ability of corals to produce calcium carbonate. Coral polyps use CO32- in order to produce CaCO3 for their skeletal structure. The coral takes in seawater that contains HCO3-, CO32- and Ca2+ ions, which in turn can allow the production of CaCO3 for their skeletal structure.

In this particular study, the effects of prolonged exposure to CO2 is analyzed and compared to the bleaching of corals that are usually correlated with the warming sea temperatures. The idea is that the warmer temperature along with the abundance of carbon dioxide will have a symbiotic effect on the overall coral bleaching. Three of the hypotheses looked into are the effects of initial carbon dioxide exposure, how it affects the overall organic productivity and how it changes the rate of calcification.

In order to replicate these variables and how they affect the bleaching of corals a two-step carbon dioxide dosage, an intermediate and high dosage, was given along with a two-step temperature variable in order to reproduce the same real-life situations. As well as the use of a control that only underwent the temperature changes, this allows for comparison purposes.

Figure 1: Effects of experimental ocean acidification and warming

Results showed that the high-level carbon dioxide dosing had an effect on two of the reef-building organisms at up to 40 to 50%. Overall it is determined that prolonged carbon dioxide exposure had bleaching impacts on two of these reef-building organisms. Although, in the Acropora species at the intermediate carbon dioxide rate the net productivity was maximized. This could be due to the abundance of carbon dioxide being directly used in the photosynthesis process, but at the higher dosage of carbon dioxide, the productivity decreased suggesting that abundance still has a negative effect.

The next step of understanding these coral reef deterrents is the combination of all variables and how they deter the growth of these corals. It is obvious that acidification is not occurring in isolation and that corals are not the only organisms that are being affected by this increasing amount of carbon dioxide in the water. It can easily be seen that we are affecting these organisms negatively and it is important to figure out how we are. That is why this study is significant because it challenges previous studies done that suggest the acidification of the ocean doesn’t impact these corals.


Anthony, K. R., Kline, D. I., Diaz-Pulido, G., Dove, S., & Hoegh-Guldberg, O. (2008). Ocean acidification causes bleaching and productivity loss in coral reef builders. Proceedings of the National Academy of Sciences, 105(45), 17442-17446. doi:10.1073/pnas.0804478105

Can Your Sunscreen Be Harming Coral Reefs?

It's a well known fact that wearing sunscreen is good for you. Whether it is preventing painful sunburns or skin cancer, sunscreen is an essential for many people. However, this innocuous product can potentially destroy coral reefs by affecting their health in several ways.

In a study published by Danovaro et. al. in 2008, sunscreen chemicals were found to cause rapid bleaching of hard corals by the induction of viruses that target the symbiotic zooxanthellae living on the corals. Coral bleaching occurs after a disturbance causes a coral colony to expel the zooxanthellae that live with it. Although this doesn't kill the coral, the colony becomes much more susceptible to disturbances and mortality.

Sunscreen gets into the environment by washing off of people's bodies when they swim, snorkel, or otherwise submerge in the water. Sunscreen concentrations are especially high in areas with a lot of tourism, and has become such a problem that some areas ban tourists from wearing sunscreen. The authors of this study estimated that some where between 4,000 to 6,000 tons of sunscreen enter the oceans each year, threatening around 10% of coral reefs to chemical bleaching.

Sunscreen contains a multitude of chemicals; one being parabens. Parabens are slowly being removed from personal care products because they have estrogenic qualities, so it's not surprising that such a compound would be harmful to marine life as well. Along with parabens, butylparaben, ethylhexylmethoxycinnamate, benzophenone-3 and 4-methylbenzylidene camphor caused complete bleaching of hard corals, even at very small doses. Whether a coral bleached or not was not concentration dependent, however, the rates of bleaching increased as concentrations of these chemicals increased. Sunscreens contain other chemicals besides these, but they were shown to have little to no effect on coral bleaching. The bleaching effect is caused by the release of viruses from the corals and zooxanthellae into the water surrounding the corals. This phenomenon was only observed with the exposed corals and not the controls, suggesting that the chemicals stimulate the viral expulsion.

Impact of sunscreen addition on nubbins of Acropora.
Untreated (brown) and treated (bleached)
 nubbins of (A) Acropora cervicornis (Caribbean Sea, Mexico); (B)
 Acropora divaricata (Celebes Sea, Indonesia);
(C) Acropora sp. (Red Sea, Egypt); and (D) Acropora ...

But, how do you go about measuring coral bleaching? One method is to quantify the bleaching by performing colorimetric analysis on digital photographs of the corals before and after the experiment. The effect of the chemical on coral bleaching is calculated by taking the difference between the color value given for the coral before the study and the color value of the coral after the study. The significance of the difference was taken using an ANOVA one-way analysis of variance test. With each chemical isolated, this test allowed the authors to determine which chemicals bleached corals and which had little or no effect.

This study, cited over 200 times, suggests that chemicals in sunscreen can cause coral bleaching. However, the authors did claim that the levels of chemicals were likely higher than those seen in the environment. Because coral bleaching occurred at such low doses and was not concentration dependent, it is likely that the same effects would be seen in the environment. Overall, tourists need to be conscious of their sunscreen use and how their activities are affecting the marine life. People should avoid wearing sunscreen when visiting coral reefs or choose sunscreens that are free of cinnamtes, camphor derivatives, parabens, and benzophenones. Recognizing how we impact the surrounding wildlife is important for the health of the environment. Studies like Danovaro et. al. bring to light how a seemingly safe product like sunscreen could actually be harmful.

Danovaro, R., Bongiorni, L., Corinaldesi, C., Giovannelli, D., Damiani, E., Astolfi, P., … Pusceddu, A. (2008). Sunscreens Cause Coral Bleaching by Promoting Viral Infections. Environmental Health Perspectives, 116(4), 441–447. http://doi.org/10.1289/ehp.10966

Better ways of protecting Coral Reefs?

With coral reefs being destroyed by bleaching and ocean acidification new methods of conservation must be approached.  One of these approaches is by not putting all efforts into the coral reefs directly buy by better conserving the land around the reef.  Researchers Carissa Klein, Stacy Jupiter, Matthew Watts and Hugh Possingham tested six different conservation techniques on coral reef ecosystems in Fiji.  The primary objective of each approach was to achieve terrestrial conservation or to minimize land-based runoff.  They also compared these results with other conservation plans on how well they benefit coral reef conditions.

The researchers found that when terrestrial conservation was the primary goal that the reefs benefited by  7.7-10.4% greater than other protected areas that weren't focused on terrestrial conservation.  However, 31-44% of the terrestrial conservation was not achieved which means that there could be a higher percentage of benefit if terrestrial conservation can be achieved better.  These results are being used by the Fiji's protected area committee to better define conservation boundaries on land.



Another method that is being researched is to take more of a gardening approach to the reefs.  Studies are being done on how successful coral reefs, grown in labs, that are modified to withstand current oceanic conditions.  Artificial reefs such as concrete structures are also being used.

A more abstract study looks into if electrical currents can stimulate coral reef growth.  On Vabbinfaru Island, Maldives a 12 meter metal cage that weighed 2 tonnes was placed in the ocean and a small electrical current ran through it.  The electric current stimulates a chemical reaction that draws calcium carbonate out of the water and gets deposited on the cage.  Studies have also been done that found that the electric current helps them filter and adapt to warmer conditions because less energy is needed to form a skeleton.  One of the steel cages used is hard to distinguish now because of all of the colorful reef growth on the cage.

Unfortunately using these steel cages on a global scale would be extremely costly.  The only benefit of these artificial reefs would be from tourist areas or areas that are hit by temporary damage such as oil spills or boat impacts.  Many of the coral reef researches believe the only way to save the reefs is to greatly slash carbon dioxide levels across the globe, but they don't see that being accomplished.  Researcher Peter Sale said "By 2050, we may still have corals, and things we'll actually call 'reefs', but they will be massive limestone structures that were built in the past, with tiny patches of living coral struggling to survive on them." He adds "The world will go on without reefs, but its going to be very much inferior to the planet we have now."

References:
http://www.sciencedaily.com/releases/2013/12/131217155329.htm
http://www.sciencedirect.com/science/article/pii/S0308597X13002261#
http://www.bbc.com/future/story/20120905-save-our-dying-coral-reefs

Coral Bleaching & Disease

      Coral reefs support the worlds most biologically diverse marine ecosystems with many organisms relying on them for food and shelter. Nonetheless, coral reefs only cover a tiny fraction of the Earth's surface (less than 1%). Unfortunately, humans are a major threat to these ecosystems as our lifestyle brings devastation these diverse environments. Some of the threats caused by humans include pollution, destructive fishing, changing ocean chemistry, and last but not least, climate change. Due to the stressful conditions coral reefs are exposed to, they experience a phenomena called coral bleaching. Coral bleaching can be defined as a breakdown in the symbiotic relationship between coral and a unicellular algae (zooxanthellae). These algae live within the corals to help them grow and obtain food. When stresses, such as thermal stress arises, the corals will expel their zooxanthellae giving them a characteristic bleached appearance. Other stresses such as high light intensity, low salinity, and pollution are also linked to coral bleaching and the presence of coral diseases.

Bleached Coral Reef

     In reviewing an article by Ove Hoegh-Guldberg on coral reef ecosystems and anthropogenic climate change, he suggests that our current levels of carbon dioxide in the atmosphere are much too high to ensure the survival of coral reef ecosystems. I will further explore his interpretations of coral bleaching and microbial infections. Furthermore, I will investigate the idea that corals have different susceptibilities to different stresses, meaning the devastation of one species of coral does not mean devastation for all. The remainder of the article will be analyzed to see how much devastation coral reefs can take and the implications of the loss of coral-dominated reef systems.

     

     My analysis of another paper on the conditions of coral reefs in south Florida will include a presentation of percentages of coral reefs that are diseased and bleached to help indicate the condition of this ecosystem. This paper also looks at different diseases that affect corals and shows which diseases are most prevalent in southern Florida coral reef communities. The authors of this study found large amounts of coral devastation in the Florida Keys which will be analyzed in further detail in the research paper. 

     A final paper I will analyze studies the influence of habitat devastation (dead and/or bleached corals) on fish replenishment. More specifically, the fragmentation and degradation of marine ecosystems such as coral reefs due to anthropogenic climate change are expected to have devastating effects on the organisms that call coral reefs home. By monitoring daily fish settlement patterns, the authors of this article found that fish were ten times more likely to settle on healthy coral than bleached/dead coral. Further examination of this article will show that coral bleaching will affect the settlement of reef fish, reef organism distribution, and population dynamics.

Coral Bleaching

In the spirit of talking about coral reefs I decided to discuss the topic of coral bleaching.  As we discussed in class coral survive based on their symbiotic relationship with the zooxanthellae living directly in their tissues.  
When conditions are not favorable for the zooxanthellae( i.e. too cold/warm, too many pollutants in the water, corals have disease, etc) they are expelled from the coral and are therefore unable to continue giving the corals the energy they need.  This does not cause coral death but is extremely stressful to the coral to survive without the zooxanthellae.
These events of coral bleaching are causing not only the coral to die but are removing essential habitat for many organisms.  Since these coral reefs are the most productive areas of the ocean the removal of this habitat is a huge problem and the recent warming changes have reduced this habitat.  It is causing reduction of many fish because of lack of habitat areas to hide.  Continued bleaching of these corals could lead to extreme changes in these ocean areas.

References
Science Daily
Wikipedia Coral Bleaching
NOAA
World Press

Good Bacteria Turns Bad

This article ties in with the presentation that i will be presenting on next week. Coral bleaching is the whitening of coral, from the loss of their symbiont. Coral bleaching is an increasing problem due to the increased water temperatures. Coral reefs are very important to the human economy and to a vast diversity of animals.

This article talks about the bacteria that live on coral reefs, in normal conditions these bacteria produce a mucus layer that protects the corals. This mucus layer prevents the corals from getting infections from bacteria. However, with the increasing temperature of the water the mucus layer breaks down and the good bacteria are replaced with pathogenic (bad) bacteria. This model has also shown that once the water temperatures return to normal the pathogenic bacteria remain on the corals. The mechanism is not quite understood to explain the pathogenic bacteria remaining on the corals when temperatures return to normal. The water temperatures have been increasing over the past years and many steps need to be taken to improve coral reef habitats before they are lost forever.

Good Bacteria Turns Bad

Presentation Topic

I would like to present on global warming and the effects of El Nino's on Coral Reefs. Specifically, i would be looking at coral reef bleaching and most likely some ecological impact that bleaching has.

Here are three sources that i have found so far.

Climate change and coral reef bleaching: An ecological assessment
of long-term impacts, recovery trends and future outlook

The coral reef crisis: The critical importance...


Poorly cemented coral reefs of the eastern tropical
Pacific: Possible insights into reef development
in a high-CO2 world

Cold Erases Color

Coral colonies off the coast of the Florida keys were hit with so much cold recently, they turned white. It turns out, this idea is called "coral bleaching" and it occurs because of a major fluctuation in temperature. Between January 2nd and January 13th, the water temperatures around the keys were astonishingly lower than average. Normal winter averages for this area are somewhere between 18 and 23 degrees celsius. During this time, the temperature reached a low of 11 degrees celsius.
So where did the color go? Well, the beautiful coloration of coral comes from the algal organisms living on coral, creating a mosaic of colors depending on the algae species. So, when the temperature gets too cold, the algae die, leaving the coral a "bleach white" color. Not only did the cold snap affect the coral, many sea turtles and manatees reportedly died, along with an abundance of fish.
The recovery of a traumatic event such as this varies. Sometimes, the coral will make a complete, or almost complete recovery; however divers in this area are reportedly seeing many dead patches in the colonies.

The entire article can be found here