First Spontaneous Mutant Coral Symbiont Alga Found

Japanese researchers have recently identified the first spontaneous mutant coral symbiont alga that does not maintain a symbiotic relationship with its host. The alga have devised a system where the simple addition or depletion of a nutrient can switch the symbiosis on and off, experimentally. This alga, which is mutant, enables the development of a genetic transformation system. This system will eventually be a powerful tool for researchers studying coral-algal endosymbiosis.

Figure 1. Symbiotic and non-symbiotic state of the sea anemone E.pallida, respectively. 

A great source of biodiversity in the sea is coral reefs. Stable symbiotic relationships between host cnidarian animals and the symbiont dinoflagellate are what the ecosystem relies on. Environmental changes due to globing warming can collapse this symbiosis. An example of this is “coral bleaching”. Understanding mechanisms for maintaining stable symbiosis is extremely difficult.

Figure 2. Coral Bleaching Reference 

The mutant in these coral is deficient of uracil which is a basic compound of nucleic acid. This has appeared to have lost the ability to maintain symbiosis with a model organism. The model organism used in this case is the sea anemone. This is what indicates the simple addition or depletion of the nutrient which can be used as a switch for controlling the symbiotic relationship. The next step in this research is to introduce genetic mutations that are going to be capable of reversing uracil deficiency in the mutant dinoflagellate. This can hopefully provide clues for identifying algal genes responsible for symbiosis.

Source for Article and Figure 1: Tohoku University. 2018. New Mutant Coral Symbiont Alga Able to Switch Symbiosis Off. ScienceDaily. https://www.sciencedaily.com/releases/2018/02/180222103416.htm

Figure 2 Source: 

http://sites.psu.edu/ichen/wp-content/uploads/sites/38297/2016/04/coralbleaching.jpg

Hermit crab uses 'walking coral' as home

Hermit crabs are well known for making their homes out of empty shells. They will go from shell to shell throughout their lifetime trying to find the perfect fit and to gain better protection. However, it has recently been discovered that shells are no longer the only objects hermit crabs are using for protection. A species of hermit crab located in the Amami Islands, which is part of a chain that stretches southwards from Japan towards Taiwan, has been found to be using solitary corals for their shelter. This species of crab is named Diogenes heteropsammicola, after the species of coral that they inhabit.

Hermit crab (Diogenes heteropsammicola)

This relationship has proved to be mutually beneficial for both the hermit crab and the coral. By using coral as its protective armor the hermit crab no longer has to continue to search and search for new and better shells as it continues to grow. The space in the coral in which the hermit crab sits grows with the crab, so it does not need to search and compete among its species for new homes. In addition, the coral is able to sting, which helps to further protect the crab from predators such as starfish, larger crabs, and octopi.

A type of coral the hermit crab will use (Heteropsammia cochlea)

This relationship is also able to be favorable for the coral as this species of coral is a solitary coral instead of a reef-building kind. Solitary corals are often found on shallow sandy seabeds. With this type of habitat, the solitary coral runs the risk of being buried by sediment and overturned by strong currents. To combat this, corals will develop a partnership with other animals to assist them out of the sand and do the ‘walking’ for them. This is usually seen with marine worms, but is now prevalent in this hermit crabs species as well.

Coral skeleton after being used by hermit crab

Though more research needs to be done, it is thought this relationship with hermit crabs developed similarly to how the marine worms use the coral for protection. In the case of the marine worm, a young coral will settle on a small shell that has already been colonized by the marine worm. The coral then grows over and beyond the shell, providing a cavity for the marine worm, which is continuing to grow as well. These hermit crabs likely acquire coral shelter and develop this symbiotic relationship in a similar manner such as this one.




Mynott, S. (2017). Newly discovered hermit crab species lives in 'walking corals.' The Conversation, 12 March 2018.

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

Ocean Acidification

Ocean acidification has not yet been a major contributor to ocean problems but more and more studies have been focusing on this.  According to NOAA the ocean absorbs approximately a quarter of the Carbon Dioxide we release into the air every year.  As we discussed in class acidification of waters can happen through the reaction shown below and has the potential to hurt many habitats.  

Since this is just recently becoming noticeable in the oceans first signs of effects on the wildlife are beginning to appear.  The most noticed problem is inability to form calcium carbonate structures, which has been effecting mostly corals and animal that secrete shells.  

In one study done at Oregon State University there was signs that acid environment during larval development of oysters lead to an inability to grow correctly and to low recruitment levels   This immediately has an affect on businesses using oysters and other shelled animals to make a profit, but will soon be noticeable in the environment.  The reduction of these animals may be an indication of future problems to come and act as a sort of "canary in the coal mine" for the ocean.   

Although the results of this ocean acidification have not been immediately evident there are beginning to be signs that it is affecting the wildlife.  Since there are calcium carbonate animals such as corals that are already being greatly reduced in numbers it is important the situation becomes controlled as soon as possible.  Also, since areas of upwelling will soon be bringing waters that were previously acidified the situation will not just get better on its own.  

References

Science Daily

NOAA

Cool Coral Communities

Corals are animals in the Phylum Cnidaria, a coral polyp the main organism in the reef is made up of  a skeleton of CaCO₃. The coral polyps are not the only ecosystem engineers of this community; sponges, bryozoans, sea anemones, fish, crabs, worms, and many other animals all call the Great Barrier Reef home. Being the world's richest area of diversity the animals all work together to survive in such a complex ecosystem. There are fish, Parrotfish, that play a major role in the life of coral reefs because the fish eat the seaweeds that over grow the coral. Even though this is a benefit to coral, Parrotfish also eat coral adding to the complex ecosystem found within coral reefs. Coral reefs provide not only food but protection for many animals. Because corals are so fascinating and unique many people desire to visit them. Tourism in the Great Barrier Reef is a huge economic advantage as well as a potential danger to the corals themselves. Runoff into the reef can pollute the ecosystem causing the corals to die off. The pollutants can cause disease and death with in the corals. This destroys one of the most beautiful places on earth.

 Tourists can break coral off while scuba diving or snorkeling slowly diminishing the reef little by little. Since the tourism of the reef is such a huge economic advantage for Australia, receiving two million visits a year, researchers have been discovering ways to protect the reef. NOAA's Coral Reef Conservation Program has been working on methods to preserve the reefs around the world. There is ongoing research around the world, the University of Miami in Florida is researching how to protect the reefs off the coast. While the University of Sydney is also doing research on understanding the coral communities. Much of the protection is regulating the tourists and the public to specific activities at certain times. Monitoring the fishing and the amount of water entering the reef are both ways the universities are helping to maintain their corals. The research on coral reproduction helps to place time frames for some restricted activities. Researchers are working on understanding the coral lifestyle to better protect the areas. Finding the presence of benthic organisms helps to define the habitat. On some reefs the benthic organisms are the problem, and others it is the fish. Depending on the characteristic of the reef, only specific organisms need protected to maintain the reef population. As more and more information is discovered about the fish and other creatures within this habitat better protection can be made.



http://www.nature.com/nature/journal/v429/n6994/full/nature02685.html
http://www.media.australia.com/en-au/factsheets/3311_7931.aspx