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

The "Hoodwinker"

The Hoodwinker is a new species of sunfish that has been discovered in an interesting way. Sunfish are the largest heaviest known bony fish in the world. Adult fish can weigh anywhere from 250 to 1000 kg reaching lengths of 11 feet long. Sunfish are uniquely known for the back fin they are born with that never grows. This fin instead folds into its self as the fish grows creating a clavus or a rounded rubber for the species.

Sunfish can be found frequently in tropical and temperate waters in the oceans of the world. Spending their time in deep waters scavenging for jellyfish is their main prey consumption. They also eat smaller fish and a large number of zooplankton. The teeth of a sunfish are somewhat fused together causing a beak like structure. The fish is not able to  fully close their mouth.

Sunfish may also spend their time near surface waters taking in the sunlight. When near the surface, sunfish are commonly mistaken for sharks when their dorsal fins are above the water. As well as coming to the surface to sunbath, sunfish come to the surface to deal with the parasites infested in their skin. The sunfish take advantage of the feeder fish at the surface to remove the parasites. Seagulls will also scrap the parasites off the fish while they lay on their side close to the surface of the water. 

The Hoodwinker species was discovered before it was spotted. Researchers were analyzing large numbers of DNA samples from sunfish. The genetic sequencing showed that there were four separate species but only three of the species were known: Masturus lanceolatus, Mola mola, Mola ramsayi, and the unidentified DNA. The hunt for finding the new species then began. 

The hunt for the new species was not an easy task for the fact that all sunfish species look similar. The researchers started their hunt differently by looking on social media for  different photos of sunfish that have been posted and seeing if they're any identifications in photos of a different species. Observers from Australia and New Zealand caught a sunfish within a net receiving a photo and a genetic sample to give the researchers. 

The photo of this fish had a small structure on the back fin that was never spotted before on other sunfish. Later on at the same beach there were four sunfish stranded. The research team was notified of the fish and was on their way to the site to observer the stranded fish. The fish on the island turned out to be exactly what the researchers had been looking for, the hoodwinker, matching the DNA of the unknown within the lab.  The Hoodwinker was then properly named the Mola teca, for the species that was hiding in plain have site for many years.

Figure: Hoodwinker Sunfish found stranded

Hookwinker, Mola teca, are not known to grow bumps on their body, instead their body sizes stay around the same from juveniles to adults. Another distinctive factor is that their back fins are separated into two half's by a small piece of skin, into an upper and lower half. The Hoodwinker is mostly known to be found in colder waters. Not a tremendous amount of details of the species is known for the fact the sunfish are found in an area that is hard to reach by humans.

Murdoch University ( 2017). The four-year treasure hunt for the hoodwinker sunfish. Retrieved from           5https://theconversation.com/the-four-year-treasure-hunt-for-the-hoodwinker-sunfish-81265

National Geographic (2018). Ocean Sunfish. Retrieved from
         https://www.nationalgeographic.com/animals/fish/o/ocean-sunfish/

Pistol Shrimp's Bizarre Method of Protection

If you find yourself under the coastal tropical waters you may just hear what sounds like a popping noise. Originally these sounds were thought to be the jaws of shrimps closing, it actually turned out to be something different. A species of shrimp called the pistol shrimp are actually what are making these sounds. They can be rather loud as well, louder than a .22 caliber rifle, this would be the second loudest noise in the ocean next to sperm whale clicks.

Pistol Shrimp

 A group of marine scientists wanted to figure out the details of these shrimp and their gunshot-like noises. It turns out that the shrimp is forcing out still water from in-between their claws and that creates a vortex-like motion. This swirling vortex that comes from the claw creates a void in the center and as it travels that void will collapse. The whole process happens in just a short time, less than half a millisecond to be more precise, but the vortex can travel as fast as thirty meters per second. One researcher said that you wouldn’t want to stick your hand in a tank with one because the force does hurt rather badly.



These shrimps are only known to grow to about five centimeters in size so they’re gunshot vortex is only useful against other individuals with a similar size. They don’t use this technique to stun prey or anything in that manner. This is due to the fact that these shrimps are scavengers that feed mostly on what they can find laying on the ocean floor. They typically are known to do this if they are trying to protect a mate or their homes. When two pistol shrimps duel it out these shockwaves aren’t fatal to them, but it will leave some puncture wounds and can even tear off a claw. These tiny underwater gunfights can still cause some potential damage.

 References:

Woodward, A. (2017, October 27). How a tiny shrimp fires a savage shock wave using just its claw. Retrieved January 28, 2018, from https://www.newscientist.com/article/2151700-how-a-tiny-shrimp-fires-a-savage-shock-wave-using-just-its-claw/

Blue Sharks: Bioindicators of Pollution and Health in the Atlantic Ocean

Pollution is becoming an ever-prevalent problem for marine ecosystems. Many of these ecosystems are being affected by contaminants produced from human activities. Pollutants can cause harmful effects at lower levels of biological organization, such as the organism level or at the gene and cellular level. In this study, these effects were examined in blue sharks (Prionace glauca).

Blue Shark (P. glauca) 

Blue sharks are one of the more common species of shark consumed by humans. They are also apex predators, meaning they are at the top of the food web. These components make them a prevalent species to study as it allows for examination of bioaccumulation, as well as the effect it could potentially have on humans. This particular study aimed to measure if Atlantic blue sharks have high levels of POPs and metals in their tissues that could effect human health as well. The contaminant body burden levels correlated with biochemical responses of stress in the organism were measured as well.

Twenty blue sharks (12 female and 8 males) were captured at a depth of approximately 20 meters in the Atlantic Ocean, southwest of Portugal. All individuals caught were considered to be juvenile sharks. After capture, liver, muscle, and brain tissue were collected for analysis. After preparation of these tissues, statistical analysis was done to determine the amount of contamination present.

Marine apex predators, such as blue sharks, tend to accumulate pollutants and contaminants in their bodies at higher levels that the majority of other animals in their food chain. When examining the tissues from this sample of blue sharks it was found that the liver tissue contained higher levels of persistent organic pollutants (POPs) than the muscle tissue did. This was to be expected as POPs typically accumulate in tissues that have higher lipid content, such as the liver. POP analysis also revealed that non dioxin-like polychlorinated biphenyls (NDL-PCBs) were the most abundant contaminant present in blue sharks. NDL-PCBs have been shown to produce toxic effects, and can affect fish behavioral responses. Some of the blue sharks sampled even had levels of NDL-PCBs present higher than what is legally allowed for human consumption. In addition to NDL-PCBs, brominated flame retardants (BFRs) were also found to be at high levels in these blue sharks captured from the Atlantic Ocean. BFRs have also been shown to have dangerous consequences to both marine organisms and humans, as they can impair organs such as the brain or thyroid.

Figure 1: Amounts of POPs found in liver and muscle tissue

Even more significant, as stated earlier, is the fact that all individuals were juveniles. Bioaccumulation has been proven to increase with size and age, so it is estimated that these already high levels of bioaccumulation of dangerous contaminants would have only continued to increase if the juveniles would have grown to full adult size.

Also examined in this study was the bioaccumulation of metals. In contrast to POPs, metals had higher levels of bioaccumulation in muscle tissue than liver tissue. These specimens showed higher levels of Mn, Cd, Fe, and Cu. However, in a previous study done approximately two decades ago that contained bigger organisms, showed lower levels of these contaminant burdens. This result raises red flags as it could indicate the possibility of a historical increase of contamination of these Atlantic Ocean waters. Mercury levels were also found to be above safe consumption levels. This is again troublesome as these blue sharks were juvenile and mercury levels are known to only increase as the size of the organism increases.

Because marine animals are constantly surrounded by xenobiotics, physiological alterations in response to stress could potentially be induced. When a Canonical Correspondence Analysis (CCA) plot was conducted of the liver tissue, it was discovered that nearly all contaminants had a positive association with DNA damage, which seems to indicate that when these blue sharks are exposed to POPs and metals, they are not able to counter the effects of the radical oxygen species (ROS) produced and prevent DNA damage.

Figure 2: CCA of liver tissue

It was concluded the lipid peroxidase (LPO), DNA damage, and inhibition of the enzyme glutathione peroxidase (GPx) were the main effects due to exposure to POPs and metals, which indicates they may be the best options to use for future biomonitoring. These contaminants can lead to ecological damage as well in terms of the blue sharks’ swimming, feeding, and reproduction habits. This conclusion can be seen and summarized in the figure below.

Figure 3: Blue sharks as bioindicators

This study also shows the prevalence of bioaccumulation and the potential human health risk it could have as blue sharks are a common species of sharks that are consumed by humans. In future studies, it would be beneficial to examine the individuals' stomach contents as well to see how feeding habits may influence bioaccumulation. It would also be important to examine larger sampling areas in the Atlantic Ocean as well as other oceans to see how contamination and pollution affect populations there as well.

Alves, L., Margarida, N., Marchand, P., Bizec, B., Mendes, S., Correia, J, Lemos, M., & Novais, S. (2016). Blue sharks (Prionace glauca) as bioindicators of pollution and health in the Atlantic Ocean: Contamination levels and biochemical stress response. Science of Total Environment, 563-564, 282-292.

Largest Sea Turtle Population changing due to Environmental Warming

Sea Turtles have temperature-dependent sex determination. Meaning that the sex of the hatchlings are determined by the incubation temperature during embryonic development. The critical point of development, the thermosensitive period, is during the middle of the third period in incubation. The pivotal temperature is the point at which half of each gender is hatched; while colder temperatures produce more males, warmer temperatures will produce more females.

The transitional range is based around the pivotal temperature, to where all males or females will be hatched. The pivotal temperature only differs by a few degrees ether way to produce all of one gender in the hatch. With global warming causing temperatures to rise above the pivotal point more females are being hatched. The climate change is also causing the mortality rate of the hatchlings to rise.

In Australia there are two breeding populations of turtles the Southern Great Barrier Reef stock (sGBR) as well as the northern Great Barrier Reef stock (nGBR). Turtles mate along the area of their nesting beaches. Females can lay multiple clutches of eggs each with around 100 eggs. Each clutch that is laid is incubated around 55 days. These hatchlings make their way into the open ocean and stay there till they reach the age of sexual maturity, around 25. At this time in their life they return to the same beach they were hatched at to mate.

Figure 1: Nesting Areas

The northern Great Barrier Reef population is one of the largest green sea turtle populations in the world. The figure above shows the area of Australia where the two populations nesting sites. The population is estimated to have around 200,000 females nesting. The population has shown that there is an increase of nesting females despite the fact that there was a signs of declining population in the 1990's. Research has been completed on this population of turtles to better understand the way the climate changes affect the gender and growth of the population.

To test this effect the best approach would be to estimate the exact number of males and females that are being hatched during nesting season. The issue with recording this data is you are unable to see the sex of a turtle upon hatching. Researchers are able to determine the sex of the hatchlings by histological examining the gonads. However, this would mean sacrificing the hatchling's life which would go against the point of the research of studying the population’s growth, not to mention the ethical issue as well. There are tests though that can be run on the dead hatchlings found left over in the nest.

There is a foraging ground that is also labeled in figured one, Howick group of island. Genetic testing and tagging that have been completed show if the turtles are from the nGBR or the sGBR, they age and gender. At this area researchers tested turtles laparoscopic to determine the gender and genetics of the sexually immature turtles at the feeding ground. Also data was taken from three age ranges. The results show that all ages of the turtles were found to be mostly female.  

Figure 2: Data of Howick Islands

Another point of the analysis was to estimate the temperature of the sand over the years that these turtles would have been incubated in. There was no recorded numbers for the sand over the years but there was recorded temperatures of the air and sea surface. These numbers were used to find around what temperature the sand would have been at the time. Figure 3 shows the estimated temperatures based around 0 the pivotal temperature. The majority of the graph shows that the temperature would have been above the pivotal point. The information of the estimated sand temperature correlates to the data in figure 2, showing that mostly would have been hatched in previous years. 

Figure 3: estimated sand temperatures

The researchers are noticing the number of females increasing every year with the temperatures being above the pivotal point. The large number of females is concerning for the future of the turtle population. There is no way to tell for sure how many males are needed to sustain the population and/or to keep the same large numbers present. With the females continuing to outnumber the males in the population there will be less sperm to repopulate. The lacking number of males has already decreased the population’s number but the concern is if this trend continues the population will reach extinction over time. The sea turtles may have the ability to adapt to the climate change but these adaptations will take time to occur. While the rate of global warming is happening much faster than the progression of the adaptation. The idea for solving this problem is to slow down global warming and help the preserve the turtle population as best as possible.

Jensen, M., Allen, C., Eguchi, T., Bell, I., LasCasella, E., Hilton, W., Hof, C., & Dutton. P. (2018).
            Environmental Warming and Feminizarion. Retrieved from
            https://www.sciencedirect.com/science/article/pii/S0960982217315397?via%3Dihub

NOAA. (2017). What Causes Sea Turtles to be Male or Female? Retrieved from
            https://oceanservice.noaa.gov/facts/temperature-dependent.html

Nesting activity of sea turtles, Caretta caretta and Chelonia mydas, at Patara Beach over four nesting seasons

The loggerhead turtle known as Caretta caretta is the most common sea turtle that exists in the Mediterranean. Some of the major nesting areas for these turtles are in Greece, Turkey, Libya, Egypt, Israel, Italy, etc. The green turtle, which is known as Chelonia mydas, is well known in the Mediterranean. But this turtle is densest in Turkey, Cyprus and Syria.

Caretta caretta

Chelonia mydas

 Based on the first research of the Turkish coast of turtle nesting areas there are seventeen important nesting beaches on the Turkish Mediterranean coast, this number was then again upgraded in 2003 to 20 important nesting beaches and then to 22 in 2004. In a study the number of C. caretta females are annually nesting on the coast varies between 2280 to 2787 another study estimates in 2010 that C. caretta is 7200 and about 1500 for C. mydas.

The first detailed research that shows nesting activity on Patara Beach in Turkey started in 1989. The highest number of nests was shown in 2006 and it had 127 nests and the lowest number of nests was 33 in 1994. The goal of this study was to show information on nesting activity and show distributions of nests, etc.

In this study about 556 loggerhead emergences were recorded per year over a four year period. About 32 percent of this number resulted in nests and about 180 nests were made per year. On the Patara beach there were 113 nests in 2010, 138 in 2012, 207 in 2013 and 195 in 2014. In the Kumluova beach there were 3 in 2010, 31 in 2012, and 32 in 2013. Kumluova has some wetlands that exist within the beach area and there is more predation which is why there is a higher amount of nests in  Patara. There are also the green turtle emergences, which only had 17 in the 4 year period which were all in Patara. There were only 3 nests that were resulted out of these turtles 1 in 2010 and 2 in 2012.

Figure 1

Figure 1 shows that the nesting season starts in May but the amount of nesting that occurs in may is low. Figure 1 also shows an incline of nesting activity towards the end of June but the peak nesting time take place in July and then dies off again in August which is the end of the nesting period. In May nesting success what at approximately 4.03%, in June it was about 44.93% in July it was 45.62% and in August it was 5.42%.

Table 2

Shown in Table 2 the researchers excavated loggerhead nests. In 2010 they excavated 115 nests, 162 in 2012, 224 in 2013 and 190 in 2014. The overall total of eggs counted was 47,129 eggs and 676 nests. One of the key parts of this study was the amount of hatchlings that were produced from each nest. And they found that 17,929 of the 47,129 eggs were able to make it to sea (38.04% of eggs). There were also 218 green turtle eggs counted and 121 of those eggs produced hatchlings and 94 were able to make it to sea (43.12% of eggs).

Predation affected the nests over the four-year period. 142 of the loggerhead nests were partially predated on and 256 were completely predated on. 55.36% of the nests were affected by predation. Some of the predators include Fox (Vulpes vulpes), dogs (Canis lupus), badgers (Meles meles), and wild pigs (Sus scrofa). There was also some predation by crabs. Some of the nests were provided with metal grates to help with survival. The hatchlings with the protection had a higher survival rate than those that were in natural settings because the predation was lower.

OLGUN, K., BOZKURT, E., CEYLAN, S., TURAL, M., ÖZCAN, S., KARASÜLEYMANOĞLU, K. Ş., & GEROĞLU, Y. (2016). Nesting activity of sea turtles, Caretta caretta (Linnaeus, 1758) and Chelonia mydas (Linnaeus, 1758) (Reptilia, Cheloniidae), at Patara Beach (Antalya, Turkey) over four nesting seasons. Turkish Journal Of Zoology, 40(2), 215-222. doi:10.3906/zoo-1505-8