Can We Help Corals Evolve to Survive Global Warming?

With ocean temperatures rising and coral bleaching events becoming more and more common, attempts to reduce or reverse climate change may seem to be too little too late, and we are left wondering if there is anything that can be done to save the coral reefs.

One form of helping repair damaged reefs is to grow corals in nurseries and transplant them to the reef.  This technique has been successful and useful for replanting damaged reefs.1 In coral nurseries, researchers, and therefore the corals, have access to greater, more controlled resources, which also allows greater protection from predation.   Abiotic factors are those nonliving, physical and chemical attributes that can influence an environment or ecosystem. In some cases, abiotic factors that could be harmful can also be restricted in coral nurseries, such that temperatures, pH, light, and other factors are strictly controlled. However, if these corals are not suited to the natural environment in which they will eventually be placed, where temperature stress cannot be controlled, they still most likely will die.1

Assisted evolution, is the process whereby researchers help speed along natural selection through different methods to enable corals to be better equipped with traits that will allow them to survive predicted changes in ocean conditions. Dr. Madeline van Oppen and colleagues argue that assisted evolution may be extremely important in helping corals survive, despite rising ocean temperatures. They propose that there are four main ways that assisted evolution could be used in coral reefs, shown in figure 1.  These researchers further state that all methods need more research to be developed well enough to be implemented.1

Fig. 1: The assisted evolution diagram shows the four proposed approaches to assisted evolution in order of increasing intensity of intervention and the actions that would be taken with each and how these methods would be applicable. Source: van Oppen et. al. 2015.

The first approach involves exposing corals to stressful conditions so that they will be better able to acclimate in the future.1It has been shown that exposing some corals to moderate light and temperature stress enables them to better resist bleaching during future stressful events.1 Exposure to stressful conditions may change corals’ sensitivity to heat stress through epigenetics, changing which gene is expressed and to what extent. Essentially, the corals are increasing their tolerance to conditions of unusual light and temperatures.

The second method of increasing coral resilience is through modifying the microbial community associated with coral.1 All corals live with other creatures in their ecosystems.  When the creatures coexist in a mutually advantageous way, they are said to be symbiotic. Exposure to stress allows the corals to change the relative abundance of different types of symbiotic algae contained in their tissues in favor of a higher abundance of those symbionts more suited for future conditions.1   Symbiodinium are algae composed of one cell, that tend to live in harmony with corals.  Their photosynthetic biproducts are used by the corals.   Dr. Robert Rowan has shown that a group of Symbiodinium, called clade D, function better in higher temperature water than another group, clade C.3 When exposed to stressful temperature conditions, clade D exhibited better functioning of chlorophyll than clade C. These results indicate that high temperature causes photoinhibition of clade C, while it causes photoprotection in clade D.3 By introducing heat tolerant Symbiodinium to corals, the heat tolerance of the corals may actually increase.1

A third way that assisted evolution could benefit corals is by selective breeding.  The authors suggest selective breeding only those individuals with higher heat tolerance and thereby speed along the process of natural selection.1 This approach has not been researched in corals; however, it could be done through selective breeding or hybridization of species.1 A naturally occurring Acropora hybrid, a coral found in the Caribbean, has occasionally shown increased fitness compared to the parent species.1 Because corals bred through either of these procedures would have unknown effects on the environment, these individuals would need to be raised in a lab to minimize threats to the naturally occurring ecosystem and to identify genotypes that are most suited to predicted future conditions.1 In addition, it is unknown if many phenotypic traits observed in corals are due to heritable genetic factors or environmental factors. Selective breeding would only work with heritable factors.1 What limited research exists only shows limited heritability for heat tolerance in coral.1 Corals that already exist on naturally warmer reefs could also be moved to naturally cooler reefs that are experiencing high temperatures and losing coral cover.1

Finally, it might be possible to artificially evolve and select for Symbiodinium that show greater heat tolerance.1 This might be done by inducing a high mutation rate in lab-grown Symbiodinium and raising them in stressful environments mimicking predicted future environments to select for those strains with the highest fitness.1 The well-suited strains could then be introduced to corals. This method is only theoretical at this point and has not been tried in corals.

This research no doubt has some ethical questions attached to it. Should we really be “playing God” and choosing what traits these organisms have?  Or should we just allow nature to take its course, even though we humans are causing the rise in greenhouse gases, which subsequently leads to increased air and ocean temperatures?2 But there are also some very real ecological questions to be answered regarding assisted evolution. For instance, what effects would organisms that were bred in the lab have on native organisms, and could these organisms potentially harm other native species?1 Van Oppen and her colleagues admit that, while she does not propose drastic changes such as genetic engineering, but rather techniques more along the lines of artificial selection, there could be negative outcomes.1 They also believe that what types of intervention are involved, the potential risks to the ecosystem involved, the health of the coral, and projected future reef health all must be analyzed and considered before taking action to increase coral resilience.

Even though these techniques seem to be promising ways that scientists can prepare corals for future conditions, it is still imperative that the issue of climate change be addressed. It is our job to do what we can to reduce our own contributions to climate change.


  1. van Oppen, M.J.H., Oliver, J.K., Putnam, H.M., and Gates, R.D. (2015). Building coral reef resilience through assisted evolution. Proceedings of the National Academy of Sciences 112, 2307–2313.
  2. van Oppen, M.J.H., Gates, R.D., Blackall, L.L., Cantin, N., Chakravarti, L.J., Chan, W.Y., Cormick, C., Crean, A., Damjanovic, K., Epstein, H., et al. (2017). Shifting paradigms in restoration of the world’s coral reefs. Global Change Biology.
  3. Rowan, R. (2004). Coral bleaching: Thermal adaptation in reef coral symbionts. Nature 430, 742–742.
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Corals of the Caribbean: Yellow-Band Tales

Halo’s on Reefs…Could this be a sign of the angels coming to save the coral reefs in the Caribbean? Wrong.

My previous posts have focused on diseases that affect corals in the Caribbean and as you may have deduced from the similarity in the titles, this one will be no different. Today’s disease focus will be the Yellow Band (also referred to as Yellow Blotch) disease. The name is acquired from the circular band that is found on the infected corals. The disease is characterized by yellow colored blotches on the coral that continue to spread in an o-ring shape as seen in Figure 1.1 As the old infected coral is left in the middle of the halo, it begins to fill with algae and sediment.

        Figure 1. Yellow Band Disease affecting a                                Montastraea faveolata                        Copyright. “Yellow Band-Disease Overview.” Common Identified Coral Diseases. NOAA, n.d. Web. 19 Apr. 2017.

On an individual scale the tissue loss due to Yellow Band Disease (YBD) is minimal, only accounting for a couple centimeters per year. However, the issue lies in the fact that it is affecting large, century old colonies that provide the basis of some marine ecosystems in the Caribbean.1 The affected species include Montastraea annularis (Boulder star coral) and Orbicella faveolata (Mountainous Star Coral).2 A study was done in Bonaire, an island in the Caribbean to determine the amount of coral affected by YBD. In Figure 2, we see the results of the study showing that more than 80% of the Montastraea species, are affected by the disease.3 The coral in this area has been affected since 1997, and has not been able to recover since.3 This is a prime example of how this disease is affecting corals in the Caribbean.

Figure 2. Results for survey of Montastraea species in Bonaire. Across all depths it is clear the coral is greatly affected.
(Important note: “Healthy coral” is that unaffected by YBD, but it can have other diseases                              or deterioration)                               Copyright. Richards Dona, A., J.M. Cervino, V. Karachun, E.A. Lorence, E. Bartels, K. Hughen, G.W. Smith, and T.J. Goreau. “Coral Yellow Band Disease; Current Status in the Caribbean, and Links to New Indo-Pacific Outbreaks.” 11th International Coral Reef Symposium 7 (n.d.): n. pag. Reef Relief. 7 July 2008. Web.

In a study done by Cervion et al. (2004) they identified the bacteria present in healthy coral versus that affected by YBD. Their results showed that there was a prevalence of Vibrio bacteria in infected corals.4 This was reconfirmed by another experiment done in 2008.5 This provides more hope than research done on other coral diseases. Since the culprit is now identified and confirmed, scientists can now focus on ways to attack this bacteria and protect corals.

Furthermore, these studies suggest that this disease may not actually affect the coral tissue directly but rather it targets the algae (zooxanthellae) that have a mutualistic relationship; where they rely on one another to survive. The zooxanthellae releases chemicals that affect the bacteria and mucus composition that lies on top of the coral.4  In the experiments, it was proven that the lack of color was due to the loss of the zooxanthellae. The affected coral tissue could survive if it was removed from stressful environmental conditions. However, when exposed to high water temperatures and infected with YBD, the tissue would also begin to die off and the coral skeleton would be visible.These findings lead to the conclusion that a rise in sea surface temperature (SST), causes the disease and deterioration of the coral to spread more rapidly.

Yellow band disease signs can sneakily camouflage amongst bleached corals. Coral bleaching occurs when corals are put under stressful environmental conditions (ie. Warm waters). In response they excrete the zooxanthellae that lives within them.5 This causes the coral to lose its color and be more vulnerable and susceptible to disease. So, due to the similar discoloration patterns, if a coral is affected by both the YBD and bleaching it is hard to distinguish the two. Both of these attacks on corals are affected by higher SST and when combined the survival rate of the coral is much smaller, sometimes going down by 40% (see Figure 3).4/5

Figure 3. Results of relationship between high temperatures and YBD. a) Coral will expel some of their zooxanthellae and survival will decrease b) When affected with bacterial infections, the survival rate is much lower due to higher zooxanthellae degradation.                                                                                 Copyright.  Cervino, James M. et al. “Relationship of Vibrio Species Infection and Elevated Temperatures to Yellow Blotch/Band Disease in Caribbean Corals.” Applied and Environmental Microbiology 70.11 (2004): 6855–6864. PMC. Web. 23 Apr. 2017.

The rise in SST is due to the global climate change and ever increasing temperature of the Earth. This is due to the depletion of the ozone (protective) layer of the Earth’s atmosphere. This is exacerbated by human actions. A recurring theme in my posts is that humans even if indirectly play a role in the depletion of coral reefs. However, we can also play a role in the conservation and protection. For one last time, I urge you to take action and be a proactive citizen. You do not have to be a marine biologist or participating in extensive scientific research to make a difference. Reduce. Reuse. Recycle. Learn more about coral reefs and other in danger ecosystems. Reduce energy and water waste. Avoid using plastic. Please, please just stay informed and lead a more eco-friendly lifestyle.


1. “Yellow-blotch/Yellow-band Disease.” Reefball. N.p., 2016. Web. 19 Apr. 2017. <>.

2. “Yellow Band-Disease Overview.” Common Identified Coral Diseases. NOAA, n.d. Web. 19 Apr. 2017.

3. Richards Dona, A., J.M. Cervino, V. Karachun, E.A. Lorence, E. Bartels, K. Hughen, G.W. Smith, and T.J. Goreau. “Coral Yellow Band Disease; Current Status in the Caribbean, and Links to New Indo-Pacific Outbreaks.” 11th International Coral Reef Symposium 7 (n.d.): n. pag. Reef Relief. 7 July 2008. Web.

4. Cervino, James M. et al. “Relationship of Vibrio Species Infection and Elevated Temperatures to Yellow Blotch/Band Disease in Caribbean Corals.” Applied and Environmental Microbiology 70.11 (2004): 6855–6864. PMC. Web. 23 Apr. 2017.

5. Cervino, J.M., Thompson, F.L., Gomez-Gil, B., Lorence, E.A., Goreau, T.J., Hayes, R.L., Winiarski-Cervino, K.B., Smith, G.W., Hughen, K. and Bartels, E. (2008), The Vibrio core group induces yellow band disease in Caribbean and Indo-Pacific reef-building corals. Journal of Applied Microbiology, 105: 1658–1671. doi:10.1111/j.1365-2672.2008.03871.x


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What Next for Deep Water Corals?

So deep water coral reefs are a thing, and they’re being threatened by human action, but what comes next? We are far from knowing everything about these hidden forests of biodiversity and even farther from adequately protecting them from the damage we’re inflicting on them. In the coming decades it is of utmost importance to expand our knowledge of deep water reefs and enact new legislation to protect them.

Due to the recent discovery of these reefs and the inherent difficulty in studying ecosystems 4000m (13000ft) under the sea, there is much we don’t know about these communities.  From large scale issues like where in the oceans are these deep water systems and what physical factors affect where they can grow to smaller scale questions like analyzing how they interact with plants and animals in the area and what kind of relationships they have with microbes that are present in the reef, there is a lot of knowledge left to discover on these reefs. And although this may sound like a lot, all of these goals are achievable with existing technologies. Using mapping techniques like multibeam sonar devices to create topographic maps of the ocean floor, we can create low resolution maps in areas that are likely to have reefs and determine we should be looking for these elusive habitats. From there these reefs can be examined and sampled by deep water submersibles that are able to travel to the depths of these reefs. Samplings of coral can help us better understand the amount of diversity present in these reefs and possibly give insight into microbes present.1,2,3

A deep water submersible used to study habitats up to 3000m deep.
© Harbor Branch Oceanographic Institute

On a more legislative side, more needs to be done to protect these reefs. Currently Australia, Canada, the Canary Islands, Ireland, New Zealand, Norway, UK and the United States all have created marine reserves or halted destructive activity like trawling and commercial drilling in areas with deep water reefs, but it’s not quite enough. Although many of known areas are protected areas, many are not or are still in the reviewing process. In addition, we are lacking full scientific data on where reefs are located. Hopefully this can be solved with new mapping techniques being used to find these reefs.1,4

1Svensen, E. Coral reefs: Cold water corals. WWF.
2Watling, L. Auster, P. J. (2017) Seamounts on the High Seas Should be Managed as Vulnerable Marine Ecosystems. Frontiers in Marine Science. 4:14
3Ocean Portal. Deep Sea Corals. Smithsonian Museum of Natural History
4Roberts JM (2006) Reefs of the Deep: The Biology and Geology of Cold-Water Coral Ecosystems. Science 312:543–547.

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ENSOs of The Future: The Necessity of Diligence

In the years to come, understanding the effects of El Niño-Southern Oscillation events on coral reefs is instrumental to preserving the beauty and function of these valuable oceanic resources. El Niños, as far as experts can tell, have been occurring for thousands of years, and so they alone are not the concern; the worry is how their growing strength (in connection with global warming) will affect overall climate trends and the natural world. Numerous studies have demonstrated how the 2015-16 El Niño was extraordinarily impactful in this regard, and so these are great tools for putting a finger on just how potent a strong ENSO can be on coral reef ecosystems.

The obvious connection between the increasing global effects of climate change, and bleaching of coral reefs, is the associated elevation of sea surface temperature1. As the Earth’s oceans continue to be heated as a result of human-induced pollution and warming, the severity of temperature increases such as those resulting from El Niño become more and more devastating to reefs. However, this is not the only factor that could potentially affect the survival of coral during future El Niños.

Figure 1: A reef off the coast of Bali, Indonesia Image Credit: Coral Staff, Coral Reef Alliance

A 2016 study published by experts from the European Geosciences Union highlights a different potential cause of coral mortality during the 2015-16 El Niño: sea level fall2. It focused on the reefs of Indonesia (Figure 1), a region known for its high diversity and flourishing tracts, where coral bleaching is common during ENSO cycles; this is a result of the added warmth and dryness during its first phase3. They not only saw that traditional warming-related threats arose, but also that additionally, sea level had lowered considerably in the area (Figure 2)2.

Figure 1: Sea level variance from Overall Mean on coral near Bunaken Island, Indonesia (1993-2016)
Image Credit – Eghbert et al. 2016 (See Ref. 2)

They collected data from years in the past, and noticed that in previous years with strong ENSOs, (such as 1997), sea level had also fallen noticeably. The establishment of an association between these two negative effects on coral reefs allowed them to conclude that sea level fall was likely not seen as a notable detriment of past El Niños2, and that this new factor is a major concern moving forward with the study of reefs during ENSO cycles.

As is made evident in this case study, it’s easy (even for scientists) to overlook the wide range of impacts that ENSOs can have on coral reef health. Sea surface temperature anomaly is the most obvious, and pressing issue involving global warming and the survival of these majestic underwater ecosystems, but others do exist, and should not be ignored. As climate change worsens, El Niños continue to become stronger, and so do their effects on the living world. Some, as we have learned, may still not even be discovered.

Therefore, it is crucial to remain diligent when attempting to quantify and study the adverse challenges presented by global warming. Coral reefs can only be saved through mass cultural understanding, both by experts, and members of the community (like YOU!). If we are to combat the growing strength of ENSOs in the coming decades, it starts with the small things, including comprehending the gravity situation we are confronted with.


1- “El Niño prolongs longest global coral bleaching event.” News and Features – NOAA, pub. online 23 Feb. 2016. Web. 20 Feb 2017.

2- Eghbert, Elvan A., et al. “Coral Mortality Induced by the 2015-2016 El-Niño in Indonesia: The Effect of Rapid Sea Level Fall.” Biogeosciences, vol. 14, no. 4, 2017, pp. 817-826. SciTech Premium Collection., doi:

3 – Lindsey, Rebecca. “Global impacts of El Niño and La Niña.” – NOAA, pub. online 9 Feb. 2016. Web. 20 Feb. 2017.



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Coral Reefs: Guardians of the Coast


One aspect we typically don’t think about with regards to how coastal economies survive, is the longevity of the land itself. Beaches and other coastal areas are constantly changing under erosion, and if these places do not receive the proper protection, the land could disappear over time, taking with it many people’s livelihoods.

This is where coral reefs come in. Last time, I discussed ecotourism, an important producer of revenue for many coastal economies surrounded by reefs. Another important economic service coral reefs provide coastal economies with is protection against erosion, although it’s not just economies at stake. Somewhere upwards of 30 million people live on low coral islands and atolls, and the disappearance of these land masses would mean millions of people being uprooted from their homes, giving coastal protection programs even greater significance (Image 1).

Image 1. Low-lying islands and reefs of Kwajalein Atoll in the Marshall Islands.
Credit: Curt Storlazzi/USGS

It has been found that live corals, along with seagrasses and mangroves, protect coastal areas more than any single habitat or combination of habitats1. Corals specifically, have been shown to limit the impact of waves and storms on coastal areas1, protecting them in the long term. Even more good news, reefs near coastal areas can potentially reduce wave height by up to half a meter in some locations2. This reduction in wave height could significantly reduce erosion on a land mass over time. Although it does not completely put erosion to a stop, it extends the time that the area will be habitable by human populations living there and bringing in revenue from the resources off the coast.

One large factor in whether it is worth maintaining reefs near coasts for the protection they provide is cost. Fortunately, natural defenses for the coast, such as reefs and mangroves, are two to five times cheaper than manmade breakwaters2. This is hugely important because no matter how effective reefs are in protecting coastal areas, and subsequently, their economies, if it is not financially feasible, it will not be done.

Image 2. Artificial reefs being prepared to be stationed near the coast of Riviera Maya in Mexico.

In areas particularly prone to large storms and hurricanes, even artificial reefs have been shown to effectively defend coastal areas, although currently, it is not known how to help these reefs last and support life long-term(Image 2). However, because studies have consistently shown that coral reefs provide significant shelter to coastal areas from frequent erosion, I think it is well worth it for coastal economies to invest in the protection of reefs, if not for the reefs’ sakes, but for their own.


1 Guannel, Greg, et al. “The power of three: coral reefs, seagrasses and mangroves protect coastal regions and increase their resilience.” PloS one 11.7 (2016): e0158094.

2 Narayan, Siddharth, et al. “The Effectiveness, Costs and Coastal Protection Benefits of Natural and Nature-Based Defences.” PloS one 11.5 (2016): e0154735.

3 Silva, Rodolfo, et al. “An artificial reef improves coastal protection and provides a base for coral recovery.” Journal of Coastal Research 75.sp1 (2016): 467-471.

4American Geophysical Union. “Climate change reduces coral reefs’ ability to protect coasts.” ScienceDaily. ScienceDaily, 22 July 2015.

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Artificial Reefs and Ways to Take Action

Richard Branson, controversial British business magnate and founder of the Virgin Group, is already known for his massive, unorthodox, and multi-million dollar projects. The billionaire has attempted to commercialize civilian space travel, broken records for hot-air ballooning, and he has just completed his latest project: creating an artificial reef using a historic ship complete with an 80-ft kraken sculpture. The project, which was sunk on April 10th in the British Virgin Islands, is supposed to support swimming education in the BVI, increase awareness for marine conservation, provide scientists with a new study site, and generate revenue for repairs through tourism to the dive site.1

An artificial reef is, “a manmade structure that may mimic some of the characteristics of a natural reef” according to the National Oceanic and Atmospheric Administration,2 and they are often used for fisheries, commercial dive sites, or marine ecosystem conservation. Artificial reefs have been around for hundreds of years, but it wasn’t until the 1960’s that the United States government began researching artificial reefs in earnest.3 Today, artificial reefs are made up of specially made concrete or fiberglass structures, sunken ships, sculptures and artwork, subway cars, and more. But are these having any effect on coral recruitment and growth, or is this just another way for humans to dispose of their junk? A 2016 study analyzed artificial reefs off of the coast of Singapore after a ten-year gap in monitoring. The scientists found that these reefs had successfully recruited stony corals, and they pointed out that these corals had reached sexual maturity and could participate in mass spawning events, which is crucial for reef growth and conservation. The figure below shows the changes in species composition before and after the ten-year gap, with a promising increase in hard coral cover.4

Figure 1. The percentage cover on exterior walls of artificial reefs in Singapore in 2004 and 2014, by lifeform category. This figure shows changes in species distribution over time, with a slight decline in some algae and a notable increase in hard corals. Source: Ng et al in Aquatic Conserv: Mar Freshw Ecosyst

Another paper showed that large artificial reefs can support diverse and abundant coral and fish communities at higher percentage coral cover than nearby natural coral reefs in Dubai. However, artificial reefs had lower coral diversity, which highlights the need to conserve natural coral reefs instead of replacing them entirely with artificial reefs.5 The high coral cover does provide an opportunity, however, to grow coral for transplantation later, or as hubs of reproduction.

There is a lot to consider when attempting to sink giant terrestrial objects as artificial reefs. Contamination of ocean waters and stability on the ocean floor are both huge risks, as these reefs can actually do more harm than good if not properly prepared. Ships have to be cleaned out to remove any substances that can contaminate waters, and certain materials, like rubber tires, can leak chemicals into the water and cause physical harm to existing reefs.6 Now, the United States has a National Artificial Reef Plan, which strictly limits what is thrown to the bottom of our oceans, and how. There is additional concern among the scientific community that artificial reefs will distract efforts away from conserving natural reefs, and warn that they can help in recovery of degraded or destroyed reefs but are second-best when it comes to conserving reefs.7 Additionally, artificial reefs can concentrate sought-after fish away from natural reefs, which makes them targets for fishing boats.6

Artificial reefs are undoubtedly only local solutions with low efficacy on a global scale, but they provide one positive solution when done correctly. Artificial reefs will never be able to fully replace coral reefs, as such a project would be far too expensive, disruptive, and the species diversity may never reach natural levels. However, they provide hope as they can be used as places for fish species to take refuge as corals continue to die off, and once coral species on these artificial reefs reach sexual maturity, they can contribute to the growth of natural reefs as well.

Lastly, I want to provide tips on how to contribute to coral reef conservation as an individual. If you want to get involved in reef conservation, look for local groups promoting beach cleanups or educational events near you, stay informed on upcoming legislation and what your candidates for local government stand for. Keep an eye out for algae and beach cleanups in your area, and try to eat sustainably sourced fish. And of course, reducing your CO2 consumption and overall living an environmentally friendly life will benefit the ocean as well as various other ecosystems. 8 We can’t all spend millions of dollars to sink giant ships or designate large swaths of ocean as Marine Protected Areas, but we can still try to make a positive human impact on our oceans.

Works Cited

  1. Ekstein, Nikki. “Richard Branson’s Latest Travel Project Is Underwater.” Bloomberg, April 7, 2017.
  2. National Ocean Service. “What Is an Artificial Reef?” Ocean Facts, January 23, 2014.
  3. “A Brief History of Marine Artificial Reef Development in U.S. Waters.” Powerpoint presented at the NOAA/ASMFC Artificial Reef Workshop, Alexandria, VA, June 9, 2016.
  4. Ng, Chin Soon Lionel, Tai Chong Toh, and Loke Ming Chou. “Artificial Reefs as a Reef Restoration Strategy in Sediment-Affected Environments: Insights from Long-Term Monitoring.” Aquatic Conservation: Marine and Freshwater Ecosystems, January 1, 2017, n/a-n/a. doi:10.1002/aqc.2755.
  5. Burt, J., A. Bartholomew, P. Usseglio, A. Bauman, and P. F. Sale. “Are Artificial Reefs Surrogates of Natural Habitats for Corals and Fish in Dubai, United Arab Emirates?” Coral Reefs 28, no. 3 (2009): 663–75. doi:10.1007/s00338-009-0500-1.
  6. Harrigan, Stephen. “Relics to Reefs: Why Fish Can’t Resist Sunken Ships, Tanks, and Subway Cars.” National Geographic, February 2011.
  7. Sheppard, Charles R. C., Davey, and Graham M. Pilling. “Restoration of Reefs.” In The Biology of Coral Reefs, 297–99. Oxford: Oxford University Press, 2012.
  8. Correa, Adrienne S. “Reef Solutions” Coral Reef Ecosystems, 13 April 2017, Rice University, Houston TX. Class Lecture.
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The Future of the Aquarium Trade: What Will YOU Do?

When you think of how aquarium fish are caught, you might be reminded of the scene from Finding Nemo, where the main characters are struggling against a fisherman’s net. However, one cannot catch aquarium fish the same way as how one may catch fish for eating. Aquarium fish are prized because of their colorful bodies and unique morphologies. To preserve these aspects of the fish, harvesters can’t risk damaging them, and their economic value, with clunky nets.

Instead they turn to more insidious methods, like cyanide. Around 90 percent of all imported aquarium fish in the U.S are caught with cyanide, according to a 2008 report from the National Oceanic and Atmospheric Administration1. This is especially concerning, because cyanide is a highly toxic chemical compound that not only harms fish health, but also devastates the reef environment on which the fish reside. Fish collectors in the aquarium trade capitals of the world (like the Philippines, Sri Lanka, and Indonesia) crush sodium cyanide and dissolve it in spray bottles which they then use to stun fish. Once, the fish are stunned, they can then easily be collected.

A collector using cyanide to capture reef fish. Source:

However it is not as simple as that. Fish will suffer greatly as the cyanide comes into effect—gasping as they lose respiratory activity, quite a number of the fish will die before they can even be sold3. The cyanide pollutes the coral reef and causes coral bleaching or even, in cases of high doses, immediately kills the coral2. According to biologist Sam Mamauag from the International Marine Life Alliance, “each live fish caught with cyanide destroys about a square yard of coral1.” Over prolonged misuse of cyanide, many of our coral reefs may become compromised beyond any hope for repair. Considering the importance of coral reefs to our international economy and culture, as I discussed in previous blog posts, this excessive use of cyanide can be a serious threat to coral reefs’, and therefore our, future livelihood.

Coral destroyed by cyanide fishing practices. Source:

So what are some solutions to these unsustainable and environmentally unfriendly fishing practices? First off, standardized and more strictly enforced legislation should be implemented. Although global laws on the aquarium trade are getting better, they are still not fully carried out everywhere. The Philippines, Sri Lanka, and Indonesia have all banned cyanide fishing, yet it still happens on a large scale1. A new petition calls on the National Marine Fisheries Service, U.S. Customs and Border Protection, and U.S. Fish and Wildlife Service to use already existing legislation to require stricter testing of imported fish for cyanide fishing.

Secondly, and perhaps a quicker method, is the aquaculture industry. In recent years, aquaculture has been proposed as a (at least partial) solution to the devastation of the aquarium trade. With current aquaculture technology, only a handful of marine fish can be successfully bred in captivity3. Marine Ornamental fish aquaculture mostly uses a completely closed tank culture, although freshwater ornamental fish aquaculture practices also include using ponds, or in cages in ponds3. One reason for the limited number of ornamental fish aquaculture facilities is that only developed countries have the required financial support and adequate infrastructure to support aquaculture. In the future, more research and resources given to aquaculture could be a sound alternative to the harmful fishing practices currently in play3.

A tank based aquaculture facility. Source:

Understandably, it will be a long and arduous road to globally enforcing aquarium collection laws and finding solid alternatives to aggressive fishing. However, as a voter, you can make an impact by politically advocating for further action on preserving our marine environments. This could be through protesting, disseminating further information or even just letting everyone you know why it matters. With the connectivity of the world through the internet these days, you could start a petition about a deficiency you see in the system, which even if it doesn’t result if codified legislation, it can always raise more awareness and discussion about the issue. Other possible conduits for change could but through writing blog posts, podcasts, art or music. Whatever method you choose, just go out there and do it! Change starts with YOU.




1 Bale, Rachael. “The Horrendous Way Fish are Captured for Your Aquarium—With Cyanide.” National Geographic. National Geographic Society, 14 Apr. 2017. Web. 20 Apr. 2017. <>.

2 Reksodihardjo-Lilley, Gayatri, and Ron Lilley. “Towards a sustainable marine aquarium trade: An Indonesian perspective.” SPC Live Reef Fish Information Bulletin 17 (2007): 11-19. SPC. Web. 20 April. 2017.

3 Tlusty, Michael. “The benefits and risks of aquacultural production for the aquarium trade.” Aquaculture 205.3 (2002): 203-219. Science Direct. Web. 20 April. 2017.


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It’s a Fish Eat Fish World: Parasitism on Coral Reefs

As my previous blog posts have discussed, coral reefs are not only ecologically diverse but also diverse in the types of interactions expressed between individuals and communities. My first post explored some examples of mutualistic relationships on coral reefs while my last post used the remora as a classic example commensalism on reefs. Today, I will talk about the third main type of symbiosis: parasitism.

Unlike commensal relationships, which are often difficult to categorize (because few interactions are wholly commensal), parasitic relationships are abundant in many of Earth’s ecosystems. On coral reefs, parasitic interactions are incredibly common and varied, as reef fish are excellent and abundant hosts. Because of this diversity, this post will focus on several different examples of the many kinds of parasitic mechanisms found on reefs.

The main parasites that are found in or on reef fish are isopods and copepods, which are small crustaceans1. A famous example of parasitism on reefs is the tongue-eating louse of the species Cymothoa exigua. Also referred to as “fish lice”, this marine isopod is known to remove the tongue of fish hosts by extracting blood, and then to replace the organ by acting as the fish’s new tongue! Though the isopod seems scary (in fact, it was the inspiration behind the 2012 horror film The Bay), little harm is done to the fish aside from the removal of its tongue. The isopod’s body acts as a functional tongue, and feeds on mucus secreted by the fish. This is actually the only parasitic animal known to functionally replace one of its host’s organs2. Image 1 below depicts a tongue-eating louse inside of a reef fish.

Image 1: The crustacean Cymothoa exigua lives inside the mouth of a fish of the subfamily Amphiprioninae, replacing the fish’s tongue.

Another common example of parasitic reef dwellers are flatworms. Ranging in size, color, and species, these animals of the phylum Platyhelminthes are parasitic on reefs in many different ways. Some species are corallivorous, which occasionally poses a threat to ecosystems that are already seeing heavy loss of coral cover. A study on the Acropora-eating flatworm Amakusaplana acroporae, which has only been found once in nature (in the Great Barrier Reef) but several times in aquariums, found that it could be a major threat to Acropora-heavy areas3. The flatworm’s unique camouflaging tactic is accomplished by ingesting the coral’s symbiotic algae (Symbiodinium) and distributing some of it (undigested) throughout its body. This gives Amakusaplana the appearance of its Acropora host, allowing it to feed on the coral undisturbed by predators. Image 2 shows how closely the flatworm resembles its coral host.

Image 2: Camouflaged Amakusaplana on a host coral.
Credit: The University of Southampton.

The varied and numerous instances of parasitism on reefs are usually kept in balance through natural coral reef ecosystem processes. Sometimes, however, these natural processes are interrupted by the introduction of invasive species. This is the case in Florida, where in the 1990’s, two species of lionfish (Pterois volitans and Pterois miles) were introduced into the Atlantic and Caribbean. Their progression through these areas since their introduction is shown in Figure 1 below. Native to the Indo-Pacific, lionfish eat almost anything they can fit into their mouths4. They can be considered parasites of the entire coral reef ecosystem, as their broad diets can interfere with established food chains, while they don’t have many predators because their bodies are lined with venomous spines. Lionfish are now one of the most classic examples of invasive species, as they have established themselves throughout the region and pose a major threat to native species.

Figure 1: Chronological occurrences of lionfish (Pterois volitans and P. miles) in the Western Atlantic as of December 20105.

While what can only be described as a lionfish invasion in the Western Atlantic is an unfortunate and ongoing occurrence, some ecologists see it as a way to further research on conservation ecology and marine biogeography5. By studying the lionfish, scientists at the George Washington University were able to test proposed scenarios regarding Greater Caribbean connectivity and phylogeographical breaks5. In this way, there could be a bright side to ecological issues like invasive parasites.

Well, you’ve reached the end! Thank you for reading my blog posts – I hope you were able to learn a little something about symbiotic relationships on reefs, and I encourage all readers to look into the issues discussed throughout. The impact that humans have on reefs don’t just affect their physical structures. The myriad interactions found on reefs are also disrupted by anthropogenically influenced events like coral bleaching and the introduction of invasive species to non-native habitats. In order to curb the negative impacts of these occurrences, human societies have to engage in symbioses of our own, mutualistically working toward bettering the rainforests of the sea.


1“Ocean Parasites: More Common Than You Think.” Aquanews Online Scuba Magazine. Leisure Pro, 13 Aug. 2016. Web. 17 Aug. 2017.

2Brusca, Richard C., and Matthew R. Gilligan. “Tongue Replacement in a Marine Fish (Lutjanus Guttatus) by a Parasitic Isopod (Crustacea: Isopoda).” Copeia, vol. 1983, no. 3, 1983, pp. 813–816.,

3Hume, B.C.C., D’Angelo, C., Cunnington, A. et al. Coral Reefs (2014) 33: 267. doi:10.1007/s00338-013-1101-6

4Morris, J.A. & Akins, J.L. Environ Biol Fish (2009) 86: 389. doi:10.1007/s10641-009-9538-8

5Betancur-R., R., Hines, A., Acero P., A., Ortí, G., Wilbur, A. E. and Freshwater, D. W. (2011), Reconstructing the lionfish invasion: insights into Greater Caribbean biogeography. Journal of Biogeography, 38: 1281–1293. doi:10.1111/j.1365-2699.2011.02496.x

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Fishing for Change

In my last post, we analyzed some impacts of reef fishing, such as bolstering local economies while simultaneously overexploiting specific reef fish species. In order to complete our discussion of this topic, we will be taking a deeper look into potential solutions that could account for the negative aspects of reef fishing.

In regards to a more local solution, daily catch quota systems could be implemented that would prohibit fishermen from completely overexploiting specific reef fishes.1 Using survey data on the different species that inhabit each reef, local reef conservation groups could determine exactly what the daily quota for each fisherman should be. Personally, I like this method because it would allow for all parties involved—reef organisms and fishermen—to benefit. Yes, fishermen would not be able to capture as many fish as they would like; but at least, they would still be able to make some sort of financial profit. That being said, my qualms with this specific method lies in its level of feasibility. It would not be an easy solution to enforce unless some sort of security measure was also implemented.

Recall my first blog post in which I shed light on various harmful fishing techniques, such as explosive fishing and cyanide poisoning. By restricting the employment of these fishing techniques, we would be able to limit the amount of unnecessary damage that coral reefs are being subjected to. Under no circumstance should fishing ultimately lead to complete coral death. While the aforementioned techniques make it less laborious for fishermen to do their jobs, it would be remiss to not acknowledge that such damaging techniques totally undermine all coral reef conservation efforts. As was mentioned in the previous paragraph, some type of enforcement would have to be instituted in order to make sure that fishermen actually implemented this solution.

Another solution worth highlighting would have to be restocking. While the name basically says it all, this technique involves introducing specific reef fishes to coral reef environments where they have been overfished. Recently, this has been done with groupers, snappers and rockfishes.1 While many people think this solution is a step in the right direction, I am very hesitant to get behind it. In my opinion, the only way for this solution to be impactful would be if a MASSIVE amount of fish were dumped in the reefs. Furthermore, conflicting data exists regarding how well introduced fish thrive when transplanted to reef environments. Some researchers argues that introduced fish tend to have higher mortality than their native counterparts.2 However in a study conducted by Roberts et. al., they determined that Hatchery-Reared Nassau Groupers tend to thrive when introduced to coral reef environments at large body sizes.3 Figure 1 provides us with a visual representation of the reef species at the center of the aforementioned study.

Figure 1. Image of the Nassau Grouper. It is currently being reared in hatcheries before being placed in coral reefs where its numbers are limited.©
Source: The Department of Environment and Natural Resources 4

In the coral reef conservation sphere, the best known overfishing solution would have to be the implementation of Marine Protected Areas (MPAs), which “designate areas closed for fishing.”1 This allows for specific reef areas to restore themselves in various facets, such as biomass and diversity levels. While promising, this solution is fairly challenging to implement because in order to reap the benefits of such a solution, the MPA would need to be very large. This is something that many locals would not be open to given that it would negatively affect their livelihoods to a large degree. Furthermore while proving advantageous in the long-term for sedentary species, this solution does not take into account how it will keep migratory fishes from leaving the area since they are essential to reef restoration.1 Figure 2 labels the various locations of MPAs in the coral triangle, the most diverse marine region on Earth.

Figure 2. Image of Marine Protected Areas in the Coral Triangle. Red dots denote MPA location. MPAs are the best solutions for combating overfishing, yet they remain severely underutilized.©
Source: WWF 5

Over the course of this blog series, we examined the topic of reef fishing, weighed the pros and the cons associated with it and finally concluded by putting forth some potential solutions that could be implemented in order to mitigate its negative effects. While we examined the issue in great detail, I encourage you to do your own research and come up with ways that you could help with solving this problem. I’m well-aware that this issue may seem above your heads, but coral reef conservation is a topic that should be on all of our minds. Let us make a difference while we still can. Whether big or small, change is change!


1 Sheppard, C., Davy, S. K., & Pilling, G. M. (2012). The biology of coral reefs. Oxford: Oxford University Press.

2 Garrido, S., Santos, A., Hamadou, R., & Ferreira, S. (2015). Born small, die young: Intrinsic, size-selective mortality in marine larval fish. Scientific Reports, 5. Retrieved from

3 Roberts, C. M., Quinn, N., Tucker, J. W., & Woodward, P. N. (1995). Introduction of Hatchery-Reared Nassau Grouper to a Coral Reef Environment. North American Journal of Fisheries Management, 15(1), 159-164.

4 Lucas, R. (2012). NASSAU GROUPER (EPINEPHELUS STRIATUS) [Digital image]. Retrieved from

5 WWF. (2011). INFOGRAPHIC: Marine Protected Areas in the Coral Triangle [Digital image]. Retrieved from


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The Battle Against Ocean Acidification: Starting Small and Starting Now

Hi, everyone! This is my third and final post about the effects of ocean acidification on coral reefs. In my first and second posts, I explored the concept of ocean acidification and how it affects reef organisms. In this post, I will be going over some steps that can be taken to fight against the acidification process. Feel free to check out my previous posts for a better understanding of why ocean acidification is worth addressing!

Figure 1. Ocean acidification sources, with an emphasis on local contributors. © Source: Kelly et al.2

In my last post, I mentioned that ocean acidification is highly unlikely to be reversed.While this is (currently) true, several strategies demonstrate significant mitigation potential. Before we explore these ideas, I want to emphasize that although ocean acidification is a global issue, it disproportionately affects local coasts and communities.2 Figure 1 illustrates several major local sources that contribute to coastal acidification.

Considering this and the difficulty of gaining traction through national and global efforts, smaller-scale measures are becoming increasingly crucial. Local and state governments within the United States are able and motivated to modulate emissions, runoff, and land-use patterns through zoning and permitting.2 Some states have already limited residential runoff, reducing water contamination, algal blooms, and pollutants in local coasts.2

Another local approach for combating acidification involves controlling coastal erosion and reducing nutrient and sediment loading of water by increasing vegetation cover.Additionally, anti-sprawl land-use plans can reduce vehicle-miles traveled and impermeable surface cover, limiting emissions and runoff.2 Furthermore, enforcement of federal emissions limits for nitrogen and sulfur oxide by local and state governments would have immediate effects, as these pollutants have short atmospheric residence times, quickly falling into the water.2 Finally, capitalization of Clean Water Act (federal) funding by states for stormwater surge prevention, coastal and riparian buffers, intact wetlands, and improved onsite water treatment facilities would limit runoff and associated pollutants.2

Now, am I missing something? You might be thinking, “Isn’t the obvious answer to just reduce atmospheric COlevels?” Well, it’s not as easy as it seems. While essential, reducing COemissions may not be enough, given our limited time frame.3 We would have to reverse the current 3% annual increase in COemissions by 2020 to keep atmospheric COlevels below 550 parts per million by volume, and even greater reductions would be needed to maintain favorable coral growth conditions.5

Figure 2. Global fossil fuel carbon emissions from 1900 to 2014. © Source: Marland et al.4

Figure 2 depicts global trends in anthropogenic carbon dioxide emissions. Because atmospheric COlevels continue to rise despite growing awareness of the breadth and potential cost of ocean acidification, we must look to alternative solutions.3 Furthermore, even if emissions ceased, which is pretty much out of the question, excess COin the ocean-atmosphere system would persist for several millennia.3

Still, I do want to bring up one emission-related measure that should be taken: Atmospheric COis often lumped with other greenhouse gases when considering climate protection. However, as the core pollutant involved in ocean acidification, it would be better to consider it separately and to limit its emissions regardless of other greenhouse gas regulations.5

Figure 3. Neutralization reaction. This image visualizes a general neutralization in which an acid and base combine to form a salt and water. © Source: TutorVista.com6

Returning to alternative ocean acidification combat methods, one idea is to neutralize COacidity by adding base minerals to the ocean.5 Figure 3 illustrates a general neutralization reaction. While base mineral reactions in surface waters are normally slow, reacting seawater and carbonate minerals with concentrated COin flue gas or other waste streams could speed them up.Ultimately, this would consume waste CO2, avoid emissions, generate seawater alkalinity, increase calcium carbonate saturation states, and help reinforce marine biological shells at a local scale.3 In the long run, optimal application of 0.48 Gt of CaCO3 a-1 could absorb atmospheric COat a rate of 600 Mt COa-1 after 50 years.7

Another approach, although ineffective at mitigating ocean acidification itself, increases resilience against it. Compared to their wild-type counterparts, Saccostrea glomerata reared in increased COwithstand acid stress more effectively.3 Similar observations have been made in studies on Acropora hyacinthus under elevated temperatures.However, although many options exist, few ideas have been studied past the conceptual or laboratory stage.3 To discover the safest and most cost-effective solutions, further research and in situ testing is necessary, so next time you donate to a cause, consider helping fund a project related to one of these ideas!


  1. Kleypas, Joan A., and Kimberly K. Yates. “Coral reefs and ocean acidification.” Oceanography (2009).
  2. Kelly, Ryan P., et al. “Mitigating local causes of ocean acidification with existing laws.” Science 332.6033 (2011): 1036-1037.
  3. Rau, Greg H., Elizabeth L. McLeod, and Ove Hoegh-Guldberg. “The need for new ocean conservation strategies in a high-carbon dioxide world.” Nature Climate Change 2.10 (2012): 720-724.
  4. Marland, Gregg, et al. “Global, regional, and national fossil fuel CO2 emissions.” Trends: A compendium of data on global change (2003): 34-43.
  5. Logan, Cheryl A. “A review of ocean acidification and America’s response.” Bioscience 60.10 (2010): 819-828.
  6. “Acid-Base Properties of Salts.” N.p., n.d. Web. 20 Apr. 2017.
  7. Harvey, L. D. D. “Mitigating the atmospheric CO2 increase and ocean acidification by adding limestone powder to upwelling regions.” Journal of Geophysical Research: Oceans 113.C4 (2008).
  8. Mascarelli, Amanda. “Designer reefs.” Nature 508.7497 (2014): 444.
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