Ecotourism of Reefs: An Investment Worth Protecting

Not surprisingly, one of the main contributors to the economies of coastal areas near coral reefs is ecotourism. People come from all over the world to areas with vibrant and healthy coral reefs largely for the aesthetic pleasure they provide. Recent progress has been made, in fact, to allow us to mathematically measure aesthetic appearance of reefs, and these values are also correlated with the general health of the reefs³.  This is extremely significant for economies relying on ecotourism of coral reefs, as this can be done for very little cost, and can help to monitor the physical beauty and health of the reefs that bring in large amounts of revenue from drawing in ecotourists.

However, even though these economies rely heavily on the ecotourism of these reefs, there are still quite often conflicts of interest. These exist between those wanting to preserve reefs in the interest of ecotourism and those who bring in revenue via other forms of tourism. For example, in Bermuda, there has recently been conflict concerning the construction of wider and deeper pathways for cruise ships bringing in tourists. The danger for coral reefs nearby lies in the risk of their being smothered overtime by the mass amounts of sediment brought up by heavy ship traffic¹. The permanent damage or loss of these reefs would have a huge negative impact on the revenue brought in by ecotourism in Bermuda.

Even though some may argue that there is always the possibility of restoration of these reefs, although it is typically physically possible, just because a reef is restored, does not guarantee that it will survive long-term. Also, it is not always financially feasible to restore reef ecosystems. In 2010, the average restoration cost of one hectare was about $1,600,000, with the total cost often being two to four times greater¹.

The good news is that in some cases, there are new ways of getting funds to preserve revenue earning reefs. Because the divers that visit these reefs prefer healthier reefs over damaged or dying ones, it has been found that most of these individuals (with regards to reefs in Guam) are more than willing to contribute to reef management via fees when diving (Image 1). If required, this could potentially positively benefit many reefs heavily visited by ecotourists .

Image 1. Several divers in the “Blue Hole” site of Guam. (Source:

In Guam’s reefs alone, it was estimated that large fish biomass brought in about $2 million a year (Image 2) and the presence of sharks and turtles together brought in anywhere from $15-20 million in a year². The preservation of these reefs should at the very least gain more attention by policy makers for not only the large revenue they currently bring in, but for the potential economic disasters that could take place if such vital revenue were to be lost.

Image 2. A school of fish around one of Guam’s reefs. (Source:



¹ Bayraktarov, Elisa, et al. “The cost and feasibility of marine coastal restoration.” Ecological Applications 26.4 (2016): 1055-1074.
² Grafeld, Shanna, et al. “Divers’ willingness to pay for improved coral reef conditions in Guam: An untapped source of funding for management and conservation?.” Ecological Economics 128 (2016): 202-213.
 ³ Haas, Andreas F., et al. “Can we measure beauty? Computational evaluation of coral reef aesthetics.” PeerJ 3 (2015): e1390.
¹Lester, Sarah E., et al. “Environmental and economic implications of alternative cruise ship pathways in Bermuda.” Ocean & Coastal Management 132 (2016): 70-79.



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Toxic Air: How Ocean Acidification Affects Reef Organisms

Hello, everyone! This semester, I am writing a series of blog posts about the effects of ocean acidification on coral reefs. If you are unfamiliar with the concept of ocean acidification, please check out my last blog post, “When Air Meets Water: Carbon Dioxide And Ocean Acidification.” You will find an explanation of the ocean acidification process and an examination of the negative relationship between atmospheric carbon dioxide and calcium carbonate concentrations. Furthermore, the post shares projections for atmospheric carbon dioxide concentration, oceanic pH, and calcification rates, as well as describes how ocean acidification lowers aragonite (calcium carbonate) saturation and threatens reef building and reef organisms.

In this post, I will be expanding more upon the effects of ocean acidification on reef organisms. As mentioned in my last blog post, relative to pre-industrial rates, corals, calcifying macroalgae, and other reef-building organisms are expected to calcify 10-50% less by 2050.As a result, corals will become rarer, and reefs and reef organisms will experience more difficulty functioning.Furthermore, the decline in production and rise in dissolution of calcium carbonate will lessen breakwater effects that shield coastlines and generate habitats for mangroves, seagrass beds, and more.1

Figure 1. Coral community calcification rate changes in the Biosphere 2 coral reef mesocosm with respect to decreasing aragonite saturation state. Corresponding atmospheric pCO2 levels (ppm) and Ωarag values shown: 280 = pre-industrial, 390 = present, 560 = 2X pre-industrial. Shift from net calcification to net dissolution at Ωarag = 1-2. © Source: Kleypas et al.1

Ocean acidification decreases skeletal growth in reef-building corals and coralline algae, which likely cannot adapt to these changes, by lowering calcification rates.1 Figure 1 shows that as aragonite saturation states decreased, coral community calcification rates in the Biosphere 2 coral reef mesocosm also decreased. While calcification will increase if ocean acidification is reversed and aragonite saturation states increase, it is highly unlikely that ocean acidification can be reversed.1 (If so, then what? I will be writing about possible future steps in my next blog post!)

Table 1. Proposed calcification functions in organisms. © Source: Kleypas et al.2

Calcium carbonate secretions from organisms help provide skeletal support, protection, and many other functions, as indicated in Table 1. Thus, reduced calcification may cause organisms to lose beneficial functions. For example, with lessened protection, a species may get a microbial infection or be subjected to predation.2 Alternatively, reduced ballast (balance) could make it difficult for a species to maintain its position in the water column.2 In corals and coralline algae, significant skeletal growth elevates the organism into better light (increased light gathering) and flow (more resilience against hydrodynamic forces) conditions, while slower or more fragile growth lowers reproductive success.2 For example, size (not age) determines reproductive maturity in Goniastrea aspera, and skeletal fragmentation in Acropora palmata reduces sexual reproduction potential.2

Reef-building corals may exhibit other harmful responses to reduced calcification as well. First, they may decrease their linear extension rate and skeletal density.3 Alternatively, they may maintain physical extension rates by reducing skeletal density, increasing risk of hydrodynamic damage and promoting bioerosion by parrotfish, which prefer to remove carbonates from lower-density substrates.3 Ultimately, coral reefs would have lower structural complexity, habitat quality, and diversity.3 Lastly, in response to reduced calcium carbonate saturation, corals may maintain skeletal growth and density by investing more energy in calcification.3 However, this diverts resources from reproduction, reducing larval output from reefs and making recolonization following disturbances difficult.3

Figure 2. Variation in pH, algal cover, and species abundance at carbon dioxide vents south of Castello d’Aragonese from April 18 to May 9, 2007. (a) Mean s.d. (cross bars) and range (dotted lines) of pH. (b) Calcareous (triangles) and non-calcareous (circles) algal cover. (c) Sea urchin, O. turbinata, limpet, and barnacle abundance. © Source: Hall-Spencer et al.4

As mentioned previously, ocean acidification can alter ecosystem dynamics and reduce reef diversity. Figure 2 illustrates relationships between pH, algal cover, and species abundance that were determined using a volcanic carbon dioxide vent system. In Figure 2B, as pH drops, non-calcareous algae overtakes calcareous algae in cover dominance. In Figure 2C, sea urchins, which help maintain ecosystem complexity and stability,4 disappeared first (pH = 7.4-7.5) as the pH dropped. On the other hand, calcitic organisms like barnacles, which can close their rostral plates around supplies of ambient water,4 survived until pH dropped to 6.6. Finally, under pH 7.4, adult Opuntia turbinata and limpet gastropod shells are weakened, increasing risk of predation,3 as evidenced by the drop in gastropod abundance.

Ultimately, it is clear that reef organisms suffer from and are unable to effectively respond to ocean acidification. With time, the loss of certain functions in specific organisms can lead to a general decrease in reef diversity and structural complexity. Without intervention, coral reefs are destined to lose their rich vibrancy and become dull, empty piles of rubble and dead coral. So think long and hard about how you can help slow down the ocean acidification process! (And if you have any trouble, I will help you out in my next post. :))


  1. Kleypas, Joan A., and Kimberly K. Yates. “Coral reefs and ocean acidification.” Oceanography (2009).
  2. Kleypas, Joan A., et al. “Impacts of ocean acidification on coral reefs and other marine calcifiers: a guide for future research.” Report of a workshop held. Vol. 18. 2005.
  3. Hoegh-Guldberg, Ove, et al. “Coral reefs under rapid climate change and ocean acidification.” science 318.5857 (2007): 1737-1742.
  4. Hall-Spencer, Jason M., et al. “Volcanic carbon dioxide vents show ecosystem effects of ocean acidification.” Nature 454.7200 (2008): 96-99.
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Local Relief but Global Uncertainty in Marine Protected Areas

Lately, coral reefs have been making headlines across the world because of their drastic decline and severe bleaching, but one story this week gives us a glimmer of hope. On March 20th, the Sun Sentinel reported that a proposal was unanimously passed by a Florida House of Representatives panel to create the “Southeast Florida Coral Reef Ecosystem Protection Area.”1 While this does not ensure any action on its own, a separate appropriations bill and Senate bill must be passed as well, this will allow monitoring to begin in the area so future plans can be prepared. This is a step in the right direction in a time when environmental budgets are being slashed across the country.

But what are protected areas, and why are they important?

The three main threats to coral reefs are eutrophication, overfishing, and climate change.2 While climate change is a global phenomenon, overfishing and eutrophication can be remedied on a more local scale, which is where marine protected areas come into play. There are various types of marine protected areas, or MPAs, but broadly, they are aquatic areas where human activity is limited or restricted for conservation purposes. The image below depicts both current MPAs across the globe as well as the number and location of MPAs that scientists believe is necessary going forward.

Figure 1. There are currently 980 registered marine protected areas globally. (Top) This figure displays the location of each MPA as well as a categorization of each MPA in terms of meeting attributes described in Mora et al. (Bottom) Each dot here represents a MPA needed to adequately protect coral reefs on a global scale. Source: Mora et al. in Science.5

There has been a lot of recent scientific literature lauding these protected areas in efforts to conserve coral reefs. In a report in Science, experts stated that at least 30% of coral reefs should be designated as no-take areas (NTAs), which are strict forms of MPAs where any form of exploitation is forbidden.3 This helps drastically in preserving the ecosystem of coral reefs, as reef fish are very influential in the trophic web and help keep macroalgae at bay.2 In 2014, Edgar et al. reported five main traits that dramatically increase MPA effectiveness: no take, well enforced, old (>10 years), large (>100 km2), and isolated by deep water or sand.4 This study reported greater large fish diversity and an increase in large fish and shark biomass, and concluded that more attention needs to be paid to MPA design, durable management and compliance to ensure that MPAs achieve their desired conservation value.4

However, not all scientists agree that MPAs are the way to go for reef conservation. Another paper in Science looked at the global effects of marine protected areas, instead of a local scale, and found them largely ineffective for reef conservation.5 This is due to global threats such as climate change, but also the widely dispersed nature of coral reefs. The authors claimed that throughout the current network of MPAs, only 2% of all coral reefs meet adequate attributes for conservation.5  The bottom image in figure 1 shows the proposed network of MPAs by the authors. While this is an important aspect of marine protected areas to consider going forward, it is my personal opinion that this study reinforces the need for large scale MPAs and extensive networks to properly protect coral reefs globally. Even if they are not effective in their current form, there is still hope for the future.

Overall, while there is active discussion on whether or not marine protected areas are the most efficient form of global conservation in their current form, they are effective management techniques for protecting reefs from local threats. MPAs are one way that humans are positively impacting, or at least reducing their negative impacts, on coral reefs, which is why they were featured in this blog on positive anthropogenic effects. There is still a lot of work to be done to research the best practices for these areas, as well as funding these projects and getting them approved by various governments, but if this network can be expanded, there may be hope yet for corals across the world.

Works Cited:

  1. Sweeney, D. South Florida coral reef protection bill passes House panel. Sun Sentinel (2017).
  2. Correa, A. S. Coral Reef Ecosystems. (2017).
  3.  Hughes, T. P. et al. Climate Change, Human Impacts, and the Resilience of Coral Reefs. Science 301, 929 (2003).
  4.  Edgar, G. J. et al. Global conservation outcomes depend on marine protected areas with five key features. Nature 506, 216–220 (2014).
  5. Mora, C. et al. Coral Reefs and the Global Network of Marine Protected Areas. Science 312, 1750 (2006).
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In order to Save Coral Reefs . . . We need to Save the Mangroves

The rainbow parrotfish (Scarus guacamaia) is the largest herbivorous fish in the Atlantic Ocean.1 As such, it plays an important role on coral reefs by grazing on and limiting the macroalgal biomass. A single juvenile parrotfish can take 28,000 bites per day!2 Clearly, the importance of these strong-jawed fish as grazers cannot be overstated.

Figure 1. Scarus guacamaia, commonly known as the rainbow parrotfish. These fish graze on macroalgae and are the largest herbivores in the Atlantic. (Source:

Interestingly, the rainbow parrotfish is one of seven known Caribbean fish species that are not present or have reduced adult densities on coral reefs when mangroves are absent.3 The rainbow parrotfish is confined to shallow reefs that neighbor mangroves; however, mangroves’ being present is not the only condition required for a habitat to be suitable for rainbow parrotfish juveniles. These fish cannot survive in mangroves that have rapidly fluctuating salinity levels. Additionally, rainbow parrotfish presence is positively correlated with large changes in temperature. Depth and distance from offshore channel openings are also factors that affect the parrotfish suitability of mangrove habitats.4

Another parrotfish species, the Scarus iserti or striped parrotfish, is also a common grazing species, although it is smaller and therefore less impactful than the rainbow parrotfish (although still important nonetheless). While not functionally dependent on mangrove habitats like the rainbow parrotfish, the biomass of this species was found to be 42% greater in reefs neighboring mangroves versus in reef systems lacking mangroves.1 Therefore, mangrove connectivity can greatly increase the macroalgal grazing pressure on coral reefs by affecting the abundance of these two important grazing species.

Parrotfish graze predominantly by scraping epiphytic macroalgae from corals.4 In Figure 1, a rainbow parrotfish can be seen grazing on macroalgae. Their role in removing macroalgae is very important for coral health. This is because when macroalgal abundance becomes too high, settlement space for corals is reduced, and the mortality rate for coral recruits is increased.1 Figure 2 shows a coral colony that has been overgrown by macroalgae. Both of these effects can lead to a decrease in live coral cover. It has been shown that high levels of grazing by parrotfish have doubled the rate of recruitment of corals.4 Also, grazing by parrotfish can increase the probability that coral populations will recover from sudden phase changes, such as hurricanes, as a result of their reducing the levels of macroalgae.1

Figure 2. A coral colony dominated by macroalgae. Overgrowth by macroalgae can lead to coral cover loss. (Source:

Hopefully, it is clear by now that parrotfish, especially S. guacamaia, are very vital members of the coral reef ecosystem. Alarmingly, the rainbow parrotfish is currently considered “vulnerable” by the International Union for Conservation of Nature. The reasons for this status are reduction in the size of individuals due to fishing pressure, and the reduction of suitable habitats (which, as mentioned, must be fairly specific). Scientists are concerned that declines in rainbow parrotfish will accelerate coral declines due to the reduction in macroalgal grazing that will occur.4 Currently, the main threat to rainbow parrotfish is habitat loss. For this reason, it is crucial that, in order to preserve coral reef ecosystems, we must also take measures to preserve mangrove forests situated near reefs.

Mangroves are currently a threatened habitat, having been heavily exploited in recent years for aquaculture farming and timbering.5 Figure 3 shows an aquaculture farm for producing shrimp in what was originally a pristine mangrove habitat. If mangrove decline continues at current rates, they will be completely gone in 100 years.6 Without mangrove forests present, there will not be any rainbow parrotfish on coral reefs. Keep in mind that this would mean that, for every individual fish lost, there would be between 28,000 and 16,000 less bites, depending on the age of the individual, to the macroalgae biomass every day.2 This would mean over 480,000 less bites each month per individual lost and that corals would have a much harder time competing with macroalgae. Steps must be taken to conserve mangrove habitats so that we will have the aid of the powerful rainbow parrotfish in combatting coral decline.

Figure 3. Aquaculture farming of shrimp in a mangrove forest. Aquaculture farming has led to a loss in magrove habitats, which can have devastating effects on rainbow parrotfish populations. (Source:

The Nature Conservancy, Conservation International, and the World Wildlife fund have teamed up to create the Mangrove Alliance with the goal of strengthening mangrove conservation efforts and raising awareness about their importance.6  A plan of action is currently being developed, and hopefully mangrove populations will be able to recover.


  1. Mumby, P. J., Hastings, A. “The impact of ecosystem connectivity on coral reef resilience.” Journal of Applied Ecology, 45, 854-862.
  2.  Dunlap, M., Pawlik, J. R. “Spongivory by Parrotfish in Florida Mangrove and Reef Habitats.” Marine Ecology, 19, 4, 325-337.
  3.  Nagelkerken, I. “Are non-estuarine mangroves connected to coral reefs through fish migration?” Bulletin of Marine Science, 80, 3, 595-607.
  4.  Machemer, E. G. P., Walter, J. F., Serafy, J. E., Kerstetter, D.W. “Importance of mangrove shorelines for rainbow parrotfish Scarus guacamaia: habitat suitability modeling in a subtropical bay.” Aquatic Biology, 15, 87-98.
  5.  Ilman, M., Dargusch, P., Dart, P., Onrizal. “A historical analysis of the drivers of loss and degredation of Indonesia’s mangroves.” Land Use Policy, 54, 448-459.
  6.  “Environmental groups plot course to reverse loss of mangroves during World Ocean Summit.” Yucatan Times, 8 March 2017.

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Fish Out of Water: Impacts of Reef Fishing

In my last post, we analyzed reef fishing and took a deeper look into some of the techniques, such as fishing with explosives and poisons, utilized by fishermen to catch more fish while putting forth minimal effort. In order to shed even more light on this topic as was promised in my last post, we will be taking a closer look at the potential impacts of reef fishing.

For the sake of maintaining a moment of positivity, I would like to begin by delving into a benefit of reef fishing. As has been seen on many different occasions, reef fishing has resulted in the bolstering of many local economies, most notably in Southeast Asia and East Africa.1 Prior to the introduction of reef fishing, most citizens in places such as the Philippines and Tanzania faced the issue of not being able to provide a livelihood for their families. However as a result of being introduced to the reef fishing realm, they were able to capture large amounts of fish and sell them to eager buyers at various prices.2 Some more luxurious species are valued up to half a million dollars. For example as shown in Figure 1, a Platinum Arowana sells for ~$400,000. Imagine being a poor fisherman in Tanzania, making this rare catch and being able to bring that amount home to provide for your family. It would be life-changing.

Figure 1. Image of the Platinum Arowana reef fish. It is currently the most expensive coral reef fish mainly due to its rarity and appearance. ©
Source: Aquarium Base3

Unfortunately, it is time to examine the more dire impacts of reef fishing. Given the amount of money that exists within the reef fishing industry, it should come as no surprise that different reef fish species are often overexploited, or overfished. This is an issue because these unnatural changes to reef fish composition change the dynamics of the coral reefs. Every individual organism plays a specific role in the coral reef ecosystem, and when a vast majority of them are no longer available to do their jobs, the ecosystem becomes more susceptible to other threats, such as the long-term starvation of a fellow fish species. For example with the ‘fishing down the line’ phenomenon, we see fisherman overfishing smaller reef fishes that serve as food sources for bigger reef fishes.1 Consequently thus further disrupting reef dynamics and resilience, the bigger fishes are left without food, and many ultimately starve to death.

Keeping with this topic, it is important to note that overfishing also has long-term effects on reef organisms other than fish. For example when grazing herbivores are overfished, algae can grow almost completely unencumbered. The presence of algae is beneficial to the ecosystem, but only at a certain amount. Excess algae “increases a reef’s susceptibility to coral bleaching”  given the fact that it has the potential to introduce pathogens, disrupt helpful bacteria and inhibit oxygen from coming in.4 Furthermore in another example, predators of grazing urchins keep the urchin population and bioerosion levels in check. However when their predators are overfished, the urchin population and bioerosion levels multiply exponentially.4 Figure 2 shows what some of these grazing urchins look like.

Figure 2. Image of grazing urchins that can heavily contribute to bioerosion if their population is allowed grow uncontrollably. ©
Source: Phys.Org5

Fishermen can also be negatively affected by overfishing. While the reef fishing industry is fairly profitable, it can only remain that way when there are actually fish present in reefs to catch. Overfishing has led to the rapid decline in a variety of reef fishes, such as the kala and bluefin trevally.1 Because of this, reefs as a whole are declining in the number of fishes they actually house. Consequently, fishermen are at an impasse where they must decide whether to continue or stop fishing altogether in order to allow these fish populations to rebound and return to equilibrium. Most fishermen have decided to continue fishing, and as a result, their businesses are suffering due to decreased product availability.

By delving deeper into the effects fishing has on coral reefs, we were able to see both the highs and lows of such human actions. That being said while humans are able to benefit financially, it appears that, as a whole, reef fishing tends to have a negative effect on every organism involved, even the aforementioned humans. Therefore in my subsequent blog post, I hope to shed light on possible solutions that could be implemented in order to address these negative impacts. Because if things are allowed to continue down this path, many coral reef ecosystems will soon find themselves beyond repair.


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

2 Jackson, J. B., Kirby, M., Berger, W., Bjorndal, K., & Botsford, L. (2001). Historical Overfishing and the Recent Collapse of Coastal Ecosystems. Science, 293(5530), 629-637. Retrieved March 23, 2017.


4 Bellwood, D., Hughes, T., Folke, C., & Nyström, M. (2004). Confronting the coral reef crisis. Nature, 429, 827-833. Retrieved March 23, 2017.



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Conserving the Treasures of the Deep: How and Why Deep Water Reefs Should Be Conserved

Coral reefs around the world are changing. Human’s detrimental impact on the world’s reefs through nutrient runoff, ocean acidification, physical damage, and rising sea temperatures and levels are threatening the diversity and even existence of many coral reefs. While this is readily apparent in many shallow water reefs, the hidden deep water reefs sites might be even more danger than their shallow cousins due to a combination of harsh conditions and low awareness about damage caused by human actions.

Coral reefs of all kinds around the world are vital sites for conservation and deep water reefs are no exception. Deep water reefs share many of the benefits that shallow water reefs are acclaimed for such as homes for many commercially harvested fish, producing compounds that are used in modern medicine for their anti-viral and anti-inflammatory properties, and serving as habitat for huge amounts of biodiversity.  In addition, deep water reefs have some unique benefits of their own. For one, deep water reefs are old. Not old like your grandfather or even like the United States, but old like the use of bronze tools. Coral colonies have been recorded at over 4,000 years old and the reef skeletons they leave behind can be many many times that. This gives the deep water coral Leiopathes glaberrima the title of oldest marine organism on record and gives scientists an excellent way to study past conditions. For as these corals grow and build the reef they leave little rings in the structure around them. These rings, similar to the rings in the trees, can tell scientists about the temperature, salinity, and nutrients available in the ocean thousands of years ago. This information on ocean conditions so long ago is invaluable, especially in a time where it is more and more crucial to understand how ocean’s temperatures can change over millennia. Protecting these reefs in order to preserve the potential for large amounts of scientific data is paramount especially in the face of mounting threats against deep water reefs1,2,5.

Leiopathes glaberrima, the oldest known marine organism.
NOAA photo library

Of all the threats on deep water coral reefs, the greatest one is pure physical damage. These deep water reefs live in temperatures as low as 4C with no light for photosynthetic activity and must snatch what nutrients and food there is floating around in the ocean depths. These conditions mean that these reefs grow at a rate that’s best measured in mm per year. So when an errant chain or anchor plows through a field of deep sea coral, its destroying not years but millennia of work. And nothing damages these corals more often or more heavily than deep sea fishing trawlers1,4.

A diagram of a trawling net at work. The heavy doors in front of the net cause scarring by dragging over and through reef material.
By NOAA –, Public Domain,

Fishing trawlers work by dragging nets along the ocean floor in order to catch fish that may inhabit the lower depths of the ocean. These nets can go up to 1500m (~5000ft) deep, and often favor the continental shelf regions that are so valuable for deep water reefs. Their conical nets are held open by heavy beams or doors and may be weighed down with large wheels or chains. The structures that weigh these nets down to the bottom, whether they be gates, wheels, or just iron or lead weights, can cause catastrophic damage to deepwater reefs, leading to huge scars through reefs. Countries such as the United Kingdom and Norway have already enacted legislation to protect known reef areas from fishing activities that heavily damage the sites, and many more are attempting to follow their lead. In order to curtail damage to these reefs, and let them begin the long, slow process of healing we need to both direct efforts to finding these elusive deep water sites, as well as protect them from damaging activities3,6.

  1. Roberts JM (2006) Reefs of the Deep: The Biology and Geology of Cold-Water Coral Ecosystems. Science 312:543–547.
  2. Rogers AD (1999) The Biology of Lophelia pertusa (Linnaeus 1758) and Other Deep-Water Reef-Forming Corals and Impacts from Human Activities. International Review of Hydrobiology 84:315–406.
  3. Freiwald, A (2004) Cold-water coral reefs: Out of sight – No longer out of mind. UNEP report.
  4. Svensen, E. Coral reefs: Cold water corals. WWF.
  5. Ocean Portal. Deep Sea Corals. Smithsonian Museum of Natural History
  6. Rogers A (2004) The Biology, Ecology and Vulnerability of Deep-Water Coral Reefs. IUCN.
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Eureka! Another species…and another… and another

While unknown species continue to disappear, researchers look to find undiscovered species and to document them. I wish to address the process of finding and documenting new species to the scientific community and rates of species discoveries. The rate of recovery is paramount to estimating total species diversity in both terrestrial and marine ecosystems.

Once a potentially undocumented species is found the following process (more or less) id followed1:

  1. A type specimen is collected
  2. The type specimen is compared to documented species
  3. IF found to be unique from known species, researchers write formal documentation
  4. The description is submitted to journal
  5. Peer experts review the submission for validity
  6. IF approved, the species description is published and circulated (Image 1 below)

Image 1. Screenshot of news article announcing newly described nudibranch species. Link provided below. Article written by Tim Stephens, Photocredit : Kevin Lee. Primary literature linked below7.



Overall the formal taxonomic process can be quite long, taking years sometimes after the initial discovery. However the instances of discovery offer another means of research. The rate of discoveries and the prediction of future rates of discovery are used in the process of estimating diversity2. Ecologists estimate diversity using the assumption that as discovery rates decrease, scientists are approaching the total diversity. Researchers have not reached this point yet for marine environments – the rate of new species descriptions are at the highest ever3. As seen in Image 2 below, approximately 2000 species are described per year. And while diversity estimates are made using mathematic modeling, it is still mathematical guesswork. This guesswork is made more reliable through more exhaustive sampling and the recognition of patterns of diversity. Patterns also guide further sampling efforts.

Image 2. Black shows the number of accepted valid species per year. Grey shows the number of species described per year.  Year on x axis. Appeltans, Wards et al.3  

Some marine habitats have been under sampled just as they have been under-researched. In some cases this is still due to inaccessibility or insufficient equipment (a common theme). In marine environments depth adds complexity to patterns. Benthic (sediment bottom) communities are being used to study patterns of diversity4, 5. Sampling found both coastal and deep-sea benthic communities have high species richness, however coastal communities have been much more thoroughly sampled4. Latitudinal gradients are also observed in marine communities, as they are in terrestrial habitats5. Other factors such as temperature and productivity further complicate patterns.

As technology improves, sampling becomes easier. Fewer species are likely to be missed, but the line between species is sometimes blurred. Genetic testing lumps or splits previously described species, redefining previously accepted species boundaries. Also ongoing speciation changes the species categories that have already been accepted. As species continue to evolve, changes must be accounted for as we attempt to find answers to the question of diversity.


2 Wilson, S. P. and Costello, M. J. (2005), Predicting future discoveries of European marine species by using a non-homogeneous renewal process. Journal of the Royal Statistical Society: Series C (Applied Statistics), 54: 897–918. doi:10.1111/j.1467-9876.2005.00513.x

3 Appeltans, Ward et al. (2012), The Magnitude of Global Marine Species Diversity. Current Biology,22(23): 2189 – 2202

4 Gray, J. (2002) Species richness of marine soft sediments. Marine Ecology Progress Series, 244:285 – 297

5 Wittman, et al. (2004) The relationship between regional and local species diversity in marine benthic communities: A global perspective. PNAS, 101 (44): 15664 – 15669

Stephens (2017) Colorful new species of sea slug named after Long Marine Lab’s Gary McDonald

Uribe, R.A., Sepúlveda, F., Goddard, J.H.R. et al. Mar Biodiv (2017). Integrative systematics of the genus Limacia O. F. Müller, 1781 (Gastropoda, Heterobranchia, Nudibranchia, Polyceridae) in the Eastern Pacific. doi:10.1007/s12526-017-0676-5

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Osteoporosis or Osteo-porites: Can corals cure bone disease?

When people think about medical advancements, their minds often revert to rare chemicals and intricate biochemical reactions (at least mine does). In my last blog post, I talked a lot about how some coral reef organisms are able to produce chemicals that can be used to treat a variety of human diseases. However, when we constantly are thinking in such precise detail, we can overlook simpler treatments that can be just as effective. Today, I want to talk about this phenomenon as it relates to medical uses of coral, specifically with your body’s durable framework: bones.

Bone grafting is a surgical process whereby damaged bone is replaced with healthy bone in some area of the body; the graft then integrates together with existing bone, eventually biodegrading away.¹ For a long time, bone grafting was a very consequential procedure; often to avoid rejection from the immune system, grafts would have to be take from some other area in the same individual (for example, bone could be taken from a femur in the leg to replace a diseased bone in the arm). However, this meant multiple different surgeries were usually necessary, which led to more complications and longer periods of postoperative therapy.

In the 1980s, Professor Eugene White had a revelation while scuba diving in the South Pacific; he realized he could use coral skeletons as bone grafts.² This would decrease both the number of surgeries and the time of postoperative therapy. He combined the coral skeleton (made of calcium carbonate) with heat, water, and phosphates to produce hydroxyapatite, the same chemical compound that comprises human bones (Figure 1).¹

Figure 1: Diagram of the formation of human bone via hydroxyapatite crystal deposition (McGraw-Hill)

For a long time, scientists have noticed the chemical and structural similarities between coral and bone, especially corals of the genus Porites (Figure 2) Numerous studies have indicated that coral grafts are able to function as “adequate carrier[s] for growth factors and allow cell attachment, growth, spreading and differentiation.³

Figure 2: Comparison between hydroxyapatite made from a coral skeleton and an actual human bone. Both materials are durable and porous, allowing coral skeletons to act as effective bone grafts. (Mueting Media)

There was only one problem: this bone-like coral compound failed to biodegrade completely as new bone formed, leading to some unfavorable complications. As a result, coralline grafts were limited to very specific surgeries in certain situations.¹² However, a team at Swansea University in the United Kingdom found a possible solution to this issue.4 Instead of simply transforming the calcium carbonate coral into hydroxyapatite, they covered a calcium carbonate scaffold with a layer of hydroxyapatite to form a material called coralline hydroxyapatite/calcium carbonate (CHACC). Unlike pure hydroxyapatite, CHACC was found to completely biodegrade as bone growth occurred, which is ideally how a tissue scaffold functions (Figure 3).

Figure 3: Diagram of bone regeneration using a coral scaffold. The coral scaffold eventually completely integrates into the regenerated bone. (Stanford University)

Further clinical trials of this new treatment are in progress, but CHACC may be a huge development in the field of orthopedic surgery, significantly lowering the rate and length of postoperative complications. So the next time you twist your ankle, just remember that coral may become your new best friend.



¹Agnew, M. (2014, October 21). Sea Coral: It’s (Soon to Be) in the Bones. Modern Farmer. Retrieved from

²Fessenden, M. (2014, October 23). Sea Coral Makes Excellent Human Bone Grafts. Smithsonian Magazine. Retrieved from

³Demers, C., Hamdy, C.R., Corsi, K., Chellat, F., Tabrizian, M., & Yahia, L. (2002). Natural coral exoskeleton as a bone graft substitute: a review. Biomed. Mater. Eng. 12(1): 15-35.

4Paddock, C. (2013, November 2013). Bone grafts may be better with new sea coral material. Medical News Today. Retrieved from

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King of the Western Atlantic, the Lionfish

While lions are considered the kings of the jungle, lionfish seem to be exerting their reign over the Atlantic coast of the United States as well as the Caribbean. Lionfish may seem like an innocent beauty, with they’re intricately patterned spines and stripes, but really they are not as harmless as they seem. You may have heard of the saying, “one bad apple spoils the barrel”, well, the lionfish appear to be having a similar effect on the reefs of the Western Atlantic. As lionfish population numbers in the Atlantic increase, they seem to be wiping out other native fish species, upsetting the ecosystem and food web of the native reefs.

So how sizable was this lionfish invasion? Well, lionfish abundances increased to account for 40% of the total predator biomass in the Caribbean and Gulf of Mexico region between 2004 and 2010.1 Figure 1 shows the gradual increase in population sizes of the lionfish in the Western Atlantic during this time period. These invasive lionfish have progressively been taking over the Atlantic coast of the United States, as well as the Caribbean region, which has been drastically impacting the ecosystem of the native reefs. Lionfish have successfully established populations along the Atlantic coast of America ranging from Florida, all the way to North Carolina and even Rhode Island.2 They have also been successful in invading Bermuda, Bahamas, and Caribbean Sea.2 But how exactly were these lionfish introduced to the Western Atlantic if they are not native to this region? To give a little background on this notorious fish, lionfish are actually native to the western Pacific region, so they have traveled a long distance to invade the Atlantic.3 It is believed that these fish were introduced through their release from aquariums or even possibly though ballast water (a method I mentioned in more detail in my previous blogpost).3 It is due to human impact that we are seeing such detrimental effects to the western Atlantic.

Figure 1. Map of the Atlantic Coast of the U.S. and Caribbean region, showing the increase in lionfish population on a yearly basis between 1999 and 2010. Red dots indicate lionfish occurrences. Journal of Biogeography 2

What makes the lionfish such a successful invasive predator? The answer to this question would be, the several unique physiological and biological characteristics, as well as the new ecological niche the lionfish adopts in non-native waters. A characteristic specific to the lionfish that gives it an advantage over other species is its venomous spines which are used as a defense mechanism (Figure 2).3 Since the lionfish has invaded non-native waters, the lack of predators also serves as an advantage and encourages the survival of the species.3 Invasive species are more likely to survive if they are successful at evading predation and the lionfish exhibits this quality in the Western Atlantic. The lionfish’s spawning rate is year-round and at a frequency of every four days, also factoring into its successful establishment and expansion.2 Overall, this fish knows what it is doing and has exerted its dominance in the Western Atlantic.

Figure 2. Image of an adult lionfish and its venomous spines. Marine Ecology Progress Series3

We’ve talked a lot about what makes the lionfish a successful invasive species in the Western Atlantic, but we haven’t really touched on the effects the lionfish may have on the native reef habitats. Lionfish have had a dramatic impact on native small-bodied reef fish. The influence of the invasive lionfish can be seen from data collected in the Bahamas region where there was a 65% decline, between 2008 and 2010, in the combined biomass of 42 small-bodied reef fish species, which serve as prey for the lionfish.1 This change in biomass can be seen in Figure 3 below.

Figure 3. Graph of the change in biomass of different groups of organisms during the study on lionfish conducted in the Bahamas, between 2008 and 2010. The graph shows that there was a 65% decline in small-bodied fish that served as prey for the lionfish. The graph also shows a decline in other competitors of the lionfish as well as other large-bodied non-competitors. On the other hand, the biomass of small-bodied species that were not prey for the lionfish stayed the same during this time two year time period. PLOS1

This kind of dramatic decline in fish biomass can have negative effects on the food web of the ecosystem. Introduction of the invasive lionfish can impact native fish, whether it be through predation or competition, produce cascade effects (indirect impacts on other species and components of the ecosystem), leading to the disturbance of the food web.4 Any small, direct, influence an invasive species has on the native habitat, will eventually create larger, indirect, ecological impacts on the ecosystem. If lionfish run out of their preferred prey in the Atlantic, they may resort to feeding on the juveniles of fisheries species which are economically important.5 Caribbean coral-reef aquarium fish trade is also of great economic value, but, of the top 20 ornamental species in the Western Atlantic, 7 are included in the top 10 families that constitute the diet of the lionfish in the Bahamas.5 These are examples of some of the economic impacts of the lionfish invasion, what about ecological impacts on a larger scale? Well, because invasive lionfish lead to a dramatic decline in native species in the Western Atlantic, this direct influence can also lead to the destruction of coral reefs in the region. Lionfish are known to prey on parrotfish and other herbivorous fish, and dramatic declines in these species have been known to lead to the demise of reef-building corals and algal overgrowth, which would be detrimental to reefs.5

Further research on the ecological and economic impacts of the invasive lionfish in the Western Atlantic can help us combat the damage that has been done to the native reef habitats. Understanding the role invasive species, such as the lionfish, play in non-native habitats will help identify a problematic invasive species and help prevent critical damage. And finally, raising awareness on specific cases of invasive species, will educate people on the human impact we have on our oceans and the coral reefs. I hope that through raising awareness, we can also encourage advocacy on conservation of coral reefs, which promote such biodiversity and serve us both economically and ecologically. The lionfish has been an invasive species that scientists have been analyzing for the past several years, stay tuned, for my next post, to find out what invasive species we should be looking out for in the near future.



1 Green, Stephanie J., John L. Akins, Aleksandra Maljković, and Isabelle7 M. Côté. “Invasive Lionfish Drive Atlantic Coral Reef Fish Declines.” PLOS ONE. Public Library of Science, 7 Mar. 2012. Web. 21 Mar. 2017. <>.

2 Hines, Andrew, et al. “Reconstructing the lionfish invasion: insights into Greater Caribbean biogeography.” Journal of Biogeography 38.7 (2011): 1281-1293.

3 Whitfield, Paula E., et al. “Biological invasion of the Indo-Pacific lionfish Pterois volitans along the Atlantic coast of North America.” Marine Ecology Progress Series 235 (2002):     289-297.

4 Arias-González, Jesús Ernesto, et al. “Predicted impact of the invasive lionfish Pterois volitans on the food web of a Caribbean coral reef.” Environmental research 111.7 (2011): 917-925.

5 Albins, Mark A., and Mark A. Hixon. “Worst case scenario: potential long-term effects of invasive predatory lionfish (Pterois volitans) on Atlantic and Caribbean coral-reef communities.” Environmental Biology of Fishes 96.10-11 (2013): 1151-1157.

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Remoras Galore: Commensalism on Coral Reefs

In my first blog post I explained that coral reefs provide us with some of the most complex and visually stunning ecosystems in the world. In environments as ecologically diverse as these, interesting symbiotic relationships are bound to occur. To recap, symbiotic relationships are categorized as mutualistic, commensal, or parasitic. My first post described how many mutualistic relationships on modern reefs are threatened by rising global surface temperatures and human activities that push reef abiotic conditions to the extreme. While my last post involved ways in which humans have impacted reefs, much of today’s post will focus on how the existence of commensalism on reefs has allowed us to expand our phylogenetic knowledge of reef dwellers.

Commensalism on reefs is a relationship between two marine organisms from which one individual benefits while the other is not affected at all. Though seemingly straightforward, classifying commensal relations can be difficult, as new information can lead to the realization that a relationship is somehow impacting both of the organisms involved, thereby making it either mutualistic or parasitic. Because of these restrictions, this post will demonstrate the above information chiefly through one example: remoras.

The most classic example of commensalism on reefs is the remora. Commonly called “suckerfish” or “sharksuckers”, these fish (of the family Echeneidae) attach themselves to the skin of larger marine animals like sharks and manta rays via a specialized organ on what we might consider their back. This organ, which acts as a sort of suction cup, allows the fish to travel with their host without damaging tissue, collecting food particles that the larger animal unwittingly distributes. This relationship is pictured below.

Image 1: A reef manta ray (Manta alfredi) acts as host to many remoras; Credit: Esteban Toré.

This strange adaptation of remoras remained mysterious until a recent study in which researchers with the Smithsonian Institution found that the suction cup-like organ was in fact the dorsal fin of the remora’s ancestors¹. In contrast with previous hypotheses claiming that the suction disc evolved independently as an entirely new structure, the new research suggests that it instead evolved through a long series of small changes to the typical dorsal fin found in other modern fish species². Image 2 gives a close-up view of a remora’s suction disc.

Image 2: Head of a 26.7 mm Remora osteochir in lateral (A), dorsal (B), and frontal (C) view¹.

It has been suggested that because of the extra drag on the host while swimming, a remora’s presence could be harmful, technically making it a parasite. However, because its body composition evolved ideally for traveling with a host, the remora has a streamlined body that slows its host down minimally, if at all. In the past, remoras attached to the hulls of ships were blamed for slowing down ocean voyages, and were even thought to be capable of stopping a ship in its tracks. Image 3 from the Hortus Sanitatis captures this idea. The Latin word remora means “delay”, so the fish derived its name from this false mythology³. Unlike fellow marine hitchhikers like barnacles, which can actually prove harmful to living hosts if biofouling (the accumulation of organisms on wet or underwater surfaces) reaches a critical point, remoras are simply commensal organisms, neither benefitting nor hindering their live or crafted hosts.

Image 3: Six “ship-holders” delay the passage of a ship. From the first Strassburg edition of the Hortus Sanitatis, 1497. Credit: E. W. Gudger³.


1 Britz, R. and Johnson, G. D. (2012), Ontogeny and homology of the skeletal elements that form the sucking disc of remoras (Teleostei, Echeneoidei, Echeneidae). J. Morphol., 273: 1353–1366. doi:10.1002/jmor.20063

2 “Scientists Confirm Theory regarding the Origins of the Sucking Disc of Remoras.” – News and Articles on Science and Technology, 6 June 2013. Web. 22 Mar. 2017.

3 Crew, Becky. “How the Sharksucker Got Its Suction Disc.” Editorial. Scientific American 4 Feb. 2013: n. pag. Scientific American Blog Network. 06 Aug. 2013. Web. 23 Mar. 2017.

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