The Reading Process: How Essential are Letters?

Catalyst Volume 8

Reading is such a basic, yet vital, component of our lives. Without the ability to read, we would be unable to comprehend a street sign telling us to stop, a crucial headline in the daily news, or an email telling us that the class we hate the most has been cancelled. Unfortunately, there are people whose ability to read is either impaired or entirely nonexistent. Much research has been done on the reading process and how it is affected by brain impairment; at Rice University, Dr. Simon Fischer-Baum and his team are currently studying the reading deficiencies of stroke patients. Before examining a special case of someone with a reading deficit, an understanding of the fundamentals of reading is necessary.

As English speakers, we might assume the reading process starts with the letters themselves. After all, children are commonly taught to identify each individual letter in the word and its sound. Next, the individual strings the individual sounds together to pronounce the word. Finally, once the words have been identified and pronounced, the person refers to his or her database of words and finds the meaning of the word being read.

While letters are the smallest tangible unit of the words being read, they actually depend on an even more basic concept: Abstract Letter Identities (ALIs). ALIs are representations of letters that allow a person to distinguish between different cases of the same letter, identify letters regardless of font, and know what sound the letter makes. It would appear that the ability to read is entirely contingent on one’s knowledge of these letter identities. However, certain scenarios indicate that this is not entirely true, raising questions about how much influence ALIs have on reading ability.

Dr. Fischer-Baum’s lab is currently exploring one such scenario involving a patient named C. H. This patient suffered from a stroke a few years ago and, as a result, has a severely impaired capacity for reading. Dr. Fischer-Baum and David Kajander, a member of the research staff, have given C. H. tasks in which he reads words directly from a list, identifies words being spelled to him, and spells words that are spoken to him. However, his case is especially interesting because he processes individual letters with difficulty (for example, matching lowercase letters with their uppercase counterparts), yet he can still read to a limited extent. This presents strong evidence against the importance of ALIs in reading because it contradicts the notion that we must have some knowledge of ALIs to have any reading ability at all. It has become apparent that C. H. is using a method of reading that is not based on ALIs.

There are several methods of reading that C. H. might be using. He could be memorizing the shapes of words he encounters and mapping those shapes onto the stimuli presented to him, a process called reading by contour. If this were the case, then he should have a limited ability to read capital letters since they are all the same height and width. C. H. could also utilize partial ALI information and making an educated guess about the rest of the word. If that were true, then he should be very good at reading uncommon words since there are fewer words that share that letter sequence.

In order to pursue this hypothesis, Dr. Fischer-Baum’s lab gave C. H. a task derived from a paper by Dr. David Howard. Published in 1987, the paper describes a patient, T. M., who shows reading deficiencies that are strikingly similar to those of C. H.¹ A new series of reading tasks and lexical decision tasks from this paper required C. H. to determine whether or not a stimulus is a real word. For the reading tasks, a total of 100 stimuli, 80 words, and 20 non-words were used, all varying in length, frequency, and ease of conjuring a mental image of the stimulus. For the lexical decision tasks, 240 stimuli, 120 words, and 120 non-words were used, all varying in frequency, ease of forming a mental picture, and neighborhood density (the number of words that can be created by changing one letter in the original word). Additionally, each of the word lists was presented to C. H. in each of the following formats: vertical, lowercase, alternating case, all caps, and plus signs in between the letters. These criteria were used to create the word lists, which were then presented to C. H. in order to determine which factors were influencing his reading.

After the tasks were completed and the data was collected, C. H.’s results were organized by presentation style and stimuli characteristics. For reading tasks, he scored best overall on stimuli in the lowercase presentation style (30% correct) and worst overall on stimuli in the plus sign presentation style (9% correct). Second worst was his performance on the vertical presentation style (21% correct). For the lexical decision tasks, we saw that C. H. did best on stimuli in the all capital letter presentation style (79.58% correct) and worst on stimuli in the vertical presentation style (64.17% correct), although his second worst performance came in the plus sign presentation style (65% correct). Across both the reading and lexical decision tasks, he scored higher on stimuli that were more frequent, shorter in length, and easier to visualize. In the lexical decision tasks, he scored higher on low-neighborhood density items than high-neighborhood density items.

These results lead us to several crucial conclusions. First, C. H. clearly has a problem with reading words that contain interrupters, as evidenced by his poor performance with reading the plus sign words. Second, C. H. is not using contour information to read; if he were, then his worst performances should have come on the all caps reading tasks, since capital letters do not have any specific contour. Evidence suggests he is indeed using a partial guessing strategy to read because he performed better on low-neighborhood density words than on high-neighborhood density words. These conclusions are significant because they suggest further tests for C. H. More importantly, these conclusions could be especially helpful for people suffering similar reading deficits. For example, presenting information using short, common, and non-abstract words could increase the number of words these people can successfully read, increasing the chance of them interpreting the information correctly. Dr. Fischer-Baum’s lab plans to perform further tasks with C. H. in order to assess his capacity for reading in context.

References

1. Howard, D. Reading Without Letters; The Cognitive Neuropsychology of Language; Lawrence Erlbaum; 1987; pp 27-58.

Recycled Water: The Future of the American West

Catalyst Volume 8

The Western United States has always been dry; San Diego, for example, derives only 15% of its annual water needs from rain.¹ Engineers have constructed creative but short-sighted solutions to the problem of water shortage in response. Rivers have been diverted hundreds of miles to major cities, enabling further urban growth in areas that would otherwise not be able to support it.² This rapid growth, however, comes at the cost of depleting these rivers. Letting entire cities, such as San Diego, Las Vegas, or Phoenix wither away is unrealistic, so scientists must create solutions that are sustainable, environmentally friendly, and relatively easy to implement in order to facilitate the survival of the Western states. Enter the concept of recycled water. Known as “toilet to tap” by its adversaries, recycled water is wastewater that, once cleaned of pathogens, viruses, pharmaceuticals, chemicals, and biological matter, is redistributed as drinking water. In order to sustain the existence and growth of Western cities, recycled water must be accepted and utilized.

To understand the need for recycled water, it’s helpful to look at the typical water shortages in the Western United States. Since 1950, there has been a 127% increase in water use nationwide, putting extreme strain on the existing infrastructure and environment.² This increase in water usage has occurred despite the worsening droughts that affect the area. Studies conducted in Salt Lake City show that an increase by even one degree Fahrenheit causes as much as a 6.5% drop in local stream water flow per year.² The increase in temperature will also strain and eventually exhaust the sources from which Western cities get their water. The West is faced with an issue that few wish to confront: if they continue to rely only on traditional water sources, Western cities will literally dry up, forcing residents to move elsewhere and creating massive economic instability nationwide.

One possible solution to water shortages is recycled water. The process of recycling water is intensive, which is understandable given the dangers of contamination. Wastewater is first sent to a sewage treatment plant where filters remove solids and dissolve biological material.³ The wastewater then undergoes normal groundwater treatment. First, microfiltration removes bacteria and protozoa. Then, reverse osmosis is utilized to remove viruses, salts, and pharmaceuticals. Finally, ultraviolet light and hydrogen peroxide destroy “trace organics.”³ After these steps are taken, the treatment plant adds in minerals and discharges it into a reservoir. Months later, the water from the reservoir is treated again and distributed to households.

It is a subject of debate whether water is clean enough after the treatment to be directly distributed without mixing it with reservoir water. Some say that the water produced by the treatment plant is even purer than reservoir water.⁴ Others, however, say that directly releasing treated water into the reservoir instead of letting it percolate through various ground layers permits impurities to remain in the water.⁵ Whether the water is safe enough to be directly consumed depends on the regulatory standards themselves as well as the plant producing the water. When produced according to Environment Protection Agency (EPA) guidelines, recycled water is as safe as traditionally obtained water.⁶

Another concern about recycled water is that treatment plants are unable to entirely remove pharmaceuticals, chemicals, and bacteria such as E. coli. The presence of E. coli could be the result of organic material remaining in the water after treatment. Traces of pharmaceuticals also pose a risk to the consumer. When medicine is flushed down the toilet or sink, it remains in the water supply and can be redistributed to other consumers. Although studies do not deny claims that such trace pharmaceuticals are found in recycled water,⁷ it is important to put this into perspective: even non-recycled water contains trace amounts of pharmaceuticals and is deemed safe for public consumption by the EPA.

Furthermore, many scientists who were once wary of recycled water have changed their opinions. In 1998, the National Research Council (NRC) reported that discharging recycled water into reservoirs was acceptable, “although only as a last resort.”¹ Many people opposed to water reclamation cited this study, emphasizing the fact that it should only be used as a last resort, and not otherwise. The Western states are, however, facing water shortages that will soon require last resorts. More importantly, however, is the NRC’s new statement about wastewater treatment technology: “the possible health risks associated with exposure to chemical contaminants are minimal.”⁶ Thus, those opposed to recycled water cannot continue to use the NRC’s previous stance as backing for their claims. Recycled water that adheres to the EPA’s health and safety guidelines is necessary for the survival of states in the Western U.S.⁸

In addition to safety, cost is also an important factor to consider in the production of recycled water. Currently, the production of recycled water is not subsidized by the government. Due to the additional treatment that waste water requires, the production and distribution of recycled water costs four times more than that of groundwater.¹ If recycled water were to be subsidized, as it is in Orange County, water production would cost only 0.0018 cents per gallon to produce, a small increase from traditional tap water’s cost of 0.0015 cents per gallon.¹ With the U.S. government’s support reclamation plants in the West, the prohibitively high cost would no longer be an issue. Even if recycled water were not subsidized, the added cost could provide long-term societal benefits. By increasing the cost of tap water by introducing government recycling, thus moving the cost from taxpayers in general to those who specifically use the water, cities could decrease water use over time. Residents would, if confronted with rising water prices, make an effort to consume less which would decrease stress on the treatment plants themselves as well as natural resources.

The biggest challenge to recycled water, however, is not its cost or purported health risks, but rather its public perception. The unflattering name, “toilet to tap,” hardly brings to mind the sparkling springs associated with “safe” bottled water. There are large groups of detractors who state that recycled water can’t be trusted, and to some extent, they have reason to maintain this stance. In the past, recycled water facilities released non-potable recycled drinking water in four cities.⁵ Although this potential issue cannot be ignored, the benefits of recycled water when it is produced in a fully functioning facility with enforced safety standards cannot be ignored either. These isolated incidents do not indicate that all recycled water is unsafe, but rather that it must be better regulated.

Despite a number of vocal public groups in opposition to recycled water, there is growing support for the construction and utilization of reclamation facilities. In San Diego, a 2004 poll revealed that 63% of citizens opposed water reclamation; in 2011, this number dropped to 25%.¹ Education is the most influential method for obtaining a higher proportion of positive response. The most common objection to using recycled water revolves around the concept being “disgusting.”⁴ For many, the phrase “toilet to tap” induces an image of the contents of a toilet bowl flowing directly to their kitchen sink. When they are shown the intensive treatment process, though, they understand that the water is safe to drink and environmentally friendly. About 95% of people who have taken tours of the water recycling agree it is feasible.³ If people in the Western states and nationwide are exposed to the method in which wastewater is treated, recycled water may gain popularity.

Recycled water, if able to defeat the social stigma that surrounds it, could be a literal life-saver in the Western United States. While Los Angeles shut down a reclamation facility built in 2002, there has been an effort to reopen it. Doing so could reclaim 9.7 billion gallons of water per year.⁹ While recycled water cannot supply cities like Los Angeles with all the water they need, it is a step in the right direction. By increasing the cost of water to a level where overuse would be discouraged and by instituting water reclamation facilities, the cities of the Western U.S. may be able to survive. The major obstacle to the implementation of recycled water is public disapproval due to ignorance about the process of water recycling and the purity of the final product. However, if educated about the process of water recycling, the public might come to see reclaimed water as a safe and effective water source.

References

1. Barringer, F. As ‘yuck factor’ subsides, treated wastewater flows from taps. The New York Times, Feb. 9, 2012. http://www.nytimes.com/2012/02/10/science/earth/despite-yuck-factor-treated-wastewater-used-for-drinking.html?pagewanted=all&_r=0 (accessed Apr. 8, 2014).
2. Ferner, M. These 11 cities may completely run out of water sooner than you think. Huffington Post, Dec. 4, 2013.  http://www.huffingtonpost.com/2013/12/04/water-shortage_n_4378418.html (accessed Apr. 6, 2014).
3. Chu, K. From toilets to tap: How we get tap water from sewage. USA Today, Mar. 3, 2011. http://usatoday30.usatoday.com/money/industries/environment/2011-03-03-1Apurewater03_CV_N.htm (accessed Apr. 8, 2014).
4. Weissmann, D. Texas town closes the toilet-to-tap loop: Is this our future water supply?. Marketplace, Jan. 6, 2014. http://www.marketplace.org/topics/sustainability/texas-town-closes-toilet-tap-loop-our-future-water-supply (accessed Apr 1, 2014).
5. Royte, E. Bottlemania: Big business, local springs, and the battle over America’s drinking water. Bloomsbury: New York, 2008.
6. Than, K. Reclaimed wastewater for drinking: Safe but still a tough sell. National Geographic, Jan 31, 2012. http://news.nationalgeographic.com/news/2012/01/120131-reclaimed-wastewater-for-drinking/ (accessed Mar. 29, 2014).
7. Research Foundation. Recycled water: How safe is it?, 2011. http://www.athirstyplanet.com/sites/default/files/uploadsfiles/PDF/RA%20Backgrounder_6.4.11_Lo.pdf (accessed Apr. 1, 2014).
8. Mayor opposes ‘toilet-to-tap’ water supply proposal. ABC News, Sept. 13, 2007. http://www.10news.com/news/mayor-opposes-toilet-to-tap-water-supply-proposal (accessed Apr. 8, 2014).
9. Fleischer, M. Don’t Gag: It’s time for L.A. to embrace ‘toilet to tap’. Los Angeles Times, Feb. 4, 2014.  http://articles.latimes.com/2014/feb/04/news/la-ol-drought-toilet-to-tap-water-20140204 (accessed Apr. 1, 2014).

The Bright Future of Solar Energy

Catalyst Volume 8

Renewable energy is the dream of countless environmentalists and active citizens. Adopting hybrid electric vehicles and domestic sources of sustainable energy are some of the goals of renewable energy. The increasing price of energy derived from crude oil and concerns regarding energy security have stimulated investments in sustainable resources such as solar energy.

The search for and extraction of oil are negatively impacting the environment around oil platforms. Offshore drilling platforms report spills every year that kill an estimated 315 thousand birds per platform.¹ Additionally, the waste fluids ejected from the drilling process harm marine life that rely on filter feeding; these pollutants then travel up the food chain in a process called biomagnification.^2-4 Research and development efforts in renewable energy sources promise to minimize these harmful practices by reducing society’s dependence on oil.

One such alternative to oil-derived energy lies in residential and commercial photovoltaic solar panels that convert sunlight into electric current. Depending on the weather, the sun provides between 3.6—6 kWh/m² (kilowatt-hours per square meter) per day in the U.S.5 Homeowners are beginning to capitalize on this source by installing residential, small-scale “rooftop panels,” which are labeled as photovoltaic (PV) systems. These systems work to create electric current by harnessing the excitation of electrons from sunlight. These systems are becoming commonplace as their cost continues to decrease. In 2011, the cost of installing PV systems was 11—14% lower than that in 2010, and in 2013 prices were even lower.⁶

The most widely adopted material in these products is silicon, a material known for its conductivity. Development in conducting materials and manufacturing methods has greatly accelerated since the first application of silicon, improving energy collection. Now, total global grid-connected systems produce seven million kW.7 As the average American home uses between 2—5 kW per year, this grid system can support two to three million U.S. homes.8 A second viable option for solar energy is Concentrated Solar Power (CSP). Known as “power towers,” CSP uses mirrors to concentrate the sun’s rays, generating enough power to heat water and operate a turbine. Water is not the only fluid utilized: in a parabolic mirror system, oil is heated to 400 °C to convert water into steam via subsequent heat transfer.⁹

CSP plants are expanding globally; they are expected to produce a total of 5000 MWh (megawatt-hour) by 2015. This is an increase from the 2011 figure of 1000 MWh. As one might expect, these towers are set to be installed in sunlight-rich areas, with the majority of this planned construction taking place in California. Towers will also be installed in China, Israel, South Africa, and Spain.⁷ Typical CSP systems today can generate one MWh of electricity for every 4—12 square meters of land space, which, according to the Royal Academy of Engineering Ingenia, “can continuously and indefinitely generate as much electricity as any conventional 50 MW coal- or gas-fired power station.”¹⁰ This is relatively small, given that the average U.S. residential home occupies about 405 square meters. The average 1000 MW U.S. coal-fired power plant requires 1—4 square kilometers of land space, translating into 6—18 GWh (m2/gigawatt-hours), or 4—20 square meters per GWh. However, including the amount of land needed for mining and waste disposal, this figure can include an upper limit of 33 m2/GWh.¹¹ This factor of land efficiency leads to these newly installed CSP plants to produce one kWh worth of electricity for $0.10—0.12, given the costs of installation and maintenance as well as other fixed and variable costs. In Houston, Texas, rates for oil-derived electricity can range from $0.08—0.15/kWh, which makes CSP a very competitive alternative.¹⁰

Opposing arguments based on the high cost of photon-collecting technology and the intermittency of solar rays are losing ground. In the U.S. alone, the PV market has grown considerably. For example, California experienced a 39% growth in residential PV system installations in the fourth quarter of 2012 (Fig. 1).¹² Thus far, the cost of these systems has declined over 30% in the past few decades, and the U.S. Department of Energy’s (DOE) SunShot Vision Study is attempting to further reduce costs by 75%. With this initiative, the DOE plans to “meet 14% of U.S. electricity needs via solar energy by 2030 and 27% by 2050.”¹³ It is believed that this goal will be possible once solar electricity generation reaches the cost of $0.06/kWh, near the range of current fossil-fuel based generation methods.¹³ The SunShot Vision Study has implemented a “Rooftop Solar Challenge” aimed at improving the logistical requirements of installations in order to apply its initiative to states across the U.S.

Applications for solar energy can range from using solar cookers with the CSP model to portable solar chargers for personal electronics. These forms of energy can be scaled to any size, and their full integration into society is only hindered by the current dependence on oil. To make energy production sustainable, solar technology must be further developed and implemented. Statistical models need to be considered, academic and industrial research needs to be funded, and a united effort in adopting these technologies needs to take place. Significant progress has been made in homeowner PV system adoption and the DOE’s SunShot Vision, which serve as testaments to the viability of a sustainable energy economy. When comparing the advantages of oil against the advantages of solar energy, it is clear that solar energy has the potential to provide more efficient and environmentally friendly results. These alternatives still need technological advancement, proper location, and governmental support; once these are completed, solar alternatives will be able to meet our energy needs. Although we as a society may find ourselves too dependent on oil, there is hope for a more sustainable, responsible, and environmentally friendly world.

References

1. Tasker, M. L. et al. The Auk. 1984, 101, 567-577.
2. Wiese, F.K. Marine Pollution Bulletin. 2001, 42, 1285-1290.
3. Wiese, F.K.; Robertson, G. J. Journal of Wildlife Management. 2004. 68, 627-638.
4. Ocean Discharge Criteria Evaluation;  General Permit GMG290000; US EPA: 2012; 3. http://www.epa.gov/region06/water/npdes/genpermit/gmg290000_2012_draft/ocean_discharge_criteria_evaluation.pdf (accessed Feb. 1, 2014).
5. George Washington University GW Solar Institute. How much solar energy is available? http://solar.gwu.edu/FAQ/solar_potential.html (accessed Feb. 1, 2014).
6. Chen, A. Lawrence Berkeley National Laboratory. The installed price of solar photovoltaic systems in the U.S. continues to decline at a rapid pace. http://newscenter.lbl.gov/news-releases/2012/11/27/the-installed-price-of-solar-photovoltaic-systems-in-the-u-s-continues-to-decline-at-a-rapid-pace/ (accessed Feb. 1, 2014).
7. Hamrin, J.; Kern, E. Grid-Connected Renewable Energy: Solar Electric Technologies; United States Agency of International Development (USAID): Washington, D. C. http://www.energytoolbox.org/gcre/mod_5/gcre_solar.pdf (accessed Oct. 28, 2013).
8. Solar Energy Industries Association. Solar Energy Facts: Q3 2013. http://www.seia.org/research-resources/solar-industry-data (accessed Feb. 1, 2014).
9. Concentrating Solar Polar (CSP) technologies. http://solareis.anl.gov/guide/solar/csp/ (accessed Feb. 3, 2014).
10. Müller-Steinhagen, H.; Trieb, F. Concentrating solar power: a review of the technology. Royal Academy of Engineering, Ingenia. 2004, 18, 43-50.
11. Fthenakis, V.; Kim, H. C. Renew. Sust. Energ. Rev. 2009, 37, 1465-1474.
12. Solar Energy Industries Association. U.S. Solar Market Insight 2013. http://www.seia.org/sites/default/files/4Y8cIWF6ps2013q1SMIES.pdf?key=58959256 (accessed Nov. 10, 2013).
13. U.S. Department of Energy. SunShot Initiative.  http://www1.eere.energy.gov/solar/sunshot/about.html (accessed Nov. 10, 2013).
14. U.S. Department of Energy. Updated capital cost estimates for utility scale electricity generating plants. U.S. Energy Information Administration: Washington, DC, 2013. http://www.eia.gov/forecasts/capitalcost/pdf/updated_capcost.pdf  (accessed Nov. 7, 2014).

Coral Reef and Algal Interactions

Catalyst Volume 8

To look at a coral reef is to see a fantastic world of color and life. But what is perhaps most interesting lies within the chaos. Beneath the busy surface of a coral reef lies a symbiotic relationship unknown to most. This is the world of algae, specifically the algae that live within the coral themselves. It is this partnership that drives energy production within the reef and keeps alive the diverse species found therein. They are the primary producers of this underwater world, using light energy to produce nutrients that in turn feed not just themselves but the entire reef. Without these algae, coral reefs—and much other marine life—would cease to exist.

The majority of corals in the taxonomic phylum Cnidaria host within their tissues species of symbiotic algae from the genus Symbiodinium.² The algae capture light and perform photosynthesis, giving nutrients to their coral hosts in return for shelter and protection.² These algae are not born into the coral; rather coral polyps ingest them throughout their lives.² This allows for the change of different species of Symbiodinium, which are separated into groups called clades, within a particular coral.² As it turns out, different clades may be responsible for many different phenomena in corals separated by geographical distance or depth.

An interesting phenomenon is that many corals have the ability to change out their dominant Symbiodinium species symbionts after an event called bleaching, in which a coral or group of coral expel all of their symbiotic algae and lose their color, appearing ‘bleached’ afterwards.¹ This appears to be a way for coral to adapt to changing ocean conditions. For instance, in recent years as the ocean acidifies, coral that can more easily change their clades may have an evolutionary advantage over those that cannot. At the same time this results in the use of fat stores to sustain the coral, a process that over the space of just a few weeks can lead to serious damage or death.² Because they cannot physically move to change their environment, changing symbiont clade may be one of the few ways a coral can adapt to changing environmental pressures. In addition to ocean acidification, water pollution from factories and tourism spots have caused massive amounts of light-scattering debris to accumulate in coastal areas where reefs are found. If long-term ocean debris clouds the water around a coral, it may expel its symbionts in favor of a clade with different photosynthetic capabilities. Recently, these changes due to human interaction with the environment have led many coral species, sometimes in huge conglomerates, to bleach.⁶ This could be the corals’ attempt to change their symbiotic algae in hopes to adapt to the warmer climate, as increases in temperature also stress the coral metabolically.⁷ Changing the type of symbiont may allow regulation of the uptake of oxygen or the usage of light to create energy at a different rate than would otherwise be possible. However, it also appears that coral will expel their algae in response to external stressors that may or may not have anything to do with photosynthesis, including salinity changes, bacteria, and chemicals.² This points to a much more complex relationship between coral and their algae symbionts. Although Symbiodinium species in general have a positive effect on their hosts, it is possible that upkeep of the symbiotic relationship could become energetically unfavorable for the coral, causing the coral to expend energy in times of stress. This could result in bleaching, allowing the coral to save on some of its energy sources.

Light does not pass as freely through water as it does through air. Certain light waves do not effectively penetrate the water’s surface; this is why water appears blue. Because of this, coral and their symbiotic algae cannot use the same mechanisms for light absorption that land plants use. Another consequence is that at different depths, different spectra of light dominate. In areas near the surface, red, yellow, and green light waves still reach the organisms that live there. However, at the deeper reaches of the ocean the majority of light is blue. This means that coral must adapt their choice in algal symbionts to the depth at which they live. In fact, it appears that the major species or clade within a particular coral may be a result of competitive exclusion in which different algal species fight over the limited space within the coral’s tissues until the best suited species or clade effectively outcompetes all other species.¹ This points to the ability of coral to change the major clade that resides within them through bleaching in response to new external conditions like pollution. That said, there are several documented coral species that show a high specificity of symbiont preference.¹ If some coral species have a specific clade with which they are always associated, that is, if they cannot as easily switch clades, this could allude to a relative advantages of certain coral species over others in rapidly changing environmental conditions like those facing our oceans today.

The dynamic relationship between coral and algae is of upmost importance for the continued balance of reef and ocean ecosystems. Corals not only put large amounts of energy into the ocean, but they also provide a home for reef fish and other organisms.² As corals bleach and die, their skeletons are dissolved by the water and degraded by other organisms. Without fresh growth, this ends in the loss of habitat for countless fish and invertebrates. Coral is the glue that holds a reef ecosystem together, and symbiotic algae are similarly the glue that holds coral together. Without symbiotic algaes, reef ecosystems would cease to exist, affecting millions of human lives and eliminating one of the most amazing and diverse examples of speciation on the planet. Keeping this relationship alive and well is crucial to the continued wellbeing of our oceans. Currently, the reef ecosystem is under threat from ocean acidification, a direct consequence of increased carbon dioxide in the atmosphere from human consumption.⁷ This makes it harder for coral to grow which in turns slows reef growth as a whole.⁷ If this trend is not reversed, it could spell disaster for coral reefs around the world.

The reality of bleaching is obvious, regardless of one’s stance on global warming. The masses of bleaching, if anything, offer a concrete proof that our global environment is rapidly changing at the cost of the stability of one of the world’s most important ecosystems. It seems that a large part of the destabilization comes from the breakdown of this relationship between coral and algae. As the coral expel their symbionts in favor of other clades, they stress themselves to the point of starvation and death. Mass death of coral leads to a domino effect throughout the rest of the reef, with all organisms affected in some way or another. In a sense, coral reefs affect just about every ecosystem on the planet. They provide energy to other reef organisms that are harvested by marine and land animals alike, including humans. Beyond that, they help to block coastal areas from large waves, which can protect these areas from flooding. Coral reefs are an extremely important part of our world, and if we continue to pollute the oceans and allow corals to acidify, we risk losing them.

References

1. Baker, A. C. Annu. Rev. Ecol. Evol. Syst. 2003, 34, 661-689. 
2. Borneman, E. H. Aquarium Corals: Selection, Husbandry, and Natural History. Charlotte, VT: Microcosm: Charlotte, Vermont, 2001. 
3. Favia favus. The IUCN Red List of Threatened Species. http://www.iucnredlist.org/ details/133569/0 (accessed Apr. 1, 2015). 
4. Levy, O. et al. J. Exp. Biol. 2003, 206, 4041-4049. 
5. The IUCN Red List of Threatened Species. www.iucnredlist.org (accessed Apr. 1, 2015). 
6. Working Together Today for a Healthier Reef Tomorrow. Australian Government Great Barrier Reef Marine Park Authority; 2011. 
7. Doney, S. C. et al. Annu. Rev. Mar. Sci. 2009, 1, 169-192.