According to the United Nations Intergovernmental Panel on Climate Change (IPCC) andvarious climate-change models, the temperatures of the waters in tropical regions are to increaseby 1.8-4°C over the next century due to climate change (Bates et al. 58). This increase is inaddition to the 1°C increase in temperature of global waters over the course of the twentiethcentury (Schmidt 294). Warmer waters can cause a destructive phenomenon called coralbeaching where coral turns white and death is almost certain. Climate change also increases therate at which coral reefs are being destroyed by other factors such as pollution and overfishing,which have plagued coral reefs for decades. Due to the damaging effects of global warming, thetemperature of waters surrounding coral reefs are beginning to increase to rates that cause coralbeaching at a massive scale. Marine ecosystems and the human population will feel a backlash ifcoral reefs were to disappear: marine organisms and fish will lose safe shelter, undiscoveredorganisms in coral reefs will be lost to science and medicine, economies (both local and state)will no longer be supported by tourism, and tropical coastline will erode with no protection.This could be a good place for thesis/topic statement before you get into the biology, etcCoral reefs are built with calcium carbonate deposited by corals and calcareous algae.They provide shelter to about 25 percent of marine species and as such, are sometimes known asthe “rainforests of the sea” (Buddemeier, Kleypas, and Aronson Foreword). Found mainly intropical waters, coral reefs have lived for many years due to stable temperatures in their habitat.But climate change has increased the temperatures of the waters and mass bleaching events, suchas in 1998 where 16 percent of the world's coral reefs were destroyed, are occurring morefrequently (Anthony et al. 173). Coral bleaching is one of the top threats facing reefs since itweakens coral causing them to be more receptive to disease and to lose the nutrients formed bythe zooxanthellae alga.
1. Coral Bleaching:
While coral reefs provide shelter for many different organisms, their livelihood is basedon a symbiotic relationship with zooxanthellae, a single-celled alga. Zooxanthellae are embedded in the coral tissue and supply the reefs with nutrients, such as carbon, created throughphotosynthesis (Schmidt 292-293). At the same time, the coral reefs provide shelter close enoughto sunlight for the zooxanthellae to successfully create nutrients. As ocean temperature increases,zooxanthellae are unable to produce minerals and nutrients due to high temperatures and highlight levels and are released by corals (Buddemeier, Kleypas, and Aronson 15). The whitecalcium carbonate skeleton is exposed since zooxanthellae alga is one on the main sources ofcolor for coral reefs (Schmidt 293). Coral reefs then starve to death because they do not receivethe carbon and other nutrients provided by zooxanthellae.
There are two types of bleaching thatare applicable to present-day events: Algal-stress bleaching and physiological bleaching. Algalstress bleaching occurs when algae inside coral reefs are unable to create nutrients throughphotosynthesis due to high light and temperature levels. Physiological bleaching occurs whencoral reefs are unable to hold algae and are instead using the energy to counteract the effects oflong periods in high temperature waters (Buddemeier, Kleypas, and Aronson 15). Bleachingcauses coral to be more susceptible to diseases since they are weak with low minerals andnutrients.There have been many mass coral bleach events in the history of the Earth, but the massbleaching event in 1998 of coral reefs around the world stands out as the worst bleaching eventin history (Anthony et al. 173). Over the course of a year, 16 percent of all coral reefs in tropicalseas around the world were affected by coral bleaching. Parts of the Indian Ocean, SoutheastAsia, and the western Pacific had a high mortality rate where 50-90 percent of affected reefs were destroyed (Wilkson 20). There are many effects where coral reefs disappear due to coralbleaching: Marine organisms and animals lose shelter, tourism money generated from coral reefsis lost, humans lose the ability exploit reefs for medicine and food, and tropical coasts are at riskof erosion.
2. Effects of Coral Bleaching:
2.1 Disappearing Shelter
As stated above, reefs provide a safe place for about 25 percent of marine life to takeshelter from natural predators (Buddemeier, Kleypas, and Aronson Foreword). Due to climatechange, reefs are losing the ability to hold marine organisms that produce limestone to buildreefs, such as coral and calcareous algae and are instead using energy to catch fish or to removesediment from coral (Schmidt 297). To put quite simply, without a safe place to live, manyorganisms will become endangered, which will ultimately lead to extinction. With the bottom ofthe food chain gone, one can only imagine what consequences will be felt throughout the wholeocean ecosystem. One devastating effect of disappearing marine life on reefs is how the reefsbecome more venerable to diseases such as the black-band disease that occurs in the Caribbean((Buddemeier, Kleypas, and Aronson 25). When shelter for marine organisms is destroyed,humans lose out on the ability to exploit resources such as fish and algae for food, medicine, andscientific advancement.
2.2 Economic Loss
Just as coral reefs protect marine life, the economies of many states are greatly supportedby the tourism that is created from reefs. According to Eileen Clauseen, President of Pew Centeron Global Climate Change, tourism and fishing of reefs provide $30 billion to local and stateeconomies each year (Buddemeier, Kleypas, and Aronson Foreword). Also, The Great BarrierReef pumps about $6 billion into the Australian economy each year through tourism alone(Access Economics 45). As coral reefs disappear from climate change and other sources, the standard of living will most likely fall in local societies around reefs. As the standard of livingfalls, exploitation of the reef will increase, leading to the destruction of more reefs. Chemical andblast fishing will become more common as the society struggles to survive (Buddemeier,Kleypas, and Aronson 30). A specific example is the loss of tourism felt after the 1998 bleachingevent to the island of Palau in western Micronesia and the Maldives. In Palau, the massbleaching event caused 50 percent of their reef to die off; and in the years to follow, tourismdropped by about 5-10 percent (Buddemeier, Kleypas, and Aronson 30). In the Maldives, tourismdecreased and an estimated $0.5-3 million of revenue was lost between 1998-1999 (Buddemeier,Kleypas, and Aronson 30). Without coral reefs, many economies will be thrown into turmoil asthey search for ways to make up lost revenue. Fishing in coral reefs is also very important to thelivelihood of many people.It is estimated that 25% of the fish caught each year come from reefs. This amount of fishcaught also feeds about 1 billion people (Schmidt 294). Without coral reefs, overfishing in EEZ’sand other areas will increase, leading to endangering marine animals.
Established in 1997, theReef Check Program surveyed thousands of coral reefs from 1997-1999 to monitor their health.The main way volunteers in the program determine a reef's health is by counting how manyindicator organisms are on the reef under examination (Hodgson, and Liebeler 23). The moreindicator organisms on a reef, the healthier it is. Lobsters, Large Groupers, Butterfly fish, andGiant Clams are among the selected indicator organisms of a healthy reef due to their sensitivityto changes in the reef and surrounding ocean (Hodgson, and Liebeler 23). Sadly, according to the1997 survey, many of the indicator organisms were not present on reefs at all. While this is not adirect result of coral bleaching (since the 1998 mass bleaching event had not occurred yet) it canonly be assumed that the amount of healthy reefs dropped severely due to bleaching caused byclimate change. This assumption is supported through evidence collected after the mass bleaching event where affected coral reefs experienced a mortality rate of 50-90 percent(Anthony et al. 173). With disappearing reefs, the science community is not given the ability tostudy all marine organisms residing in coral reefs, and will lose the ability to discover new drugsfound in marine organisms.
2.3 Scientific Loss
It has been estimated that reefs support 800 types of coral, 4,000 fish species and animmense number of invertebrates (Schmidt 294). Some scientists estimate that hundreds ofthousands of other species living in reefs are still uncounted for. Due to the fact that corals andother immovable marine organisms cannot escape predators, they must rely on chemicalsproduced naturally to divert enemies and diseases (Schmidt 294). Some examples of medicineproduced by organisms housed incoral reefs are the antiviral drugs vidarabine andazidothymidine and the anticancer medicine cytaraine (Schmidt 294). Due to the large number ofundiscovered marine organisms residing in coral reefs, there is no way to estimate how many lifesaving drugs can be created through chemical compounds produced by the uncounted marineorganisms. While reefs could potentially advance medicine, coastal waters will lose the naturalbodyguards against waves and other types of erosion. Very good – your organization is great andreally helps the clarity of your presentation/argument.
2.4 Coastal Erosion
As climate change causes the sea-level to rise and coral reefs to die out though coralbleaching and disease, erosion will have a greater affect on coastal areas. For example, if the sea-level along the coast of Bonaire rose by 0.5 meters it is estimated about 38% of coastalbeaches will be lost, reducing the amount of tourism to Bonaire which will lead to a weakereconomy (Bates et al. 112). The sediment from eroded coasts flow into the ocean and largeamounts fall onto reefs. Bleached reefs are affected the most from large amounts of sedimentssince they have to spend energy clearing the sediment from their system instead of catching food(Schmidt 297). The already weak reefs become weaker due to low nutrients in their system. The sediment also covers areas in reefs where coral larvae could possibly settle and grow (Schmidt298). With no possibility of reproduction, coral reefs are destroyed at an increasing rate whenother factors such as overfishing, pollution and disease are taken into consideration. Even thoughcorals are disappearing at an alarming rate, studies done on different types of reefs show there isa good chance reefs will adapt to higher surface temperatures and will come back faster andstronger after a coral bleaching event.
3. Coral Adaptation:
Because reefs are found throughout the tropical and subtropical waters in the world, theyexperience coral bleaching and other stresses differently betweenthe different reefs(Buddemeier, Kleypas, and Aronson 2). There are also differences between the types of corals.Corals with rapid growth rates and thin tissues are more reactive to coral bleaching, while coralswith thick tissues and slow growth rates are known to recover from most coral bleaching eventsexcept the most deadly (Buddemeier, Kleypas, and Aronson 16). The ability for reefs to adapt toclimate change and recover from coral bleaching depends on two key circumstances: First, thedegree at which coral bleaching has affected the reef. And second, the amount of time it takes forreefs to return to their original state before coral bleaching.For example, if a minor bleach event occurred over the course of two days and onlycaused a portion of the more vulnerable zooxanthellae to be expelled, corals could easily recover.The new space allows for hardier alga to move in and form another symbiotic relationship withthe coral (Buddemeier, Kleypas, and Aronson 28). Secondly, if coral reefs are to recover from acoral bleaching event, they must do so quickly if they are to reach the level corals were at beforebeing bleached. A recent study conducted in Dubai, United Arab Emirates showed that after amajor bleaching event, reefs will return even after ten years, but the strength and diversity of thereefs will be decreased significantly (Bartholomew, Burt, and Usseglio 33). Although, anotherstudy done through the Great Barrier Reef Marine Park Authority have found evidence showing how major bleaching events can lead in increased thermal tolerance in reefs. Three coral genera(Acropora, Pocillopora, and Porites) were studied between 1998 and 2002 on whether or notreefs will return after a bleaching event with a higher heat capacity. The results showed all threecoral genera experienced coral bleaching at a much lower level than what was estimated eventhough thermal stress in 2002 was almost double than what coral reefs experienced in 1998(Anthony et al. 177). To help with stronger reefs, conservation efforts through many types oforganizations are moving to educate the population about reefs, create marine sanctuaries for atrisk reefs, and study the effect climate change is having of coral reefs.
4. Conservation of Reefs:
After the 1998 mass bleaching event, many people noticed the need for conservationefforts to help protect vulnerable reefs. The creation of Marine Protected Areas was offered as away to reduce stresses such as land-pollution, over-fishing, and climate change. Also, there was acall to study how climate change is affecting coral reefs at a global scale (Wilkinson 20).Organizations such as the National Oceanic and Atmospheric Administration (NOAA) try toeducate citizens about the sensitivity of coral reefs and when there should be as close to zerohuman contact with reefs during peak thermal stress (Schmidt 298). MPA's can successfully limithuman contact which will cause bleaching events to be less severe since a large portion of coraldegradation through human contact is lessened.
If economies, medicine, costal lands and marine life are to advance, coral reefs need to beprotected from climate change. Coral bleaching is affecting almost all coral reefs in tropical andsub-tropical waters. With the disappearance of zooxanthellae and other alga from increased watertemperature, coral reefs lose nutrients produced by the alga and will degrade unless the bleachingevent is shorten and the alga are given the chance to return. If the bleaching event drags on,marine life loses safe shelter and is at risk to be eaten by predators. Many marine organisms will become endangered since coral reefs hold about 25 percent of marine life (Buddemeier, Kleypas,and Aronson Foreword). With disappearing zooxanthellae, coral reefs lose the color that makesthem so famous to divers and tourists. Local economies dependant on reefs will be severelyhampered if coral bleaching continues to cause reefs to turn white while degrading slowly. Withdisappearing reefs, the unknown marine organisms will remain undiscovered and the possibleadvancement in medicine will not occur. Since many drugs have been discovered throughchemicals in alga and fish, the possibility of what lies underneath the coral is endless. Coral reefsalso serve as a barrier against waves and other types of erosion. Without coral reefs, coastalwaters will erode at a much faster rate, such as what is happening in the Island of Bonaire (Bateset al. 112). Even though coral reefs are degrading, there is hope through natural adaptation andconservation efforts by organizations. Minor bleaching events cause weaker alga to be expelled,letting stronger alga move in and continue the symbiotic relationship with the reef. Whileconservation efforts by agencies will help educate the public, create marine sanctuaries, andadvance scientific research on the effect climate change is having on coral reefs. In the end, coralreefs are the most important ecosystem in the world because they truly are the "rainforests of thesea.”Excellent on threats; could use a clearer thesis statement and really needs quite a bit more onconservation efforts.