The Susceptibility of Corals to Human Activities

This topic submitted by Brian Kelly ( at 12:48 PM on 6/8/02.

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Corals are colonial animals which exist in low-latitude areas. Corals are temperature-sensitive and roughly reside in the regions whose temperatures do not go beyond 64ˇF. While Australia houses the longest coral reef, coral genera worldwide is diverse with each reef having its own uniqueness. The marine ecosystems that all corals are both part of and major contributors to are ever-changing, but happen to be very sensitive to greater degrees of change imposed on them directly and indirectly from humans.

All corals are clearly sensitive to temperature, but are so integrated into their respective marine communities that a general understanding of their biology and ecosystem role is necessary to better comprehend the negative affects humans historically placed, and continue to place, upon coral communities. The biology of corals and symbiotic relationship with algae are important to note to better understand how corals function.

Corals and algae live together. The algae, also referred to as zooanthellae, reside in the coral. The algae relies on the sun, planktonic food and other important environmental factors to exist. While the algae relies on the corals for nutrients and also create the dynamic colors coral reefs exhibit, the corals in turn rely on the algae for food.

The value of coral reefs is so great that their protection from humans is easily justified. To simplify this, a general composition of some of the corals most important functions provides the background for this belief. Within the marine systems that corals are a part of, countless marine species outside of the algae already noted rely heavily on the food, habitat, and protection that reefs offer.

The proximity of corals to coastlines make the reefs quality nursery's for various tropical fish, crustacean and other marine species. Corals reefs provide the habitat and protection that many developing marine life requires in order to exist. Various marine species find shelter within the corals. Some have evolved to change colors in order to blend into the coral background to escape prey.

Nursing marine young also subsist on the food that is located in or near the corals. Adults also rely on the coral reefs for food. The role of the reefs as nursery to many species attracts all sorts of marine like to these delicate and life-giving systems. Food webs exist in the reef systems integrating the planktonic community as well s fauna and flora species; benthic and pelagic animals. The corals themselves are directly consumed by species such as the parrotfish which crush and digest the coral in order to gain the nutrition from the algae.

Humans also rely heavily on the coral reefs. It is clear that the food webs that the coral reefs support also extends itself to humans since we also consume many of the species that are nursed and housed in coral communities. Coral reefs also act as buffers between the coastline human communities and oceans. The reefs are great wave-breakers.

Obviously, corals also attract people in droves for recreational purposes. Snorkeling, scuba and boating are popular attractants for these crazy humans. Often, people tend to act first and think later. Recreational uses of coral systems act as good lead-ins to the destructive force that humans have become to the very communities we've grown to appreciate.

Historically, the beauty of corals has lead to the taking of chunks of coral by the people who have grown to appreciate the aesthetic and ecosystem value of the reefs. While the taking of coral for souvenirs is now forbidden, it was permissible until the last few decades and significant damage was done to coral reefs since only the outer most layer of the coral is a living animal. The corals continue to grow upward and outward leaving behind the lifeless limestone skeleton which actually creates the foundations and bulk of the coral reefs. By destroying the top layer of the coral reef, you are in effect killing the coral animal itself since it is the living part of the reef.

People have also lead to the destruction of corals directly through recreational boating. The upper layers of the coral reefs are easily damaged or destroyed if contact is made between the boats and the reefs. Fishing, while it does provide a great resource, especially to native, local human communities, can be detrimental to corals. Anchors, nets or fishing lines can get tangled in the corals, breaking off or damaging sections of the reef, and making it difficult for the recovery of the damaged area.

The taking of marine fauna and flora species residing in the coral communities can also be very detrimental. Though corals and algae have a mutualistic relationship, countless marine species have relationships with the corals that are also mutually beneficial. The loss of individual marine like or great loss to individual species can have a domino affect on the other marine species which can subsequently directly or in directly negatively affect the health of the corals.

Another significant detrimental human activity is the damage done from runoff from land. While these forms of sediment and nutrient pollution are indirect in nature, the affects can be devastating. The influx of sediments to can cloud the waters, depriving the marine communities of sunlight and oxygen. The sunlight is so important to the corals and the marine life dependant on them, that sediment discharge interferes by blocking sunlight and also depositing on the coral reefs, choking out life as it settles.

The influx of nutrients also is clearly damaging to coral reefs. Entire sections of coral communities have been destroyed by nutrient and sediment contamination. While coral communities, like most estuarine or other coastal communities rely heavily on nutrients for food, an overabundance of nutrients acts negatively.

The influx of great amounts of nutrients from human activities such as agriculture and development over saturates the areas and creates chemical and biological imbalances that starve the inundated areas of dissolved oxygen and creates too much nutrition for the existing ecosystem to process.

Accelerated global warming is a beast that is not easily tackled. It had been noted that corals and the rest of the communities relying on them, are very sensitive to and limited by changes in temperature. The Industrial Age has given humans a great deal of benefits, but has also created environmental problems that we are only beginning to deal with. Corals do not benefit from the combustion of fossil fuels though they are highly susceptible to many of the human uses of these carbons.

By unleashing these carbons that have been stored underground in deposits for up to millions of years, humans are injecting huge amounts of CO2 and other greenhouse gases that accelerate global warming. The average annual temperatures worldwide have been increasing at an accelerated rate for well over 100 years, and will continue to prove very destructive to numerous ecosystems such as coral reefs. The stemming of human accelerated global warming needs to be continually addressed the people and governments of today in order to responsible prevent accelerated global warming while we still have an option that can lessen the damage done to corals due to increased temperatures and the rising sea levels that will accompany it.

On June 3, 2002, the Bush Administration finally popped out of the Stone Age and recognized the widely held belief within the scientific, international and nonprofit communities that accelerated global warming is occurring and is due directly to human activities. While it is apparent that Bush and Company have been pacifying US fossil fuel and related industries by dragging their feet and disputing an over-abundance of evidence that has supported this belief for some time, it is an important milestone. This acknowledgement solidifies international government recognition of this tremendous threat to our atmosphere and the incalculable affects of most ecosystems, including corals, that accelerated global warming will bring.

Specific prevention of each and every anthropogenic activity damaging to corals can be attained. The most obvious one was to halt the use of coral as souvenirs by people. Education is clearly the most productive way to reach people, whether it addresses indigenous people or non-native recreational users.

While it appears that greater awareness exists today, especially in the case of human visitors to coral reefs, knowledge will combat damaging human activities. While the lifestyles of indigenous peoples are often much less taxing on the ecosystems than those lifestyles of the more developed countries, continued education geared towards native peoples is important to promote good policies towards the corals. Certain fishing practices are at times harmful to coral communities.

Non-native peoples over the past century have been much more damaging to coral reefs worldwide than have been fishing practices of native peoples. The detonation of atomic bombs by the US in the Bikini Atolls during the 1950's is an extreme example of a gross abuse of coral reefs. A valuable lesson was learned. The detonation of a nuclear weapon on a centuries or millennia old, delicately evolved and formed biodiverse ecosystem like a coral reef is bad.

Heading back towards reality, the continued education of coral reef recreation users is paramount to continuing the environmental health of coral systems. Prohibitions to damaging coral reefs in any way are significant deterrents to stem human recreational-based damage. Restrictions are not sufficient though since enforcement isnŐt easy considering the locations and expanse of coral reefs.

Boating, fishing snorkeling, and other man-made damages resulting from recreational activities have been greatly prevented by sign postings, informed tour and dive guides, along with other forms of education. Informed people who understand the value of corals and the damaging affects people can have on these communities are a great defense.

Government action, most notably in the case of global warming, is necessary in order to protect coral reefs from significant coral bleaching. The control of rapid sea level rise will be out of the control of humans should it continue to be influenced by the emissions from fossil fuel combustion. People need to act preventatively in the case or global warming because a reaction will not suffice.

The aims of international actions such as those espoused in the Kyoto Protocol are righteous in that they are geared towards recognizing and slowing global warming. Until international consensus is reached in regards to policy combating global warming, coral reefs, along with just about every ecosystem worldwide are at great risk over the next century.

As is the case with runoff problems stemming from agricultural and development practices along coastlines free of corals, those problems need to continually be addressed. Two things will continue to help limit the amount of damaging runoff that negatively affects coral communities; education and newer practices.

Once again, gearing education towards the individuals and industries responsible for creating the runoff, people are able to increase awareness and promote sound farming and development practices. By incorporating the use of more sound practices in the educational materials, farmers and developers can more easily implement the ideas to help decrease the amount of sediment and nutrient runoff occurring because of the current practices.

Restoration of damaged coral reef habitats can also be done by planting healthy pieces of coral in the damaged areas. Some success has been reached through this "gardening" approach (Rinkevich). While it is costly to do, it serves a good purpose as long as the damage done to healthy coral reefs is minimal while harvesting bits of healthy coral for this use.


Doggett, Tom & Baltimore, Chris. "Global Warming due to human activities, US finally concedes." The Star-Ledger, June 4, 2002.
Thurman, Harold. Essentials of Oceanography. Prentice Hall, Upper Saddle River, NJ, 1999. Article focuses on coral bleaching and relies on current data for analysis of problem. Presents much statistical analysis. Article pertains to diver-related damages to corals in the Red Sea This article highlighted a study of corals worldwide, and concluded that there was no evidence of recovery in W Atlantic coral once it was damaged.
Article discusses damages to coral reefs from human and other natural sources.
Damage to corals due to blast fishing. by Nancy Knowlton. The Future of Coral Reefs. 2002 Coral Bleaching: Causes and Consequences by B E Brown 1997. Discusses causes of coral bleaching Rapid Transition in the Structure of a Coral Reef Community. 2000 Brighter Prospects for the World's Coral Reefs? Elizabeth Penisi Steps towards the evaluation of coral reef restoration by using small branch fragments R. Rinkevich. 2000.

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