Students hard at work on the "Mangrove Challenge"! (Sierpe River, SW Costa Rica)
Coral reefs provide billions of dollars a year in resources for humans, with an overwhelming amount in the area of food from various fish populations. Developing countries owe twenty five percent of their fish catch solely to coral reef fish (Hoegh-Culdberg 2005). However a majority of fishing techniques used to catch large quantities of fish employs the use of cyanide. Both unregulated international fish trade and countries that lack laws banning the use of cyanide, fuel cyanide use in fishing. Cyanide stuns fish and makes them easier to catch, but in the process kills non-target species and harms coral (Best 2005).
The use of cyanide creates issues that not only “snowball” into more problems for marine ecosystems, but also for the fishermen who use them. The cyanide allows for fishermen to catch fish in areas already under-populated, but damages the food source of the target fish. Also over fishing creates a “funnel” effect on the fish population by making it less and less likely for fish to encounter mates and replenish populations (ETE 2004). Since the 1960’s, more than one million kilograms of cyanide has been spread onto Philippine reefs alone (Best 2005).
Cyanide use is not the only problem that results from over fishing. A popular fish in coral reefs is the grouper, which is very popular to eat. The grouper is a natural predator of the damselfish (ETE 2004). Damselfish make their home in coral by making pockets in the reef itself. These pockets create an area for algae to grow, which the damselfish feeds on. Studies have shown damselfish are able to cultivate and modify algae populations in their territories to suit their needs. This increase in the algae population comes despite the fact that the surrounding area consists of an environment hostel to excessive algae growth (Ceccarelli 2005). If left unchecked, the damselfish will create many pockets in which algae can start to overgrow surrounding coral. While poor fishing habits create problems for coral reefs, mans quest for more food from terrestrial environments has also damage coral reef environments.
Both agricultural and coastal development contributes to increased sediment output from watersheds into marine zones where coral occurs. Coastal development destroys vegetation that when left in place secures soil and sediments and prevents them from entering the ocean. With coastal populations set to double in the next 50 years, sediment run off only shows signs of increasing in the future (Best 2005). Sediment blocks out light that coral need in order for their photosynthetic algae to produce the necessary sugars for the coral to survive.
Agriculture not only contributes to increased levels of marine sediment, but also increases the amount of nutrients and poisons in the water from pesticides and fertilizer. Nitrogen and phosphorous are key components of fertilizer and manure, and while in certain levels beneficial to all organisms, it can lead to coral reef damage. In large amounts, the nitrogen and phosphorous fuels algae blooms that go out of control causing devastating effects like the Red Tide. In other extreme cases, high levels of nutrients produce “dead zones” as organisms consume all the available oxygen in the nutrient-rich water. “Dead zone” events of the Mississippi Delta have been regularly recorded and “dead zones” also been documented on a smaller scale along a majority of the Florida coastline. The pesticides that are introduced from agricultural runoff devastate coral communities by killing sea grass beds and change the reef community structure by making conditions more hospitable to sponges and algae. Sewage, human waste, is also a huge problem especially in the area of the Florida Keys. With almost no sewage treatment in developing countries and vast septic systems in areas like the Florida Keys, enough human was is introduced to have similar effects of fertilizer and manure runoff (Risk 2004).
Key ecosystems destroyed by coastal development are the mangrove forests. Mangroves and coral reefs can form in many cases and interdependence on one another. A key function of mangrove forests for coral reef systems is the fact that mangrove roots clump together sediment and reduce the amount of nutrients introduced into the marine environment. Also mangroves provide a safe haven for many coral reef organisms to develop to the point where they can better survive on the reef. Mangroves also provide valuable resources to humans, such as anti-inflammatories and other pharmaceuticals, along with wood and honey. Also mangrove forests provide excellent barriers for land against sea storms that would easily erode coastal areas (Saenger 2002).
Another human interference in coral reef health and activity is a combination of tourism and organism collection for aquariums. Tourism results in increased human interaction with coral reefs, many times to the disadvantage of the coral. Many things happen when humans visit reefs, boats that drop anchor often damage coral reefs below, while divers break fragile branched corals (ETE 2004). Tourism also contributes to coastal development by requiring new “pristine” land to be cleared and housing developed for the tourists and as well for those that reside permanently in the area (Risk 2004). Collection of specimens for aquariums is far more harmful than most people think.
While the United States prohibits the collection of specimens from its own reefs, the United States imported eighty percent of the collected live coral in the 90’s (Best 2005). Periodic removal of shells has been linked to disrupting the natural predators of the crown of thorns starfish. The crown of thorns starfish eats coral polyps, and in recent years the population of this starfish has skyrocketed. This overpopulation of starfish has caused massive devastation to many coral reef communities. Even the periodic removal of coral itself has had profound effects on coral reef communities. Usually the target species for collection are rare, and therefore are vital to the reef for any hope of the species bouncing back to a safe size in population. With coral, the more valuable species are usually the ones that have the slowest rate of growth. Combining a slow growth rate with an ever-increasing market demand for these exotic coral, and the result is major loss of coral species in many areas of the world (Risk 2004).
Despite the many actions humans take that have adverse effects on coral reefs, there is also an effort to have positive impacts. The United Nations Environment Programme established a Coral Reef Unit in December of 2000. This organization is leading international efforts to save the earths coral reefs by working actively with international partners around the globe to increase coral conservation. One big focus of the Coral Reef Unit is to help educate people on the benefits of conserving coral reefs, and regulating fishing tactics. The four regional areas the Coral Reef Unit is active in are the Caribbean, Eastern Africa, East Asia, and the South Pacific (UN 2006).
Coral reefs offer humans a wide variety of things; from a beautiful natural wonder to a vital source of food. Many humans would be worse of without coral reefs around, still humans choose not to respect the coral reefs. While efforts have been made to save coral reefs, without widespread proper management of land development and responsible use of resources, we may be looking at the possible extinction of these natural phenomenons. With only 5 percent of the possible medical applications of coral reefs applied (Baker 2005), and the ever-growing needs for food and coastal protection, humans continue to have an ever-growing dependence on coral reefs. Hopefully humanity can find some way in the near future to become less of a negative impact on coral reefs; and maybe even a positive influence.
Best, Barbara; Moore, Franklin The World’s Coral Reefs Are Threatened Are the World’s Coral Reefs Threatened? 2005 Greenhaven Press Farmington Hills, MI. Book Editor: Charlene Ferguson. At Issue Series.
Hoegh-Culdberg, Ove Global warming causes coral bleaching Are the World’s Coral Reefs Threatened? 2005 Greenhaven Press Farmington Hills, MI. Book Editor: Charlene Ferguson. At Issue Series.
United Nations System-Wide Earthwatch 2006 http://earthwatch.unep.net/emergingissues/oceans/coralreefs.php Accessed: May 19
ETE Exploring the Environment: Coral Reefs 2004 http://www.cet.edu/ete/modules/coralreef/CRanthro.html Accessed: May 21
Ceccarelli, Daniela; Jones, Geoffrey; McCook, Laurence 2005. Effects of territorial damselfish on an algal-dominated coastal coral reef.
Burke, Lauretta; Maidens, Jonathan. 2004. Reef’s at Risk Word Resources Institute. Washington D.C.
Saenger, Peter. 2002. Mangrove Ecology, Silviculture and Conservation. Kluwer Academic Publishers Norwell, MA.
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