THREATS TO CORAL REEFS

By David Anderson

INITIAL RESEARCH During the 1970s and 80s scientist begun

extensive research into the changes reefs were going through and if they were human induced. They found that the coral reefs were changing faster and faster with larger areas that were being effected. In their research they found concluded that coral reefs were very fragile ad easily influenced by human activity. Up until these sets of research were conducted many people believed that the coral reefs were a very fragile ecosystem but instead found major damage and disease in the last 35 years.

DISEASE As found out by the recent research, corals are

very susceptible to pathogens and parasites that cause harmful diseases. One of the first coral diseases recorded is “black band disease” which effected many species of brain coral in the Caribbean. The disease is cased by cyanobacteria called Phormidium entering the brain corals tissue and then produces a black band that quickly spreads throughout the coral. The cause of this disease and eventual death is that cyanobacteria creates anoxia which kills coral tissue. The black band has been known to spread move very fast growing a couple millimeters every day leaving bare skeleton.

STORMS, CYCLONES AND HURRICANES Storms, serious and minor, can cause reef

destruction by causing waves that lead to the destruction of branching corals and even corals that are on the slopes of reefs because of falling debris from higher up the reef. Since the coral reefs are found in mostly shallow waters they are very susceptible to the damages storms bring and can also take the lives of surrounding fish populations that could get crushed by falling coral. Reefs can look very different in different parts of the world. In the Cyclone belt (10 to 25 degrees north) many fast growing corals dominate the reefs as they easily regenerate and bounce back from the destruction of cyclones. The same fast growing corals are found dominating reefs struck by hurricanes.

CLIMATE CHANGE As the theory of global warming and

greenhouse gasses are released, the rising temperatures will end up effecting many ecosystems. With a climate increase concerns of corals weakening, degrading and the long term impact of increased climate causing more frequent intense storms. In deeper waters corals will be greatly impacted as they are already getting limited light so if the ocean levels rise they are even further away from the sunlight and they wont be able to do photosynthesis resulting in death.

CORAL BLEACHING The bleaching of corals in an internal

response to stress which causes the essential zooxanthellae to leave the corals tissue and expose the corals skeleton. The most common associated stress is the increase in temperature. Bleaching can cause decreased growth and reproductive activity and then death if bleached for too long. The exposed skeleton of corals then is taken over by green algae which can end up over taking a reefs and competes with coral. In this kind of environment more herbivores can be found as more algae is increased.

CORAL BLEACHING PART 2 In the years of 1997 and 1998, a large

global increase in temperatures cause a lot of bleaching and eventual death of most of the coral reefs found around the world. The numbers of mortality were staggering. Between 70% and 80% of coral cover was lost in many reefs. The Indian Ocean was hit the hardest and up to 90% of coral cover died. This large death has had a prolific impact on the communities that rely on reefs for a source of food and income.

CROWN-OF-THORNS STARFISH The Crown-of-Thorns starfish is a large

species of starfish that feed on living coral and if in large numbers have been known to kill large areas of reefs. Females are free spawning reproducing species that have females producing between 12 and 60 eggs in one spawning season. The starfish eats corals by throwing their stomachs onto the coral and releasing an enzyme that degrades coral tissue. Outbreaks of this species of starfish can cause coral populations to be decimated. The first major outbreak was found in the Great Barrier Reef in Australia.

POLLUTION, SEDIMENTS AND NUTRIENTS Increased sediment loadings on coral reefs are

because of deforestation that leads to run-off. Once a forest is cleared the soil is no longer being held down by the roots of the trees so sediment flows very easily when a rain storm comes through the area. The rain washes the sediment into the ocean and with is comes deposits of nitrates. Also during agriculture seasons pesticides and fertilizers high in nitrates and phosphates are used on the crops. When is rains the water washes these nutrients into the ocean. Nitrates and phosphates are the two biggest nutrients that contribute to algae outbreaks which begin to compete with corals. The Oil Spill in 2008 caused thick layers of oil to blanket coral populations and kill off many coral populations.

CONCLUSION Coral reefs are not as hardy as we first

believed so it is important to think of the activities that was do that cause coral death and disease. This ecosystem is one of the most fragile but has thrived for many millions of years but recently the balanced has been shifted and now they are rapid declining because of human impact. Unless serious measures are taken to preserving the coral reefs, their decline and extinction could be in the near future.