Coral reef conservation

The Global Coral Reef Monitoring Network (GCRMN) highlighted in a 2004 report* that up to 70% of the world's reefs may be lost in the next 20-40 years mainly through human threats such as poor land management practices, overfishing, destructive fishing techniques and pollution. It noted that:

• 20% of the world's reefs have been destroyed (>=90% coral loss and unlikely to recover)
• 24% are in a critical state (50-90% coral loss and potentially destroyed in 10-20 years) while 26% are threatened (20-50% loss, potentially destroyed in 20-40 years)

In Southeast Asia alone, 38% of reefs have been destroyed, 28% are in a critical state and another 29% threatened.

More recently, with the increased focus on the impact of global warming and climate change, scientists have claimed that many of the world's coral reefs are under threat from increasing sea temperatures which have caused coral bleaching and fatal epidemics in coral reefs across the globe. Already, a long-term study in the Seychelles has shown that many of the bleached corals were not able to recover, leaving a trail of coral rubble covered in algae. In addition, recent large earthquakes have also lifted up shorelines in Ranongga island in the Solomons and Simuelue island off Sumatera in Indonesia, raising entire coral reefs out of the water which then bleach and die.

The disappearance of coral reefs is of great concern because many people depend on them economically.

Many fishes that we eat like groupers and wrasses come from coral reefs. Reefs sustain one-quarter of all known marine life: over 4000 fish species, 700 species of coral and many other plants and animals.

Reefs provide a means of income and revenue for millions of people worldwide who depend on them for survival, including those in the fishing and tourism industry. Many countries with healthy coral reefs attract recreational visitors from all over the world. People visit places like Redang to see fishes and corals. Resorts, dive operators, travel agents, transport providers and many others earn their income from these visitors.

Coral reefs protect coastal communities from storms. In the December 2004 tsunami, reefs acted as natural barriers, minimizing the destructive force and saving many lives and properties. Most of the reefs in the Indian Ocean escaped without serious damage from the tsunami. Reefs prevent coastlines from erosion and provide sand for beaches. They are part of an ocean ecosystem that helps to stabilize our climate, create rain for crops and oxygen in the air.

Scientists are also beginning to derive new medicines from reef species for a wide range of illnesses, including heart disease and HIV. Certain coral skeletons are being used in reconstructive bone surgery as they resemble human bone. As with the rainforests, there is still much to explore and discover and it is highly likely that future cures for certain diseases may come from biochemical extracts of coral reef species. One day, you and I may owe our lives to medicines derived from coral reefs!

Coral reefs take many years to form

Many established coral reefs are thousands of years old. The rate of growth depends on the species of coral, water temperature, oxygen level, salinity, turbidity, and availability of space and food around them.

Staghorn corals can grow at a rate of up to 20 cm (8 inches) each year, while massive boulder corals like brain corals and ridge corals grow only 5 to 25 mm (1/4 to 7/8 inch) per year. This slow growth rate means that reefs will not regenerate quickly enough when subjected to high rates of destruction.

Under normal conditions, reefs are quite resilient and can recover from destruction caused by storms, disease and natural predation. However human-in duced threats such as pollution, sedimentation and destructive fishing techniques place excessive stress on reefs to the point that they are unable to recover from damage. Vast areas of coral reefs have been wiped out in places where dynamite fishing is prevalent and many countries today have banned such practices.

Pollution and sedimentation are caused by littering, discharge of industrial and organic wastes and soil erosion from deforestation. It is important that resorts in reef areas operate in an environmentally-friendly manner to prevent their wastes and pollutants from reaching the sea. Visitors should also ensure they do not litter and avoid stepping on corals and damaging them. It takes just a moment of carelessness to destroy reefs that take many years to form.

Corals are made up of tiny animals called polyps

Corals are colonies of tiny animals called polyps. These belong to the group of animals known as cnidarians which include hydroids, jellyfish and sea anemones. Some cnidarians like jellyfish are free floating while others like coral polyps remain fixed in one place. A coral polyp is like a fixed, upside-down jellyfish while a jellyfish is like a free floating upside down polyp! In fact, jellyfish spend their early life as polyps which later bud off as free floating tiny juvenile jellyfish.

Polyps are found in hard and soft corals, anemones, sea whips and gorgonian fans. All cnidarians possess stinging cells known as nematocysts. Polyps use tentacles covered with these stinging cells to catch and feed on plankton brought in by intertidal currents. The size of an individual polyp can be less than a millimeter to as large as 25 cm in a mushroom coral.

Unlike other animals that can move around to find mating partners, polyps stay fixed to one place. To reproduce, the entire coral community engages in a mass synchronized spawning event once or twice a year. Coral species can be male, female or hermaphrodite. Egg and sperm are released at exactly the same time, one species after another. The entire event releases so many eggs into the sea simultaneously that despite many being eaten by fish, many others survive and are carried away by currents. These eggs are sometimes visible as a coloured slick on the water's surface. Fertilized eggs become swimming larvae known as planula. When larvae settle on the reef, each one metamorphosizes into a single polyp and begins its own colony under the right conditions.

Like cell division, a single polyp can subdivide into two polyps which in turn subdivides into four polyps, then eight and so on. Whole colonies of polyps can come from just a single polyp and are genetically alike.

A polyp's best friend is a plant

Coral reefs are found in shallow water because they need sunlight to live. Coral polyps contain algae inside their tissues called zooxanthellae. Algae are plants and require sunlight to convert carbon dioxide and water into simple sugars (food) and oxygen through the process of photosynthesis. Polyps are animals and require oxygen and food for respiration, producing energy and carbon dioxide as by-products.

The zooxanthellae present in the polyp tissue supplies the polyp with oxygen and shares its food with the polyp. It is estimated that polyps can absorb up to 98% of the sugars produced by the algae. Furthermore, the algae helps the polyp to extract nutrients such as nitrogen from the sea and increases the rate at which polyps secrete corallite to build the reef. In return, the algae gets physical protection, nutrients and carbon dioxide from its host. This mutually beneficial relationship is known as a mutualistic symbiotic relationship.

The algae present in the polyps give corals their colour - polyps are transparent to allow sunlight to reach the algae. When this relationship ends, the algae is expelled by the coral and the coral appears white which is the colour of their limestone skeletons. Dead and bleached corals do not contain algae and appear white.

Reefs are built by hard corals

Coral reefs are built mainly by reef-building hard corals. Coral polyps in these hard corals continuously secrete a hard calcium carbonate limestone skeleton called corallite under and around themselves which form the base for the colony to grow on and which provides protection for the polyps. This skeletal base grows as polyps die and new polyps grow over them, continuing the process of limestone secretion.

Coralline algae help to cement the reefs together with a calcium carbonate base called thallus which is covered by a thin layer of plant tissue. Coral larvae are attracted to this algal surface, settle and develop into coral colonies. Many fish also feed on the coralline algae.

Over time, coral polyps subdivide, grow and form large fields of stony coral reefs like staghorns, table corals, ridge and brain coral. All of these different colonies form a coral reef. During the day, these stony corals look like lifeless rocks because the tentacles of the polyps are retracted. As night falls, many polyps extend their tentacles to feed on zooplankton. Under the cover of darkness, polyps may fight for space with polyps from neighbouring corals, extending their gut over them and digesting them alive.

A metropolis of life

Coral reefs provide habitats and protection for a large variety of marine life such as sponges, tubeworms, feather stars, molluscs, crustaceans, starfish, urchins, anemones, jellyfish, fungi, turtles and fish.

All of these reef organisms play a part either in directly building the reef or by being part of the food chain and life cycle of the reef.

For example, many organisms which feed on algae become food for other predators. Waste products and other sediments that fall to the bottom feed bottom-dwelling scavengers like certain crustaceans and fishes. Some organisms like cleaner shrimp and cleaner wrasse provide cleaning services for other reef life, while others live in symbiotic relationships with other organisms. The coral reef is a remarkable place where everything is recycled and nothing is wasted.

With such a great biodiversity of life dependent on the living reef and on one another for survival, when a coral reef is destroyed, the entire chain of life is affected, and many of these organisms disappear, leaving behind an almost desolate landscape of dead coral and coral rubble.

Natural threats

Storms and monsoons bring about powerful wave action that can damage corals and churn up the seabed causing sedimentation, which block sunlight needed by the zooxanthellae.

Diseases that affect the coral polyps and coralline algae can kill them. These may be caused by infectious parasites like bacteria, virus and fungi, or due to non-infectious causes like poor nutrition and exposure to certain environmental conditions.

Predation by reef animals usually do not cause widespread damage unless there is an outbreak in the number of predators. An outbreak of crown of thorns starfish is one of the most damaging. A single starfish can eat as much as 2 to 6 square metres of coral a year. A significant increase in their population can decimate entire reefs. The drupella sea snail and nudibranch (a kind of sea slug) also feed on coral polyps, digesting the animal tissue and excreting the zooxanthellae. Sometimes, the nudibranch will also keep the nematocysts and algae for their own use.

Parrotfish also feed on coralline algae on rocks and stony corals. They use their powerful jaws to bite through rock and coral, eroding the coral - one can actually hear them crunching the coral when underwater. These are ground up, ingested and excreted as fine sand. A single parrotfish can produce up to 300 lbs of sand every year! Next time you enjoy the beautiful white sand under your feet, remember you may be stepping on parrotfish poo!

The reef can often recover from such short-term stress and in some cases, these might even benefit the reef due to recolonization of damaged areas by a greater diversity of organisms.

Human threats

Global warming has a catastrophic impact on coral reefs. Corals are sensitive to water temperature and will bleach and die when their upper temperature threshold is exceeded. The El Nino phenomenon of 1998 destroyed a high percentage of coral cover globally through mass bleaching and only about 40% of the damaged reefs are recovering well or have recovered. Greenhouse gas emissions arising from human activities in industrialized parts of the world are a major contributor to global warming. Rising temperatures on earth have already resulted in ice shelfs melting and breaking off at the poles and more extreme weather conditions around the world.

Sewage and toxic discharges generated from domestic, agricultural and industrial runoffs containing pesticides and chemicals, and sedimentation from land clearing can cause stress to reefs. Long-term exposure to water containing these contaminants weakens the reef and causes their eventual destruction. Other related ecosystems like mangroves, which provide safe habitat for the young of many marine animals, are also affected by such contaminants. The destruction of mangrove areas worsens the general health of the reef as they, together with mudflats and sea grasses, all belong to the same bigger ecosystem.

Coral reefs are very sensitive to water quality. Too much organic matter and nutrients will create widespread growth of algal blooms that can smother corals, blocking out space & sunlight required for their survival. Too much sediment in the water also has the same effect of blocking sunlight from reaching the corals and smothering the polyps when the sediment settles on them. Without sunlight, the algae present in coral tissue cannot photosynthesize food, and the coral polyps will die. Control measures must therefore include proper treatment of all sewage and wastewater, and proper control of run-off using drains and silt-traps.

Other human threats include coral damage caused by anchoring on coral reefs, coral breakage caused by careless or irresponsible visitors, and coral mining where corals and marine life are collected for sale or export. In many other parts of the world, irresponsible fishing practices using cyanide or explosives have killed large areas of reefs but fortunately, these practices have been banned and outlawed in many countries with coral reefs.

According to a year 2000 study (see footnote 1) of 3 marine parks (Pulau Redang Marine Park, Pulau Tioman Marine Park and Pulau Tinggi Marine Park), the east coast of Peninsular Malaysia has a very high coral & fish species richness and is considered to be a globally important area of coral biodiversity. Specifically, the study at Pulau Redang Marine Park was carried out at Teluk Mat Dollah, Chagar Hutang, Terumbu Kili, Pulau Ling, Pulau Lima and Pulau Lang Tengah.

The coral & fish species identified in this study were almost 80% of the number of species identified in the ‘Coral Triangle’, an area bounded by Papua New Guinea, Indonesia & Philippines, which is known to have the greatest coral diversity on earth. The health of the reefs in the surveyed areas were rated as 'fair' to 'good' based on the amount of coral cover (42.2%), the amount of non-coral algal cover (<10%), low percentage of recently-killed coral (5.3%, mostly caused by marine life feeding on corals) and good water visibility (average of 14m). However, there is a lack of previous data to compare with, so long-term data such as the rate of decline of coral cover in Redang has not been clearly established.

Coral reefs at Redang were among the less severely affected during the outbreak of El Nino in 1998, which wiped out coral reefs in some other parts of the world. Nevertheless, it brought about a reduction in coral cover in Redang. Other threats in Redang were identified as nutrient run-off from sewage/wastewater discharge in some populated areas and sedimentation due to deforestation. Lesser threats included discarded rubbish & refuse, irresponsible diving & snorkelling, mechanical damage due to boat anchors, 'ghost' fishing nets, and reef-eaters such as crown-of-thorns starfish and drupella.

It was noted that in general, many procedures were already in place to protect the marine environment at Redang, such as the ban on fishing within marine park waters, the presence of mooring buoys for boats, observance of park regulations by resort operators and boatmen, and the availability of wastewater treatment facilities at some populated areas.

More recently, in October 2003, a Reef Check (see footnote 2) was organized to collect data about the health of coral reefs in Redang. Volunteer divers conducted checks on six sites around Pasir Panjang. The results showed that coral cover was healthy at the North house reef (56.9%), Mini Mount (57.5%) and Pulau Paku Kecil (54.8%) while the other three sites had fair cover - the South house reef (45%), the deep reef at Pulau Lima (33%) and the shallow reef at Pulau Lima (47.8%). The Reef Check process is an important step in enabling regular monitoring of the health of the reefs in Redang by local resort operators and volunteer organizations. Over time, such quantitative data will paint a more accurate picture of the overall condition and the rate of deterioration of the reefs.

Effective protection begins with the proper formulation and enforcement of environmental policies and regulations (not just those covering resort & village operations but also those that govern the development of Redang), continual long-term monitoring of environmental indicators such as water quality, regular maintenance of equipment & facilities, and most importantly, changing people's mindset and attitudes towards coral reefs. Educating resort staff and visitors about the importance of conservation can help them to be more aware of their actions and to minimize the human impact on the marine environment.

Footnotes:
1: Status Report on the coral reefs of the East Coast of West Malaysia 2000 by Harborne, A., D. Fenner, A. Barnes, M. Beger, S. Harding and T. Roxburgh. The pdf report is available from Reefbase.

2: Reef Check is an international program that works with communities, governments and businesses to scientifically monitor and manage coral reef health.