Paradise in Peril

By Hagen Schmid
Well-known and respected amateur naturalist, diver and author of several books on the marine environment of the Red Sea

Coral reefs are home to some of the greatest diversity of life forms on our planet. They are living structures consisting of thousands of different creatures. The coral polyps themselves are one of the principal builders of these amazing formations. 'Modern' reef building corals are descendants of organisms which lived in our seas more than 225 million years ago, and are quite hardy little creatures which have survived many climatic changes in the past. However, they have never before been faced with the multitude of environmental problems that now confront them.

Approximately 400 species from about 100 genera of coral are the main reef builders in our tropical seas. Their life cycle, shape and feeding habits differ so much from any other living creatures we know that they were not fully understood by early scientists, who described them as plants or plant-animals (Zoophyta). Only in 1725 were they correctly classified as animals by the French scientist, Peyssonnel.

With the help of highly specialised algae called Zooxanthellae, that actually live within the coral polyp, they extract calcium and carbon out of seawater and build their protective exterior skeletons. Every different species constructs a particular shape and size of colony. Because this building work can only take place with the support of the zooxanthellae and sufficient sunlight, we find nearly all reef building corals in rather shallow water around the Equator, where there is an ample and steady supply of sunshine.

With and around the corals live hundreds of other species that directly or indirectly depend on the structures produced by these tiny builders. Tubeworms or shells bore their way into the solid, protective calcium deposits. Fish, invertebrates and crustaceans hide between the branches. Many animals consider the coral polyps themselves as a nourishing food source, from the small butterfly fish, which feeds only on single polyps, to the large bumphead parrot fish which, with the help of their strong, fused front teeth break off coral pieces and grind the skeletons down to extract the nourishing polyps. They release the undigested remains onto the reef forming sandy patches, which provide a home for other types of animals. When coral polyps die, their stony foundations provide soft corals and sponges with an ideal base on which to settle and start their own colonies. Pieces of broken coral can be cemented together by calcium-producing algae to provide further areas for such life forms to grow. Some fish, and other animals like sea urchins, play an important role by grazing on algae or sponges that might otherwise overgrow and suffocate the corals.

For millions of years these kingdoms were able to flourish, hidden beneath the sea. The ballooning of the human population in the mid 1980's to 5 billion (and in the 1990's to 6 billion), and the accompanying economic and social problems of feeding and settling all these people, has dramatically influenced our environment. Coral reefs, once fished in a sustainable fashion when demand was light, are now plundered and abused by dynamiting, cyanide fishing, shell collecting, pollution, overfishing, and excessive tourism. These once majestic coral formations are now in deep trouble worldwide.

During the last few years scientists around the globe have become increasingly alarmed by the rapid decline in the health of coral reefs. This marked decline has taken place in most of the tropical seas. In the Red Sea the reefs have, so far, remained in a relatively robust state as most of the coastal regions are rather thinly populated. However, there have been local problems around the larger cities like Jeddah, and Yanbu in Saudi Arabia, and on the extensively visited diving sites along the Egyptian coastline.

hen suddenly in August 1998 extensive coral bleaching was observed along the central Red Sea coast , the once healthy reefs joined the general decline also seen in the Pacific and the Caribbean. Under a combination of negative environmental circumstances, corals expel their zooxanthellae. These algae normally give the coral colonies their colour, and the loss causes the colony to turn white. The reef building corals affected are mainly those with a massive life-form such as Porites, Favia, and the brain corals, along with leather corals (Alcyoniidae) other soft corals (Nephtheidae), and sea anemones (Stichodactylidae). In some areas 80-90% of the leather and soft corals were affected or killed. Once colourful coral gardens have become stony-white underwater deserts.

The percentage of bleached corals was not constant. There was a significant variation in different areas. It appears that reefs which have had to cope with other additional sources of stress are much more sensitive to the causes of bleaching. Reefs to the north of the city of Jeddah, where most coastal development is currently taking place, showed much more damage (20-30%) than reefs to the south of the city (5-10%) where relatively little or no development has taken place.

Many possible causes for this sad phenomenon have been suggested. One of the most widely accepted explanations is prolonged higher water temperature, although corals can tolerate quite high temperatures. The damage in shallow areas, where the water can heat up above 40 °C in the summer months, was less than in deeper ones where the temperatures were not as high and were more constant, 28-32° C, depending on the season . Changes in sunlight intensity have also been put forward as a possible cause; however, corals under overhangs or in caves were affected, whereas others in direct sunlight were not.

By October it seemed that the bleaching had come to an end. Some corals appeared to recuperate very slowly but most were dead, and green algae were seen growing on the skeletons. A brownish tint returned to the sea anemones. However it seemed that they had lost some of their stinging ability because wrasses could be seen swimming in and out of the mouths of these once aggressive animals.
With the pollution of our planet we undermine the healthy functioning of our ocean ecosystems, which were in equilibrium over millennia without us in the equation.

The question now is how much abuse can the living ocean-system continue to take? Let us remember that our oceans are among the main producers of oxygen for the atmosphere, and a valuable source of food. They should not be used as a site to dispose of our waste and should not be contaminated with pollutants from the land or the air. We need to live compatibly with nature and not to continue to systematically destroy our supporting ecosystems.

From: Al Sanbouk 12 (in press)