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Volume 29, Number 4July/August 1978

In This Issue

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Life in the Gulf

Written by Robert Arndt and John Burchard
Additional photographs by John Hardy
Additional illustrations by Lisa Bobrowski

In 1977 Aramco published a 285-page, superbly illustrated book entitled Biotopes of the Western Arabian Gulf: Marine Life and Environments of Saudi Arabia.

As the somewhat disconcerting title suggests, the book is aimed at specialists and well-informed laymen, rather than at popular book clubs. But perhaps all the more for that, it is an important book with an important goal: to summarize—for professional and amateur ecologists, marine biologists and other scientists—the findings of an intensive five-year study of the Arabian Gulf and its Saudi Arabian shores.

Behind that study—some aspects of which are still continuing—lies a far-sighted decision made several years ago by officials of the Saudi Arab Government arid Aramco executives to examine the ecology of the Arabian Gulf, given the mounting tempo of petroleum production and shipping in the Gulf, along with increased industrialization (see Aramco World, January-February 1977) and modernization of farming and fishing methods. Concerned lest such developments affect the Gulf's delicate ecology, specialists to Aramco's Loss Prevention and Environmental Affairs Department to study and assess the Gulf today. They also provided funds, equipment and laboratory space. Biotopes is not Saudi Arabia's only contribution to the Gulf's ecology; this April the Kingdom also participated in an eight-nation conference in Kuwait to discuss joint measures to protect it. But the Biotope study is far and away the most important to date.

Starting in 1971, the team—Philip Basson, a marine botanist, John Burchard, a marine biologist and ethologist, John Hardy, an ecologist, and Andrew Price, a marine zoologist and ecologist—set out to establish a biological "baseline," a norm against which any future ecological changes could be measured. The data they collected could also be used by planners to predict the environmental impact of proposed industrial plants, or industrial activity such as dredging, on Gulf ecology and on the other industries—like fishing—that depend on the continued good health of the Gulf. It could also be used by the Saudi Arab government to draw up environmental standards that, embodied in laws, would help protect the country’s natural heritage and ensure that the Gulf remains the living sea that it is now.

The Gulf was not always a sea. Some 20,000 years ago—only yesterday, in geological terms—it was a shallow, 600-mile-long river valley through which the combined waters of the Tigris and Euphrates Rivers ran toward the Arabian Sea. Then, with the end of the latest ice age, sea levels began to rise and the valley began to change into an ocean gulf. The process required some 15,000 years and when, about 3000 B.C., the Gulf reached its present depth and configuration, it was an anomaly among the world's seas: much shallower and warmer, far saltier and more isolated than most.

By then, of course, man was already harvesting the riches of its teeming life, particularly its fish, shrimp and pearls, and on primitive craft was criss-crossing its surface. Traders from the great Mesopotamian civilizations, for example, had begun, via Bahrain/Dilmun, to reach the Mohenjo-Paro civilization of the lndus River (see Aramco World, January-February 1970), the prelude to the later voyages of Arab seamen to Africa, India and China.

Despite such activity extending over thousands of years, man's knowledge of the Gulf was limited to what was obvious and essential: where fish and shrimp were plentiful, where the precious pearl oysters could be found, where the dangerous shoals threatened their craft and where, on the sea-floor, springs of fresh water madcit possible to stay longer on the fishing grounds. But then, in the 20th century, oil was discovered in many countries around the Gulf, and industrialization got underway—a new scale of human activity with greater effects on the natural world—and previous ignorance could no longer be tolerated, especially in a world newly alerted to potential ecological problems. Thus the Aramco study and the publication of Biotopes of the Western Arabian Gulf—a quantum leap in knowledge and understanding of this strange body of water.

Aramco’s study, it should be said, is by no means the first marine exploration of the Gulf. A Danish survey expedition visited the Arabian Peninsula in 1762, and its zoologist published the first scientific descriptions of many marine animals and plants later also found in the Gulf. Several other expeditions—Danish, Japanese and German—worked in the Gulf in the following 200 years, and scientific teams from the United Arab Emirates, biologists from the Kuwait Institute of Scientific Research and fishery experts from Saudi Arabia and other countries have all contributed information in specialized fields.

Yet the Aramco study is by far the most extensive. It provides charts and diagrams, methodological information, a bibliography and list of references and, above all, a 65-page species list of the animals and plants inhabiting the Gulf,—more than half of them never before reported there and some, perhaps, entirely new to science. For the non-scientist with an interest in ecology, the book also contains a glossary and reading list to help him explore an unfamiliar subject, plus fascinating illustrations and a lively, readable text that makes clear the web of connections that links all the Gulf's life forms—including man.

The Biotopes study, furthermore, differs from the previous Gulf studies in concept. Its concern is not so much with individual life forms—isopods or algae or echinoderms—or with particular processes like sedimentation or coral reef growth, as with the connections among the various species and habitats and conditions that exist in the Gulf. In effect, it inventoried the plant and animal communities of the Gulf and began the study of what one might call their "sociology:" their interrelations and how they are affected by those relationships.

Thus came the word "biotopes" into the title of the book Webster's defines a biotope as a "region uniform in environmental conditions and in its populations of animals and plants for which it is the habitat." In the real world, of course, there is no such thing as a region uniform in environmental conditions; those conditions are constantly changing, and even the kind of change going on is subject to change. Nonetheless, in each major biological "province"—such as the open water, the subtidal sea floor, or the intertidal zone between the high and low tide marks—there exist certain "communities" in which the relationship between the physical place and the plants and animals that live in that place is fairly stable, and can be studied. These are "biotopes." One example is the shallow-water grassbeds of the Gulf, with their population of shellfish, snails, shrimp larvae, turtles, algae, fish, crabs and worms, their topography of flat "meadows" and tidal channels, and their input of sunlight, sediment and plankton. All these creatures, and conditions, and the connections that link them together, constitute the "grassbed biotope," a convenient subdivision of the overall ecology of the Gulf.

That ecology is shaped and made unique by the three characteristics that distinguish the Arabian Gulf from most other bodies of salt water—that have made it an anomaly among the world's seas. The Gulf is, first, an extremely shallow sea. Its maximum depth is only about 325 feet, its average depth is just over 100 feet, and large areas near the coast are less than 30 feet deep. It is the very gentle slope of the Arabian Peninsula's eastern edge—less than two feet of drop per mile of distance, continuing under the water—that accounts for the Gulf's lack of depth. And that in turn determines other ecological factors. Shallow water warms and cools faster, so Gulf life forms must be able to tolerate an annual temperature range of some 45 degrees Fahrenheit; shallow water is more easily mixed by wind and tide, so the temperature of Gulf water changes relatively little with depth; mineral nutrients recycle more efficiently in shallow water than deep, thanks to densely populated sea-floor communities that don't exist in the ocean depths.

The Gulf is also a remarkably salty sea. Less—sometimes much less—than 10 inches of rain a year falls on the surrounding land, and there are few rivers to contribute a flow of fresh water—none at all, in fact, on the Saudi coast covered by the Aramco study. And because of high temperatures, the shallow Gulf water evaporates faster than it is replaced by the inflow from the Tigris and Euphrates Rivers and from the smaller rivers of the eastern shore. Thus, though the salinity of the world's oceans averages 35 parts per thousand, in the Gulf the study found salinities ranging from 38 to 70 in open waters, from 60 to 200 in shallow lakes and lagoons and—in one extreme case—as high as 330 parts per thousand! The high salt content of the water, like high temperatures, is a stress that Gulf creatures must be able to tolerate if they are to survive; many, in fact, have learned to thrive on it.

The third characteristic is the Gulf's relative isolation from the rest of the world's salt waters. The only connection is through the Strait of Hormuz—only 30 miles wide and not radically deeper than the rest of the Gulf—through which Gulf water flows out along the bottom, to be replaced by a current of less salty water from the Indian Ocean flowing inward on the surface. Because of the narrow passage, the volume of this water exchange is too small to have much of a damping effect on the Gulf's high salinities and wide temperature swings, and it is to those stressful conditions that the biotopes of the Aramco study are exposed—and adapted.

Despite these stresses, which generally decrease the variety and diversity of creatures exposed to them, the Aramco biologists found that Gulf marine life was far richer than they had expected, even though some of the species live at the very limits of their ability to adapt to the harsh environment. The fact that more than half of the species the scientists found living in the Gulf and on its Saudi shore had never been recorded there before gives an idea of the scope of this unexpected diversity.

Besides diversity, ecologists also look a productivity as a possible measure of the health of an ecosystem. "Primary productivity is the rate at which organic matter specifically, plant tissue—is produced in biotope. Plant tissue is important because photosynthesis by green plants, and the plants' resultant growth, is the only way in which the energy that fuels all life is take; from sunlight and brought into a biotope. Once converted into plant tissue, the plants and then to the creatures that eat the plant-eaters—and finally, perhaps, to man. Though deep open oceans are no more productive than deserts or arctic tundra; the Aramco study found that three of the major biotopes of the Gulf are enormously productive: the grassbed biotope outproducing even tropical forests and growing—without human aid—more than six times as much greenery as average agricultural land.

In practical terms that statistic is significant. The grassbeds cover large parts of the inshore Gulf waters: aerial surveys showed that 66 percent of Tarut Bay, for example, is carpeted with grassbeds that make large amounts of energy available to animal species—shrimp, fish, oysters and turtles—that are of value to man, as well as to other species important in maintaining other Gulf biotopes. The annual productivity of the grassbeds of Tarut Bay alone, the study's authors calculated, comes to 140 billion calories at the very least: as much energy as there is in 95,000 barrels of crude oil.

But in today's world, protein is as important as oil. If those same grassbeds were "grazed" by snails and the snails were eaten by fish—a food chain that exists in that biotope—the undersea meadows could produce over five million pounds of fish a year, worth eight million dollars on the local market. If the end product of the chain were shrimp—and both fishing and shrimp trawling are important local industries (see Aramco World, September-October 1966)—the product would be worth nearly $12 million. And the authors carry their calculation one step further to a point that must bring a gleam to the eye of local entrepreneurs. If the Tarut Bay grassbeds were used as intensive pasturage for the green sea turtles that are common in the Gulf—and turtle ranches do exist elsewhere in the world—the annual production of turtles could be over 25,000 tons with a market value of $46 million.

The biologists call such figures "hypothetical," because their realization would require different patterns of exploitation than currently exist, and because they assume that the biotope's energies would all be channeled into one product. But the magnitude of the resource that the Gulf grassbeds represent is clear. In fact, the study has shown the grassbed biotope to be the foundation of today's Arabian Gulf shrimp industry, for it is in the grassbeds that the young shrimp shelter and feed from the spring till the summer—and during that time,—thanks to the richness of the biotope, they increase their weight about 2,000 times.

Of the more than 500 animal species that the study identified in the grassbeds, few would be visible to the casual scuba-diver, for the shelter the 10-inch interlacing leaves provide to vulnerable creatures is an important factor in the variety of the grassbed population. Yet there are conspicuous and even spectacular residents: two species of sawfish, of which one reaches a length of "at least" 20 feet; several species of large sting rays, up to 13 feet long wkh a five-foot "wingspan"; green turtles, one of four Gulf sea turtle species, all in danger of extinction worldwide; venomous but unaggressive sea snakes that bear their young alive and afloat; two-foot-long sea cucumbers; large carnivorous snails; pen shells, a relative of the pearl oyster that shares its 15-inch shell with a pair of freeloading commensal shrimp; large edible swimming crabs; and several species of small striped fish. These animals, along with many other plant and animal species, form a diverse and abundant biotope that must be considered as one of the most important of the Gulf.

Far less important economically and biologically—but also full of surprises for the Aramco biologists—were the hyper-saline (super-salty) biotopes of the Gulf. These exist especially where water circulation is even more limited than in the rest of the Gulf and where evaporation concentrates the salt content to abnormal levels: in shallow bays, lagoons and salt lakes along the coast. This hypersaline biotope is a world of its own: water temperatures range up to 92 degrees in summer, and the oxygen content of the water is so low that some of the photosynthetic bacteria that inhabit the biotope carry out their vital function using hydrogen sulfide instead of water, and producing sulfur instead of oxygen as a byproduct.

The prize example of this very hostile environment is a salt lake at the head of the bay Dawhat Zalum, which many local western residents call Half Moon Bay. The lake is small and only 13 feet deep; its bottom contains astonishing quantities of crystals of pure salt. Summer salinity levels are as much as 330 parts per thousand: almost ten times the salt concentration of the oceans, and one and a half times as salty as the Dead Sea—which itself is supposed to be able to support only bacterial life (see Aramco World, November-December 1966).

Yet this lake supports a thriving community, poor in number of different species but rich in numbers of individual creatures—a distinction symptomatic of a stressed environment. One alga was counted at a peak population of 18 million individuals per quart of water, enough to stain the lake blood red along its shore. Besides the alga, the Aramco scientists found a score of different plankton species, five types of small crustaceans, a flatworm species, and several varieties of nematode worms—all living and reproducing successfully in water far saltier than scientists had previously believed could support any kind of multicelled life.

Other algae found on the shore of this lake and on other hypersaline beaches in the Gulf play, oddly enough, an important role in the traditional architecture of Saudi Arabia's Eastern Province. The algae precipitate magnesium carbonate in the shallow water that cements sand, gravel and silt together into a stone called faroush. In the past, the stone was gathered from the shallows in chunks and plates and was widely used as a building material; it is strong enough so that a few buildings made of it 40 years ago can still be seen today.

Even where salinity was less extreme than in the Dawhat Zalum salt lake, the Aramco study found a large number of species thriving at higher salt levels than had ever been recorded for those creatures before. Some of the species are economically important, such as sea grasses, shrimp and hamour, a grouper that is one of the most highly prized eating fish of the Gulf; as a result, the study's salinity data will have to be taken into account in any future projects involving food from the sea.

Besides the grassbeds and the hypersaline shallows, Biotopes of the Western Arabian Gulf also records the Aramco biologists' examination of a number of other communities, some of them even richer and more remarkable in their population and diversity—and beauty. Sandy beaches and rocky ones, mud flats, sand flats, rock flats and tidal creeks, rocky sea-floor and soft sea-floor, coral reefs and artificial structures such as oilwell platforms, and the open water itself all support their own distinct and complex communities of living things. And all those plants and animals, from the single-celled plankton to the shrimp to the shark, grow, eat, reproduce their kind and are eaten, interacting with their environment, with each other and with man in the ecological web that ties the world together.

Robert Arndt, Assistant Editor of Aramco World Magazine, is co-author of Cevre ve Sen, a book on the environment for Turkish children.

This article appeared on pages 18-25 of the July/August 1978 print edition of Saudi Aramco World.


Check the Public Affairs Digital Image Archive for July/August 1978 images.