Marsigli had tied white-painted cork markers to the line, at regular intervals. At first, as he paid out the line, he watched the markers moving aft, slowly born westwards by the current flowing from the Black Sea. But then, peering intently over the side, Marsigli saw what he had hoped to see.
The deeper markers, glimmering below him, were beginning to move in the opposite direction. Very slowly, they shifted along until they were under the bows of his boat and the weighted line took the shape of an arc, streaming out west near the surface and then, at a greater depth, curving round to point east. Now he knew. There were two currents in the Bosporus Narrows, and not one. There was an upper flow, but there was also a deeper counterflow, running below it from the Mediterranean into the Black Sea.
Marsigli was only 21. He was to have a long, adventurous and useful life. He was briefly captured by Tatars near Vienna, became an officer in the Habsburg armies on the Danube, and later established Europe's first research centre for oceanography at Cassis, in the south of France. But nothing he did later was more important than his discovery of the Bosporus undercurrent. In methodology and implications, it was a landmark in the new science of the sea. It was also the first step towards the study of the Black Sea for its own sake: not as a ring of shore inhabited by strange people, but as a body of water.
After Marsigli, other scientists, most of them Russians, began to explore the strange and stubborn nature of the Black Sea. Marsigli had shown that the Sea's water was less salty and dense than that of the Mediterranean, and he had explained a mystery: why its shore-level did not fall in spite of its outflow through the Bosporus. But it was left to others, much later, to uncover the basic fact about the Black Sea which makes it unlike all other seas: almost all of it is dead.
On the atlas, the Black Sea appears as a kidney-shaped pond, connected to the outer oceans by the thread-like channel of the Bosporus and the Dardanelles. And yet it is a sea, not a fresh-water lake: a salt-water mass some 630 miles across from east to west and 330 miles from north to south - except at its "waist", where the projecting peninsula of Crimea reduces the north-south distance between the Crimean shore and Turkey to only 144 miles. The Black Sea is deep, reaching down to more than 700 metres in places. But there is a large, shallow shelf in its north-western corner, off the stretch of coast which reaches round from the Danube delta in Romania in the west to Crimea in the north. This shelf, less than 100 metres deep, has been the breeding-ground for many of the Black Sea's fish species.
Travelling clockwise round the Sea from the Bosporus, the Bulgarian and Romanian shores are low-lying, like most of the Ukrainian coastline. Then come the towering sea-cliffs of the Crimean mountains. The eastern and southern coasts (Abkhazia, Georgia and Turkey) are mostly mountainous, sometimes fringed with a narrow coastal plain and sometimes - as in north- eastern Turkey - plunging steeply down to the Black Sea in forested ridges and gorges.
But it is the rivers which dominate the Black Sea. Only three major rivers - Rhone, Nile and Po - run into the far bigger Mediterranean. But the Black Sea receives five: the Kuban, the Don, the Dnieper, the Dniester and, above all, the Danube, whose drainage basin extends across the whole of eastern and central Europe and almost to the borders of France. The Danube alone carries 203 cubic kilometres of fresh water into the Black Sea every year, more than the entire flow of river water into the North Sea.
It is these rivers, source of so much life, which over tens of thousands of years extinguished life in the Black Sea depths. The inrush of organic matter from the rivers was too much for the bacteria in sea-water which would normally decompose it. They feed by oxidising their nutrients, using the dissolved oxygen normally present in sea-water. But when the organic inflow is so great that the supply of dissolved oxygen is used up, then the bacteria turn to another biochemical process: they strip the oxygen from the sulphate ions which are a component of sea-water, creating in this process a residual gas: hydrogen sulphide, or H2S. This is one of the deadliest substances in the natural world. A full breath of it is usually enough to kill a human being. Oil workers know and dread it; they watch for its rotten-eggs reek and at the first whiff they run. They are right to do so. Hydrogen sulphide almost instantly destroys the sense of smell, so that after the first sniff it is impossible to tell whether one is inhaling more.
The Black Sea is the world's biggest single reservoir of hydrogen sulphide. Below a fluctuating depth of between 150 and 200 metres, there is no life. The water is anoxic, without dissolved oxygen, and impregnated with H2S; because much of the Black Sea is deep, this means that some 90 per cent of the Sea's volume is sterile. It is not the only place in the oceans where H2S has accumulated. There are anoxic areas on the floor of the Baltic Sea, and under some Norwegian fjords where water circulation is slight. Off the Peruvian coast, hydrogen sulphide is sometimes brought welling up from the depths to the surface in the periodic catastrophes known as "el Nino", where it kills the entire ecosystem, destroying the coastal fisheries and reacting with paint on ships' bottoms to turn them black (the "Callao Painter" effect). But the Black Sea deeps remain the largest mass of lifeless water in the world.
And yet, until the last 100 years, the Black Sea has seemed to human beings a place of almost monstrous abundance. The poisonous darkness lay far below, unknown to anyone. Above the 100-fathom line, the "haloclyne" or "oxyclyne" which marks the upper limit of anoxia, the sea boiled with life. Salmon and huge sturgeon - the beluga can reach the length and weight of a small whale - crowded up the big rivers to spawn (caviar was so plentiful that in 14th-century Byzantium it was the food of the poor). Along the shores and on the shallow north-western shelf of the Black Sea, there lived spiny turbot, sprat, goby, ray, grey mullet and whiting, most of them feeding off underwater prairies of Zostera sea-grass.
Out in the open waters, among the schools of dolphin and porpoise, two fish species performed a slow, gyratory migration around the Black Sea, their progress almost as punctual as a shipping schedule. One was the bonito (palamud), a member of the mackerel family so important to food and trade that its image appears on some Byzantine coins. The other was the hamsi, or Black Sea anchovy.
To this day, the shrunken remnants of the anchovy hordes spawn off the Bay of Odessa in July and most of August, setting off on their anti-clockwise journey round the Sea between the last week of August and the first days of September and travelling about 12 miles a day, in groups whose biomass even now weighs up to 20,000 tons of fish each. One estimate of the total hamsi biomass, done before genocidal overfishing collapsed the species in the Eighties, suggested that something approaching a million tons of anchovies swam in this circular pilgrimage every year.
Fish brought the Black Sea into history. There were, of course, other factors too: other prodigious sources of food and wealth. The south Russian plains, for example, the so-called "Pontic Steppe", formed a level expanse of prairie stretching for almost 800 miles from the Volga river to the foothills of the Carpathian mountains in the west, a band of open country some 200 miles deep between the sea-coast and the forest country to the north. The grasslands of the Pontic Steppe could feed the horses and cattle of a whole nomad nation; later, its best soil was ploughed up and grew the finest wheat in the world before the cultivation of north America. In the mountains of the Caucasus, whose snowy summits were visible from far out at sea, there were both timber and gold. Across the river deltas wandered flocks of eatable birds which darkened the sky with their migrations. But in all that apparently infinite plenty of natural life, the fish mattered most.
The voyage of the Argo is a Bronze Age legend. When Jason crossed the Black Sea, ran his boat up the river Phasis in Colchis (part of modern Georgia) and tied her fast to the trees overhanging the bank, he was after magical treasure - the Golden Fleece of Colchis. But gold is for heroes. All along the Black Sea coasts, inshore dredgers bring up from the sea- bed big stones pierced with a hole: the anchors of Mycenaean ships. These carried the real Bronze Age venturers. They brought with them from the Aegean luxurious trade goods like ornamental pottery and decorated rapiers, but they were looking for food to bring home, and what they took away seems to have been mostly fish: sun-dried, or cured with salt from the Dnieper and Danube estuaries. When the Mycenaean kingdoms passed away and were replaced by small, hungry city-states perched on Greek and Ionian headlands, the ships returned to the Black Sea on the same errand, which became steadily more desperate as the city-states grew more populous and their small arable hinterlands grew less fertile through over-cultivation. By the seventh century BC, the Ionian Greeks were establishing coastal colonies all round the Black Sea, settling into communities whose first business was the curing, packing and exporting of fish.
Satisfying this need, a very simple one, led unexpectedly into one of the formative moments of human history. The significance lay not just in the meeting of settled, literate people with pastoral nomads. That had happened before, and would happen again. It was important because the literate people brooded on this meeting, and constructed from it - the first "colonial" encounter in European experience - a series of questioning discourses which still remain with us.
One discourse concerns "civilisation" and "barbarism". A second is about cultural identity, and about where its distinctions and limits should be drawn. A third is a deep self-criticism which imagines that technical and social sophistication entails not only gain but loss - a departure of conscious and rational behaviour from what is "natural" and spontaneous.
All three themes, provoked by the encounter in the Black Sea, were debated in the Classical world. They receded after the dissolution of the western Roman Empire in the sixth and seventh centuries AD. But in the early modern period they returned to European consciousness with a steadily more commanding urgency, prompted by the encounters with the Americas, Africa and Asia and, later still, by the developing ideology of nationalism. On the Black Sea itself, however, these matters were not so much debated as lived. Around the fish-drying screens and the smokehouses, typical patterns of ethnic and social mingling arose which have still not entirely passed away.
AT THE outset of his famous book, Iranians and Greeks in South Russia, the Russian scholar Mikhail Rostovtzeff wrote: "I take as my starting- point the unity of the region which we call south Russia: the intersection of influences in that vast tract of country - Oriental and southern influences arriving by way of the Caucasus and Black Sea, Greek influences spreading along the sea routes, and Western influences passing down the great Danubian route; and the consequent formation, from time to time, of mixed civilisations, very curious and very interesting."
But it was not only around the northern fringes of the Black Sea, and not only in the Classical period, that these "very curious and very interesting" communities appeared. The city of Byzantium (to become Constantinople and finally Istanbul) was such a society through the Middle Ages and up to the fall of the Ottoman Empire in the 20th century. So was the Grand Comnenian Empire of Trebizond (on the south coast of the Sea) during the medieval period, and so was 19th-century Constanta near the Danube delta, and the city of Odessa on the Ukrainian coast which was founded only in 1794. So, too, on a smaller scale, were towns like Sukhum and Poti and Batumi on the coast of what was once Colchis, which began as Greek colonies and survived until the end of the Soviet period as sites where peoples of many different languages, religions, trades and descents lived together.
They were "curious" because power in those places was not concentrated. Instead it was dissolved, like oxygen in the warm upper layers of the Sea, among many communities. The title of supreme ruler might belong to a man or a woman whose family origins were among pastoral steppe nomads, Turkic or Iranian or Mongol. Local government and regulation of the economy might be left to Greek, Jewish, Italian or Armenian merchants. The soldiery, usually a hired force, could be Scythian or Sarmatian, Caucasian or Gothic, Viking or Anglo-Saxon, French or German. The craftsmen, often local people who had adopted Greek language and customs, had their own rights. Only the slaves - for most of these places kept and traded in slaves during most of their existence - were powerless.
Sudak, on the Crimean coast, was a Greek, then a Byzantine and finally a Genoese colony. Now there remains only an enclosure of medieval Italian walls and towers, perched on the slanting sea-cliff west of Cape Meganom. Here I was shown a stone tomb, dug among Byzantine foundations, which had contained the body of a Khazar noble.
The Khazars were Turkic-speaking pastoral nomads who arrived out of central Asia in the eighth and ninth centuries AD, and put together an "empire" around the northern shores of the Black Sea, including Crimea. Offered conversion to Christianity by St Cyril, the Khazars preferred to adopt a form of Judaism. So it came about that this particular warrior, with his ancestry in shamanistic Asia, chose to be buried by the Jewish ritual in a city whose overlords were Greek Christians. And there was one extra touch, neither Christian nor Judaic. The funeral was completed by a human sacrifice, and the victim - brained by an axe blow - was thrown into the tomb to lie beside its Khazar occupant.
Peoples who live in communion with other peoples, for a hundred or a thousand years, do not always like them - may, in fact, have always disliked them. As individuals, "the others" are not strangers but neighbours, often friends. But my sense of Black Sea life, a sad one, is that latent mistrust between different cultures is immortal. Necessity, and sometimes fear, binds such communities together. But within that binding-strap they remain a bundle of disparate groups - not a helpful model for the "multi-ethnic society" of our hopes and dreams. It is true that communal savagery - pogroms, "ethnic cleansing" in the name of some fantasy of national unity, genocide - has usually reached the Black Sea communities from elsewhere, an import from the interior. But when it arrives the apparent solidarity of centuries can dissolve within days or hours. The poison, upwelling from the depths, is absorbed by a single breath.
THEY SAY: "The Black Sea is dying." I open an American newspaper and read: "The Black Sea, the dirtiest in the world, is dying an agonising death." I am told, on the authority of a UN document, that the Black Sea constitutes "the marine ecological catastrophe of the century" because "90 per cent of the basin is now anoxic."
Here are treasures in the museum of self-accusation, the international gallery of eco-doom. It is entirely true that the Black Sea is nine-tenths dead, and that its waters below the 200-metre oxycline are poisoned with hydrogen sulphide gas. But they always were.
When the Argo fled back from Colchis to the Danube delta, with the navy of King Aeetes in pursuit, she was flying over a lifeless gulf nearly half a mile deep. Had she sunk on the journey, her timbers and the Argonauts themselves would still be sitting intact on the blue-grey bottom mud, for there is no oxygen in the water which would allow them to rot. Down there, only metal is consumed. Their bronze swords and helmets, the studs on their belts and the rings on their fingers, would have been dissolved away to nothing. As for the Golden Fleece, it would have lost all the bullion glare that made it worth the voyage from the Pagasaean Gulf in Greece to Colchis. It would lie there to this day, across the laps of dead Jason and Medea, but now returned to its old innocence, whiteness and sheepishness.
This death or near-death of a sea was not caused by the human race. It apparently annoys some fanatics that an ecological catastrophe can be achieved by ecology itself, without any need to call on human assistance. All the same, it was the natural action of natural forces which brought about this huge act of pollution: the decay of billions of tons of up- country mud and leaves and living ooze and dead micro-organisms, poured on to the sea floor since the last Ice Age by the five great rivers of the Black Sea.
It was not our fault. This is a fact, but a fact which might excuse the human race many other sins if it were too widely known. In consequence, journalism and propaganda about the condition of the Black Sea seldom mention hydrogen sulphide. If they do (as in the case of that UN document), they slip in a hint that the anoxia is in some way connected with human crimes against the environment.
What is dying, or rather being murdered, is not the Sea but its creatures. What is being polluted by human agency is not the main body of water (apart from the tipping of drums of toxic waste by Italian ships), but the surface layer whose abundance has shaped the whole prehistory and history of the Black Sea littoral. These are not small distinctions. Something terrible and perhaps final really is taking place. But there is no way to appreciate the scale of this threat without drawing back and surveying the precariousness of the entire Black Sea system: a surface film of life stretched over an abyss of lifelessness.
Out of 26 species of Black Sea fish being landed in commercial quantities in the Sixties, only six now survive in numbers worth netting. The hamsi anchovy provided 320,000 tons of fish as recently as 1984; within five years it has fallen to a mere 15,000 tons. The fish catch from all species is less than one-seventh of what it was 10 years ago, and many species are now almost certainly extinct. As for the mammals of the Sea, the monk seal is now extinct, reputedly because a Bulgarian hotel-builder dynamited its last cave-refuge, while the three species of dolphin or porpoise have been reduced from almost one million in the Fifties to anything between a third and a tenth of that number.
Monstrous plankton blooms have begun to appear on the shallow north-western shelf of the Black Sea, where the bottom is above the anoxic level and where many of the important fish species spawn. "Red tides" formed from dying phytoplankton began to occur with regularity in the early Seventies. The worst of these, in the Bay of Odessa in 1989, reached the horrifying concentration of 1kg of plankton for every cubic metre of sea-water. Hydrogen sulphide, generated in the shallows rather than rising from the depths, began to reach the surface so that the stench spread through the city streets and the Bay was covered with dead fish; much of the same happened that season off Burgas, in Romania. The penetration of light in these increasingly turbid coastal waters has dropped by anything between 40 and 90 per cent, killing off bottom-living creatures like flatfish, molluscs and crustaceans and destroying almost the entire pasture of sea-grass.
The meaning of these facts and figures is that, for the first time, mankind is about to extinguish life in an entire sea. Some forms will survive: sterile algae or jelly-like drifting creatures. But the living creatures with whom the human race grew up here - the billions of silvery fish migrating round the same track since the last glaciation, the grinning dolphins whom the Greeks appointed the patrons of Trebizond - these are about to leave us.
The causes are known. All of them, with a few consciously criminal exceptions like the dumping of toxic waste, derive from human immaturity. At least 160 million people now live in the Black Sea basin - that is to say, in the area drained by rivers which run into the Sea - and among them are farmers, industrial workers, fishermen and seamen. But in the past 15 or 20 years, their trades have all been overwhelmed with technical innovations, with modern fertilisers, supertankers, industrial processes based on hydrocarbons, dioxin or CFCs, electronic fish-location gear and modern drift-nets. Learning to operate these technologies takes all the mental concentration of Black Sea people, and for the wider questions of what these novelties do to the Sea and its life-systems and even to its human inhabitants they can spare almost no attention. When boats were made of wood, when peasants strewed their own dung on the fields and the worst industrial effluent was chlorine or sulphuric acid, there was at least more time to reflect; more opportunity for estate owners, iron-masters or ships' captains to take a broader and more inclusive view of the consequence of what they were doing. But now the toy has grown so big that it plays with the child.
The biochemical disaster is about "eutrophication", an excess of organic and chemical nutrients. These are mostly nitrates and phosphates from agriculture and the residues of detergents. The phosphate concentration on the north-western shelf, for example, multiplied by nearly 30 times in the 10 years between 1966 and 1976. The Danube's own phosphate discharge is 21 times greater then it was 15 years ago, and the river also carries down 50,000 tons of spilled oil a year (worth $7.2 million at current prices, which would be enough to finance an ecological rescue programme for the entire Black Sea). It is the impossible surfeit of nutrients which causes "red tides", plankton blooms and the loss of light and dissolved oxygen which is devastating the only area of the Sea's floor where life can exist.
There is also heavy-metal pollution, radioactive contamination since the Chernobyl accident in 1986 and the damage done by reckless use of sophisticated pesticides and insecticides. And then there is simple, traditional human filth: domestic rubbish and sewage. The Turkish novelist Yashar Kemal has described the Golden Horn at Istanbul: "that deep well surrounded by huge ugly buildings and sooty factories, spewing rust from their chimneys and roofs and walls, staining the water with sulphur- yellow liquid, a filthy sewer filled with empty cans and rubbish and horse carcasses, dead dogs and gulls and wild boars and thousands of cats, stinking... A viscous, turbid mass, teeming with maggots." The sewage of a city of 10 million people (increasing at the rate of one a minute) gushes almost untreated into the Golden Horn and the Bosporus. Few towns on the Black Sea are any cleaner. Swimming off the north Turkish coast, far from the nearest village, I have often had to dive under floating islands of ordure.
IT WAS IN the early 1980s that Soviet marine biologists trawled up a creature unknown to them. It was an unimpressive little being, a bell- shaped thing of transparent jelly found swimming in the shallow waters of the north-western shelf. The scientists recognised that this was a species of ctenophore, an organism not unlike a jellyfish, and within a few months they identified it as Mnemiopsis leidyi, a native of the shallow estuaries on the eastern seaboard of the United States. Pretty clearly, it had been brought to the Black Sea in the water-ballast of freighters.
As Black Sea people know only too well, a weakened polity attracts invaders who can settle without meeting resistance. They find a niche, and flourish. Much the same applies to ecologies. Mnemiopsis was not the first alien settler in waters whose natural defences - the biological diversity of other species - were in steep decline. The big marine snail Rapana, probably brought from the seas off Japan in the same way, had already decimated the Sea's oyster stocks before itself becoming the target of a profitable fishery. But nobody was prepared for the consequences of Mnemiopsis.
In the late Eighties, mostly between 1987 and 1988, there took place one of the most devastating biological explosions ever recorded by science. Mnemiopsis, an animal with no known predators to control it, spread suddenly and incontinently through the Black Sea. It fed voraciously on zooplankton, the food of young fish, and on fish larvae. In the sea of Azov, Mnemiopsis consumed almost the entire zooplankton population, which in 1989 and 1991 collapsed to one-600th of its normal average. Its total biomass in the Black Sea and the Sea of Azov reached 700 million tons of translucent jelly, and its impact was entirely catastrophic. No recorded destruction by human pestilence or locust swarm compares with this damage to fish and their resources, and that was only the most obvious part of the disaster. Zooplankton feed upon phytoplankton, which, liberated from their normal predators, multiply uncontrollably into the vast "blooms" which consume dissolved oxygen and destroy life in shallow waters.
The Mnemiopsis disaster, more than anything else, finally convinced the governments of the Black Sea states that they must take action. A series of international conferences, guided by United Nations agencies, is now trying to draw up detailed rescue programmes to cut back pollution discharge and face the consequences of overfishing. But Mnemiopsis itself, with no known natural enemies, is also immune to governments. Nobody knows what to do about it. One radical school of thought holds that the breakdown of the old Black Sea ecosystem has to be accepted as irreversible, and that the only hope now is to introduce other alien species selected to prey on these invaders - fish, jellyfish, ctenophores and molluscs - and eventually construct a new but stable ecological balance. Other scientists regard this as reckless, and prefer to concentrate on slow but predictable measures like the reduction of nutrients coming down-river.
Meanwhile, unexpectedly, a change has come over the Mnemiopsis hordes. Like some of the nomad invaders of the Pontic Steppe who ran out of grass for their horses and set off for fresh pastures, Mnemiopsis appears to have eaten the Black Sea bare. The total biomass is thought to be falling. In some areas, the creature is descending to greater depths, closer to the oxycline, and attacking the tiny organisms which until now have survived as the main food of Black Sea sprats. More ominously, outlying raiding parties have begun to turn up in the Sea of Marmara and even off the Aegean coast of Turkey. Mnemiopsis is heading west. The spectre arises of an annihilating plague breaking out in vulnerable parts of the Mediterranean: the Nile delta, the Tunisian coast, even the Gulf of Lyon off Marseille.
BEHIND ALL predictions of what will happen to the Black Sea, there creeps a nightmare. It is a possibility so terrible that most scientists prefer not to discuss it. Many of them - to be fair - have brought forward good reasons to argue that it need not be taken seriously. It is a Black Sea apocalypse.
This nightmare is known by the harmless word "turnover", a phenomenon which has been observed in lakes whose depths are anoxic and charged with hydrogen sulphide. "Turnover" means a sudden rolling-over of water layers, as if the whole balance of pressures and densities which had kept the heavier mass below the lighter, fresher mass were reversed and overthrown. With "turnover", in some lakes an annual event which takes place in autumn, the deep and poisoned waters burst through to the surface, annihilating all life.
It is possible to define the Black Sea as merely the biggest of all anoxic lakes. If "turnover" were to take place in the Black Sea, it would be the worst natural cataclysm to strike the earth since the last Ice Age, more devastating in its human consequences than the eruption on Thera in about 1500 BC which destroyed the Minoan cultures, or than the Krakatoa eruption in Indonesia in 1883.
A first warning sign would be a rise of the anoxic water-level. A few years ago, American researchers on a study voyage in the Black Sea claimed that the oxycline, the upward limit of the poisonous undermass, had risen by 30 metres in only 20 years. Pollution and the effect of reduced river flows on the Sea's water- density, they concluded, were beginning to create the conditions for the ultimate disaster.
They were probably wrong. Russian oceanologists at once pointed out they had been measuring the oxycline level for far longer than the Americans, and had registered variations of up to 30 metres upwards and downwards since they began surveys some 70 years before. The British marine environmentalist Laurence Mee, who runs the Global Environment Facility task force for the Black Sea at Istanbul, calculates that the rivers would have to run at half their present flow for more than a century before the density balance of the Sea could be seriously affected. All this is reassuring; the weight of scientific evidence suggests that the Black Sea is not about to capsize. But, as Mee allows, "the debate continues". An edge of fear, a shadow of apocalypse, has entered all discussions on the rescue of the Black Sea, and it will never quite go away.
! Adapted from `Black Sea', by Neal Ascherson, published on 29 June (Jonathan Cape, pounds 16.99)Reuse content