To Light: Murray’s Reefs - Reef Madness: Charles Darwin, Alexander Agassiz, and the Meaning of Coral - David Dobbs

Reef Madness: Charles Darwin, Alexander Agassiz, and the Meaning of Coral - David Dobbs (2005)

Part II

Chapter 10. To Light: Murray’s Reefs

Sir John Murray, age forty, in 1SS1. His notions about coral reef genesis would set Alexander on a long search for a more comprehensive alternative to Darwin’s.

I

IDREAD THE MOMENT when I shall reach home,” Alexander Agassiz wrote a friend from Lake Titicaca in spring of 1875, “or rather my house, for no place can henceforth be a home to me.” He indeed found his faith in hearth tested. In August, just four months after he returned from Chile, his sister Ida and her husband Henry Higginson lost their six-year-old daughter, Cecile, to meningitis. Alex and son George carried the bier to the grave. The following May, Mimi, in whose company Alex had taken such comfort in the first year or two after Annie’s death, lost a child in her eighth month of pregnancy. A week later Theo’s brother Fred lost both his wife and child in childbirth. The family started to fear, always, a new tragedy lurking. “That little boy of mine!” Theo wrote of the still healthy son that Mimi had given birth to two Novembers previous. “He may fade in a night; but then too, he may live to close my eyes. Let us hope for the good, ever ready to be resigned to evil.”

This hail of loss, begun by the deaths of his father and wife in December 1873, marked Alexander Agassiz the rest of his life. Through his remaining years he alternated through a series of wanderings and returns driven on the one hand by the desire to escape and to accrue knowledge (for he was a sort of empiricist magpie, compelled to gather facts) and, on the other, a deep ambivalence about the prospects of home. The home he returned to from Chile- a new summer mansion he had built across Narragansett Bay from Newport, Rhode Island-was itself an escape, letting him vacate Cambridge every summer to live in the salt air and do his research. After that first winter back in Cambridge in 1875-1876, he usually went elsewhere in the cold months as well, traveling almost every year to some warm place, sometimes down the coast to Florida or the Caribbean, sometimes to the globe’s farthest points. While he grew more comfortable at his home in Newport, he would never again live extensively in Cambridge, and his winter range expanded as he aged. By his last decades he traveled less to indulge his restlessness than to work, and he traveled then particularly to solve the mystery of coral reefs.

2

He took his first trip with any real purpose at the end of 1876, to Scotland. Since returning from the Andes he had spent most of his time close to home, tidying things at museum and mine and trying to work through his sorrow even as the three new deaths in the family deepened it. Sandwiched between those losses, his own more per sonalloss, marked by the ghosts of his wife and father waiting every December, had made that first winter back in Cambridge intolerable. When he received an invitation from Scotland to help sort the specimens from the just completed voyage of the Challenger, he jumped at the chance.

The Challenger voyage, a three-and-a-half-year, round-the-world oceanographic expedition, did for oceanography what James Cook’s voyages had done for navigation a century before: It established the first reliable, comprehensive baseline of worldwide oceanographic data. The first long marine expedition devoted exclusively to science, the Challenger essentially founded oceanography as a discipline.

The expedition’s main focus was the exploration, via sounding line and dredge, of the deep sea, an area so unknown, yet suddenly considered so crucial to knowledge of the planet, that the trip inspired the kind of interest that the first manned spaceflights evoked a century later. Only twenty years before the Challengers voyage, scientists had been in agreement that virtually nothing lived deeper than three or four hundred fathoms, despite a few starfish pulled up from deep-water soundings. In 1860, however, a telegraph cable laid one thousand fathoms deep in the Mediterranean three years earlier and now pulled to the surface for repairs came up encrusted with more than a dozen kinds of bottom-dwelling animals. This erased the well-entrenched notion of a lifeless deep.

Darwin’s just published theory of evolution, meanwhile, held that evolution proceeded rapidly in fast-changing environments and slowly amid stasis. If this was true, the presumably static deep might include unchanged species-“living fossils”-from the evolutionary past. This notion was encouraged when deep-sea dredging in the 18 60s (deep for the time, anyway: up to two thousand fathoms) found a few crinoids (primitive cousins of starfish) and other simple animals closely resembling known fossils. And Thomas Huxley (an able working biologist when not writing or debating) had found in some specimen bottles from these same early deep-sea expeditions a mysterious, protoplasmic goo-a “primordial ooze” or “living slime”-that he proposed might be both the base of the ocean food chain and the bottom rung of the evolutionary ladder. He called it Bathybius haecklii after his Darwinist compatriot Ernst Haeckel. Discovering more about Bathybius and other deep-sea forms was a major goal of the Challenger as it set sail in December 1872.

Setting off with 144 miles of sounding rope, a large onboard lab, and nine scientists, the 238-foot Challenger sailed amid great expectations. Scientists and the popular press alike followed its reports closely. Led by renowned zoologist Wyville Thomson and his sec- ond, John Murray, the expedition did not disappoint. Even while under way, the Challenger answered crucial questions about the life and topography (or bathymetry, as it is known) of the ocean bottom. It found and named the Mid-Atlantic Ridge running the full length of that ocean, confirmed the Pacific’s astonishing depths and charted some of its contours, and verified that even the deepest parts reach able-over five miles down-held life. To Huxley’s disappointment, however, the voyage showed that this life did not include Bathybius. One day, when one of the Challenger scientists poured a large quantity of alcohol into a bottle containing deep-sea ooze and the mixture almost instantly produced something remarkably like the mysterious Bathybius, they realized that Huxley’s ancient slime was simply a new goo produced by the reaction between alcohol and the quite ordinary ooze made up of planktonic skeletons. The stuff in Huxley’s tubes had apparently been formed more slowly by traces of alcohol left after washing. Thomson immediately wrote Huxley, breaking the news with remarkable tact, and Huxley promptly sent the letter to be published in Nature along with a graceful and funny letter confessing his error.

Yet if it lacked Bathybius, the Challenger returned to Britain in July 1876 with plenty: Having traveled 68,930 miles (averaging just over a walking pace), the boat brought home more than 13,000 kinds of animals and plants, including more than 4,000 new species; 1,441 water samples; and hundreds of seafloor deposits. All of these needed to be tagged, packed, and distributed to the specialists for description and examination.

Thus the call to Alexander Agassiz. Thomson, who shared Alex’s fascination with echinoderms, had met Alex in 1869, when Alex traveled to Great Britain, and again in 1873, when Agassiz had visited the Challenger in Halifax, after the ship had completed a loop in the first, Atlantic stage of its journey. Impressed at both meetings, and further impressed in the meantime by Revision of the Echini, Thomson knew that Alex had experience organizing and handling large collections and coordinating their examination and the publication of findings. He also knew that Alex, as de facto director of the Museum of Comparative Zoology, was owed favors from many specialists on both continents. He now asked Alex to come help sort and distribute the Challenger haul.

Alex happily obliged. Having followed the trip in the journals and through direct correspondence with Thomson and Murray, he recognized the Challenger voyage as a milestone in the study of the ocean.* To a discipline long on questions but short on hard data, the Challenger results gave a badly needed boost.

Thomson, the leader of several short but groundbreaking expeditions in the 1860s, had already been a prominent figure in ocean studies when he started the Challenger project in 1872, and Murray, five years Alex’s junior, had gained similar status by helping lead the Challenger expedition. Murray had actually been a last-minute addition to the voyage, taking the place of someone who had fallen sick. But he had come into his own on the trip and was now Thomson’s second on shore as well. The two decades of sorting, study, and reporting that lay ahead would make him known as a founder of oceanography.

Murray and Alex hit it off immediately. Murray had already met and worked with much of the crème of European science, unpacking boxes with everyone from Haeckel to Huxley, but he held a special regard for Alexander’s ability to find a no-nonsense way through the thicket of theories and ideologies that marked the times. When Alex had visited the Challenger in Nova Scotia the summer of 1873, many of the ship’s younger scientists, enthusiastic Darwinists, had expected him to share his father’s antievolutionism, and Murray had admired the matter-of-fact way in which Alexander made known his acceptance of a measured evolutionism without either fashioning himself a Darwinist or casting a bad light on his father. At a time when the polarized debate over evolution made it hard to find real independence of thought, Murray recognized the strength this required of Alex.

Now he saw this strength tested, even three years after the deaths of Louis and Anna.

“When he arrived in Edinburgh,” Murray later recalled, “I referred to the death of his wife, but he held up his hands and said, ‘I can not bear it.’ His expression was such that the subject was never again mentioned.”

* The full Challenger report, which took nineteen years to publish and occupied fifty volumes, proved not only astonishingly comprehensive but quite durable. For decades, new findings tended to supplement rather than revise its findings, and much of the data was still being used and cited even at the end of the twentieth century

Alex did not socialize much during his two months in Edinburgh. He declined all invitations even during the holidays, and he never traveled down to London to renew his many acquaintanceships there. He proved a tireless and ceaselessly curious workmate for Murray. The two worked almost every daylight hour, unpacking, sorting, and repacking thousands of specimens of starfish, urchins, and sea stars for Alex to take home and thousands of specimens of other taxa to ship to other specialists. As they worked, Murray told Alex of the weird mix of exhaustion, boredom, unexpected pleasure, and sudden agonies that, typical of the era’s expeditions, had made up the Challenger tour. On many days the shipboard routine stretched out interminably and noisily: The dredge often took hours to reach the bottom, and everyone would then wait even longer for the miles of rope to be drawn in as the steam engines thumped and the winch screamed. If the equipment survived (one trawl reached deck with its main beam snapped by the submarine pressure, the wood so com pressed the knots stood out a quarter inch), it might hold some new wonder or virtually nothing. The first samples from great depth contained only worms.

But the scientific crew brightened, at least at first, as they found more than four thousand new species. Of those, more than three thousand were radiolarians-microscopic, single-celled plankton that secrete exoskeletons of silica shaped like tiny vases, starbursts, or burrs from which they extend pseudopods to snag even tinier plank ton to eat. It was Murray who realized that the beautiful, glasslike skeletons of these animals, drifting down by the billions, compose much of the “ooze” that covers the deep-ocean floor. Occasionally the dredge fetched something that at least approached the antiquity the crew had hoped to find common. One day they sieved from the muck a dead-but recently dead-spirula, a small squid identical to fossilized forms. They also found shark’s teeth millions of years old encased in globules of manganese; astonishing variations in temperature even at great depths; bits of metal Thomson recognized as meteor fragments; a surprising biological diversity in the extreme deep and dark; and, on a more mundane level, that the Galápagos tortoises they had captured had eaten the crew’s pineapples. They shot the Straits of Magellan in a howling, ecstatic seventeen-knot run. They picked their way among pack ice and icebergs on the Antarctic Circle, walked long curves of lovely beach in Tahiti, and brought souvenirs and syphilis home from the scores of harbors they visited.

The trip strained patience and health. Of the 243 people who sailed (214 sailors, 20 officers, and a scientific crew of 9), 61 deserted and 10 died. The first was sailor William Stokes, killed by a block and tackle fired across deck by a snapped dredging cable; he was lowered the next day into four miles of water. Several more succumbed to various accidents, two more to drownings, two to suicide, one to food poisoning, and one, the voyage’s last fatality, to erysipelas, a purulent skin infection that kills rarely but painfully. Chief scientist Thomson returned exhausted. He would live only another five years.

Murray, however, had recovered both health and enthusiasm in the six months since the ship’s return. Alex, in his subdued way shared Murray’s excitement about the information and specimens the ship had collected. Alex had seen how vital fieldwork and collections were to terrestrial earth science; only work like the Challengers could provide the same crucial piles of information about the ocean and answer basic questions about how its life was distributed, how its currents flowed, and how its bottom formed and shaped. He felt certain that these questions of environment, geology, and zoology would often be linked. How could they not be? Such issues always entwined on land, where geology not only told the story of former life but set limitations for present forms. In the Andes, for instance, the rising terrain exposed yesterday’s fossils and, as in the high, almost sterile waters of Titicaca, dictated what might live today. The ocean could hardly be otherwise.

Alex took particular interest in Murray’s discovery that plank-tonic debris (the skeletons of radiolarians and other minuscule floaters) formed a thick blanket over much of the deep seabed. Thomson, half hoping to find Bathybius or something else fantastic, had initially resisted this pedestrian explanation of ooze. Alex admired Murray for his independence in proving the less glamorous answer, against the resistance of his boss and mentor, by painstaking microscopic examination (never fun, worse at sea) of ooze and near-surface plankton to find conclusive similarities.* This was Alex’s kind of science: Damn the theories and authorities; work closely and heed the specimen.

Now Murray told Alex of another implication of all that plank ton: Plankton floated in such numbers and fell so thickly he believed, that they not Darwin’s slowly sinking mountains, provided the platforms on which coral reefs grew. It seemed far-fetched that tiny animals could build these platforms. But Murray was not suggesting that dead plankton piled up thousands of fathoms thick to bring deep bottom near the surface. Rather, they accumulated atop existing mounds or ridges that already reached to within a few hundred fathoms of the surface and eventually raised them to coral-friendly heights. Only banks at these modest depths-up to five hundred or perhaps a thousand fathoms-gained significant height this way, for only at those depths did the rain of skeletal debris out pace the corrosion that the tiny skeletons faced on their descent. At depths beyond one thousand fathoms, the carbonic acid in seawater dissolved most of the tiny skeletons before they could reach bottom and hide from its solvent action; this Murray and Thomson had con cluded from the scarcity of surface-plankton debris at such depths. But at shallower depths, especially between one hundred and eight hundred fathoms or so, the minute skeletons of surface plankton fell faster than seawater could destroy them. Over millions of years, they piled high enough to give corals a foothold.

Two Challenger discoveries had convinced Murray of this. The first, revealed by the expedition’s hundreds of soundings, was the existence of scores of mounds and ridges that came to within one thousand fathoms of the surface. The second was the incredible density of plankton that Murray found in tropical waters. To gauge this density he towed, in four separate samplings, a twelve-inch-diameter sieve through a half mile of water at a depth of a few fathoms, then boiled the trapped plankton in a caustic solution. This left only the animals’ skeletons. He weighed these remains. Then, extrapolating from his half-mile-long, square-foot-wide tows, he figured the total mass of planktonic skeletal material that would occupy a volume of water a mile square and one hundred fathoms deep. It worked out to over sixteen tons.

As most plankton live only days or weeks, this ever-replicating sixteen tons would send a steady rain of skeletons to the bottom, slowing adding to any mounds within a thousand fathoms of the surface. Mollusks, brittle stars, starfish, anemones, and other mid-depth bottom dwellers would stabilize the mound as it grew. Some mounds might also be lifted by seismic forces, speeding their rise. When a mound or ridge reached within one hundred fathoms of the surface, corals would take over and bring the mound to just beneath the surface. Once at the surface, the bank would begin to expand sideways, especially to windward, because coral is nourished by cur rent-borne plankton. The surf would break off coral that would tumble seaward, creating an ever-thickening talus slope on which the reef could further expand. As the reef grew seaward on this thickening talus slope, the surface corals behind the leading edge-those left unwashed by incoming seas as the reef expanded outward- would die. These dead inner corals would eventually dissolve, creating behind the breakwater a lagoon, which, cut off from a new food supply, would deepen over the years from further solution. Thus the reef would form either an expanding ring-that is, an atoll-or, if the reef had formed around a volcanic island, a barrier reef that would expand ever outward. This combination of planktonic accumulation, solution of inner corals, and outward expansion atop the talus slope could account for the barrier reefs and atolls that Darwin had claimed as proof of subsidence.

Alex liked this idea immediately. He had long had trouble fitting Darwin’s theory either to his own limited coral reef experience or to the observations he had read about. Certainly Darwin’s model did not seem to explain the reefs Alex had seen with his father two decades before in Florida. Those reefs were thin veneers rising from broad, shallow slopes that stretched out all around. Louis had noted this at the time in his reports, though mutedly, for not only was this before his feud with Darwin, but Darwin himself had conceded in 1842 that most of the Caribbean reefs, which lay in broad banks in shallow water, were probably exceptions to his subsidence theory.

To Alex and Murray, however, it seemed that most of the reefs that other researchers had examined since that time also appeared to be exceptions, casting doubt on the rule. The main support for Dar win, meanwhile, seemed to come from the work of James Dwight Dana (the same Dana who had given Louis so much trouble in the 1860s), who in a Pacific expedition just after Darwin’s had found Darwin’s theory confirmed by his own extensive examination of the Fijis and briefer looks at many other Pacific archipelagoes. Dana admitted he was convinced more by the reef forms than by any direct evidence of subsidence, but then again, subsidence tended to bury its direct evidence. Alex knew Dana to be a good geologist-the most renowned in the United States, in fact. But he felt that Dana’s confirmation of Darwin’s theory, based mostly on indirect evidence hurriedly observed, hardly proved that Darwin’s theory explained most of the world’s reefs.

To the extent that Alex had thought about it, then (and up to now he had not thought about it very much), coral reef research since the 1840s suggested that Darwin had oversimplified and overreached. A more flexible theory-or perhaps a package of explanations-was needed to account for the world’s reefs and atolls. Alexander knew that other scientists more familiar with the problem, including leading researchers in America, Britain, and the Continent, felt the same unease with Darwin’s model. Yet, unable to suggest an alternative (and cognizant of Darwin’s ever-growing reputation), no one had seriously challenged it. Though it had been weakened, Darwin’s theory remained the most accepted and comprehensive explanation.

Murray, however, now appeared to offer one far superior. Like Darwin’s theory, his explained how every variety of reef could be formed, but without requiring the seemingly unproveable subsidence that Darwin called on. All Murray’s key processes were easily observed. And his theory rose not from speculation deduced from broad concepts about huge movements but from measured, repeated observations. It was, in other words, more scientific.

The two young oceanographers, quite conscious, as they un packed the Challengers goods, of being part of a new, more rigorous oceanographic discipline, discussed Murray’s idea at length. The more they talked, the more Alex liked it. By the time he left to return to Cambridge, in February 1877, he had not only tentatively adopted this new hypothesis; he had decided to take up the job of testing and verifying it.

“I never really accepted the theories of Darwin,” he wrote Murray on returning home. “It was all too mighty simple.”

*Murray’s interest in seafloor muck also led to his discovery that in some areas the ooze was mostly volcanic debris and-a new find-metallic clumps shed from meteors.