Life Everlasting

by Bernd Heinrich

  Beyond these two ecosystems is a unique third one, which depends on dead whales. Like the salmon traveling hundreds of miles upriver to die, those whales come from a different ecosystem, namely, the top layer of the ocean, which is driven by photosynthesis.

  At depths below 2,000 meters there is almost no free oxygen, and temperatures range from 30 to 36 degrees F. In these conditions bacterial decay as we know it is either nonexistent or very slow. This point was proved in an unplanned experiment by the submersible vessel Alvin, built in 1964 and operated by the Woods Hole Oceanographic Institute, which takes two scientists at a time to great depths. In October 1968, while Alvin was being transported by a ship, a steel cable snapped, and the submersible sank 1,500 meters (5,000 feet). When Alvin was recovered ten months later, a cheese sandwich that had been left inside had not changed visibly, and someone was able to eat it. In those conditions, how would a 160-ton blue whale carcass be disposed of?

  After being recovered, the Alvin was rebuilt, and since 1977 it has made hundreds of dives to advance our knowledge, especially of the deep hydrothermal vents at the midocean ridges. In November 1987 Craig Smith, a University of Hawaii oceanographer, was on a routine mission of the Alvin, using scanning sonar to explore the muddy bottom of the Pacific Santa Catalina Basin at a depth of 1,240 meters (4,070 feet), when he thought he saw a fossilized dinosaur. Instead it turned out to be the 21-meter-long skeleton of a blue whale. The crew was astonished to see it surrounded by mats of bacteria and clams. This sighting marked the beginning of the study of “whale falls,” as they are now called. Since that first discovery, other whale falls have been found, and some have been deliberately created so that scientists can examine the progression of scavengers. The ongoing observations and studies show many specialist undertakers on whale carcasses, including previously unknown animal species.

  We now know that, despite the low temperatures, the whale’s flesh is fairly rapidly consumed by a succession of mobile scavengers after the carcass first settles on the sea floor. Numerous large, slow-moving sleeper sharks, which can live at great depths, move in, followed by swarms of eel-like hagfish, which burrow into the meat and absorb some of its nutrients directly through their skin. Rattail fish, stone crabs, and millions of amphipods (tiny crustaceans with laterally compressed bodies) also join the feast. This stage of feeding may be completed in months or a year, or up to two years with a very large whale. The bones take the longest to be recycled because their great bulk makes them resistant to access. Herman Melville, in Moby Dick, vividly describes the massive forty-odd vertebrae in a ninety-ton sperm whale as a “Gothic spire”; the largest vertebra “in width measured something less than three feet, and a depth of more than four.”

  After the soft tissues are consumed, a mat of bacteria colonizes the bones, and limpets and snails graze on them. The carcass becomes surrounded also by a dense mat of polychete worms, each around five centimeters long and superficially similar to centipedes. The worms cover the whole carcass in densities of up to 40,000 individuals per square meter. They take everything they can, and after they leave, an abundance of other species moves in. These thrive mainly on the nutrients remaining in the fat within the bones. Bacteria break down this fat in the absence of oxygen and produce sulfur dioxide as a byproduct; this, in turn, uses chemotrophic synthesis (as in the thermal vents) to produce organic molecules, much the way plants fix carbon dioxide through photosynthesis. As in a sunshine-driven ecosystem, animals in the whale-fall community live off the chemotrophic producers, some of which live inside the bodies of others, just as chloroplasts (from ancient algal symbionts) live in plants. Certain clams and tube worms don’t need a gut because the chemotrophic bacteria they contain produce organic molecules directly within their bodies. Small Osedax “zombie worms” (Osedax is Latin for “bone devourer”), also with no digestive tract, tunnel into the bones to allow symbiotic bacteria to feed on fats, which the worms absorb into their bodies.

  More than four hundred species of macrofauna (this category excludes bacteria) have been identified in whale falls, with at least a hundred at any one carcass. Tens of thousands of individual animals of many kinds may be at work decomposing a single skeleton at any one time. This stage can last ten years, and some think it may be close to a hundred years before the whale’s decomposition is complete.

  A whale fall is like a species-rich island. It is colonized by yet unknown means, in that the colonizers appear as if out of nowhere. Whale falls are habitats that contain specialists; they are hot spots of species diversity as well as sites of evolutionary novelty. The massive reduction in whale populations from excessive hunting in the nineteenth and twentieth centuries has surely spread these temporary “islands” of life far apart. We may wonder how far apart they can be before they are beyond the reach of colonizers, which would then die out.

  THE FATE OF the gargantuan whale carcasses, with their specialized undertakers, contrasts sharply with that of the skeletal remains of minute marine plankton bodies, which also drift to the bottom. Like most organisms, whales are usually recycled down to the level of molecules, so they make their way back into new biological life. But in the case of some marine plankton, what endures after death is an astonishingly important geological building block, shaping the contours and geology and soil of continents, and hence what can grow on them, and also determining the earth’s atmosphere and hence its temperature and the life it can support. In sheer volume, the aggregate mass of these marine plankton at any one time far exceeds that of all the whales. The most important present-day plankton already existed in the same form hundreds of millions of years before the first whalelike creatures plied the seas. The immortal remains of these plankton are chalk and the stone derived from it.

  The story of chalk was originally and most famously enunciated in 1868 by Thomas Henry Huxley, the British naturalist probably best known as “Darwin’s bulldog” because he vigorously defended Charles Darwin’s thesis of natural selection. In a lecture titled “On a Piece of Chalk,” delivered to “the working men of Norwich,” Huxley noted that heating chalk causes the evaporation of carbonic acid and yields lime. So chalk is a carbonate of lime, the same substance as stalactites and stalagmites. Huxley examined thin slices of chalk under the microscope and found out that it was much more than a white chemical substance. Revealed were “hundreds of thousands of . . . bodies, compacted together.”

  These bodies, about one hundredth of an inch in diameter, have various forms; one of the most common looks something like “a badly grown raspberry” and consists of a number of nearly globular chambers of different sizes congregated together. Some chalk is made up of little besides these microfossils, a highly compacted mass of calcareous skeletons of one-celled, exclusively marine protozoa called Globigerina, one of the most dominant genera of chalk. There are about four hundred species of them in chalk that is 100 million years old or more, and thirty of these species are still living in our oceans.

  In 1853, when a transatlantic telephone cable was being laid, the first samples of the ocean floor were retrieved, from a depth of around 10,000 feet. Mud dredged up from the bottom, when examined under the microscope, was found to consist almost entirely of the skeletons of a still-existing Globigerina species, along with the calcium carbonate skeletons of round, single-celled phytoplankton algae called Coccosphaerales, more commonly known as coccoliths. In short, the Atlantic mud, which stretches over a huge plain of thousands of square miles, is raw chalk.

  Thomas Huxley is credited as being the first to see the single-celled plankton skeletons in his examination of ocean-bottom mud. One very important species, Emiliania huxleyi (Ehux for short), is named after him, and this species is by far the dominant coccolith in the oceans. It creates blooms covering tens to hundreds of thousands of square kilometers of ocean, giving the water a bright turquoise color that is visible from space. In the Upper Cretaceous, when hot magma from the spreading continental plates created large volcanic eruptions and greenhouse
gases, global temperatures rose and melted the ice caps, and ocean levels rose to flood the continents some 600 meters higher than present levels. Ehux may have helped to reduce global warming at that time. The role of Ehux in contemporary global warming is currently being debated, since these algal blooms reflect light and heat and also remove carbon dioxide from the atmosphere to create the calcium carbonate plates that settle on the ocean bottom. Ehux has removed inestimable amounts of carbon dioxide from the atmosphere and locked it into chalk and limestone.

  Chalk is found underground the world over; it underlies England, France, Germany, Russia, Egypt, and Syria, over an area about 3,000 miles in diameter. The chalk layers in some places are more than a thousand feet thick. Underground deposits of chalk are generally exposed at geological faults, but it is prominently exposed only on cliffs, perhaps most famously on the Cliffs of Dover, facing the English Channel.

  In addition to its primary component, microfossils of sea plankton, chalk contains exquisitely preserved sea urchins, starfish, nautilids, and other mollusks, as well as plesiosaurs—in all, some thousand or more distinct species that plied the oceans in the Cretaceous. Sometimes the chalk contains streaks of black flint, which also comes from recycled animal remains, though its formation is not fully understood. The implication of Huxley’s microscopic examination of a piece of chalk was tremendous: he was proposing that the vast areas of chalk-covered land had at some ancient time been at the bottom of an ocean. Huxley noted that about 5 percent of the Atlantic mud consisted of skeletons of silica rather than calcium carbonate. The silica is derived from diatoms—algae with a silica shell—and from the skeletons of sponges. From this one can deduce that the diatoms had to come from surface waters, where they could get light. In addition to making up what we call “diatomaceous earth,” these organisms are thought to be a component of petroleum.

  The origin of limestone is similar to that of chalk. It is a sedimentary rock consisting largely of calcium carbonate derived from the skeletal fragments of single-celled marine plankton, often mixed with the remains of clamshells, crinoids, and corals, which have created oceanic islands. The free-swimming larvae of corals attach themselves to a solid substrate and then build a calcium carbonate base that serves as a skeleton. When the coral animals die, this skeleton remains, and other individuals then attach themselves to it, building on the others and eventually forming a limestone reef. Limestone, and its metamorphosed form, marble, have been important building materials since antiquity. The pyramids are man-made mountains of limestone. The Romans were the first to make cement, by roasting limestone to about 440 degrees F to liberate a molecule of carbon dioxide from the calcium carbonate, leaving a powder that, when mixed with water, makes a binder for concrete.

  The Roman Colosseum was built in part by sacking the city of Jerusalem, using the labor of an estimated 100,000 Jewish prisoners. But the construction would not have been possible without the then-recent invention of concrete. It was concrete mortar that set the travertine limestone, quarried twenty miles from Rome, and the marble for the seats and outer walls. Concrete was used to build the aqueducts bringing water for crops, life, and power to Rome. The material from which the Romans built their civilization almost 2,000 years ago we still use in public and private constructions of all sorts. I used concrete to bind the foundation rocks of my cabin in the Maine woods. We literally live on the remains of ocean life of past geological ages.

  OUR HUMAN BODIES, too, are built from the lives of much earlier life. Our DNA not only holds the legacy of our own line reaching back to the dawn of life, it also incorporates the life of other lines of descent. The mitochondria in our cells—the powerhouses that allow us to burn carbon compounds and release the energy of the carbon-carbon bonds that we borrow ultimately from plants—are derived from ancient bacteria that set up life in our cells and that learned to live within their means by not multiplying, not using up more resources around them than their environment at the moment offered.

  The ancient worlds live on even now. Many corals contain algal symbionts that give them their bright colors. The algae find a home in the coral and in return provide organic chemicals as food for them. Warm water temperatures may kill the algae, resulting in bleaching and eventual death by starvation. It was Charles Darwin who first hypothesized that coral reefs (and the islands that form from them) are created by the constant deposition of carbonate skeletons that do not disintegrate. Such reefs are one of the richest and most diverse—and most threatened—ecosystems on earth today.

  The unrecycled remains of the sea world may have had the greatest geological and atmospheric effects, but on land the remains of the ancient world—mainly the unrecycled or incompletely recycled plant bodies that form peat, coal, and oil deposits—live on as well. In cold and oxygen-deprived conditions, plant remains are not recycled; they turn first into peat and then to lignite (which is less than 10,000 years old and still contains fibrous material), then bituminous or soft brown coal. With further aging, it becomes anthracite or “hard coal.” (The origin of crude oil is still in question. One theory is that oil is not the result of incomplete decomposition of ancient plant life, mostly algae and zooplankton; the other, leading, theory is that it is.)

  Coal came from the vast wetlands when the first amphibians crawled onto land and giant dragonflies flew through tropical forests of tree ferns and club mosses. Massive accumulations of mainly this plant life alternately sank and were flooded and then covered with sediments. Under high pressures and temperatures, these plant remains gradually turned to rock in a process that is still ongoing.

  The vast amounts of coal that sparked and fueled the Industrial Revolution, made our massive population explosion possible, and that is still mined and burned now, was produced in the Devonian and Carboniferous periods, 360 to 290 million years ago. But much more ancient plant communities would by then already have remains left in anthracite. As this coal got folded deep into the earth by the colliding continental plates, to depths of 140 to 190 kilometers, it was subjected to a combination of intense pressures and temperatures that turned the coal into diamonds, the hardest naturally occurring substance.

  Diamonds are to us a symbol of permanence and purity. Given their origin from life, they are also, it seems to me, an apt symbol of life’s permanence, as well as its renewal through love. A diamond is a fossilized piece of life everlasting, forged in the context of the evolutionary history of the life of the planet. But if a diamond proclaims the preciousness of life, it is of all life through the ages, and not the bumper sticker version of potential lives of only one species now.

  V

  CHANGES

  Culture is like the chalk and limestone made from the organisms of past ages under our feet. It’s the residue of our knowledge, foibles, and aspirations that have accumulated over the ages. It’s the nonmaterial life that we absorb into our brains through our eyes and ears, the way plants absorb nutrients through their roots and the stomates of their leaves and turn them into sugar and DNA. And, like limestone, this nonmaterial that we inherit and absorb has huge material implications for our own lives and for future lives. There is no clear boundary between physical and nonphysical recycling.

  The mechanisms of cycling vary, but they all differ from the instant transitions of appearance only. A Nicrophorus burying beetle changes “instantly” into what looks and sounds like a bumblebee, and some caterpillars make themselves look like a snake or a twig merely by changing their posture. Such fake transitions mask the fact that they haven’t really changed at all. Real cyclings take a long time to accomplish and involve one body and mind metamorphosing into another with different physiology, behavior, and ecology. Physical transitions are routine in insects and amphibians, and to a lesser extent they also occur in other vertebrate animals.

  Before there was a science of biology, observations of natural transitions, such as that of a tadpole to a frog, undoubtedly led people to suppose that some equal magic might turn a princess in
to a toad or vice versa. And why not? The transitions in our own development from prepubescence to adulthood are based on processes roughly similar to those that cause a tadpole to metamorphose into a frog. Indeed, as developmental biology now teaches us, a human embryo is like a fish in the aquatic womb, where it makes the transition to what looks like a baby mouse before being born a human being. However, and this is an important point for us, we continue to metamorphose. We are cycled not only in the physical realm but also in mental and spiritual realms. And even more important, we are the only animal who has some control of our own metamorphosis, and of others’, by our decisions.

  Metamorphosis into a New Life and Lives

  We make a living by what we get, but we make a life by what we give.

  —Winston Churchill

  AS OUR FAMILY STEAMED TOWARD THE NEW YORK SKYLINE one morning in the spring of 1951 on our way to becoming Americans, my father was preparing me to see both the Statue of Liberty and Kolibris (hummingbirds). I was especially looking forward to the latter, and my joy on seeing the first one—a male ruby-throat—a few days later in Maine was tremendous. It took a while before I had one in my hand, though; although I was skilled with a slingshot, this bird was a challenge. But nothing prepared me for a catch I made a month or two later.

  There are 339 recognized species of hummingbirds in the Americas. Many are major plant pollinators. They cause the miracle of transforming flowers from sheer beauty to seed-producing organs. I had no idea where in America hummingbirds lived, how many and what kind there might be, or what they might look like. But I had heard about a particularly marvelous hummingbird—the tiniest one, the bumblebee hummer—and when I saw what I thought it should look like—tiny like a bumblebee but hovering rather than perching at flowers in our yard in Maine, its tiny wings whirring, its short tail flared as it darted from flower to flower—I wanted it. Badly. It was tame, so I ran into the house and got my father’s insect-catching net, ran back, and in one swoop had it in the net. In this moment of triumph, watching it flutter behind the gauze, my excitement turned to surprise; I saw its pair of antennae—and knew then that it was a moth.