The Extreme Life of the Sea

Stephen R. Palumbi, Anthony R. Palumbi

• Publisher: Princeton University Press
• Year: 2014
• ISBN:
  9781400849932
• Topic: Biological Sciences
• Subtopic: Marine Biology
• Index: Biological Sciences

A thrilling tour of the sea's most extreme species, written by one of the world's leading marine scientists The ocean teems with life that thrives under difficult situations in unusual environments. The Extreme Life of the Sea takes readers to the absolute limits of the ocean world—the fastest and deepest, the hottest and oldest creatures of the oceans. It dives into the icy Arctic and boiling hydrothermal vents—and exposes the eternal darkness of the deepest undersea trenches—to show how marine life thrives against the odds. This thrilling book brings to life the sea's most extreme species, and tells their stories as characters in the drama of the oceans. Coauthored by Stephen Palumbi, one of today's leading marine scientists, The Extreme Life of the Sea tells the unforgettable tales of some of the most marvelous life forms on Earth, and the challenges they overcome to survive. Modern science and a fluid narrative style give every reader a deep look at the lives of these species. The Extreme Life of the Sea shows you the world's oldest living species. It describes how flying fish strain to escape their predators, how predatory deep-sea fish use red searchlights only they can see to find and attack food, and how, at the end of her life, a mother octopus dedicates herself to raising her batch of young. This wide-ranging and highly accessible book also shows how ocean adaptations can inspire innovative commercial products—such as fan blades modeled on the flippers of humpback whales—and how future extremes created by human changes to the oceans might push some of these amazing species over the edge. An enhanced edition is also available and includes eleven videos.

CHAPTER 1 THE EARLIEST

The history of life is full of fast starts and odd experiments.

A poisonous beginning

This planet did not start out as a cradle of life—in its earliest years, it was a hellscape. We wouldn’t recognize our world; a time-traveling visitor would need a space suit to survive for even a second. The atmosphere was a thin gruel of carbon dioxide (CO2) and nitrogen, entirely devoid of oxygen. The ground was streaked with lava, the sky sundered by volcanic lightning. Noxious chemicals bubbled to the surface and into the atmosphere: ammonia, sulfates, formaldehyde.1 The oceans grew, condensing out of the planet’s crust or falling from the sky as rain, but also being delivered piecemeal by incoming asteroids that bore frozen water.2 And complex chemicals were suspended dilutely in that ice from deep space, seeding the young planet with the molecular materials of life.3 It was in that alien, chemical stew that the very first elements of life appeared: nucleic acids and proteins. Just a few hundred million years after the crust cooled from magma, life had a lease on Earth.

That life would thrive, but not without crises, and not without experiments and failures and eventual successes. And in those early eons, the oceans swaddled the life of Earth, nurturing it and testing it and setting the conditions for life to persist. Eventually, the living tenants of the oceans grew abundant enough to change its chemistry, altering the very atmosphere of Earth, and building in the sea a complex web of species that exploded in diversity. Life took these skills onto land and transformed that realm as well. But while the cousins of mudskippers colonized the shores and eventually led to human beings, life continued to evolve into nearly every corner of the sea, finding food sources, then becoming food sources, and evolving the abilities to thrive in every kind of environment.

The very first

“Omne vivum ex viva,” Louis Pasteur once glibly proclaimed: life springs always from life.4 Intuitively it seems that the first life would be an exception, but it all depends on your definition of life. The very first self-replicating organic forms weren’t organisms per se; they were simply large molecules— molecular machines—and they probably began in the sea.5

The process was rapid. The first evidence of life—a signature shift in the isotopes of carbon found in rocks—appears 3.85 billion years ago in the Isua Supracrustal Belt of western Greenland,6 just 550 million years after the planet’s crust finally cooled from magma. Not only did life accrete quickly; it was also sufficiently robust to endure some serious punishment.

The early solar system was a new construction site, littered with asteroids left over from planet building. Careful cataloging of the Moon’s craters paints a picture of the rain of asteroids and comets onto our young planet. In those early eons, a series of cataclysmic asteroid strikes had enough power to vaporize the young planet’s oceans and sterilize its surface.7 New early-Earth models suggest that life might have survived these catastrophes, but only if it were already widespread when they occurred. A microbial community that spanned the globe could perhaps hide in deep ocean crevices, buffered from the devastation of planet-killing asteroid strikes and feeding off chemicals bleeding from the molten mantle. Once cellular life had sunk tendrils into ocean habitats as diverse as shallow pools and the deep sea, and once the early solar system was cleared of some of its original debris, life on Earth gained a permanent foothold.

The Great Oxygenation Event

Although life on Earth emerged fairly quickly, it took a long time to evolve past the basics. Recognizable living cells were present on Earth and common enough to form microscopic fossils 3.4 billion years ago.8 Rocks 3.4 billion years old in South Africa have a series of laminations and filaments suggestive of microbial mats formed in a shallow sea.9 Yet the world was still devoid of anything but microbes; for two billion years the only living things on our planet were single celled. Their sputtering metabolisms weren’t powerful enough to sustain anything grander. Life needed a new kind of metabolic engine to compete at the next level, and it was only invented in response to the planet’s first toxic waste crisis. That nasty poison was oxygen, loosed into the atmosphere by the worst of all primordial polluters: photosynthesizing microbes.10

The curves show the upper and lower estimates of oxygen in the atmosphere billions of years ago. Our modern atmosphere has an oxygen concentration (PO2) of 0.21 atmosphere (atm). Redrawn from Holland, H. D. 2006. “The oxygenation of the atmosphere and oceans.” Philosophical Transactions of the Royal Society B 361:903–915.

Photosynthesis uses sunlight to form sugars from CO2. The first forms of photosynthesis arose as early as 3.8 billion years ago and were thought to have been profoundly different from those common today. Most importantly, they did not yet produce oxygen.11 Oxygen is a home wrecker. The oxygen atom itself binds easily to other atoms, disrupting their chemical bonds. Oxygen atoms insinuate themselves slyly into nearly everything they encounter, breaking bonds faster than after a celebrity marriage. The word “oxygen” is itself derived from oxys: Greek for “acid.” And because of its disruptive chemical properties, oxygen destroys delicate RNA and DNA molecules, and even disrupts the more stable proteins of cellular life.

Single-celled microbes called cyanobacteria first started eating sunlight and producing oxygen more than two and a half billion years ago,12 dumping foul oxys into an early-Earth atmosphere that was likely nitrogen heavy.13 Various chemicals in the atmosphere and the soil absorbed that oxygen, “reducing” it and thereby protecting life’s fragile foothold. The balance held for a while, but as the cyanobacteria multiplied and oxygen production soared, something had to give. About a billion years ago, oxygen started to accumulate like junk in the garage.14

The Great Oxygenation Event was a catastrophe for life on early Earth. Only a few organisms were prepared to make use of the now-ubiquitous poison. But, as Jurassic Park’s Ian Malcolm declared, life finds a way. It found a way to feed on oxygen, using the crackling chemical energy of its bonds to power a new and mighty metabolic engine. If we think of metabolism without oxygen as a puttering outboard motor, then metabolism burning oxygen is a roaring Ferrari sports car.

Most of what we consider as “advanced” cell features, embodied in a line of cells called the eukaryotes, followed in the wake of this transition to an oxygen metabolism. These features importantly include subcellular organelles called mitochondria, which capture oxygen and burn it chemically to release its energy for the cells’ benefit. Mitochondria were once free-living bacteria with oxygen metabolisms:15 they were co-opted by the cells of our earliest ancestors, and they gifted these cells with the ability to burn oxygen too. Our existence as a species—indeed, the entire organization of life on Earth as we know it—is the unintended consequence of the use of oxygen after this toxic waste dumping.16

Archaea

Long before the Great Oxygenation Event, the family tree of life on Earth had its trunk split in two. Of course, both bifurcations consisted of microbes— there was nothing else alive at the time. The first branch was composed of the cyanobacteria and other “normal” bacterial microbes. The second branch emerged around the same time, made up of microbes evolving to endure in stressful environments17 or living on a chemical diet without sunlight. They are Archaea—the extremophiles—the toughest creatures ever to live.18

They’re nothing much to look at: tiny oblong masses beneath an electron microscope. For a long time, we thought they were just bacteria. With the advent of gene sequencing, biologists noticed a huge genetic gulf between these extremophiles—found in salt lakes and deep-sea sulfur vents—compared to typical bacteria. In response, taxonomists created a name for this entirely new domain of life: Archaea.19 More and more of these creatures have been discovered at the margins of the world, living in places where little else could survive: the hot springs of Yellowstone National Park,20 the hydrothermal vents on the floor of the ocean, the oxygen-poor deep sea. As creatures of early Earth, Archaea tend to get crowded out by latter-day microbes. So they remain in extreme environments, in the closest analogues to the planet they lost.

Archaea can grow at temperatures exceeding 230° F (110° C), well above the boiling point of water. The Archaean Pyrolobus fumarii coats hydrothermal vents, 6,000–8,000 feet below the ocean surface, where sulfur and other toxic chemicals spew from Earth’s crust at temperatures of hundreds of degrees. These creatures hold the world record for growth at a high boil. They can survive an hour at autoclave temperatures of 250° F (121° C) and find temperatures of 203° F (95° C) too cold to reproduce well.21 No multicellular animal or plant can grow at such temperatures (see Chapter 8), and so the hottest places on our planet are solely tenanted by microbes. But microbes used to rule not just in high heat, but everywhere.

The Cambrian Explosion

For a long moment in evolutionary history, across our entire planet, tiny microbes qualified as the most complex organisms on the planet. Eventually, some were able to form larger structures: thin layers of bacterial cells and secreted limestone piling one atop the other into mounds called stromatolites that persist three billion years later. These were still microbial constructions; no organism bigger than a single cell existed on Earth for eons.

Precisely when or how the jump was made from microbes to animals is not recorded. Fossil records are notoriously patchy, like the picture on an old television set. Static swells the further back you go. Large jelly-like organisms of many species all lumped together under the generalized name Ediacara appear in 575- to 542-million-year-old mud deposits.22 Other early cell clusters look like embryos of large creatures, though they might just be groups of single-celled protists.23 Tiny swimming discs like the bells of jellyfish wafted through the sea. On the floor were soft organisms that looked like disks, bags, toroids, or quilts.24 Whether these lines diversified into the life on modern Earth is ultimately unknown. They could be failures—snipped-off stubs on the evolutionary tree—or they could be the ancestors of all current animal life.

Our understanding of these early experiments in multicellular life completely changed in 1909 when paleontologist Charles Walcott walked into a quarry in British Columbia, Canada. He stood agog: before him spread an ancient deposit of ossified mud, more than 500 million years old and about the size of a city block. Dubbed the Burgess Shale, it remains to this day the planet’s best-preserved record of ancient marine organisms. This hunk of old ocean floor might be the most important discovery in modern pale-ontology.25 It documented, for the very first time, a worldwide biological revolution.

This enigmatic Ediacaran fossil represents one of the first multicellular species. But whether it is an animal, a fungus, a lichen, or something entirely unlike life today remains a mystery. Photograph by Meghunter99.

Cataloging a fossil dig like the Burgess takes a long time and an enormous amount of work. As Walcott, his family, and an army of paleontologists mined away and meticulously recorded their findings, based on more than 65,000 specimens, amazement with the newly discovered species grew. The creatures of the Burgess Shale were hard to fit into the normal taxonomy of living invertebrates. Their bodies were like unique jalopies assembled from random spare parts. Odd feeding trunks, long spiny legs, bony lobed fins, the wrong number of compound eyes—all these and more were trapped in the mud, slapped haphazardly onto animals that looked more like sci-fi cartoons than actual living creatures.

Wiwaxia was a small, scaled slug-like creature studded with petal-like flaps. Marrella resembled a brine shrimp wearing a motorcycle helmet, trailing long graceful tentacles from its mouths past its tail. Odaraia looked a bit like a fish in a hot dog bun, its torpedo-shaped body bulwarked on either side with large translucent carapace shells. Two compound eyes made of many facets, tiny feeding appendages near the mouth, and a bizarre three-finned tail rounded out Odaraia’s alien appearance.

The m...