April 2, 2014

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Too often, we see the open ocean like the space between stars.

We imagine a void, vast and hollow, characterized by emptiness and populated by ghosts. Water becomes a medium, a barrier, something crossed en route to something of substance. To the sea we consign the ashes of our dead, symbolically releasing them from this world as though the watery realm weren’t part of it.

It is, of course, very much part of our world, and it is far from empty. In fact, the open ocean comprises planet Earth’s most powerful bio-engine. Though its inhabitants can barely be seen and have only recently come to science’s attention, they form an integral part of the marine biosphere. They undergird the valuable resources human beings extract from the ocean—resources we’ve come to depend on.

Naturalists as far back as Charles Darwin could look through microscopes to see amoebae and protozoa swimming in water samples. The smallest fish, Darwin rightly assumed, persisted on these creatures.  “But on what,” he wondered, writing in 1845, “in the clear blue water, do these [microbes] subsist?”

80 years ago, another naturalist famed in his day, William Beebe, led the very first deep-water diving expeditions in a primitive bathysphere off the Bermuda coast in the 1930s. Breathing air leeched of its carbon dioxide by a simple vial of soda lime, Dr. Beebe peered through a single solid plate of quartz at a world never before glimpsed by human eyes.  “Only dead mean have sunk below this,” he scrawled in his journal, sensing the weight of untold liquid tons above him. But what he saw turned his fear to wonder. He saw lights, blue and green, winking and twinkling and seeming to chatter at one another in the sunless sea. Though Beebe had no way of making this connection, his mysterious lights and Darwin’s mysterious “empty seas” both led to the same culprit: bacteria. The powerful microscopes necessary to identify them simply didn’t yet exist. Nor did the technology to dive deeper and more reliably.

Photo: Shutterstock
Photo: Shutterstock

Much the way Dr. Sylvia Earle continued Dr. Beebe’s deep-sea pioneering, a young MIT researcher named Dr. Sallie “Penny” Chisholm kept chasing Darwin’s question. Electron microscopy led in time to her discovery of a wondrous little microbe: Prochlorococcus, quite possibly the smallest and simplest organism to have unlocked the complex process of photosynthesis. Darwin’s amoebae and protozoans were, as it turns out, giant ultra-predators of the microbial world.

A quarter of seawater contains roughly a billion bacteria—the human population of India represented in perhaps one tenth of a milligram. But those tiny bacteria have outsized metabolisms, particularly if they’re photosynthetic and thus can access the Sun’s limitless energy. Combine the world’s smallest producer with its biggest energy source, and you’re left with an incredibly potent recipe: a Prochlorococcus colony the mass of 100 human beings could, under ideal conditions, produce as much energy as a nuclear power plant. Now consider, there are an estimated trillion-trillion Prochlorococcus currently living on planet Earth—a number beyond reckoning. If every one of Earth’s 7 billion people sprinkled the 10 trillion cells in each of their bodies over the ocean, we’d be just one-fifteenth of the way to Prochlorococcus’ numbers. They might be the most populous creatures on Earth, with a corresponding ecological impact. Penny Chisholm estimates 10% of our planet’s atmospheric oxygen derives from this one genus alone, and Prochlorococcus are hardly the only photosynthetic microbes in the sea. Nor are all the smallest microbes Sun-eating!

Prochlorococcus
Prochlorococcus

Photosynthesis is just one term in the bacterial equation. Just about all the “dirty” ecological work on our planet is done by microbes, breaking down dead tissue and waste matter into progressively smaller pieces until at long last it’s just tiny nutrient particles known generally as dissolved organic carbon (DOC). Cast-off biomatter falls down the food chain until it becomes DOC, at which point the very smallest bacteria can ingest it. Those bottom-feeders are eaten by larger microbes, and once again biomatter rockets upward through the food chain. This so-called “microbial loop” is the invisible underpinning to ocean ecosystems Darwin knew must exist but couldn’t name. Every tuna swimming through that “clear blue water” is supported by trillions of microbes living their own fierce, complex lives.

To understand the ocean’s true ecological structure is to appreciate that we inhabit a microbial world. Pick any square meter of open ocean surface, extending in a column to the floor, and the productivity of fish and other large organisms within that column will pale in comparison to the bacteria inhabiting it. Every year, the entire human race harvests 100 million tons of seafood. The ocean’s bacterial population produces that volume in about 90 minutes. We can’t see it; most of that mass is constantly cycled through the system’s lowest reaches. There are so many more of them, after all.  We inhabit a microbial world.

That one humbling fact places so many of our society’s environmental discussions in sharp relief. It threatens to awe, to overwhelm like the Milky Way over a darkened campsite—why do we even matter?—but like that starry tableau, it should inspire us to ask ourselves harder questions. If natural resources we take are so swiftly replenished, how have we managed to badly overfish so many regions? If environments like California’s Monterey Bay can bounce back from utter devastation to thriving kelp forests, why doesn’t that happen everywhere?

These are questions of policy. Over the past few decades, as marine science has learned exponentially more about the enormous systems powering our planet, we’ve learned valuable lessons about what’s valuable and what isn’t; what works and what doesn’t. The best solutions are those that see the ocean not as a resource to be exploited or an empty space to be crossed, but a living organism. We don’t just live beside that creature, we live within it. We need it, far more than it will ever need us. We can’t kill it; we can only change how it functions, what it accommodates. For all the damage already done, the ocean is more than strong enough to heal itself. Properly managed, it will gladly give all our growing civilization asks. If we’re conscious of its needs, from tropical reefs to thousand-mile shipping lanes, it will provide for ours.

By Tony Palumbi

Tony Palumbi is a novelist, and son of Hopkins Marine Station Director Steve Palumbi. Merging their diverse talents, they have teamed up to write the recently released, The Extreme Life of the Sea and we can’t put it down! Says The Independent, “… The Extreme Life of the Sea (is) another matter. There’s nothing forced about these creatures: they just exist, innocently, doing what they have to do. Stephen and Anthony Palumbi – father and son; biologist and science writer – are brilliant guides to this realm about which we as a species have been remarkably incurious.’

Treat yourself to this book! Available at Amazon (click photo.) E-version includes embedded videos and other extras.

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