Saturday, May 01, 2010

Finding out what is really down there

kw: book reviews, nonfiction, oceanography, photographs

In 2000, hundreds of scientists began a ten-year project to take a census of The Ocean. Considering that less than 5% of Ocean has been surveyed in any way, the aim was not to find every living thing—we can't even do that on land—but to sample intensively, comparing what was found to what had been recorded earlier to get some sense of the true number of species and their distribution.

While it would indeed be nice to have a record of every little fish, jelly, star, coral and squid (like this little Histioteuthis bonelli), that's going to take quite a bit longer, and involve many more people.

Had they just divided Ocean equally among them, each scientist would have had a space comparable in area to Belgium to explore, but consider this: About every ten meters in depth you descend, different creatures are seen. A patch of ocean over the 5-km-deep abyssal plain could be thought of as five hundred Belgiums. The average mid-water denizen seems to be more like this 5-cm squid than like the mighty bluefin tuna, but the most populous are the plankton (less than 1mm size plants and animals), bacteria (less than a 1/20 mm), and viruses, which may outnumber everything and even outweigh, in aggregate, many species of much larger size.

Now that we are well into 2010, the first books on the Census of Marine Life are being published, and the coffee-table-sized World Ocean Census: A Global Survey of Marine Life, by Darlene Trew Crist, Gail Scowcroft, and James M Harding Jr, has just been issued by Firefly Books (printed in China I might add).

This map, from page 169, shows many of the census sampling sites located over abyssal plains. These seemingly placid deeps are one of six zones into which Ocean was divided, to provide some systematic framework for the survey. Chapter seven of the book, "Unexplored Ecosystems", bravely provides a peek into the environments found in the perpetual darkness that pervades most of Ocean. The little squid shown above was found in open, deep water, most of which is "passing-through waters" to faster critters of every kind, but a permanent home to bacteria and small floating animals that feed on the rain of detritus from the plants (phytoplankton) living in the lighted zone near the surface.

We are much more familiar with plants and animals that live on or near the bottom, though this array of deep-water lobsters seems a bit bizarre. Most of us in the US know about the Maine lobsters found in supermarket tanks, and the spiny lobsters kept in some aquariums. Though there are about 35 species of clawed lobster and 60 of spiny lobster known, the relative ease with which dozens of new species were found indicates that there could be a thousand lobster species total. The frustrating thing about such a census is that we must rely on pretty radical extrapolations to make sense of the data. Frustrating, but also exciting!

These fish, swimming above manganese nodules atop a seamount in the open ocean, are Orange Roughy, a popular food fish. Don't let the small scale of the photo fool you. This species can get rather large, a couple of feet at least, so what appear to be twiggy corals on the bottom are really rather substantial hydroids and other species among pillow-sized nodules. Besides, the depth here is too great for corals to live. The main thing we know about seamounts is that they host large concentrations of fish, and are thus heavily trawled. None is known in an undisturbed state, making census-taking particularly difficult.

The strangest deepwater communities are found at hydrothermal vents on the ocean floor. This black smoker is fed by water that can be as hot as several hundred degrees, but just a short distance away, where the water's temperature is "merely" 100°C or so, bacteria thrive, fed by minerals in the emitted water, and they soon give way to incredible masses of "tube worms", pale crabs and other creatures entirely unknown before 1977.

These are fringe communities that I chose to emphasize the challenge these scientists faced over the past decade. 100 years ago Edison observed, "We don’t know one tenth of one percent of anything." The Census of Marine Life has demonstrated just how true this is. One researcher reported that he discovered a new species for about each seven hours of work. That is just one person of a thousand (the effort peaked at 2,000), and indicates that there must be millions of species still to be found. Yet the trends are more meaningful yet. Over the ten years, there was a noticeable decline in not just fish numbers (overfishing does continue unabated over most of Ocean), but many kinds of life in the open sea, and an increase in jellies (AKA jellyfish). Some speculate that jellies will come to dominate mid-Ocean species in another ten to twenty years.

Whether they are recording Ocean as it is, or archiving a "what once was" for future generations, the effort continues. Follow-on projects are being funded. Perhaps the most valuable result of this past decade's effort has been learning how to learn about The Ocean.

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