Dean Stockwell was helping Joannie Ferland identify individual species from photographs of phytoplankton she’d shot with her submergible version of the microscopic imaging machine I mentioned the other day, while I looked over their shoulders.

“Dinoflagellates,” Dean said to me; Joannie already knew that.

The dinoflagellate we were looking at, a kind of microalgae, was a single-celled creature with a round, semi-translucent “body” and tripod-like appendages, which serve to slow down its sinking rate, and two “flagella.”  We’ve been talking about phytoplankton in straightforward botanical terms, as plants that, like an apple tree, need nutrients and light to photosynthesize.  True enough, but as with so many ocean things, it’s not that simple.  What I find amazing is that these plants have animal characteristics.  Though they lack the power to swim against the current, dinoflagellates use their flagella to move—apparently with something akin to intentionality.  At sunset, they migrate vertically, actually swimming or sinking by altering their buoyancy to slightly deeper, more nutrient-richer water, then move back to the surface at sunrise.  This occurs more commonly in tropical and subtropical waters than here in the Arctic where daylight lasts 24 hours.

Nitzschia frigida

Nitzschia frigida

Some dinoflagellates’ bioluminesce, that is, they emit light.  Dean said that when being grazed upon by herbivorous zooplankton, the dinoflagellates use light flashes as a sort of alarm signal attracting other predators that might then attack the zooplankton, thus sparing the dinoflagellates.  Come on, plants with survival ploys?  “No, no kidding,” said Dean.  When first sailing offshore in heavy weather, after a bout of seasickness, I flushed the seawater head and, fascinated, watched globules of green light spun around the bowl.  Forgetting seasickness for a moment, I thought it the saltiest sight I’d ever seen; they might have been dinoflagellates, but other microalgae also bioluminesce.

Asteroplanus kariana

Asteroplanus kariana

I spent the last hour trying to describe diatoms, that most prevalent form of phytoplankton, over 10,000 species worldwide, 3,000 in the Arctic, as Joannie brought up a few of them on her computer screen, before giving up amid a mass of un-illustrative similes.  That colony of diatoms looked like discarded ribbons from Christmas-morning gifts, those individuals like delicate watch springs, others like dust-devil spirals, there a semi-folded fan, a canoe, then something like the zigzag doodles on a telephone notepad. Though I don’t like admitting it, some of nature’s physical forms—Greenland’s outflow glaciers, the curtains of Aurora borealis light, and perhaps the individual members of this oceanic world in microscopic miniature—are most evocatively revealed by visual imagery.  So best to let photography and art do the talking, while I retreat to facts, but in those there is much that amazes.

Individual diatom cells are encased in a silicate shell, a “frustule,” containing a drop of oil called a “lipid” that helps them maintain neutral buoyancy.  When nutrients become depleted in the upper layer, the diatoms consume their fats, rather like the human body when deprived of food long enough begins to its fat.  This increases the diatom’s sinking rate by decreasing its buoyancy, thus removing themselves from the unfavorable growth conditions.  They sink to the bottom where some decompose and others form nascent “resting” spores until conditions improve.

Most of us understand that terrestrial green plants and trees absorb carbon dioxide and do us the life-giving favor of exuding

Nitzschia frigida

Nitzschia frigida

oxygen into our atmosphere, while ameliorating the greenhouse effect of CO2.  But it came as a surprise to me to learn that fully half of that atmospheric oxygen is generated by phytoplankton.  Further, phytoplankton form the base of the oceanic food chain on which just about everything else in the ocean depends for its existence, hence the term “primary producers.”  In the absence of diatoms, evolved during the Jurassic, and other phytoplankton, the ocean would have remained barren, no fish, none of the marine mammals that prey on fish such as seals or the polar bears that eat the seals, no baleen whales, and significantly less oxygen.  And looking at it from an economic and human-lifestyle perspective, there would be far fewer oil and gas deposits, since sub-seabed fossil fuels are formed from sedimentary layers of long-dead phyto- and zooplankton.

Atmospheric carbon dioxide enters the ocean because air and ocean, kindred fluids, are in physical contact; someone, speaking from a planetary perspective, likened them to two coats of paint on the same billiard ball.  CO2 dissolves, entering the chemical make-up of seawater, more readily in cold, polar water than warmer low-latitude waters.  And because cold water is denser than warm, it tends to sink in certain locations in the Arctic (particularly when the cold water is also salty), taking the carbon with it.  When the winds and currents are favorable, this carbon- and nutrient-rich water upwells, sometimes a half a world away from the sinking site.  Then primary producers consume the carbon and nutrients, and when they die and sink, they return both to the deep ocean.  Some of these remain forever locked in the bottom sediment, some returned to the water column by natural mixing forces.  But of course the CO2 returns to the atmosphere when we extract and burn it in our machines.  Scientific consensus holds that, absent the role of the primary producers in this the so-called carbon cycle, which admittedly I’ve simplified, CO2 concentration worldwide would nearly double.

Among the reasons why our scientists want to measure primary production in open water, at the ice edge, and under it is to establish a baseline in the now if they are to understand how things might change in the near and long term.  For instance, the capacity of the ocean as a “carbon sink” is not infinite.  If sea surface temperatures continue to rise, the oceans’ capacity to absorb carbon will decrease.  Maybe the oceans have already reached maximum capacity.  Also, there’s the matter of ocean acidification.  When CO2 dissolves in seawater, carbonic acid forms, which acts to dissolve the carbonate shells of any ocean creatures, including bivalves, coral polyps, and others that depend on shells.  How much carbonic acid can the hard-shelled ocean creatures endure?  We don’t know.  That’s among the reasons why scientists continue to measure.

Ecologist and leading diatom researcher Eugene Stoermer casually dropped the term Anthropocene in the 1990s.  He meant it to specify the epochal extent to which humans have already altered the world.  Nobel laureate Paul Crutzen helped validate the term through usage, and now official geological organizations in the U.S. and UK are seriously considering adopting Anthropocene as a formal unit of geological time.  We are well aware of our historical capacity to uproot individual ecosystems, replace them for material gain with our works unless forestalled by ethical decision or legal statute.  But now, it is clear, we’ve gained the capacity to alter world climate.  We have become a geophysical force, like volcanoes, like ice sheets.  That wasn’t our original intention, and perhaps we’ll find the political will to act in response to anthropogenic climate change, perhaps not.  But in any case, we can’t claim we didn’t know.

Hungry for more? Why not head over to the art section and take a look at some of Chelsea’s phytoplankton drawings.

About The Author

Dallas Murphy

Dallas is an author with nine published books, a mix of fiction and nonfiction, most recently "To the Denmark Strait", an account of a 2011 oceanographic expedition with Bob Pickart. The Healy cruise will be his sixth Arctic expedition serving as outreach writer.

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