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Latest Expedition Journal

October 19:  Day 17

Posted by Thomas Young

When Fish Can Fly

Standing midnight bow watch last night, I caught a glimpse of something silver-gray moving rapidly near the water surface along the bow, zipping back and forth in evasive maneuvers, its body lit by the bright green starboard navigation lights.  At first I suspected a small seabird, but as the animal reappeared several more times, I soon noticed that the “bird” was emerging mysteriously from the water and then, after a prolonged gliding period, disappearing back into the water.  It was a flying fish!  I soon started noticing many more of them in the dark, gliding along the water’s surface at varying distances from the ship before diving into the deep.  

Flying fish are a superb example of the elegance of natural selection, their pectoral fins having evolved into elongated “wings” that allow them to glide for up to half a kilometer in order to escape predators.  Although we do not yet know whether and how flying fish are affected by ocean plastics, researcher Zora McGinnis will be examining their gut contents and tissues for signs of plastic ingestion.  After watch, I fell asleep thinking about schools of hundreds of flying fish gliding over a pristine, vast blue ocean, one of the more memorable images from my student trip eight years ago.

The next day, I awoke to a rude reality check:  my watch was assigned to counting plastic pieces from the net tows that had occurred earlier that day.  Reluctantly and with heavy hearts, we began the tedious and monotonous process of sorting plankton from plastics.  “One,” counted Noah as he tweezed a tiny piece of plastic from a bucket of water and transferred it into a sample jar.  “One,” I repeated as I tallied another mark on the datasheet.  “Uno,” called Chrissy seated just a few feet away on the lab deck, picking plastic pieces out of her own bucket.  “Uno,” echoed Trent as he recorded Chrissy’s sample.  Perched upon our derrieres along the lab deck, the four of us were using fine tipped tweezers to meticulously pick tiny pieces of plastic out of a thick goop of plankton that included pelagic snails, siphonophores (a type of colonial jellyfish), and Halobates (marine water striders).  We were tallying in two languages to avoid confusion between the two buckets we were examining, each of which came from a different type of net.  Most of the pieces were smaller than a newborn’s fingernails and were exceedingly difficult to pick out of the water even with fine-tipped tweezers.  The process was vaguely reminiscent of the arcade games where one tries to extract a plush toy from a glass cage with a large, articulated mechanical claw.  

“Uno,” Chrissy called out again as she caught another piece and transferred it to a sample jar.  “Uno,” replied Trent to confirm he had recorded one more tally mark.  At the end of the watch, four hours later, our totals reached over 1300 plastic pieces, with still many more to count.  The pieces we found included shards of white polystyrene, segments of clear monofilament fishing lines, hard blue and green plastic shards, and fragments of black plastic bags.  The day’s events were a sobering reality check for us, an existential wake-up call to the gravity of what we are studying:  the effects of human resource consumption and waste on an environment that, prior to the 20th century, had never before experienced these compounds we call “plastics.”

Although we are just beginning to delve into the extent of plastic pollution in the mid-ocean gyre, we suspect that the patterns may be highly variable as wind-driven eddies trap plastics in some areas and not others.  But the notion of a “plastisphere”—the portion of the Earth’s surface composed primarily of plastics and the organisms that associate with this new habitat—is no longer an abstraction.  As we continued picking through and tallying the plastic, it became clear that we had collected almost as much plastic as plankton:  life in the ocean, it seemed, was being inundated with human-derived plastic.  “This is really depressing,” I muttered, as I summed up our tallies and peered back into the bucket, only to find hundreds of additional pieces remaining to count.

Instantly, Trent broke out into song, cheerfully belting out “Always look on the bright side of life!”  If there’s one thing I’ve found that we can consistently count upon our shipmates for, it is to cheer us up, make us laugh, and put a smile on our faces when we’re feeling down.  So, in honor of looking on “the bright side of life” despite this sea of plastic that we are sailing into, I’m going to introduce a topic that perhaps you haven’t considered in relation to plastic pollution in the ocean:  life adapts and evolves.  Plastics are produced from petroleum, which originated as ancient phytoplankton preserved from decomposition millions of years ago.  However, humans have manipulated these fossilized algae by adding different chemicals—many of which are toxic and harmful—in order to produce plastics.  Whether and how marine life will respond to the presence of these novel petroleum-based chemicals is a critical and nascent field of study, and one actively being pursued by some of the scientists aboard this expedition.

As we pass deeper into the North Pacific mid-ocean gyre, we have entered a biological desert that is deplete with natural resources and endowed with an abundance of synthetic plastics.  To understand the importance of this disparity for the ultimate destiny of plastics, we must return to the wisdom of one of the founding fathers of modern biology:  Charles Darwin.  One of the fundamental tenets of Darwin’s theory of evolution by natural selection is that every organism produces more offspring than can possibly survive.  The forces of competition, predation, disease, and resource limitation impose strong selective pressures that weed out the hardy and adaptive from the weak and maladapted.  Variation in heritable physical traits provides a source of novel adaptations from which to draw upon as a sort of lottery system in variable environments.  Just as pathogens are rapidly developing resistance to antibiotics, and agricultural pests are evolving resistance to pesticides, it stands to reason that in such a competitive, resource-depleted environment as the mid-ocean gyre, marine organisms may be evolving methods of digesting and metabolizing plastics.  One researcher on board our expedition, Gregory Boyd, is studying the bacterial communities that associate with plastics in hopes of better understanding this process as it relates to microbes.

Although there is no doubt that human activities, including plastic use, are changing the world’s oceans rapidly, it is worth remembering that the forces of evolution have been at work in the world’s oceans for billions of years.  I thought again about the flying fish I had seen the night before; the very fact that they evolved with the ability to glide through the air to escape predators is a testament to the power of natural selection.  Plastics are not the end to life in the oceans.  They are merely a transition point, the beginning of a strange new marine world structured predominantly by human activities and whose evolutionary future is uncertain.  Amidst a sea of plastic, as we recognize our need to address our overuse of plastic and assume responsibility for the planet’s health, the “bright side of life” is that life will find a way.  And I have every bit of confidence that, with our help, the ocean will indeed find a way to weather out this storm of plastic, if only when fish can fly.