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Latest Expedition Journal

November 3:  Day 32

Posted by Michael Gil

A Hitchhiker’s Guide to the North Pacific Subtropical Gyre

By Mike Gil and Tyson Bottenus

“Always, then, in this flotsam and jetsam of the tide lines, we are reminded that a strange and different world lies offshore.” – Rachel Carson, The Edge of the Sea

Rafting biodiversity on plastics remains largely understudied and poorly understood.  My research during SEA’s North Pacific Expedition centers on better understanding the diversity of organisms living on oceanic plastics.  This project treats floating plastic debris as small "islands" to test one of the most fundamental theories within the discipline of ecology: species diversity will increase with island size, but will decrease with island isolation.  

So far on our cruise track, we have recovered and surveyed the resident organisms on more than 30 "plastic-island" ecosystems of various sizes and locations.  Most recently, we pulled up a 3.5-foot-long fishing buoy with Japanese print characters.  Many of the other pieces of debris are also Japanese fishing buoys, whose round shapes make them readily comparable and well-suited for examining the effects of plastic size and isolation on rafting species diversity.

Swim, crab, and kick!  Oh, crab, swim!  Swim until you find Queequeg’s coffin.  Generations of rafting crabs before you swam, swam, swam and kick, kick, kicked for an entire lifetime searching for a stationary island to stopOahu to the Tuamotubut you!  You are one of the fortunate rafting crabs, one of the seafaring crustaceans born of a modern century.  A century where the ocean is replete with thousands upon millions of mobile islands.  Islands of debris, islands that driftlike you, but most importantly, with youwith the currents.  Islands that haven’t been charted, islands that no one even knows exist.

This work has broad implications for biological conservation. If ecosystem diversity on floating plastic increases with the size and accumulation of debris, then as we dump more plastic into the oceans more organisms may hitchhike, perhaps even from coast to coast. Think of it this way: more islands equal more tourism.

Swim, crab, and kick!  And look!  Above the wave crest, there on the horizon.  A dark sphere, a floating orbyes, an abandoned fishing float.  It bobs in the distance, fighting the swell.  Swim, closer.  Lime green algae, tufts of hair, from some faraway coastal region pepper its underside.  Sustenance for a lifetime.  I have heard that other rafters call this derelict fishing gear home.  A nice place to rest.  To drift about.  To its inhabitants it offers unlimited sunsets and sunrises.  Oh, but watch out!  A wave!  Curse you, wave!  Veered off course, plunged underwater.  Bubbles!  Froth!  Muted sounds of the pelagic.  Float to the surface again.  Grasp a fouled toothbrush, an old shard of bucket–anything that graces the surface.  Recover.  That was a doozy.

Of course, this idea isn’t new. Organisms were "island hopping" via trees and other natural floating debris long before the advent of plastic or even the dawn of mankind.  Throughout the history of life on our planet, rafting is believed to have been a significant mechanism driving species range expansions and speciation events.  But what happens when we seed the ocean with countless plastic islands?  Will this increase species ranges faster than before?
 
The sun shines down upon you, crab, drying your colorful carapace.  Look at your shell: parts of it white as the moon.  Some blues, specks of yellow.  Hints of brown.  Who were your ancestors?  What parts of the Pacific did they float about?  Or were they of another ocean altogether? It is possible.

When hitchhiking critters do make it to new lands or waters, we sometimes refer to them as “invasive species.”  In such cases, foreign species can have grave impacts on the new ecosystems they enter.  Devastating effects of invasive species have been documented all around the world. 

A noteworthy example is currently taking place in the Caribbean Sea, where invasive lionfish are voraciously consuming resident fish species, many of which are herbivores, responsible for keeping coral reefs healthy and vibrant.  Lionfish invasions are often attributed to “The Nemo Effect”, in which tropical aquarium owners—newly introduced to the adorable characters in Disney’s Finding Nemo—set their pet fish free (including lionfish) into the sea.

Did your ancestors even float?  How did they end up on the surface?  Have you heard from your estranged family, the benthic crabs that live on the bottom of the ocean?  Or what about the thigmotactic ones whounlike you, eternal wandererenjoy confined spaces?  Crabs that, as juveniles, got swept into the hairline openings of oysters and lived there, amongst silken folds, for the rest of their lives?  Crabs who exemplify how little space we need to existnay, to thrive!

Most of the time, higher biodiversity is something conservationists celebrate and seek to preserve.  But in this instance, higher biodiversity on synthetic environments might become the catalyst for species invasions into natural environments.

Over there in the windrowan orange island.  Swim, crab, and kick!  What is it? Doesn’t matter, hop on.  It’s big.  There is space.  If I were a geologist, I’d say it was a piece of sandstone 350 million years old.  Devonian.  Coarse grained, weathered.  Layers of reddish brown claystone interbedded.  A microcontinent, perhaps.  An imitation seamount, released from the bottom, drifting.  Depressions on its surface look like epeiric seas, the shallow bodies of water where your ancestors once thrived.  But noit is Styrofoam.  From a dock, perhaps. Who knows?

It has been said that Hawaii, our destination, was once more beautiful and diverse than even the Garden of Eden, that it harbored more species of birds than are countable today.  Of course, this is before the Polynesians came.  And before the Europeans came.  And the rats. And the cattle...

So swim, crab, and kick!  You have made it.  Welcome.  Feel free to crawl around your new Styrofoam home.  You have arrived.  But where will you go next?