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Latest Expedition Journal

October 5:  Day 3

Posted by Bart DiFiore

Our Ocean Community

In our first days at sea, not only have we been building our shipboard community, we have been getting acquainted with the astounding community of life surrounding us.  In less than 48 hours we have traveled to the brink of the continental shelf, passing across the extremely productive waters of the Southern California Bight.  Throughout this region cold, nutrient-rich water locked deep in the Pacific, flows through underwater canyons in a landscape as textured as the Rockies, upwelling nutrients towards the surface.  Life in the sea occurs only through a complex interplay of nutrients and light, at the collision of currents where deep water surges upwards, rejuvenating the waters above the thermocline.  As we sail towards the edge of the continental shelf, we move through this explosion of life.  These cold, upwelled waters spur blooms of phytoplankton, which in turn sustain the entire pelagic ecosystem, from the tiniest microbe to the largest predator.    

In the short time we have been at sea we have seen many signs of riotous life below us:  sea lions, baitfish, pelicans, gulls, whales, even a mola mola (ocean sunfish), which we disturbed as it plodded along the currents.  Just yesterday, while practicing drills we crossed paths with a pod of more than 100 common dolphins, a few of whom broke off, charging and frolicking in our bow wake.   

Already we’re starting to notice changes, minute differences in sea state and sea color that show the changing waters beneath us.  We’ve left behind the gulls and pelicans of the shore, finding the shearwaters, terns, and other seabirds of the offshore world.  The green, nutrient-laden, coastal waters have given way to the crystal blue of the pelagic sea.  It’s astounding how, in such a short time, we are already passing the last vestiges of the shelf.  By morning we will have crossed the 1000- and 2000-meter bathymetric curves, entering the abyssal plains of the open Pacific.  

Before leaving, however, we encountered a last reminder of the abundance of the shelf.  At 10am Friday morning a 40-inch yellowfin tuna attacked the small feathered jig that we have been trolling behind the Robert C. Seamans.  After hand-lining the fish to the boat, we sacrificed it to the gaff in the name of science and our appetites.  The widely distributed yellowfin tuna can grow to over 300 pounds and are among the top echelon of predators.  Their position in the highest trophic level makes them prime candidates to examine the potential downstream effects of plastics pollution.  If plastic pollutants are being passed though the food chain, they may appear in species like yellowfin tuna.  Zora McGinnis, a master’s student at Hawaii Pacific University, examined the tuna’s stomach for microplastics, while Greg Boyd, an SEA research assistant, cultured bacteria from the fish’s gut to look for vibro, a type of microbe living in the ocean.   

Catching the yellowfin was particularly near and dear for me.  I have been fishing, researching, and observing Atlantic bluefin tuna for most of my life.  The ecology and biology of tuna is a close-held passion.  I’ve spent the last eight months tracking and tagging Atlantic bluefin tuna along the eastern seaboard of the U.S. with the Large Pelagics Research Center.  Sleek, streamlined for perfect laminar flow, capable of warming regions of their bodies, and migrating across entire ocean basins, tuna act as vectors connecting our ocean environs.   While it’s all too easy to look at the tuna in isolation, it’s critical to study this species in relation to the larger pelagic ecosystem.  The farther we sail from land, the more we become a part of this ocean world.  Hopefully, we can examine the Pacific holistically, from the smallest bacteria to the largest yellowfin.   Only a wide lens of observation will show the true impact of plastic pollution.