“Morale is soaring” – Joel’s quote of the day, over a superb meal of homemade chili, cornbread, and fried rudderfish, nabbed moments before from underneath a large, tangled piece of rope debris. A story unto itself….
That crew morale should be high after seeing what were seeing out here may, perhaps sound a bit macabre. We all catch ourselves in moments, when announcing a debris sighting with great excitement - “floating bottle on port side!” “A NET! A NET!” - these findings should hardly be cause for celebration... Granted, were here on a mission, and today was a tremendously productive day.
Following our plan to sample at each degree of latitude, we began trawling at 31 degrees this morning, and pulled out our most impacted samples yet. The photo above shows the contents of our educational trawl – a bottle cap, surrounded by colorful plastic fragments. The calm winds we experienced appear to allow the smaller particles of plastic to reach the surface where they can be captured by our manta trawl.
Later this morning we received a key message from Dave Foley at NOAA. Dave is one of the co-authors of the paper “Marine Debris Collects in the subtropical Convergence Zone " and suggested that east of the international date line “most of the action is between 28 N – 32 N, around 170 West Longitude.” So we adjusted our course westward, and began heading towards what may be an even thicker plastic stew.
Marcus "kissing" a pelagic crab on a piece of plastic debris.
En route, we spotted some more plastic debris, like this detergent bottle Marcus is cradling above, carpeted with algae and bryozoans, and home to a disgruntled pelagic crab. Then, just before sending Joel and Jeff out to capture some underwater trawling photography, a tangled mess of discarded rope floated by, home to an entire ecosystem of fish swirling underneath. We immediately geared up to remove it, but thought we’d first try to supplement our dinner…
As Miriam commented in an earlier post, one side effect of marine debris is that it does indeed attract fish, mimicking Fish Aggregating Devices (FADs), a spectacle unlike anything I’ve ever seen. Here, in the middle of the ocean, this smallish rope floating on the surface harbored entire schools of fish just below. As soon as the ORV Alguita approached, masses of fish immediately “jumped ship”, darting under our boat – much better protection than a flimsy rope. Save for the two that ended up on the dinner table.
We pulled our last samples for the day – finding more of the same, and sat down to Joel’s award winning chili feast, the fresh rudder fish were an added treat.
Finally, to follow up on yesterday’s mention of what Charles found during his free dive: Equally interesting to what we found in our Manta Trawl sample was what we didn’t find. Or rather, what Charles collected with a hand held net, just beneath the Manta’s 15 cm deep opening. “This sample here I got snorkeling has debris we’d never pick up with the Manta Trawl” Charles remarked as he surfaced, cupping a handful of particles in his net. “Taking our current sample sizes, and doubling or tripling them wouldn’t be a stretch”. Joel also noted most of the debris he saw diving was about a meter down. He speculated that it may be hard to see debris right at the surface, but he did look there.
When buoyant plastic particles are reduced far enough in size, they begin to lose buoyancy, and become incorporated into the water column. In a study of dispersion of oil droplets by breaking waves, it was found that at the 20 micron size class, the droplets lost buoyancy and behaved like the water they were mixed in. So its possible that with our current sampling, skimming the surface, we are missing large amounts of small plastic fragments. And our ratios, alarming as they are, may be fairly conservative. A sobering thought…..and perhaps a question for future research. Tomorrow we'll head for Dave's recommended site. Though were all fully prepared for, and expecting to find large quantities of plastic here, its still equally shocking every time – it simply does not belong here.
As always, Aloha from the Captain and Crew of the ORV Alguita