This is the third in a series of live blog reports from our correspondent, Olga Mironenko, an environmental scientist focused on marine plastic pollution who is currently aboard a research vessel in the Pacific Ocean sailing from Hawaii to Oregon, USA. See the first report here and the second report here.
Back to my hypothesis that there seem to be no small-sized plastic particles in the northern area of the North Pacific Subtropical Gyre. Excellent hypothesis. But way off-base.
It would be excellent, indeed, if it were true: removing large objects from water is obviously easier than fishing out small, krill-sized bits. Anyways, the bad news is, my hypothesis was wrong, and it was all due to the experimental method I’d chosen. As usually happens in science, wrong methods lead to wrong conclusions.
A couple of days ago an engine strainer, a big metal strainer used to filter the water taken in by the ship’s engine to cool itself, was taken off for a weekly cleanup. Our engineers, knowing that we have an ecologist on board, suggested that I take a look. The strainer was strewn with technicolor plastic bits, as well as tiny living beings that had got caught in the strainer during the week of filtering through the ocean water at six-meter depth.
I should say, this unexpected strainer (I had no idea than an engine even had a “strainer”) gave me a much clearer vision of what is really happening in these waters.
First and foremost, this part of the ocean appears, sadly, to be full of small-sized plastic, even though you won’t see it when looking at the gorgeously, impeccably blue surface of the water. It’s beautiful in and of itself, by the way, how this principle seems to hold for everything in life: looking just at the surface, more often than not you are in for some very wrong conclusions.
These plastic bits are submerged in the water column, and establishing the layer or depth of their predominant concentration is very feasible. One has to simply filter through the chosen depth for a while. But that is not technically available to me on this cruise.
What I will have a chance to do, though, is take a good look at the engine strainer a couple more times. I’ll see how much it accumulates every week while we’re steaming away northwards from the center of the Great Pacific Gyre.
I also came across a curious problem, which I haven’t seen mentioned in any relevant research literature. The scientific method, as we are all aware, calls for quantifying and measuring. We generally consider that measurements render objectivity to our observations. Therefore, research data on marine plastic pollution will also normally contain numbers — for instance, the number of plastic bits per chosen unit of seawater volume.
The thing is, after the three hours bending over the strainer, I no longer understand how it can be possible to quantify marine plastics. You see, wave action (and pretty much any mechanical impact, which can also be wind, animal bites, etc.) and solar ultraviolet radiation are known to make plastic fragile. I knew this, but I never expected it to fall apart like some brittle calcium carbonate (the substance seashells are made of). It literally crumbles at the slightest pressure! The plastic we have on land most certainly doesn’t behave this way, or else it would be completely useless for our purposes.
So the bottom line is: what you measure today as one “piece” is guaranteed to be five pieces tomorrow.
I have to reiterate: Based on what I got to touch, it’s amazing how quickly and completely plastic loses its elasticity and durability in seawater. The bits that crumbled easier than an ice cream cone were barely covered with any algae or micro-animals (a process always occurring in the sea and known as bio-fouling), which could mean that they are relatively new to the environment and haven’t formed a tiny ecosystem yet.
Or consider, say, nylon ropes, scraps of which unexpectedly prevailed in the strainer. One scrap is made of dozens to hundreds of interwoven fibers, which are bound to eventually come loose and end up floating separately.
All of that makes me wonder: When it comes to marine plastic pollution, what exactly should we be counting, and how much of a help counting is in this case? And, more importantly, which of the numbers should we be using to assess the ecosystem damage it has caused?