May 31, 2013
The AVANI trawl glides across the sea surface from 7pm till 7am the following morning. The crew crowds around the cod end to see what the ocean delivered overnight. This time it’s quarter full with salps and jellies, man-o-war, the insect halobates, a few isopods, crabs, myctophid fish are plentiful….and a pencil. A green pencil, broken in half with it’s eraser intact, floats among the life forms. And there’s a paper nautilus (Argonauta argo). Bits of microplastic confetti complete the picture of this sample.
There are multiple origins for this trash. The pencil could have rolled off the desk of a ship captain on one of the hundreds of cargo ships passing all around us. Or maybe tossed out of a vehicle on one of the coastal roads, like the ones we drove along last year in Chenai, India during a youth summit there. Or maybe it originated in the mountains of Nepal in a school, where the broken pencil was no longer useful and found it’s way into the Bagmati River, which connects to the Ganges River flowing into the Bay of Bengal. Or a fishing boat captain, broke this pencil after writing a few coordinates in his logbook, then tossed it into the sea. These 4 sources: Fishing industry, shipping lanes, waste from dense coastal populations, and watersheds that drain to the mouths of rivers – are the dominant points of entry for trash into the ocean.
This framework of 4 sources drives the ocean model we’re using. Laurent Lebreton and his colleagues created this model, which is very different than other ocean models. This one is focused on plastic pollution, using the 4 points of entry as starting points for drifters. It paints a very different picture of where plastic pollution accumulates. In doing it this way they discover that plastic marine pollution moves to the 5 subtropical gyres, but much of it remains in closed seas, gulfs and bays. These ‘hot spots’ are more dense than the garbage patches in the gyres in some cases.
10 hours later at 5pm we haul in the AVANI trawl again. This time, among the usual characters of wildlife, there’s a glass bottle, toothpaste cap, and a shoe. The model predicted this – thicker patches of trash as we travel eastward toward Thailand.