http://www.sea.edu/plastics/journal/october_15_day_13

October 15: Day 13
Posted by Jonathan Waterman

Invasive Plastic Hitchhikers

We’re ten days and 690 nautical miles out from the nearest land in 
California. In that time, we’ve conducted 21 net deployments to collect 
and analyze plastic. We’ve counted a total of 3,323 pieces of plastic, 
most of it in the North Pacific subtropical gyre. Here in this gigantic 
eddy-like “trap,” the concentration of floating plastic has increased 
exponentially.

We’re finding grain-size and quarter-size pieces of plastic in the net 
cod ends. Occasionally nets have counts as low as ten—versus counts of 
1,372 pieces. Why? Because of the gyre’s patchiness, some places are 
loaded with plastic and others are not. On calm days, often times the 
plastic can be seen floating by the ship, other times the sea looks 
clear and free of plastic until you filter it and discover plastic 
pieces that are invisible to the human eye.

One project (among many onboard) is to count microscopic plastics that 
aren’t normally tallied with the larger and more visible pieces in the 
neuston net due to the fact that they pass out of the mesh net as it’s 
being towed. To measure these, a liter of seawater is dyed pink and 
vacuumed through a micrometer-sized filter mesh. The dye doesn’t stick 
to plastic, therefore, the pieces can be seen clear of other microbial 
life and counted through a microscope. Over the last week, microscopic 
plastic counts have ranged from 56 to 224 pieces per liter of seawat