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SEA Currents: SSV Corwith Cramer
May 29, 2020
Sampling for Plastics at Sea
As the Robert C. Seamans sails from Hawai’i to California, we’re telling the story of the Pacific through ArcGIS Storymaps. We’re reposting some of the entries here, in our SEA Currents blog, but we encourage you to follow regular updates by going directly to Pacific Crossing 2020 StoryMaps.
Today started for me by waking up around 0930, finding some leftover breakfast on the hutch, and then going back to bed to do some reading and some more snoozing. When I reappeared around 11:30 I saw that it was flat calm and we were going to have a swim call in 15 minutes. The water here is slightly colder and saltier than near Hawaii, about 24 degrees Celsius and salinity is around 34 parts per thousand. It made for a refreshing swim and some great floating.
The swim call was made possible by the force one winds and gentle rolling swells. These conditions also allowed us to see a lot of floating garbage. We are currently on the outskirts of what is referred to as the "Great Pacific Garbage Patch." Many people have heard of it, but not a lot of people really know what it looks like. For the past few days we have been seeing progressively more macroplastics, mainly fishing gear like polypro line, nets, and buoys. With today's glassy seas we were able to see many more and much smaller plastic fragments. Still, when taking a picture of the water, it is hard to see anything in it. But gazing out you can see flecks of mainly white sparkling in the waves as they roll by. The distribution is similar to a snow globe, when most of the flakes have settled, but a few are still in suspension. It's also like the morning after a big night out when you find a piece of glitter on you and then all of a sudden you see that it's everywhere. It's easy to miss at first, but once you start seeing it you can't stop.
For the past few days we were logging all of the plastic we saw, but by 1300 we were seeing so much it wasn't feasible to keep logging it. Just between 1240 and 1310 we saw 3 pieces of polypro line, a bucket lid, three buoys, a piece of a milk crate, a rubber gasket, and at least thirty small pieces of hard plastic (a couple of inches big each).
At 1330 we decided to do a Neuston Tow, a zooplankton net that tows along the surface layer for 30 minutes at 2 knots, covering about 1 nautical mile. Right before we deployed the tow we could see windrows of small plastic bits and trichodesmium. As soon as we put the net in, the water seemed to clear up, so we weren't sure what we were going to find. The amount of tiny plastic pieces (and bigger bit of net and line) was astonishing. Even though it was so clear, there was so much more plastic in the water than we could see.
It's not all negative though. We also caught a lot of juvenile fish, including a frog fish. We've also seen small fish congregating around some of the larger pieces of floating plastic that have drifted by. We didn't have time to count all of the plastic in the tow, but we will save the sample so that it can be processed later and join SEA's dataset.
Just after we finished the net the wind picked back up to a Force 3, the sea surface started to be more textured, with lots of ripples and even some small white caps, and we stopped seeing as much macroplastics, though we are certain there is still a lot there. It'll be interesting to see where our course takes us and what the oceanlooks like in the areas of denser plastic accumulation.
- Tristan Feldman, Chief Mate aboard Robert C. Seamans