Data hunt in the plastic soup of the Pacific Ocean
By Henrik Beha Pedersen, 31st October 2016
This morning I woke up before the rest of the crew on board the expedition ship SY Christianshavn, and I decided to get a cup of coffee on Venice Beach. We are in LA, right on the edge of the world’s biggest ocean taking up a quarter of the earth and containing the world’s biggest body of water. Enjoying a good cup of coffee, I walked down to the beach where the waves of the Pacific Ocean come ashore over and over again. The stroll confirmed my worst fears. A braiding of plastic and broken-down micro plastic is washed ashore from the ocean with the world’s biggest plastic soup due west of where I am.
Three weeks in the plastic soup
That is where we are heading now. We are ready for a three-week expedition from LA to Hawaii – ready to document the problem of plastic pollution in the world’s largest ocean. Joining us on board is associate professor in environmental risk Kristian Syberg from Roskilde University and research assistant and marine biologist Malene Møhl. And then there is me, I’m an environmental biologist. So I feel confident that we have strong research team on board. We want to bring home a great dataset to the labs at RUC to help us answer a number of research hypotheses.
Plastic on the surface
When we trawl plastic in the surface, we only find one percent of the total quantity of plastic that has been discharged into the sea during the last 60 years. The purpose of Expedition Plastic is to help find out where all the plastic ends up. This is done by trawling and taking samples of plastic found in the top 5 metres of the surface water. An experiment similar to this has been reported in Nature, where samples were collected in the Northern part of the Atlantic Ocean. We wish to extend this knowledge based on samples from the most polluted ocean in the world, the Northern Pacific Ocean.
Plastic deep under water
We also collect samples several hundreds of metres under the water surface. We know that the plastic that can’t be found in the surface probably can’t be found at the bottom either. That’s why we assume that a great amount can be found in the column of water. There are different hypotheses as to what might happen to the plastic in the column of water. Is it the salinity? Is it thermoclines caused by temperatures? Is it fouling of the plastic particles? The samples we collect will help us answer these questions.
We catch myctophidae fish living deep under water to have a look at the amount of plastic in their intestinal system. Due to their great numbers and the fact that they move vertically (1000 metres up and down through the water every day), it can provide valuable insight as to whether they transport plastic from the upper layers in the ocean and into the food chain, since this species is a significant food source for a number of other species. Additionally, we analyse the chemistry that is associated with the plastic and potentially ends up in the myctophidae fish.
Every single day, we trawl plastic with our fine mesh net on the manta trawl. We catch all particles that are larger than a third millimetre, and since we know the size of the entrance in the trawl and the covered distance, we can calculate how much plastic there is in the different size fractions. We can determine the types of plastic, and we can extract the chemicals that come with the plastic.
This collection of data has two important perspectives. First of all, we share all data with the 5Gyres Institute in Los Angeles, where it becomes part of a global data set allowing PhD Marcus Eriksen to model how much plastic there is in the ocean and publish these data in scientific articles. You can read Marcus Eriksen’s last article in PlosOne here:
Plastic as a sponge for chemicals?
Besides working with 5Gyres and a number of sailboats to collect data for 5Gyres, our research also brings into focus the chemistry that ”sticks” to the plastic. When the plastic reaches the large plastic soups, it is decomposed to trillion pieces of micro plastic. What was once a bottle, a bag and other packaging made of plastic now constitutes a huge surface, and it loves fat! Chemicals that we have discharged throughout history, such as PCB, flouride and PAHs, lack a host and have a high affinity for the amorphous areas on the plastic. That is why we have seen high concentrations of these historical chemicals on the micro plastic in the oceans. When the samples are processed in the lab, we can determine magnitude and the different types. The samples are supplemented with water samples, where we extract potential chemicals in micro column as well as samples of biological tissue from fish, for instance.
Finally, we catch fish! We want healthy fish and love to eat what we can find in the sea. We don’t hope that gutting fish to look at the plastic in their intestines will affect the appetite of those on board.
Research and production of data is essential to find out more about the effects of discharging plastic into the marine environment. With that said, there is no reason why we shouldn’t act right now. That is why it is essential that we have two great documentarists on board: Chris Jordan and Erica Cirino from The Safina Center. With images and video, they can provide a perspective on science and the problem of plastic pollution.