Course: Survey of marine litter in Hidaka Bay surface water: Practice of microplastic analysis

Marine plastics have been attracting attention as an environmental problem. How is marine litter being investigated? We would like to contribute to SDG 14 (LIFW BELOW WATER) by sharing the method of marine litter survey with people all over the world and getting them interested in it.
The United Nations has designated the decade starting in 2021 as the "Decade of Ocean Science," with the aim of contributing to SDGs. Ocean science, as defined by the UN, includes the field of fisheries.

The Newston net is lifted after being towed for a certain period of time. Samples in the net are flushed with water and collected at the cod end. The collected samples are taken to the laboratory.

Autumn is the season of bloom, and the amount of phytoplankton increases. As the weather gets colder and colder, the amount of plankton decreases. Then, in the early spring, there will be more plankton due to the spring bloom.

When it is windy, the flow meter floats in the air due to the swell. This can change the collection rate.

Plastics usually float on the surface of the water. If the wind is strong and the plastics are stirred up, they may sink. In this case, collected samples can be different from usual.

The collected samples are brought to the lab for processing.

The blue object floating in the water is plastic. The brown cloud contains phytoplanktons, mostly diatoms. The reason why the net looked brown earlier is that it was full of entangled phytoplanktons. The microplastics will be sorted out and picked up.

Formalin is added to the bottle to prevent the sample from decomposing.
The sample number is written on the bottle, formalin is added, and the sample is stirred well.

In general, plastics smaller than 5 mm are called microplastics. Plastic and vinyl fragments are picked up regardless of their size from the samples collected by the Newston Net.

After the fragments are picked up, they are taken photos. To confirm if they are really pieces of plastic, FT-IR, Fourier Transform Infrared Spectroscopy, is used.

The Newston net sample is divided into three jugs. An appropriate amount of the sample is scooped up with a ladle and put in a petri dish, and checked with tweezers. If there is any plastic, It is picked up and transferred to another dish. After being checked, the sample is poured into the waste container.

To find even smaller microplastics, the waste liquid is filtered using filter paper. The debris on the filter paper is collected to be checked again.

If you look at the microplastics that the students picked up during their practice, you can see that even if you just pull the net a little, you can still pick up plastic.
The amount of plastic this year is smaller than last year, but the sea area is slightly different from last year. Last year, the area was off Kushiro, just past Cape Erimo. There was a lot of litter. The reason might be that we sampled in the area where the Oyashio and Tsugaru Warm Current waters meet.

Survey of marine litter in Hidaka Bay surface water: Practice of microplastic analysis