Microplastics in the Sea

A page out of the sketchbook of our artist-in-residence, Elspeth Mackenzie
Time to catchup on the microplastics element of our RowAround today, as the weather has been great and we are ahead of our schedule! Section 3 will begin tomorrow …

As an important part of RowAround, the rowers will become citizen scientists. The skiffs will trawl a net behind them for a set distance in each leg to collect a sample of seawater; this will be analysed to see what types of microplastics are present.

The presence of microplastics in the marine environment and in the food-chain of marine species, both birds and animals, is of growing concern.

Jar of nurdles (photo credit, Queensferry Rowing Club)
A microplastic is defined as a small piece of plastic that is less than 5 mm in size, and accounts for some 92% of plastics in the sea. Some particles are easily visible to the naked eye whereas some particles or fibres can only be seen with a microscope. Primary microplastics are deliberately engineered to be small, such as microbeads in personal care products. Nurdles, tiny plastic pellets about the size of a lentil, are one of the main sources, preproduction building blocks for nearly all plastic goods, from soft-drink bottles to oil pipelines. But as essential as they are for consumer products, nurdles that become lost during transit or manufacturing become a source of microplastics in the environment and get washed into the water.

Nurdles with other plastic items (photo credit, Queensferry Rowing Club)
Others, secondary microplastics, start off as larger items that get broken down into smaller pieces by the effect of waves and sediment abrasion, and degradation in sunlight, among other processes.

Tiny strands of multicoloured plastic, derived from bigger ropes, caught up in seaweed. Photo, James Fenton
Polypropylene and polyethylene are particularly prevalent in the ocean; plastic bags are made from polyethylene, while polypropylene is used for sweet wrappers and bottle caps. Microfibres are also abraded from the inside of plastic feed pipes in fishfarms by the fishfeed pellets blown through them.
These polymers float on both fresh and salt water, enabling them to travel long distances from the initial source of pollution.

The results from this study will present a status of microplastics around Scotland’s coast; there is currently relatively little published information.

Microplastics caught in the net during the very short trail trawl
Photo, Sarah Reed
Analysis will take place at the Scottish Association for Marine Science (SAMS) near Oban, by Saz, our boffin-in-residence, and Dr Bhavani Narayanaswamy. A microscope will locate the plastics in the sample and then a state-of-the art will be used to identify the types of plastic.

The trawl rig was constructed especially for RowAround Scotland 2020 by the Field Studies Council in Millport, Cumbrae, modifying a LADI (Low-tech Aquatic Debris Instrument) design by the Civic Laboratory for Environmental Action Research (CLEAR) in USA. Many thanks to Alex MacFie and Tom Stevenson at Millport for their enthusiasm, patience and ingenuity. Ropes and other materials were very kindly donated by Highwater Sails in Plymouth, and shackles, bolts etc by SAMS. The sample bottles were very kindly donated by Dr Liz Furrie.

See: https://www.facebook.com/RowAroundScotland/videos/2582286868693240/

Field trials of the trawl, just before the lockdown, at SAMS beach at Dunstaffnage, with Saz and Sue

For more details, see Saz’s PowerPoint presentation to the SCRA’s Passage Planning for Expeditions training on the Isle of Seil in March: Microplastics around the Coast of Scotland (pptx format, 11MB)