CLiP Vanuatu Microplastics in water 2018

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The Commonwealth Litter Project (CLiP) supported Solomon Islands to take action on plastics entering the oceans. The assessment of microplastics in seawater was part of the action plan to define scientific baselines for future monitoring purposes and comparison. Samples were acquired towing a manta trawl from a 7.5m vessel for 30 mins at less than 3 knots. The trawl had a mouth of 60x18cm and a net mesh size of 335 micron. The amount of water filtered was measured by a General Oceanics mechanical flowmeter (one-way clutch). The sample was then rinsed in a jar through a 315 micron sieve and frozen at -18 degrees centigrade. High concentrations of organic matter were found in Mele Bay (coral spawning event). In the lab, visible plastic particles greater than 5mm were removed and analysed with a ATR-FT-IR to identify particle composition comparing their spectrum to a polymers library. The rest of the sample was chemically digested with 30 percent KOH:NaClO solution with an incubation of 1 day at 40 degrees centigrade. Samples were then filtered, stained with Red Nile dye and a digital image was acquired through a microscope. Number of particles was counted and corrected for blank samples. A subsample of particles (between 1 and 10 percent) was processed through a ATR-FT-IR. In case of samples with high organic content, a sieving stage through a 5mm mesh wad added at the beginning of the process. ATR-FT-IR is the attenuated total reflection Fourier Transform infrared spectroscopy. A Thermo Fisher Scientific Nicolet iS5 ATR-FTIR with an OMNIC software (version 9.9.473) was used and polymers were identified based on the percentage match of IR spectra to a polymer library. Only spectra matched greater than 70 percent were accepted Spectra were collected in the range 4000 – 650 1/cm at a resolution of 4 1/cm.