| dc.description.abstract | Microplastic (MP) in the world’s oceans is a global concern. Studies on MP are frequently published, but there is limited information on MP in the South Pacific Ocean. Here, a seawater filtration unit collected MPs down to 20 µm in size on an 11 000 km transect from Chile to Fiji in the South Pacific Ocean. Data on MP occurrence in this region is important to validate oceanographic models for the transport and fate of MPs. Two different analysis instruments were used for the quantification and characterisation of MPs. Previous studies have emphasised the significant influence of sampling methods on the quantified levels of environmental MP. However, this study goes beyond that and sheds light on the substantial impact of different analysing instruments on both the quantification and characterisation of MPs. The mean MP concentration across the whole transect was 3564 ± 2374 MP m-3 using a QCL-IR instrument, while a µ-FTIR instrument found the mean MP concentration to be 166 ± 85 MP m-3. Higher concentrations were found in the South Pacific subtropical gyre. For the first time, MP particles down to 20 µm in size are documented in the South Pacific. The particle size is crucial in determining effects on marine organisms, as higher toxicity is reported for smaller sizes. An overwhelming majority (98%) of all identified MPs were smaller than 300 µm, emphasising the importance of studying this smaller size range. μ-FTIR identified polypropylene (55%) as the dominant polymer, and QCL-IR identified polyethylene (64%) as the dominant polymer, while both instruments identified fragments as the most dominating morphology of the MP particles. The comparison of the two different analysis instruments in this study is a first step towards harmonisation and standardisation of MP monitoring at two laboratories in Norway. Standardised or harmonised quantification of marine MP levels is essential to assess changes over time and evaluate success of plastic waste management. | |
