4. Results
Identification by FT-IR spectroscopy confirmed that microplastics were abundant in all 12 sediment
samples and all coral samples. The microplastics were all fibrous in shape, were commonly 2–3 mm in
length and less than 0.1 mm in diameter (electronic supplementary material, figure S1). Plastic microfibre
abundance in the sediments ranged from 1.4 to 40 pieces per 50 ml (mean ± s.e.: 13.4 ± 3.5; figure 2), and
samples from four locations in the Indian Ocean showed that microplastics had also accumulated on
the surface of octocorals. The microfibres were mostly blue, black, green or red, although vibrant colours
such as pink, purple and turquoise were also seen. Rayon, which is a man-made non-plastic polymer, was
detected in all the samples (electronic supplementary material, figure S2a). It contributed to 56.9% of the
total number of fibres seen and was more than twice as abundant as polyester (electronic supplementary
material, figure S2b). Of the remaining fibres, polyester was the most prevalent (53.4%), followed by other
plastics (34.1%), which included polyamides and acetate, then acrylic (12.4%) (figure 2).