Due to the non-standard sampling mesh sizes used in the two
study areas, we calibrated the density of fibrous MPs in the Yangtze
Estuary with 333 lm mesh-sieves (Supplementary Information,
SI). Compared with the calibrated density value in the
Yangtze Estuary, the lower abundance of the ECS was mainly
attributed to the oceanic dilution (Mann–Whitney U test, all
p < 0.05). Simultaneously, the disparity between the original
(4137.3 ± 2461.5 n/m3) and calibrated (2984.7 ± 2219.3 n/m3) MP
densities in the Yangtze Estuary suggests that the employment of
smaller mesh sizes is more beneficial to the monitoring the MPs
in the water bodies.