Fig. 3

Comparison of segmenting microplastics and background with different softwares. A Global automatic thresholding was applied to binarize the image with the software by a microscope manufacturer. The original image was overlaid with the binary image. Measured microplastics are displayed in red with a turquoise edge. The red boxes mark small particles that were not detected by the computer algorithm. B Binary image obtained by global automatic thresholding using the Otsu’s computer algorithm in FIJI ImageJ [90]. Microplastics are shown in white. The red boxes mark the same small particles as in the left image, but in this case they were measured by the computer algorithms