Analysis of microplastics in wetland samples from coastal Ghana using the Rose Bengal stain

The use of optical microscope remains the most commonly used technique for microplastic identification and quantification despite major limitations with misidentifications and biases. We evaluated the use of the 1% Rose Bengal stain in improving the identification of microplastics after a standard microplastic isolation process. The stain discriminated organic materials from potential microplastics with significant differences between numbers observed before (6.65 ± 5.73) and after staining (2.91 ± 3.43). Numbers of potential microplastics observed under the conventional method (without staining) in sediment, feacal matter of shorebirds and the lagoon water were respectively 3.55 g, 0.8 g and 0.13 ml but reduced to 1.85 g of sediment, 0.35 g of feacal material and 0.09 ml of water after staining. Colour composition of potential microplastics under the conventional method was brown (31.0%), black (26.5%), white (20.2%), translucent (16.7%) and red (5.6%). After staining, brown (49,2%), black (30.5%) white (2.3%) and translucent (18.0%) were retained but distinction could not be made between stained organic items and red-coloured microplastics. It was clear that the stain has the potential in improving microplastic identification but requires further investigations.