Mesh selectivity of neuston nets for microplastics.

Area of Science:

• Marine science
• Environmental science
• Oceanography

Background:

• Microplastic pollution is a growing global concern.
• Accurate quantification of microplastics is essential for understanding their environmental impact.
• Neuston nets are commonly used for microplastic sampling in marine environments.

Purpose of the Study:

• To compare the microplastic collection efficiency of two neuston nets with different mesh sizes (1.00 mm and 0.333 mm).
• To estimate the mesh selection curves for microplastics using both net sizes.
• To assess the underestimation of microplastic abundance by the 0.333 mm net, a standard sampling mesh size.

Main Methods:

• Parallel towing of two neuston nets with 1.00 mm and 0.333 mm mesh openings.
• Comparison of microplastic size distributions collected by both nets.
• Application of SELECT analysis to estimate the mesh selection curve for the 1.00 mm net.
• Estimation of the selection curve for the 0.333 mm net based on geometrical similarity.

Main Results:

• The 0.333 mm net collected more microplastics (longest length ≤2.00 mm) than the 1.00 mm net.
• An estimated 60% of microplastics sized 0.4-1.0 mm passed through the 0.333 mm mesh, remaining unaccounted for.
• The 0.333 mm net retained only 1.5% of microplastics ≤0.4 mm and rarely captured particles ≤0.3 mm.

Conclusions:

• The 0.333 mm neuston net significantly underestimates microplastic abundance, particularly for smaller size fractions.
• Standard microplastic sampling with 0.333 mm nets leads to substantial data loss for particles <1.0 mm.
• Further research is needed to develop more efficient sampling methods for smaller microplastics to improve environmental monitoring.