Weathering effects on microplastic production in fishing rope hauler operations: mechanical abrasion

While land-basd sources of plastic pollution have garnered increasing attention in recent years, ocean-based sources have been less thoroughly examined. The objective of this study was to quantify and characterize the production of microplastics on the surface of fishing ropes during the operation of a hauler on a fishing boat. The simulation of the fishing process (operating the hauler) was conducted in two phases to assess quantification, size distribution, and shapes of particles produced from the fishing ropes due to mechanical abrasion with the hauler.

Initially, we simulated the fishing operation using the hauler with varying weights at 0, 5, 10, 15, and 20 kg (weight-varied hauler simulation, WVHS). Subsequently, we simulated the fishing operation using the hauler according to the frequency of hauler operation (0, 5, 10, 15, and 20 times) with weights of 5kg and 50kg (frequency-varied hauler simulation, FVHS). All fragmented particles were identified using a FTIR microscope (Nicolet iN10 MX; Thermo Fisher Scientific) equipped with a linear array detector, employing 25 μm steps over one section (~12 × 12 mm) in reflection mode.

In the results of WVHS experiment, the abundance of fragmented particles larger than 10 mm on the surface of the PP rope increased with the weight due to mechanical abrasion. The observed values were 31±1.2 particles/m (5kg), 52±21 particles/m (20kg), 69±44 particles/m (35kg), and 77±5.7 particles/m (50kg) when lifting each weight using the hauler. The estimated regression equation was y=1.383x+15.538 (F=4.585, p=0.001). In the FVHS experiment, the abundance of produced particles peaked at 10 times and subsequently sustained a steady state in particle abundance for the 5 kg weight. For the 50 kg weight, the peak occurred at 5 times of hauler simulation, with subsequent reductions and a steady state in particle abundance. Our research offers essential information to estimate the microplastic production on fishing ropes during hauler operating, providing valuable insights into the impact of fishing activities on microplastic production in marine environments.