Distinct toxicity profiles of conventional and biodegradable fishing nets’ leachates after artificial aging

Fishing nets (FNs) represent a significant source of plastic waste, but their contribution to pollution by micro- and nanoplastics (MNPs) and associated additives is poorly understood. We studied the degradation of a high-performance-polyethylene-polypropylene (HPPE-PP) trawl net and two trammel nets made of polyamide 6 (PA6) or biodegradable polybutylene-succinate-polybutyrate-adipate-terephthalate (PBS-PBAT). Accelerated artificial ageing (AA) was performed using UV irradiation under environmental or extreme conditions followed by abrasion in water with glass microbeads. FN degradation and organic compound release were studied as well as the toxicity of leachates on the marine bacteria Allivibrio fischeri and larvae of the fish Oryzias latipes . AA of FNs under environmental conditions caused slight polymer degradation and did not produce significant MNPs. However, under extreme conditions, PA6 and PBS-PBAT FNs produced 9.1×10 4 MP/mL and 2.0×10 4 MP/mL, respectively. FNs released a total of 27 organic compounds in the leachates from which 7 were quantified at concentrations between 0.35 µg/L (Phthalimide) to 200 µg/L (Succinic-acid 2-methylallyl-undecyl-ester). Only the PBS-PBAT FN leachates induced significant toxicity on bacteria, bioluminescence inhibition ranging from 26% to 56%. Exposure of fish larvae to leachates of AA FNs disrupted their behavior. PBS-PBAT FN leachates caused the highest behavior stress indicator at day 12 (8.5), followed by PA6 at day 25 (8) and HPPE-PP at day 12 (7). We concluded that the toxicity of FN leachates was related more to the release of organic compounds than to the release of MPs. The toxicity of bio-based and biodegradable FNs should be further evaluated before their wider implementation in the fishing sector. The main goal of this work was to investigate potential toxic effects for aquatic organisms of leachates of artificially aged plastic fishing nets. By studying the degradation of these materials, we have proved their contribution to plastic and organic compound pollution and their deleterious effects on aquatic species. Our findings demonstrate that fishing nets can release micro and nanoplastics and soluble organic compounds during degradation. Importantly, we have demonstrated that plastic degradation products are toxic to aquatic species of two different trophic levels. Furthermore, all the three studied fishing nets are toxic, including the partially biobased and biodegradable one, indicating that these are not yet sufficiently sustainable to replace conventional nets. In conclusion, our research highlights that leachates of plastic fishing nets could represent a threat to aquatic organisms. • Fishing nets under extreme aging conditions produced microplastics and nanoplastics • Fishing nets released soluble organic compounds that were toxic to aquatic species • Leachate toxicity varied among fishing nets and increased with aging time • Fishing net leachates significantly disrupted behaviour of fish larvae • Toxicity of biobased and biodegradable nets was similar to that of conventional nets