Ecotoxicity of fishing nets leachates after up to one year of in situ weathering in two harbors of the Bay of Biscay

All oceans are contaminated by plastics that are displaying various shapes, sizes or polymer type. Several sectors of activity can contribute to this pollution and the fishing sector is one of them. However, the toxicity of degradation products of fishing nets (FNs) to aquatic organisms remains scarcely studied to date, especially when weathered. In this study, we analyzed the degradation of environmentally weathered FNs and the toxicity of their leachates. Six different fishing nets made of polyamide 6 (PAØ33, PAØ35, PAØ95), poly-butylene-succinate-co-butyrate-co-adipate-co-terephthalate (PBSØ35, PBSØ60) and co-high-performance-polyethylene-polypropylene (HPPEØ4.25) were selected. FNs were weathered in the harbors of Arcachon (New Aquitaine, France) and Pasaia (Basque Country, Spain) during 0, 1, 3, 6 and 12 months (named hereafter T0, T1, T3, T6 and T12, respectively). The leaching of FNs was done over 24h in deionized water at 190 rpm. The toxicity of FN leachates was tested on the marine bacteria Aliivibrio fischeri and the fish Oryzias latipes at larval stage. Different endpoints were analyzed such as the inhibition of the bioluminescence for the marine bacteria, and the mortality, swimming ability and changes in the behavior for the fish larvae.

Overall, results on bacteria showed that between 0 and 78% of the bioluminescence was inhibited by FN leachates. At Arcachon, leachates of PAØ35, PAØ95 and PBSØ60 showed a higher toxicity at T3 compared to T6. Then at T12, all leachates (except for PBSØ60) showed a higher toxicity compared to T6. Regarding Pasaia harbor, the PBSØ60 leachate showed a decreasing toxicity between T0 and T1. Leachates of PAØ35, PAØ33 and HPPEØ4.25 showed a higher toxicity at T3 compared to T1 and T6, while the same samples showed a higher toxicity at T12 compared to T6. The non-linear kinetics of the toxicity of FN leachates could be due to complex interactions with the surrounding environment. Indeed, plastics can adsorb or desorb pollutants from and into the marine environment. As such, the higher toxicity at T3 and T12 could be related to the sorption of pollutants from the surrounding water and the lower toxicity at T6 may be due to the desorption of FN additives or pollutants. Nevertheless, the toxicity of FN leachates can also be influenced by other factors like the presence of a biofilm and the aging of the FN.

The toxicity kinetics of samples collected at T3 and T12 on fish larvae will also be discussed. Preliminary results show that there were no effects on spinal deformations and swimming ability for all FN leachates. The leachate of PAØ95 from Arcachon showed a slightly higher mortality at T12 compared to T3. However, all other leachates did not show any effect on the mortality of fish larvae. Nevertheless, the analysis of fish behavior will provide additional results in order to discuss the potential sub-lethality of these samples.

 

*Project funded by PNM-BA, the French Water Agency Adour-Garonne, the Spanish MCIU (FIERA project PID2021- 128600OB-I00), the Basque Government (consolidated research group IT1743-22 and postdoc to NGS), and Euskampus Fundazioa (PLASFITO project and the Laboratory for Transboder Cooperation LTC AquEus).