The fate of conventional and potentially degradable gillnets in a seawater-sediment system

Abandoned gillnets in the marine environment represent a global environmental risk due to the ghost fishing caused by the nets. Degradation of conventional nylon gillnets was compared to that of nets made of polybutylene succinate co-adipate-co-terephthalate (PBSAT) that are designed to degrade more readily in the environment. Gillnet filaments were incubated in microcosms of natural seawater (SW) and marine sediments at 20 °C over a period of 36 months. Tensile strength tests and scanning electron microscopy analyses showed weakening and degradation of the PBSAT filaments over time, while nylon filaments remained unchanged. Pyrolysis-gas chromatography/mass spectrometry revealed potential PBSAT degradation products associated with the filament surfaces, while nylon degradation products were not detected by these analyses. Microbial communities differed significantly between the biofilms on the nylon and PBSAT filaments. The slow deterioration of the PBSAT gillnet filaments shown here may be beneficial and reduce the ghost fishing periods of these gillnets. •Seawater incubation showed slow degradation of PBSAT, but not of nylon gillnets.•PBSAT degradation in seawater was associated with potential degradation products.•No degradation products were associated with incubation of nylon filaments in seawater.•Microbial biofilms on the PBSAT and nylon gillnet filaments differed significantly.•Deterioration of PBSAT filaments may reduce ghost fishing periods of these gillnets.