Analysis of bamboo fibres and their associated dye in the parasite-host dynamics of freshwater fish

Abstract With the growth of the fashion and textile industries into the 21st Century, associated pollution has become pervasive. Of these pollutants, fibre-based microplastics are the most common types of plastics recovered from aquatic ecosystems encouraging the increased trend in organic fibre usage. Often marketed as biodegradable and ‘environmentally friendly’, organic textile fibres are seen as less harmful. Here, we assess the health effects of reconstituted bamboo viscose fibres, processed bamboo-elastane fibres (both at 700 fibres/L) and their associated dye (Reactive Black-5, at 1 mg/L) on fish, with an emphasis on disease resistance utilising an established host-parasite system: the freshwater guppy host (Poecilia reticulata) and Gyrodactylus turnbulli (monogenean ectoparasite). Following three weeks exposure to the bamboo fibres and associate dye, half the experimental fish were infected with G. turnbulli, after which individual parasite trajectories were monitored for a further 17 days. Overall, exposure to reconstituted bamboo-viscose fibres, processed bamboo-elastane fibres or dye were not associated with any change in host mortality nor any significant changes in parasite infection burdens. When analysing the routine metabolic rate (RMR) of fish, we noted that uninfected fish had, on average, significantly impacted RMR when exposed to processed bamboo elastane (increased RMR) and reconstituted bamboo viscose (decreased RMR). Hosts exposed to reconstituted bamboo viscose and the associated dye treatment showed significant changes in RMR pre- and post-infection. This study bolsters the growing and needed assessment of the potential environmental impacts of alternative non-plastic fibres; nevertheless, more research is needed in this field to prevent potential greenwashing.