Abstract/Summary

Microplastics (MP) are now a ubiquitous pollutant in aquatic environments, they can be manufactured (primary) or result from degradation of larger plastics (secondary). The most numerous MP found in aquatic environments are microfibres (MF), these MF occur from degradation of rope and textiles. A novel method for producing MF and exposing the amphipod Gammarus pulex to MF using algal wafers was devised, along with a protocol to compare feeding choices between two food options. Feeding choices between uncontaminated wafers and a variety of MF were investigated. It was found that all MF <50µm were ingested (acrylic, cat hair and cotton) were ingested, but none >50µm were (Oris ovis 70µm, Human hair 50-100µm). Gammarus pulex showed avoidance to feeding on acrylic MF when given a choice of uncontaminated wafers, this avoidance was not observed with either cat or cotton fibres. This implies that acrylic MF were either not recognised as food or were in some way repellent. When given the option between combinations of wafers contaminated with different fibres, G. pulex showed avoidance to acrylic when the other choice was either cat or cotton. When parasitised by Polymorphous minutus, G.pulex have been shown to alter their feeding behaviour. However, the same avoidance of acrylic MP was observed, although this avoidance was not statistically significant, no other impact from P minutus was observed. It was found that G. pulex would not ingest glitter in sizes 800 - 100µm. The ingestion of MF seems limited by size and composition impacts feeding preferences, with organic MF or no contamination being preferred to synthetic MF contamination. While feeding preferences were impacted, no MF had any impact on either growth or mortality during a 28-day exposure. The implications for these observed impacts upon G. pulex and the environment are further discussed.