Interactions of anthropogenic microfibres with the marine macroalga, Ulva lactuca

Little information exists on the interactions between microfibres (MFs) and marine macroalgae. In this study, the translucent green seaweed, Ulva lactuca, has been exposed to ∼2 mg L⁻¹ suspensions of MFs prepared from dryer lint under controlled conditions, with MFs on the alga surface and remaining in seawater subsequently counted and characterised. MFs were mainly <2 mm and cellulosic, and contained various additives and chemicals used in textile treatment. Interactions of MFs with U. lactuca were spatially heterogeneous but correcting for pre-existent MFs on the surface, mean trapping efficiencies on a dry mass and surface area basis were 252 mL g⁻¹ and 0.858 mL cm⁻², respectively. Despite this heterogeneity, there was evidence of differential trapping based on fibre colour and length. Interactions between the amphiphilic algal surface and MFs are likely both hydrophobic and electrostatic and are not fully reversible, with only ∼30 % of trapped MFs released into clean seawater. Associations with U. lactuca have implications for the transport, fate and ecological impacts of MFs in the coastal zone, and highlight the potential for harvested seaweed to be used in bioremediation.