Marine plastispheres as interfaces for trace metal biosorption: ATR-FTIR and chemometric fingerprinting of copper- and arsenic-induced biochemical changes

The surface of plastic immersed in (sea)water is rapidly colonized by complex microbial communities embedded within a self-produced matrix of extracellular polymeric substances (EPS), forming a biofilm called plastisphere. This matrix is composed of various biomolecules containing functional groups that promote the biosorption and further transport of metals within aquatic ecosystems, which may present a serious ecotoxicological risks. The present study investigates the biochemical changes within the plastisphere induced by metal exposure. For this purpose, polyethylene (HDPE) plastics were immersed in Toulon Bay (France) for 4 weeks allowing natural biofilm development. After recovery, the colonized plastics were exposed ex situ to copper (Cu) or arsenic (As) for 1 h, 15 h and 24 h. ATR-FTIR spectroscopy coupled with chemometrics were used to highlight the biochemical fingerprints over time in the metal-exposed plastispheres and to identify chemical functions within EPS matrix potentially involved in metal biosorption. At the same time, experiments of metal biosorption dynamics were conducted to simulate the realistic drift of plastics from a metal-contaminated seawater to a non-contaminated seawater. As results, ATR-FTIR emphasized the biochemical changes in the plastisphere exposed to a metal pressure. The main functional groups involved and highlighted by chemometrics were associated with carbohydrates and proteins confirming their central role in metal interactions. The work presented here highlights the success of combining ATR-FTIR spectroscopy and chemometrics as biochemical fingerprinting tools. Plastics should be regarded as biological interfaces which participate in the metal dynamics in marine ecosystems with potential health risks associated.