Reducing the Uncertainty of Microplastic Identification and the Preferred Use of the Varnish clam (<i>Nuttallia obscurata</i>) as Compared to Other Bivalves as a Biomonitor of Plastic Pollution

By integrating both laboratory experiments and field studies, we demonstrate the efficacy of the varnish clam (Nuttallia obscurata) as a bioindicator for assessing microplastic pollution. By employing three spectral libraries: (1) a commercial library associated with FTIR instrumentation, (2) spectra derived from derelict shellfish aquaculture gear (DSAG), and (3) spectra representing six polymers commonly found in marine environments and naturally aged over 6 months, we confirm the clam’s ability to serve as an effective biomonitor and also its utility in pinpointing the origin of microplastics in biological matrices. This application enabled a direct relationship between DSAG and the microplastics ingested by the clam, as compared to approaches that report numbers of microplastics recovered from biological media without tracing their source. Furthermore, the use of targeted spectral libraries enhanced the accuracy of plastic composition identification. Use of such biomonitoring tools and the refinement of spectral libraries will help in evaluating the impact of plastic pollution mitigation policies, which in turn should facilitate progress toward a sustainable circular plastic economy.