Uptake and Retention of Nanoplastics in Quagga Mussels.

Rachel L Merzel,Mark M Banaszak Holl,Ashley K Elgin,Melissa Duhaime,Lauren Purser,Isabel Colón‐Bernal,Taylor L Soucy,Monica Olszewski

doi:10.1002/gch2.201800104

Abstract

Here, a set of experiments to assess the feasibility of using an invasive and widespread freshwater mussel (Dreissena rostrformis bugensis) as a sentinel species for nanoplastic detection is reported. Under laboratory experimental conditions, mussels ingest and retain fluorescent polystyrene (PS) beads with carboxylic acid (—COOH) termination over a size range of 200–2000 nm. The number of beads the mussels ingested is quantified using fluorescence spectroscopy and the location of the beads in the mussels is imaged using fluorescence microscopy. PS beads of similar size (1000–2000 nm) to mussels' preferred food are trafficked in the ciliated food grooves of the gills. Beads of all sizes are observed in the mussels' digestive tracts, indicating that the mussels do not efficiently reject the beads as unwanted foreign material, regardless of size. Fluorescence microscopy shows all sizes of beads are concentrated in the siphons and are retained there for longer than one month postexposure. Combined atomic force microscopy–infrared spectroscopy and photothermal infrared spectroscopy are used to locate, image, and chemically identify the beads in the mussel siphons. In sum, these experiments demonstrate the potential for using mussels, specifically their siphons, to monitor environmental accumulation of aquatic nanoplastics.

Highlights

Aquatic microplastics are currently the focus of intense research efforts and are generally recognized as a substantial problem due to their pervasiveness, persistence in the environment, and potential toxicity.[1,2,3,4,5,6,7,8,9]. Microplastics are of such interest and concern because they are ingested by aquatic organisms, either unintentionally or when they are mistaken for food, e.g., algae or plankton of similar size.[10,11,12]
The focus on larger microplastics is not surprising given the challenges associated with analyzing smaller plastics, as highlighted in this article
With the 1,000 nm PS beads, fluorescence microscopy demonstrated that the mussels move the beads through the gills in the same manner as described for food particles (Figure 1).[34]

Summary

Introduction

Aquatic microplastics are currently the focus of intense research efforts and are generally recognized as a substantial problem due to their pervasiveness, persistence in the environment, and potential toxicity.[1,2,3,4,5,6,7,8,9] Microplastics are of such interest and concern because they are ingested by aquatic organisms, either unintentionally or when they are mistaken for food, e.g., algae or plankton of similar size.[10,11,12] When ingested, they have the potential to disrupt physiological processes in aquatic life and biomagnify up the food chain, including into humans.[13,14,15,16,17] As such, there have been substantial efforts to characterize the concentrations, identities, and sources of aquatic microplastics. The term “microplastic” technically refers to plastics over the micron size range: 1-1000 m. The term has been ascribed operationally to a variety of size ranges, including 333 m to > 5,000 m,[18] 106 m to > 4,750 m,[8] anything smaller than 1 cm (10,000 m)[3] and anything smaller than 5 cm.[9] The focus on larger microplastics is not surprising given the challenges associated with analyzing smaller plastics, as highlighted in this article

Objectives

Methods

Results