Relationship of Microplastics to Body Size for Two Estuarine Fishes

Ahmed K Gad,Stephen R Midway

doi:10.3390/microplastics1010014

Abstract

In the northern Gulf of Mexico, microplastics are reported in very high concentrations, which are thought to be partly sourced from the Mississippi River. This study sought to quantify microplastics across body size in two fish species, the hardhead catfish (Ariopsis felis) and southern flounder (Paralichthys lethostigma), common to Gulf of Mexico estuaries. We hypothesized that counts of ingested microplastics would be higher in smaller fishes than larger fishes. Fish were sampled in 2018 and 2019 across coastal Louisiana and represented a balanced range of length classes. Both species in our study ingested microplastics—25% of southern flounder and 15% of hardhead catfish. There was a significant positive effect of total length on microplastic loads in hardhead catfish. Due to the biological importance and management relevance of fish length, the study of microplastic loads and effects on fish may need to move beyond aggregating a species to considerations of individual size.

Highlights

Relationship of Microplastics to BodyMicroplastics are usually defined as plastics that are less than 5 mm in any dimension; there is no consensus lower size limit [1,2]
This study focuses on two fish species common to the northern Gulf of Mexico: hardhead catfish (Ariopsis felis) and southern flounder (Paralichthys lethostigma)
The ZIP for southern flounder estimated no effect of total length on microplastic counts (β 1 = −0.002, SE = 0.003, p-value = 0.35), total length was reported as a significant positive effect on microplastic counts in hardhead catfish (β 1 = 0.02, SE = 0.01, p-value = 0.03)

Summary

Introduction

Microplastics are usually defined as plastics that are less than 5 mm in any dimension; there is no consensus lower size limit [1,2]. Microplastics can be defined according to different characteristics such as their shape (e.g., fibers, foams, fragments, beads, or films) and their composition (usually referring to polymer type [3]). Microplastics are ubiquitous across most ecosystems and species, and estuaries are no exception. Multiple studies have documented microplastics in estuarine ecosystems. Estuarine fish species have been reported to contain microplastics. 38% of 120 fish sampled in the Mondego estuary in Portugal had ingested microplastics [6]. Kazour et al [7] reported microplastics in juvenile European Flounder (Platichthys flesus); 58% of wild European

Methods

Results

Conclusion