Microplastic Intake, Its Biotic Drivers, and Hydrophobic Organic Contaminant Levels in the Baltic Herring

Martin Ogonowski,Evelyne Hamacher-Barth,Viktoria Wenman,Andreas Barth,Sara Danielsson,Elena Gorokhova

doi:10.3389/fenvs.2019.00134

Abstract

It is commonly accepted that microplastic (MP) ingestion can lead to lower food intake and bioaccumulation of hydrophobic organic contaminants (HOCs) in aquatic organisms. However, causal links between MP and contaminant levels in biota are poorly understood and in situ data are very limited. Here, we investigated whether HOC concentrations in herring muscle tissue (Clupea harengus membras) are related to MP ingestion using fish caught along the West coast of the Baltic Sea. The MP occurrence exhibited a large geographic variability, with MP found in 22.3% of the fish examined, and the population average being 0.9 MP ind-1. However, when only individuals containing MP were considered, the average MP burden was 3.9 MP ind-1. We also found that MP burden decreased with reproductive stage of the fish but increased with its body size. To predict MP abundance in fish guts, we constructed a mass-balance model using literature data on MP in the water column and physiological rates on ingestion and gut evacuation for clupeids of a similar size. The model output was in agreement with the observed values, thus supporting the validity of the results. Contaminant concentrations in the muscle tissue varied substantially across the study area but were unrelated to the MP levels in fish, suggesting a lack of direct links between the levels of HOCs and MP ingestion. Thus, despite their ubiquity, MP are unlikely to have a measurable impact on food intake or the total body burden of hydrophobic contaminants in Baltic herring.

Highlights

Plastic debris, including microplastics (MP < 5 mm), can be ingested by aquatic animals across several trophic levels (Cole et al, 2013; Lusher et al, 2013, 2015)
A commonly held paradigm states that MP ingestion can lead to decreased nutritional status (Cole et al, 2015; Ogonowski et al, 2016) and bioaccumulation of hydrophobic organic chemicals (HOCs) (Rochman et al, 2013; Wardrop et al, 2016) that sorb to the MP particles in the water and desorb in the gut lumen (Rochman et al, 2014)
Microplastics were found in about 20% of the fish. While these values are in good agreement with those reported for herring by Beer et al (2018) for the central Baltic Sea (i.e., 20% containing MP, with 93% fibers), other studies report considerably lower MP frequency of occurrence and fiber contribution to total MP in herring

Summary

Introduction

Due to the importance of commercial fish and shellfish species for human consumption, the ingestion and presence of MP in these animals has become a matter of concern (EFSA Panel on Contaminants in the Food Chain (CONTAM), 2016). To address this concern and to provide a quantitative assessment of MP ingestion in various fish species, an active research is ongoing (Foekema et al, 2013; Lusher et al, 2013; Rummel et al, 2016; Beer et al, 2018; Budimir et al, 2018; Markic et al, 2019). The relative importance of microplastics as vectors for contaminant transport remains unresolved, possibly due to the lack of field data linking HOC concentrations in biota to ingested MP in ecologically relevant settings

Methods

Results

Discussion

Conclusion