Measuring the abundance and distribution of microplastics and marine organisms across the surface of the equatorial Pacific using a Manta Net

Abstract

The increasing production of plastics and their long lifespan have led to concerns about the accumulation of microplastics in marine environments. Due to their ability to be mistaken for food, microplastics act as a source of toxic chemicals in oceanic food chains, posing a threat to organisms that encounter them. To understand how microplastics can harm marine ecosystems, we need better measurements of their abundance and distribution in the global ocean. There remains a large gap in knowledge between statistical predictions of microplastic distribution and field data across the equatorial Pacific as its remote location makes observations difficult. Aboard the R/V Thomas G. Thompson from February 23 to March 13, 2023, this study quantified the accumulation of microplastics using a Manta net across a meridional transect from Honolulu, Hawaii to Suva, Fiji. In each net tow, the diversity and relative abundance of surface organisms were quantified to determine the organisms potentially affected by the accumulation of plastics. The highest-counted organisms (20-260 #/𝑚 ) were copepods. Plastic concentrations 3 were highest (4. 2 × 10 #/ ) close to the Hawaii coast and lowest ( #/ ) at the −2 𝑚3 2. 9 × 10−3 𝑚3 equator (0°) with there being no significant variation between samples collected along the equatorial transect. Available numerical models generally over-predicted plastic concentrations. In situ microplastic measurements, as performed in this study, will provide critical data for improving numerical models to better understand the current state of microplastics in marine ecosystems.