The vertical distribution and biological transport of marine microplastics across the epipelagic and mesopelagic water column

Abstract

Plastic waste has been documented in nearly all types of marine environments and has been found in species spanning all levels of marine food webs. Within these marine environments, deep pelagic waters encompass the largest ecosystems on Earth. We lack a comprehensive understanding of the concentrations, cycling, and fate of plastic waste in sub-surface waters, constraining our ability to implement effective, large-scale policy and conservation strategies. We used remotely operated vehicles and engineered purpose-built samplers to collect and examine the distribution of microplastics in the Monterey Bay pelagic ecosystem at water column depths ranging from 5 to 1000 m. Laser Raman spectroscopy was used to identify microplastic particles collected from throughout the deep pelagic water column, with the highest concentrations present at depths between 200 and 600 m. Examination of two abundant particle feeders in this ecosystem, pelagic red crabs ( Pleuroncodes planipes ) and giant larvaceans ( Bathochordaeus stygius ), showed that microplastic particles readily flow from the environment into coupled water column and seafloor food webs. Our findings suggest that one of the largest and currently underappreciated reservoirs of marine microplastics may be contained within the water column and animal communities of the deep sea.

A Global Perspective on Microplastics

“…Polymers may be weathered and thus produce spectra deviating from virgin standards, complicating identification. In response, some researchers have created their own libraries of weathered materials to assist identification (e.g., Choy et al, ). Attenuated total reflectance FTIR and atomic force microscopy have also been used but require physical contact of the probe with the targeted material.…”

“…This is a theoretical prediction yet useful for understanding the dynamics of microplastic sinking following biofilm growth. Choy et al () sampled microplastics between 100 and 5,000 μm in water along vertical transects off Monterey Bay, California, using remotely operated vehicles. They observed maximum concentrations between 200 and 600 m. The microplastics observed were dominated by weathered polyethylene terephthalate and polyamide fibers.…”

Solving the plastic problem: From cradle to grave, to reincarnation

“…Many of the particles were of PET and thus cannot be accounted for by fishing gear, and were 'weathered', which suggests that they had been in the ocean for months or years and transported there by ocean currents. 64 It was noted that the maximum concentration present (16 microplastics m −3 ) is greater than the highest concentration found in the Great Pacific Garbage Patch (12 microplastics m −3 ); 65 although the average concentration there is far lower. 66 It is noteworthy 60 that concentrations, larger by up to 3 orders of magnitude than those determined using trawl nets, of microparticles (synthetic, semi-synthetic (e.g.…”

“…Since the levels were far higher than those measured in neighbouring areas where heavy industry operates, it appears that the amphipods are bioaccumulating these anthropogenic pollutants, which are pervasive across the world's oceans and to full ocean depth. 46 Evidence for the distribution of microplastics through the ocean column is provided by a study 64 1000 m) water columns, as measured in the offshore waters of the Monterey Bay pelagic ecosystem. The highest concentration of ocean microplastics was found at depths between 200 and 600 m (Figure 7).…”

Microplastics increase the marine production of particulate forms of organic matter

“…nano and microplastics) would facilitate their interaction with living organisms and autochthonous organic matter. In fact, such interactions may be a major pathway to the removal of plastic from the marine environment (GESAMP 2016, Koelmans et al 2017, Choy et al 2019.…”