Scientists uncover 'missing' plastics deep in the ocean

Date:
February 2, 2022
Source:
Florida Atlantic University
Summary:
A new study unveils the prevalence of plastics in the entire water
column of an offshore plastic accumulation zone in the southern
Atlantic Ocean and implicates the ocean interior as a crucial
pool of 'missing' plastics. Results show that small microplastics
are critical, underexplored and integral to the oceanic plastic
inventory. In addition, findings show that weak ocean current
systems contribute to the formation of small microplastics hotspots
at depth, suggesting a higher encounter rate for subsurface particle
feeders like zooplankton.



FULL STORY ========================================================================== About 51 trillion microplastics are floating in the surface waters of
oceans around the world. Originating from various types of plastics,
these tiny fragments (less than 5 millimeters in length) pollute natural ecosystems.

Hundreds of studies have surveyed plastic debris on the surface or near
surface of the ocean. However, these studies only "scratch the surface,"
and do not provide a complete inventory of what's lurking beneath.


==========================================================================
A study led by Florida Atlantic University is the first to unveil the prevalence of plastics in the entire water column of an offshore plastic accumulation zone in the southern Atlantic Ocean and implicates the
ocean interior as a crucial pool of 'missing' plastics.

Results, published in the journal Global Change Biology, demonstrate
that small microplastics are critical, underexplored and integral to the oceanic plastic inventory. In addition, findings show that weak ocean
current systems contribute to the formation of small microplastics
hotspots at depth, suggesting a higher encounter rate for subsurface
particle feeders like zooplankton.

"Our study highlights the urgency for more quantification of the
deep-ocean microplastics, especially the smaller size fraction, to better understand ecosystem exposure and to predict the fate and impacts of these microplastics," said Tracy Mincer, Ph.D., senior author and an assistant professor of biology at FAU Harbor Branch Oceanographic Institute and
FAU Harriet L. Wilkes Honors College.

To gain a better mechanistic understanding of how plastics sink from the
ocean surface beyond the mixed layer and ultimately to abyssal depths of
the ocean, the researchers sampled plastic particles in the South Atlantic Subtropical Gyre using in-situ high-volume filtration, Manta net and
MultiNet sampling, combined with micro-Fourier-transform-infrared imaging.

They found that abundances and distribution patterns of small
microplastics varied geographically and vertially due to the diverse
and complex redistribution processes interacting with different plastic particles. They also observed large horizontal and vertical variations
in the abundances of small microplastics, displaying inverse vertical
trends in some cases. Small microplastics abundances in pump samples
were more than two orders of magnitude higher than large microplastics concurrently collected in MultiNet samples.



========================================================================== "Small microplastics are different from large microplastics with respect
to their high abundance, chemical nature, transport behavior, weathering stages, interactions with ambient environments, bioavailability and the
release efficiency of plastic additives," said Shiye Zhao, Ph.D., first
author and a post-doctoral fellow at FAU Harbor Branch. "These distinct characteristics impact their environmental fate and potential impacts
on marine ecosystems." Higher density polymers such as alkyd resins,
used in most commercial oil-based coatings such as ship hull paints and polyamide, commonly used in textiles like clothing and ropes and fishing
nets, made up more than 65 percent of the total pump sample count in the
study. This finding highlights a discrepancy between polymer compositions
from previous ocean surface-based surveys, which are typically dominated
by buoyant polymers such as polyethylene used for packaging film and
grocery bags and polypropylene used for plastic containers and reusable
water bottles.

Compared with net-collected large microplastics, small microplastics
particles are more highly oxidized and appear to have a longer lifetime
in the water column, suggesting increased marine ecosystem health risks
through possible bio-uptake of plastic particles and associated chemicals
and potential impacts to global biogeochemical cycles.

"As plastic particles disintegrate into smaller size fractions, they
can become harmful in different and unpredictable ways that are only now beginning to be understood," said Mincer. "These micron-size microplastics
can move across the gut epithelium, become trapped in biomass, and have
the potential to transfer through marine food webs, posing an unknown ecological risk and biogeochemical impacts." As commercial fishing
efforts scale up to harvest marine species for human consumption, the researchers say that studies focusing on smaller microplastics ingestion
are urgently needed to assess the extent of plastic contamination
in biomass.

The combined analysis procedure used by Mincer, Zhao and collaborators
from the Royal Netherlands Institute for Sea Research and Woods
Hole Oceanographic Institute provided a more integrative view of the distribution, abundance, dimensions and chemical nature of plastic
particles in the interior of an ocean gyre.

Study co-authors are Erik R. Zettler, Ph.D., a microbial ecologist with
the Royal Netherlands Institute for Sea Research; Ryan P. Bos, M.S.,
a Ph.D.

student at FAU Harbor Branch; Peigen Lin, Ph.D., a research associate at
Woods Hole Oceanographic Institute; and Linda A. Amaral-Zettler, Ph.D.,
a marine microbiologist and professor at the Royal Netherlands Institute
for Sea Research.

This work was supported by start-up funds from the Royal Netherlands
Institute for Sea Research to help fund the expedition. Funds for this
study were provided by the FAU World Class Faculty and Scholar Program
awarded to Mincer; a NOAA marine debris grant (NA17NOS9990024) awarded
to Amaral-Zettler and Mincer; and the American Chemistry Council awarded
to Amaral-Zettler, Zettler, and Mincer.

========================================================================== Story Source: Materials provided by Florida_Atlantic_University. Original written by Gisele Galoustian. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Shiye Zhao, Erik R. Zettler, Ryan P. Bos, Peigen Lin, Linda A.

Amaral‐Zettler, Tracy J. Mincer. Large quantities of
small microplastics permeate the surface ocean to abyssal depths
in the South Atlantic Gyre. Global Change Biology, 2022; DOI:
10.1111/gcb.16089 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220202111755.htm

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