Study first to tally biomass from oceanic plastic debris using
visualization method
Scientists obtain quantitative number for biomass -- First estimate of
its kind

Date:
October 13, 2020
Source:
Florida Atlantic University
Summary:
Scientists examined cell abundances, size, cellular carbon mass, and
how photosynthetic cells differ on polymeric and glass substrates
over time, exploring nanoparticle generation from plastic like
polystyrene and how this might disrupt microalgae. Conservative
estimates suggest that about 1 percent of microbial cells in the
ocean surface microlayer inhabit plastic debris globally. This
mass of cells would not exist without plastic debris in the ocean,
and thus, represents a disruption of the proportions of native
flora in that habitat.



FULL STORY ========================================================================== Trillions of plastic debris fragments are afloat at sea, creating the
"perfect storm" for microbial colonization. Introduced more than 50
years ago, plastic substrates are a novel microbial habitat in the
world's oceans. This "plastisphere" consists of a complex community
comprised of bacterial, archaeal, and eukaryotic microorganisms and
microscopic animals.


========================================================================== These unnatural additions to sea surface waters and the large quantity of
cells and biomass carried by plastic debris has the potential to impact biodiversity, ecological functions and biogeochemical cycles within
the ocean. Biofilm formation in the marine environment -- a collective
of one or more types of microorganisms that can grow on many different
surfaces -- is a complex process, involving many variables.

While several studies have surveyed microbial diversity and quantified
specific members of these biofilm habitats, a new study is the
first to holistically quantify total cell inventories under in situ
conditions. This study is fundamentally different from others due to
the relatively non-biased visualization methods used to arrive at a quantitative number for biomass, which is the first estimate of its kind.

Researchers from Florida Atlantic University's Harbor Branch Oceanographic Institute and Harriet L. Wilkes Honors College, in collaboration with
Utrecht University, Netherlands, the University of Amsterdam, and The
Royal Netherlands Institute for Sea Research (NIOZ), examined cell
abundances, size, cellular carbon mass, and how photosynthetic cells
differ on polymeric and glass substrates over time. They investigated nanoparticle generation from plastic such as polystyrene, which is known
to disintegrate into nanoparticles in sunlight and ultraviolet radiation,
and how this might disrupt microalgae.

Results of the study, published in the ISME Journal, a monthly
publication of the International Society for Microbial Ecology, reveal
that by measuring the average microbial biomass carrying capacity of
different plastic polymers and, by extension, plastic marine debris in
the global ocean, conservative estimates suggest that about 1 percent of microbial cells in the ocean surface microlayer inhabit plastic debris globally. This mass of cells would not exist if plastic debris was not
in the ocean, and therefore, represents a disruption of the proportions
of native flora in that habitat.

"In the open ocean, nutrients are limiting. Just like we need to put
fertilizer on a garden, microorganisms in the ocean are limited by
nitrogen, iron or phosphorus depending upon where they are -- except in
the open ocean, there is typically no fertilizer, so something has to
die for another organism to live," said Tracy Mincer, Ph.D., lead author
and an assistant professor of biology/ bio-geochemistry at FAU's Harbor
Branch and Wilkes Honors College. "With the advantage of a surface, which concentrates nutrients, organisms colonizing plastics in the ocean are
taking up those limiting nutrients that normally would have been consumed
or out-competed by free-living microbes. So essentially, these microbes
on plastics are taking habitat space away and represent the beginning
of a regime shift for these habitats." Using confocal laser scanning microscopy with sophisticated imaging software, researchers directly
obtained data ranging from cell counts, size and the characterization of microbial morphotypes to complete three-dimensional constructs. They
tested a range of chemically distinct substrates that included
polypropylene, polystyrene, polyethylene and glass. Polypropylene is
used by the automotive industry, for consumer goods such as packaging, industrial applications and the furniture market; polystyrene is used
to make clear products like food packing or laboratory equipment; and polyethylene is the most widely used plastic in the world ranging from
products such as clear food wrap to shopping bags to detergent bottles.

Data from the confocal laser scanning microscopy showed that early
biofilms displayed a high proportion of diatoms (unicellular eukaryotic microalgae that have cell walls made of glass). These diatoms could
play a key role in the sinking of plastic debris. Unexpectedly, plastic substrates appeared to reduce the growth of photosynthetic cells after
eight weeks compared to glass.

"The quantification of cell numbers and microbial biomass on plastic
marine debris is crucial for understanding the implications of plastic
marine debris on oceanic ecosystems," said Shiye Zhao, Ph.D., first author
and a post- doctoral fellow at FAU's Harbor Branch. "Future efforts
should focus on how this biomass fluctuates with season and latitude
and its potential to perturb the flux of nutrients in the upper layers
of the ocean."

========================================================================== 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, Linda A. Amaral-Zettler, Tracy
J. Mincer.

Microbial carrying capacity and carbon biomass of plastic marine
debris.

The ISME Journal, 2020; DOI: 10.1038/s41396-020-00756-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201013105744.htm

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