European sea bass absorb virtually no microplastic in their muscle
tissue

Date:
July 20, 2020
Source:
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine
Research
Summary:
Researchers gave young European see bass feed laced with
microplastic for months, but found virtually no microplastic
particles in the fish fillets.



FULL STORY ==========================================================================
In a new laboratory study, experts from the Alfred Wegener Institute,
Helmholtz Centre for Polar and Marine Research (AWI) investigated how
many microplastic particles would be absorbed in the muscle tissue
of young European sea bass after being given feed with extremely high microplastic particle content for a period of four months. At least with
regard to this particular food fish, their findings are good news: only an extremely small percentage of the plastic particles ingested found their
way into the fish fillets; the majority were excreted. The experts take
this finding as a first indication that fish fillets can still be safe
for human consumption, even if the fish eaten are subjected to extreme microplastic pollution. Their study has now been published in the July
issue of the journal Marine Pollution Bulletin.


==========================================================================
By now, fish are subjected to microplastic particles in all of their
habitats - - in rivers, lakes and seas, as well as aquaculture. Further,
it has been confirmed that the animals ingest these tiny particles
together with their food. In a new study conducted at the Centre for Aquaculture Research, part of the Alfred Wegener Institute, Helmholtz
Centre for Polar and Marine Research (AWI) in Bremerhaven, scientists
have for the first time investigated how many of the ingested particles
make their way from the sea bass' digestive tract to the bloodstream,
and subsequently to the muscle tissue. "This question is relevant for us
human beings, especially because, as a rule, we don't eat the whole fish, including its innards, but only the fillets," explains Dr Sinem Zeytin,
an AWI biologist and first author of the study.

For the laboratory experiment, adolescent European sea bass (Dicentrarchus labrax) were fed pellets consisting of fish meal, wheat bran, vitamins and
fish oil, which the scientists had laced with a powder of yellow-orange fluorescing microplastic particles, for 16 weeks. The particles had a
diameter of one to five micrometres (thousandths of a millimetre), so as
to be representative of the smallest size category for microplastic. In
the course of the experiment, every sea bass ingested roughly 163 million
of these microscopically small plastic particles. Once the experiment
was over, the experts filleted the fish to measure the particle content,
while also gathering samples from their blood, gills, intestinal tract
and internal organs like the liver for subsequent analysis. They heated
part of the fillets in caustic potash, which completely dissolved the
muscle tissue. The resultant fluid was then pressed through a filter
that captured all of the plastic. They counted the number of particles
present using a fluorescence microscope -- first manually, and then
using an automated technique.

One to two microplastic particles per five grams of fish fillet The
results came as a pleasant surprise to the researchers. "Even though
we subjected the sea bass to extremely high microplastic pollution
in comparison to their natural setting, in the end there were only
1 or 2 particles in every five grams of their fillets," Sinem Zeytin
reports. "This, along with the fact that the fish grew very well and
were in perfect health, tells us that the fish can apparently isolate
and excrete these particles before they have a chance to penetrate their tissues. For everyone who enjoys eating sea bass, that's very good news,"
adds Dr Matthew Slater, Head of the Aquaculture Research Group at the AWI.

As Slater explains, due to the nature of the study, it's also possible
that those microplastic particles detected weren't actually in the
muscle cells, but instead in the tiny amounts of residual blood in the
fillets. "In fact, during our study we found virtually no indications that
the particles pass from the blood into the muscle cells," the AWI expert explains. That being said, initial analyses of other tissues confirmed
that the particles do pass from the digestive tract to the bloodstream.

But how do the microplastic particles get from the digestive tract to
the bloodstream? According to Sinem Zeytin, "So far, we have identified
two ways: either the microscopically small plastic fragments manage to
squeeze between two cells in the intestinal wall, or special transporter
cells actively separate the particles from the remainder of the feed and
pass them on, just like they do with minerals and nutrients." Which of
these two processes is predominant, whether there are other processes,
and just how particle transport works in each one are questions the
experts will seek to answer in future experiments.

The study was a joint project involving experts from the Alfred Wegener Institute, the University of Bremen, and the laboratory IBEN GmbH in Bremerhaven. The cultivation and killing of the sea bass for research
purposes were done with prior written consent from the Office for Consumer Protection, Veterinary Medicine and Plant Protection, part of Bremen's Senatorial Authorities for Science, Health and Consumer Protection.


========================================================================== Story Source: Materials provided by Alfred_Wegener_Institute,_Helmholtz_Centre_for_Polar_and
Marine_Research. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Sinem Zeytin, Gretchen Wagner, Nick Mackay-Roberts, Gunnar Gerdts,
Erwin
Schuirmann, Sven Klockmann, Matthew Slater. Quantifying
microplastic translocation from feed to the fillet in European
sea bass Dicentrarchus labrax. Marine Pollution Bulletin, 2020;
156: 111210 DOI: 10.1016/ j.marpolbul.2020.111210 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200720112220.htm

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