Yahoo – AFP,
Amélie BOTTOLLIER-DEPOIS, August 18, 2019
 |
Like canaries in a coal mine, mussels have long been used as 'bio-indicators' of the health of the seas, lakes and rivers they inhabit (AFP Photo/JOEL SAGET) |
Paris (AFP)
- Seafood lovers who prize the mussel for its earthy taste and succulent flesh
may be unaware of its growing potential in the fight against water pollution.
The mussel
is the hoover of the sea, taking in phytoplankton for nourishment along with
microplastics, pesticides and other pollutants -- which makes it an excellent
gauge.
One day, it
may also be pressed into service to cleanse water.
"It's
a super-filter in the marine world, filtering up to 25 litres of water a
day," says marine biologist Leila Meistertzheim.
"It's
a real model of bioaccumulation of pollutants generally speaking."
As they
pump and filter the water through their gills in order to feed and breathe,
mussels store almost everything else that passes through -- which is why strict
health rules apply for those destined for human consumption.
Like
canaries in a coal mine, mussels have long been used as
"bio-indicators" of the health of the seas, lakes and rivers they
inhabit.
Little-known
pollutants can turn up to join the usual suspects, with increasing attention
paid to microplastics containing bisphenol A and phthalates, both thought to be
endocrine disruptors.
Meistertzheim
heads a study for France's Tara Ocean Foundation using mussels to gauge the
health of the estuaries of the Thames, Elba and Seine rivers.
The
mussels, placed in fish traps, are submerged in the waters for a month before
researchers dissect them to determine what chemical substances lurk in their
tissues.
The idea of
deploying mussels across the oceans to absorb ubiquitous microplastics is just
a dream for now, but for other pollutants, the bivalves are already at work.
"In
some places, mussels are used, as well as oysters, to cleanse the sea of
pesticides, for example," Meistertzheim notes.
E. coli
busters
Richard
Luthy, an environmental engineer from California's Stanford University, says that,
in most cases, mussels harvested from contaminated waters should not be eaten.
But if the
contaminant is E. coli, mussels can be thanked for the "removal and
inactivation" of the faecal material, he says, calling the service a
"public health benefit".
The mussels
are edible because they "excrete the bacteria as faeces or mucus," he
says.
Mussels
living in waterways affected by eutrophication -- often marked by abundant
algae -- are also fit for human consumption, researchers say.
The
phenomenon is often the result of waste dumped into the waterway containing
phosphates and nitrites, such as detergents, fertilisers and sewage.
The
nutrients in these substances encourage the proliferation of algae, which in
turn starves the water of oxygen, upsetting the ecosystem.
Mussels
"recycle" these nutrients by feeding on the algae, says Eve Galimany,
a researcher of the US National Oceanic and Atmospheric Administration's
Milford Laboratory who has experimented with mussels in the Bronx River in New
York.
The
recycling principle is already at work in a pilot project titled Baltic Blue
Growth in Sweden, Denmark and the Baltic countries which grows mussels to be
fed to animals such as poultry, fish and pigs.
"Eutrophication...
is the biggest problem of the Baltic Sea, the most urgent one," says
project head Lena Tasse. Mussels "could be part of a solution".
Why feed
them to animals if they are safe for humans? Because Baltic mussels are too
small to be of interest to seafood lovers, says Tasse, adding: "Swedes
like big mussels."
Meanwhile,
the jury is still out on the effects of microplastics on human health.
A recent
report by WWF said that humans ingest an average of five grammes of
microplastics a week -- about the weight of a credit card.
A 2018
study published in the journal Environmental Pollution, based on samples from
British coastlines and supermarkets, estimated that every 100 grammes (3.5
ounces) of mussels contained 70 tiny pieces of plastic.
Should we
be worried? Meistertzheim thinks not.
"I eat
them," she says. "A dish of mussels is not necessarily worse than
organic hamburger meat wrapped in plastic."