Mussels, 'super-filters' that can help beat water pollution

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."

China permits imports of Dutch shellfish to local markets

DutchNews, May 15, 2017

Photo: Depositphotos.com 

After two years of negotiations, Chinese authorities have opened their markets to razor clams imported from the Netherlands, the Dutch economic affairs ministry said on Monday. 

Razor clams are considered a delicacy in China and the Netherlands is now one of the few countries which can export the shellfish to the Asian market. The value of the export is put at an initial €7m a year. 

The Netherlands received permission to export the razor clams to China not only because of the high quality of the product, but also because of the Dutch inspection authority NVWA which is recognised internationally. Until now Dutch razor clams were exported mainly to Italy and Spain. 

Razor clams are found on the Delta region of Zeeland province and to the north of the Wadden sea. Regulations ensure the annual catch is sustainable, the ministry said. 

High levels of antibiotic-resistant bacteria found in Asian farmed fish

DutchNews.nl, Friday 07 November 2014

(NOS)

Spot checks of fish and prawns which have been farmed in Asia found that half contain bacteria which is resistant to antibiotics, according to animal rights organisation Wakker Dier.

The foundation had 43 samples of Asian fish and prawns tested for bacteria. One prawn sample was even found to have ESBL, an enzyme which prevents many antibiotics from working. It has previously been detected in meat but never before in fish, Wakker Dier said.

Campaign leader Hanneke van Ormondt says fish such as tilapia and pangasius are raised in giant tanks in Vietnam and Thailand and given huge amounts of antibiotics to combat illness. Antibiotics are also used to stimulate the fish to grow more quickly, she said.

Checks

If the fish is not properly cooked, the bacteria can also have an impact on human health by stopping antibiotics from working.

The Dutch food safety body NVWA said in 2009 there should be a proper system of checks on fish but this has not yet been developed, broadcaster Nos says.

A spokesman for the food retailers' association CBL said this is now a priority. ‘We are going to increase our checks on fish farms and make it clear they should use fewer antibiotics,’ a spokesman told Nos.

Swedish salmon sales 'breached EU ban' over dioxins

BBC News, 8 May 2013

Related Stories 

• Horse DNA in 5% of EU-tested beef

The salmon issue again highlights the
complexity of Europe's food chain

Firms in Sweden have sold about 200 tonnes of Baltic salmon in Europe despite an EU ban targeting toxic chemicals in fish, officials say.

The ban does not apply to Baltic salmon sold to domestic consumers in Sweden, Finland and Latvia. But the sellers are required to give advice about safe limits for consumption, set by the EU.

Dioxins found in Baltic herring and salmon prompted the EU ban in 2002.

A French firm imported 103 tonnes of Swedish salmon, but no longer does so.

Pecheries Nordiques told the AFP news agency that its tests had found no problems with the fish, imported in 2011 and 2012. "Nobody told us it was illegal," chief executive Francois Agussol said.

Jan Sjoegren of Sweden's National Food Agency told the BBC that Baltic salmon had also been exported illegally to Denmark and the Netherlands from Sweden.

The agency has alerted the European Commission, which deals with national food safety authorities.

A firm in Karlskrona has been reported to the Swedish customs authorities over the salmon exports, and a firm in Hammaroe is also being investigated, Mr Sjoegren said.

Dioxin hazard

The latest alert about Baltic salmon exports follows a horsemeat contamination scandal in the EU which affected many countries.

"We don't think more salmon is being exported now, but because of the horsemeat scandal we are stepping up action on food fraud," Mr Sjoegren said.

Sweden's National Food Agency says the average intake of dioxins among adult Swedes is well below the "tolerable weekly intake" set by the EU.

Children and young women, it adds, should especially limit their consumption of wild Baltic fish because dioxins pose the most risk to babies and young children.

Dioxins spread by incineration and chemical pollution can accumulate in the body over years and can trigger cancer or reproductive abnormalities.

The European Food Safety Authority says that, on average, Baltic herring and wild Baltic salmon are respectively 3.5 and five times more contaminated with dioxins than non-Baltic herring and farmed salmon.