© image courtesy of Montgomery

Groundbreaking research suggests that one of the humblest creatures in the ocean, the blue mussel, could be the secret to saving coastal waters.

As chemicals from farming enter global waters from a vast array of sources, algal populations are blooming creating marine dead zones. Sadly this is not the only problem that our oceans face. “If you look at the FAO – the UN food organisation – they have some very nice graphs showing that the catches of wild fish globally, has been stable since 1995. Very stable. There is no more wild fish globally to catch. It’s a very stable level,” says Harald Sveier, Research and Development Manager at Leroy Seafood. It is a sustainable Norwegian fish farming company, that is the largest trout producer in the world, producing 30,000t annually as well as being a major salmon producer. Harald says that at the same time human consumption of wild fish has increased. This means that there is less fish available to go to non-human consumption. “So the supply of fish meal and fish oil globally is decreasing. At the same time the aquaculture industry globally is increasing very rapidly,” says Harald.

This means less fish meal for fish farms. “When you design a fish feed you’re using a mixture of different raw materials. Some of these raw materials should be of marine origin. And that is mainly because of the of the amino acid profile the protein quality.”

This also affects the taste of the meal. Today fishmeal accounts for between five and 10 percent of the recipe. “The rest of the raw materials is soy or gluten and fish oil, rapeseed oil and stuff like that. And why do we not use more fish meal? Well, first of all, there is no more fish meal in the world. And today, the biggest fish meal user is the pig industry in China,” says Harald.

Prices rise

“When you have a raw material where there is a limited availability of that raw material, the prices is reflected on that, the prices on fishmeal is quite high,” says Harald.

The fish does not necessarily need to eat feed with a high percentage fishmeal, although concocting an alternative that is so nutritionally perfect is a real challenge. But there is a solution. Maren Lyngsgaard is a marine biologist working at WSP in Denmark which has a big problem with eutrophication of its coastal waters. Denmark has a human population of six million, but a pig population of over 13 million, and water quality is an important area of study. “So we have what you can call a heavy nutrient load on our coastal systems. And because of that, we’ve had high micro algae productions. We have I think, two out of 219 water bodies in a good ecological state. And we would really like to improve this.”

Maren began to study something troubling. “We were looking for the coupling between the micro algae and the nutrients coming from land and into the sea. And the theory says that it’s obvious that the more nutrients you put into the ocean, the more micro-algae you will have, but it’s really difficult to show in practice.”

So, the team looked at the water column, and because the water column is often divided in more than one layer, they found that they could demonstrate and show that there was a coupling but only in the surface layer between the nutrients coming in and then an increasing production of micro algae. And this is where the blue mussels came into it.

Blue mussels magic

“Well, the main thing is that they are filter feeders. So they filter away all the micro algae. And the micro algae takes up the nutrients. And that’s what we have too much of in Danish fjords,” says Maren.

The plan is simple enough. Place a blue mussel farm at the mouth of a heavily polluting fjord. The figures show just how effective they can be. A mussel farm filters 2 million cubic metres of water per hour. The biggest artificial filter in Denmark can only filter 1,500 cubic metres per hour. This is less than 1% of the mussel farm. “So it’s really, really effective. So we wanted to have like a blue resource that takes away the excess nutrients,” says Maren

The mussels will not only feed on the microalgae and clean the water, they take in nutrients from the algae and grow rich in fatty acids meaning that they become a good source of marine protein and fatty acids themselves. “The blue mussels story is actually a combination of many projects. But the project about blue mussels and trying to establish this value chain with blue mussels, where we produce blue mussels and reprocess them into feed, and then use this feed in the aquaculture sector. This project is called Impro Feed.”

Project Impro Feed

In 2016 the team started to raise the approximately $7 million funding needed for the equipment. Once this was in place they collaborated with a company called Blue Biomass to establish 20 tubes of this smart farm system. Today they have 335 tubes in an area called Venøsund which is in the north Danish fjord. Their task was to establish a commercial route to market for the mussel produce, but also carefully examine the environmental impacts of the farm. Maren says that people have made a mistake on land by farming so intensively and that we must not make the same mistake for the ocean. “So it was very important for us to look for any, both positive and negative effects of this industrial production of blue mussels,” she says.

The effect on water quality was quite literally clear for all to see. EU regulations use chlorophyll concentrations which is also a measure of the amount of micro algae in the water. “So we measure the concentration of chlorophyll and then the concentration of micro algae and then we also measure the visibility of the water,” says Maren. “So how many metres of depth can you see down? Within the farm there was up to two metres higher visibility than outside the farm. The depth is five to six metres. So that means within the farm you can see all the way down to the depth or to the bottom and outside the farm you can’t, so it’s really something that is visible for everyone.”

This is important. Demonstrating an obvious improvement to water quality helps win-over local people, who are understandably concerned about any kind of development in their waters. This system does involve building a working 90 hectare farm, after all.

The production systems are 120m floating tubes. Underneath the tubes, you have a three metre deep nets and on these nets, sit the natural larvae of blue mussels. “From that, they grow and they just sit there in the water column and they eat whatever swims by. So you have all the lava is sitting on the nets. And sometimes you have so many larvae sitting on the nets that you have to make a thinning just as you thin your carrots in the garden. If you want to have big carrots, you need to take some of the smaller away. And that’s the same you do with the mussels,” explains Maren.

Location, location, location

Picking a good location for the farm is very important. A good flow of water is necessary to avoid an increase in organic matter beneath the farm as this could lead to oxygen depletion. “So in this place where the farm is, that has a good exchange of water because it’s a bit narrow, and the water just keeps going back and forth,” says Maren. Salty water flows in from the North Sea from the west and the less salty water enters from the Kattegat in the east.

Mussels dropping to the seafloor beneath the farm have created a substrate for marine life, actually boosting biodiversity, with some sediment species returning to the area that had not been seen since the 1940s. Maren says it creates reef which can be food for other species like crabs and fish.

“It was really interesting to see that it’s possible to place a farm in a way so it actually contributes to biodiversity instead of contributing to oxygen pollution, for example, as it is seen in other areas,” says Maren.

These findings took Maren totally by surprise. The environmental benefits were better than anyone had hoped. “It was it was not something that we expected that it would actually contribute to the biodiversity. And a lot of the species we’ve found are very a species that you don’t find in in areas with eutrophication. So the species couldn’t be there if it was without oxygen in just short periods of time.”

Beware of the ducks

The farm produces 10,000t of mussels per year, and it is projected that Denmark has the capacity to produce about 300,000t of mussels in total, creating 800 jobs and potentially removing up to 5,000t of nitrogen from the coastal ecosystems per year.But it hasn’t all been plain sailing. One of Maren’s experiments to determine the optimum time to thin the mussels failed due to the break-up of winter ice sheets in the fjord. And then there are predators such as sea stars which feed on mussels. However no predator is more terrifying to a mussel farmer than the Eider Duck. “Eider Ducks can finish a whole production system and empty the system, just within a few days, they’re very effective, and they dive down to 10 metres. And it’s really easy for them to eat these kinds of muscles, because this feels thinner. And the meat, it has a higher percentage of meat. So it’s really the very best food served for them right there in the top of the, in the ocean.”

So far the ducks have not discovered the farms. Like any good shepherd, a mussel farmer needs to be ready and a range of tools are being employed by farmers from cannons to eagles and lasers.

WSP and its partners have been collaborating with a company that produces a drone boat that acts a bit like a dog to scare away the Eider Ducks. “We found that really works with just this device that sails fast towards them. That would make them move away. And not just a few metres away, but away from the area,” says Maren.

Now the nutritional and environmental research has all been worked out, the focus has switched to the business case. They are also working on ways to reduce the visibility of the farms, to make them more appealing to local residents. This will perhaps be achieved by submerging the farm entirely, monitoring mussel growth with cameras, and deciding when to harvest with the help of machine learning. They are also waiting on action from the government to incentivise the removal of waste nutrients from the marine environment, which will cause a massive reduction in the cost of these “mitigation mussel farms”

Mussels compare favourably to other options to reduce nutrients in coastal waters. The cost is about 12 Euros per kilogram for mussels, and 28 Euros for wetlands, which is another solution. This environmental subsidy will hopefully bring the mussel meal price in line with the price of unsustainable fish meal. But there is other demand-side work ongoing. Maren has teamed up with a chef to produce a cookbook, and has also appeared on Danish morning TV to promote mussels for human consumption. They aren’t traditionally popular in Denmark, but this is changing. Denmark exports 90% of its mussels, and building domestic demand is seen as important.

Future farming

This project hinges on fish and animal feed meaning that it is people like Harald Sveier who need to be convinced. And from what he said earlier in the episode about the availability of fish meal… mussel meal just has to become viable. “It’s a question about an economy of scale,” says Harald. “Your union need to produce some 100,000 tonnes of blue mussel meals, you need some blue mussels available. It has to be industrialised, the whole process. And we have started on that journey. And I’m convinced that within four or five years, there is blue mussel meal on the market at a fair price.”

Leroy Seafood buys some 400,000 tonnes of fish feed every year. Of 400,000 tonnes, if 10% of that is fish meal, that’s 40,000 tonnes.

The 300,000 tonne potential production of blue mussels in Denmark would result in a total of about 45,000 tonnes of mussel meal for feed. This is just from Denmark, and Norway produces a lot of Europe’s salmon. But as Harald said earlier, the fish have a say in whether mussel meal will be successful. It doesn’t just come down to the nutrients, it also comes down to the taste. “The fish are very picky,” says Harald.

Initial tests on trout have shown that mussel meal performs to the same standard as fish meal, so things are looking very promising, but as exciting as it is, no single project will solve all of our environmental problems. Even one that involves a creature as special as the blue mussel. We need to think more broadly. “We are at crossroads right now, when it comes to the ocean, because everyone’s looking towards the ocean as being the great white hope. But this is the last frontier and the blue economy and we could do this right? Or we could do it wrong,” says Katherine Richardson, Professor in Biological Oceanography at the University of Copenhagen. Katherine was also Maren’s PhD supervisor. “And the wrong way to do it is the way that we’ve done it on land. And we can see the mess we’ve gotten into at the moment on land where we have very little area left for nature in itself.”

For the last 30 years, Katherine has been involved in an international team developing a new domain of research called Earth System Science. Which looks at the Earth as an organism or ecosystem in its own right. “I’m very involved in looking at, at human activities and what they mean for the functioning of the earth system as a whole. And of course, food production is one really important activity that we have.”

Katherine thinks that if we use the ocean, right, and learn from our mistakes on land, then I think we’re looking at a very we’re looking at a future where the ocean and humanity can survive in harmony. This might mean dong things differently. “Can we can we do aquaculture in connection with wind farms so that so that we, you know, use less area? Then there’s lots of things we could do, if we really respected the fact that land and ocean area are limited resource, and it’s needed for nature, and it’s needed for us and we have to find a way to use it in such a way that that, that nature also has room to develop after its own premises.”

Katherine argues that there are lots of international agreements in place already, but we are still missing the policies to implement them. To force the multipurpose use of ocean space. Although she does concede that the mussels are clever. If we are using the marine environment responsibly, we need to pick locations carefully. Katherine also likes the idea of incorporating seaweed production into areas with mussel farms. “In my vision of the future I’ve got windmills out there and in between the windmills I’m growing mussels on one axis and I’m growing seaweeds on wires on another axis. Because you know, here we have an area that you know is already basically used so why not?”

To protect water quality we have to be cleverer about the way we do things. We are faced with an increasing population, and increasing demands placed on the natural world. “So we know that if we’re going to feed 9 billion people, we can’t use any more land area, we have to be careful about our use of water, we have to reduce the amount of nitrogen, phosphorus and pesticides that we’re releasing to the open to the open environment, we have to change our relationship with biodiversity in food. And fortunately, there are being developed scenarios, that show that we can do this, it’s just that there’s not one technical solution that’s going to bring us there.”

It’s a bouquet of solutions that includes the magical blue mussel.