Making the blue greener

The take-away

  • Scientists have found “extraordinarily high levels” of persistent organic pollutants in small crustaceans known as endemic amphipods at 6,000 to 11,000 m below sea level.
  • To clean the oceans, the Race For Water team is studying pyrolysis, a technology which can break plastic waste down into gas, char and oil.

If the oceans were a national economy, they would rank seventh, with an annual value of about €2.2 trillion. This calculation comes from WWF, which notes that through seafood and natural resources marine ecosystems provide around two-thirds of the global aggregate of ecosystem services. The exploitation of this wealth has produced serious ocean misuse, however, resulting in overfishing and other damaging practices. It is now estimated that up to 85% of the world’s fisheries may be over-exploited, depleted or in recovery from exploitation.

On the political level, better protection of the oceans is at the mercy of various stakeholders with different agendas. In October, for example, hopes for a new marine sanctuary in Antarctica, promoted by France and Australia, were dashed after a meeting of the Commission for the Conservation of Antarctic Marine Living Resources failed to reach an agreement. This disappointing outcome is not unlike the difficulty of reaching international agreement on the fight against climate change.


UNESCO’s Salvatore Arico puts it mildly when he says, “Due to unsustainable human practices, there are now signs of fatigue in today’s oceans.” Ocean sustainability, in his view, is above all about reconciling human uses with the ocean’s capacity to continue sustaining the planet. “To reconcile the expectations of multiple actors in society,” he explains, “there is an urgent need for proper spatial and temporal planning of human activities in the ocean.”

The unrelenting growth in global population is making our societies even more dependent on ocean resources. At the same time, the oceans are changing more rapidly than ever before. Warming waters (mean ocean surface temperatures are now fully 1° C above the 1971–2000 average) and acidification are both damaging marine life and biodiversity.

Garbage and seaweed

The calamities of the oceans are well documented. There is the Great Pacific Garbage Patch – vast amount of drifting plastic waste. There is the overexploitation of sand for construction, which erodes coastline and destroys habitat for sea animals, especially in Africa. On the British and French coasts, there are the blooms of seaweed nurtured by nitrogen leaks. One of the least known but perhaps most worrying facts is that the deep abysses, which were generally considered immune from human activity, are also suffering.

A team of scientists from the University of Aberdeen have detected persistent organic pollutants in the deepest ocean fauna near the northwest Pacific’s Mariana Islands, as well as in the Kermadec Trench in the south Pacific. In the hadal zone (6,000–11,000 m below sea level), they found “extraordinarily high levels” of persistent organic pollutants in two species of small crustaceans known as endemic amphipods.

The proportion of polychlorinated biphenyl (PCB) was 50 times greater than that found in crabs from China’s Liao River, one of the world’s most polluted waterways. How these pollutants ended up in the abysses is still not clear, but it is estimated that one third of the world’s PCB production has sunk to the oceans’ depths.

Technological innovations

The good news is that many initiatives, some of them backed financially by the European Union, are trying to imagine a change in our relationship to the seas. Some of the most important technological innovations are in fact quite basic. They seek simply to understand what is going on beneath the water’s surface: where fish live, how they move, what chemical and biological processes take place (see boxes). Armed with this information, scientists and policymakers can move to the next level of marine protection: preventing abuses, cleaning up and, hopefully, developing practices that are truly sustainable.

How mussels absorb nutrients

At the Danish Shellfish Centre, DTU Professor Jens Kjerulf Petersen’s research is based on the sustainable exploitation of natural resources in coastal waters. “Most of our research projects focus on the exploitation of shellfish and seaweed resources, while looking at the associated environmental impact,” he says.

“Our research ranges from the environmental impact of fisheries on wild populations of shellfish to the development of aquaculture of extractive species.” Extractive species are those which are not fed, but rather grow on nutrients already present in the marine environment.

When these species are harvested, nutrients such as nitrogen and phosphorous are extracted from the water. A specific practice being investigated by Petersen is mussel mitigation farming. Through the process, mussels extract nutrients in eutrophic coastal waters and return them to land through harvesting and subsequent feeding to livestock. In this case the aquaculture of extractive species acts as a tool to reduce the negative impact of excess loads of nutrients brought to the marine environment by agricultural processes.

At the same time, mussel meal has potential as an alternative protein source, replacing fish and soybean meal as a component in feed.

“Current projects will increase production efficiency, reduce the costs of mussel farming, develop methods to process the mussels, and find ways to use the mussels that are not suitable for human consumption,” says Petersen. “The results of this research can potentially be used directly in coastal water management, as well as in developing an industry producing mussel meal for organic husbandry.”

Thinning the plastic soup

Many of us imagine the 8 million tonnes of plastic waste entering our oceans annually as a solid mass of plastic collected in ocean gyres. However, when Swiss entrepreneur Marco Simeoni, founder of the Race For Water Foundation, sailed around the world in 2015, he found the opposite: a dangerous soup of microplastics degraded by ultraviolet light and salt. The Central Environmental Laboratory at École Polytechnique Fédérale de Lausanne provided an identification of the samples collected.

The Race For Water team is now sailing the world on its next odyssey. From their custom boat/laboratory/conference centre powered by solar energy, a towing kite and a hydrogen fuel cell, they are investigating plastic pollution in water, while educating the public and decision makers on the issue.

On land, the foundation is pursuing a solution intended to create a profitable value chain for plastic waste, preventing it from getting into the oceans in the first place. It is ramping up research into the use of pyrolysis, a thermochemical decomposition technology which can break plastic waste down into gas, char and oil. Pilot tests are due to start in January in Peru, the Dominican Republic and the Pacific.

“The idea is to make an economically sound process that we can duplicate,” says General Director, Serge Pittet. “We will process the plastic, sell the energy and gas produced, and use the proceeds to employ people to gather plastics in developing countries where plastic has no value. This way, it won’t reach the oceans, where 99% of it is impossible to recover.”

Pittet says this prevention is vital because plastic is wreaking havoc on entire food chains: mutating zooplankton, killing birds and fish and concentrating pollutants in the fish we eat. “The oceans feed 50% of the planet, and if we don’t act we’ll have to find new ways to feed ourselves.”