From an environmental standpoint, marine exploitation has been a catastrophe. New research and technological innovation are showing the way towards more sustainable oceans.
If the oceans were a national economy, they would rank seventh, with an annual value of €2.1 trillion. This calculation comes from UNESCO, 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.
Hook, line and trace
Just as with humans, the unique information in fish DNA can be used to investigate the origin of any individual – and even create DNA marker tools to track where fish are caught.
A pioneer in this field, the pan-European FishPopTrace project in 2013 delivered the EU a set of DNA tools and a forensics framework for combatting illegal catches. Once analysed, genetic markers from a given fish can be compared against a database of Europe’s most important exploited fish species: sole, cod, hake and herring.
“This can help fight the environmental and economic losses from illegal fishing,” says Filip Volckaert, professor in genetics at KU Leuven and one of the FishPopTrace project leaders. “It makes up around 20–30% of fish caught on a global scale.” He says the technology is being adopted by the EU. It has already been used to prove fish origin in legal cases in Norway, and for chinook salmon disputes between the US and Canada.
Volckaert’s team was also involved in the follow-up Aquatrace project, which used DNA markers to track the genetic impact of farmed fish that escape into the wild. While the importance of aquaculture for the sustainability of global fish stocks is recognised, species-specific DNA tracking research is needed to better understand the genetic risks of aquaculture. “First, escapees start competing with wild fish for food, and then you have the escapees starting to breed with wild fish, bringing different genetic characteristics like growth, fat levels and body morphology, creating very different progeny,” says Volckaert. “So, it’s already clear that the ecological and genetic impact is quite negative.”
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.”
How fish migrate
Scientists at the Technical University of Denmark (DTU) are trying to understand the migratory habits of fish. Karin Hüssy, a researcher at DTU Aqua, is identifying the geographic distribution of fish stocks, and the extent of individual fish migrations between adjacent areas. “To avoid inadvertent over-exploitation in areas where several stocks occur, our research provides the basic knowledge for accurate assessment of a stock,” she explains.
Hüssy believes that biological knowledge provides the basis for the sustainable management of fishing practices. “Key requirements for achieving this goal,” she says, “include gaining information about stock structure and migration patterns, as well as the age and growth of the fish. This information can be obtained from fish otoliths.” Also called ear stones, otoliths are calcareous structures in a fish’s middle ear, which grow through daily accretion of calcium carbonate crystals, trace elements and proteins. The otoliths form daily and annual growth rings, much like the year rings in tree trunks.
“Sometimes the otoliths are referred to as the fish’s black box,” explains Hüssy. “They store information about the fish just as we gather information about an airplane’s activities from its black box. The annual rings serve as a proxy for time spent in relatively fresh or saline waters. By counting them, researchers can establish how old a fish was when it died. And by knowing which water a fish spent its time in during particular years of its life, the species’ migratory habits can be mapped.
Currently, DTU Aqua is focusing on two overlapping cod stocks in the Baltic Sea, hoping to extend the methodology to other stocks and species over different geographic zones in the future. Using this information, the researchers can quantify the mix of fish stocks occupying adjacent areas, and the extent of habitat use, which are important details in providing advice for stock assessments and marine spatial planning aimed at sustainable fishing practices.
By Conor Paul Purcell, Sylvain Menétrey and Joe Dodgshun