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In the spring of 2021, the Zorro research programme spread 1,800 tons of sand and gravel across a one-hectare area in a small bay outside Lilla Askerön. Then they planted 80,000 cuttings of eelgrass. When the research team returned to the site that autumn it turned out that not only had the eelgrass managed, but had increased ten-fold, says Per-Olav Moksnes, Professor of Marine Ecology.

"This was of course a very good result. But on around a quarter of the seabed the eelgrass had disappeared, leaving only sand and gravel. Last spring we discovered something unexpected. In the gravel on this surface, we found a large amount of juvenile sea mussels, whose propagation elsewhere had decreased dramatically in soft-bottom seabed along the West Coast. An increase in small predators like green crabs that eat the juvenile mussels is thought to be an important explanation. In order to investigate if the gravel perhaps protects the mussels, we laid down a number of mussels three weeks ago that we placed on lines, both in the area with a gravel seabed, as well as in an area with clay." 

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Suddenly you have a whole new research project going, and a potential restoration method for mussels that was never the intention initially!

The sausages are soon collected in a number of nets that Per-Olav Moksnes and Johan Severinson throw up into the boat. On the boat are Louise Eriander, research engineer at Zorro, and Patrik Magnestam, employee of “8 fjordar” (8 fiords), a partnership project around coastal management between five municipalities in the Bohuslän province. They immediately start to scrape off the gravel to be able to measure and count the mussels. So the theory about gravel as mussel protection seems to be correct, Per-Olav Moksnes argues.

– If so, it would be an example of one of the most fun aspects of research: while you are investigating one particular phenomenon you happen upon something else that seems interesting. Suddenly you have a whole new research project going, and a potential restoration method for mussels that was never the intention initially!

Interdisciplinary research

It was 2010 when Per-Olav Moksnes, in collaboration with Lena Gipperth, Professor of Environmental Law, started the Zorro Research Programme. The reason was that eelgrass had become increasingly rare along our coasts and that it requires expertise from more than one scientific discipline to find solutions. Zorro involves partnering across several fields, recently involving marine ecologists, environmental lawyers and environmental economists.

"Eelgrass is a plant that spends its entire life below the surface. Globally there are around 60 species, so it is a small group. On the other hand, it is widespread, and grow at all the coasts of the world, except at the Antarctic."

But along the coast of Bohuslän, eelgrass growth has diminished dramatically in many places, primarily in the southern parts from the Hake Fjord down to Gothenburg. We do not know precisely when it happened, but probably in the 1990s, Per-Olav Moksnes explains.

"Compared to plants on land we generally have a poor understanding of what is happening to sea vegetation, so nobody noticed when the eelgrass disappeared. Today, however, intensive work is ongoing with surveying and monitoring of eelgrass propagation using drones, so the situation has improved."

The nursery of the sea

Eelgrass meadows play an important role in coastal ecosystems by creating a habitat for several different fish species and invertebrates, which lead to better biodiversity. It is also important to humans, such as by keeping the water clear.

"The causes behind eelgrass diminishing are numerous, but it is primarily due to eutrophication and overfishing of larger fish such as cod. It has had a cascade effect: if the larger fish disappear small fish will profligate; they will eat small crabs that would otherwise have grazed on algae; this leads to fine-threaded algae covering the eelgrass, blocking the sunlight; then the eelgrass will start dying, which leads to murkier water that is even more difficult for sunlight to penetrate. Eelgrass is also an important nursery for larger predatory fish, leading to even fewer cod and other larger fish, and even more small fish."

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In addition, eelgrass is important from a climate perspective. The several meter deep organic sediment beneath the eelgrass meadows store carbon and nitrogen, which risk being transformed to greenhouse gases if they are disturbed.

The project at Lilla Askerön is a successful example of eelgrass planting. But even less successful attempts may be valuable, Per-Olav Moksnes argues.

"In collaboration with the County Administrative Board, in 2020 Zorro carried out a large-scale eelgrass restoration in two bays at Sydkoster. Despite good water quality, the restoration unexpectedly failed. Subsequent studies showed that large amounts of green crabs had torn the plantation to pieces. Naturally this was sad, but the outcome gave us new knowledge about how the loss of large predatory fish and unnaturally high numbers of their prey, the green crab, can cause unexpected problems for the vegetation. It helped us to better understand the causes behind the diminished eelgrass around the Koster Islands, and to develop new planting methods that work where there are plenty of crabs, which is an important result."

Growing up far from the sea

Per-Olav Moksnes has been interested in the sea since he was 5–6 years old, according to his parents. It may seem a little odd, considering that he grew up in Örebro

"But surprisingly many marine biologists in fact stem from Örebro – if you live in a landlocked town the longing for the sea can be overwhelming. As a young boy I was fascinated by Jacques Cousteau’s underwater films and I wanted to explore the sea, just like he did. But that was nothing that you could make a living from, was the opinion at the time."

After upper-secondary school he planned to study international economics but thought that he needed to improve his French.

"So I went to Paris and got a job in a restaurant. In a bookstore, I found an amazing book about European fish which I bought, even though I couldn’t really afford it. It made me think about studying something about marine life after all. In 1988, when Sweden was hit by both killer algae and seal death, oceanography suddenly became an important topic. So, I went to Gothenburg to study marine biology."

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Per-Olav Moksnes has primarily spent his time on basic research. But in 2009, when he started working part-time as an environmental analyst at the Swedish Institute for the Marine Environment, he realised the importance of research benefiting society.

"Since then, Lena Gipperth and myself have collaborated on cross-disciplinary education. For example, in 2015 we were part of starting a paired-doctor academy, which meant that doctoral students from different disciplines are paired together."

They were also involved in starting the international master’s programme Sea and society, which combines natural and social sciences, coordinated by Per-Olav Moksnes.

"The programme currently has more than 90 teachers from five faculties, as well as various public authorities and companies."

This survey of eelgrass and mussels outside Lilla Askerön is now completed.

"When Zorro started its operation almost 15 years ago eelgrass was not something that people in general were aware of; they knew that coral reefs and mangrove forests were threatened, but eelgrass? Today, I no longer need to explain myself when I tell people that I do research on eelgrass. On the contrary, people think that I am doing something really important. But for me personally research is about more than solely science; to be able to snorkel on a beautiful May morning among the green eelgrass meadows with the sun gleaming through the leaves, that is a wonderful experience."

Text: Eva Lundgren

Portrait first published in the GU Journal 3/2024