The tsunami engulfing the main building of the International Coastal Research Center (on right). The water has reached the second floor of the building, but went onto reach the middle of the third floor at its peak.
The destruction to the landscape wreaked by the tsunami that struck the coast of northeastern Japan with unprecedented power on 11 March 2011 was immediately obvious. But the extent of the damage beneath the waves was less immediately apparent. Prior to the tsunami, these productive coastal marine ecosystems were important for fisheries, which were central to the local economy and culture.
Given the magnitude 9.0 earthquake was the most powerful ever measured in Japan, the amount of damage sustained by marine ecosystems was highly uncertain. “Once things had settled down after the disaster, our priority was to find out what had happened to the ecosystems in the sea,” says Tomohiko Kawamura, a marine benthic invertebrate ecologist of the International Coastal Research Center (ICRC), a branch of the University of Tokyo’s Atmosphere and Ocean Research Institute.
Utter devastation
The first challenge confronting Kawamura was finding a vessel to conduct a survey. “In this area, everything had gone,” he recalls. Located on the shoreline of Otsuchi Bay in Iwate prefecture, the ICRC had been directly in the tsunami’s path. “The wave reached the third floor of the main building,” says Kawamura, who served as ICRC director from 2014 to 2019. “Very fortunately, all of the staff and students escaped unhurt, but our facilities were seriously damaged or completely destroyed,” he says. Among the losses were the facility’s research vessels.
Three months after the tsunami, Kawamura’s team secured the loan of a fishing boat to make an initial assessment of impacted ecosystems. That research dive became the first of many. In 2012, the Japanese government funded the multi-institute Tohoku Ecosystem–Associate Marine Sciences project to analyse the effects of the tsunami and other earthquake-associated environmental changes, as well as the subsequent recovery process. Kawamura led a team studying communities of coastal marine organisms.
Ten years on, the programme has revealed that the impacts of the tsunami were diverse, but also that marine ecosystems generally showed great resilience — findings which may serve as an inspiration to local communities. Since 2018, the ICRC has also conducted outreach to encourage traumatized local people to re-engage with the sea, which historically has been central to their culture and economy.
Impact on marine life
Kawamura’s work focuses mainly on abalone, a marine mollusk and one of the world’s most expensive seafoods. Abalone were among the species in the affected area that had been studied in detail before the tsunami. This prior work provided valuable baseline data for assessing tsunami impacts.
The strong kelp forest helped to protect adult abalone from the tsunami.
The impact varied not only by location and species, but also by life stage within individual species, Kawamura’s team has shown. They focused on rocky reef sites affected by the tsunami in Otsuchi Bay, and also Tomarihama, on the Oshika peninsula, close to the earthquake’s epicentre.
“Seeing the tsunami’s enormous impact in coastal areas, we thought our study sites would also be severely damaged,” says Kawamura. “Luckily, nature was more resilient than we had anticipated.”
They found that kelp beds covering shallow rocky reefs had sustained minimal damage. “This shows how surprisingly resilient this species is against such large disturbances,” says Kawamura. The population of mature abalone, which live within these kelp forests, seemed relatively little affected.1,2
Juvenile abalone, however, live in deeper sections of the rocky reef, and this habitat was more significantly damaged because it was more exposed to the tsunami. “Many large rocks were cracked and rotated, and there were bare rocks without any crustose coralline algae in many places,” says Kawamura. Juvenile abalone losses were about 90% at Tomarihama and 70% in Otsuchi Bay.1,2 Consequently, abalone stock didn’t decline much soon after the tsunami, but they dropped greatly about three years after the tsunami. Despite this, population levels are gradually recovering to their state before the tsunami.
On the other hand, sea urchins — another important fishery species — bounced back faster.1,2 “I was genuinely surprised at their rapid recovery,” says Kawamura.
Other marine habitat types were more severely impacted. “Seagrass habitats on sandy seafloors were flushed away,” says Kawamura. This loss left juvenile fish without a habitat. By the end of the 10-year study, however, the community structure had largely recovered.
The tsunami wasn’t the greatest disturbance to many coastal marine habitats. “The impact of human reconstruction activity could be much bigger than the tsunami event itself,” says Kawamura. “For example, reconstructed seawalls resulted in the loss of shallow-water habitats.” This means that the potential impacts of reconstruction should be carefully considered following any future events, Kawamura says.
Tomohiko Kawamura investigating the effects on the tsunami on rocky reef sites in Otsuchi Bay.
Impacts to human society
Even before the 2011 tsunami, the remote coastal communities of northeastern Japan faced challenging social issues associated with population loss and ageing. The damage from the tsunami has only exacerbated these issues, says Yuki Minegishi, a molecular ecologist at ICRC who led an outreach programme to help local people since 2018.
“Over the centuries, this area has been very tightly knit to the sea, but the disaster generated a rift between the people and the sea,” says Minegishi. “This loss of economic and social identity has caused more young people to leave the area.”
In collaboration with researchers from the Institute of Social Science of the University of Tokyo, an outreach project called the School of Marine Science and Local Hopes was initiated to re-engage local people with the sea. One project activity is an after-school club for local high school students. “The students help us with basic research activities, like sorting and measuring or cleaning aquariums — and this gives us time to chat with them,” says Minegishi.
Primary school children gazing up at ceiling mural ‘Archipelago of Life’ in the entrance of the International Coastal Research Center. They are learning about each organism, its biological characteristics and its connection to the fishery industry and the local area, as well as about the intention behind the ceiling painting.
Many students engaged highly with the programme. “One group presented their work on marine debris at a scientific conference,” says Minegishi. “Last month, one student told me he wants to study marine science at university.” The programme highlights the importance of educating the young generation so that they develop a sense of belonging and commitment to the community. “Healthy and well-informed youngsters are indispensable for social prosperity,” she adds. “We can see that happening here right now.”
Activities pioneered through the outreach project are now being transferred to local governments for their continued rollout, not only in the area around Otsuchi Bay but also to coastal communities around Japan, and potentially beyond.
The activities of ICRC demonstrate the value of adopting a long-term approach to gathering data while being nimble enough to adapt to unanticipated changes. They also highlight the importance of taking a holistic view that addresses issues facing local communities. “Working with the local people has opened up a new path of contributing to society and advancing science,” says Minegishi.
Spotlight: Disaster Preparedness