New Frontiers in Ocean Research in post-tsunami Japan – engaging discussion with Dr. Masaru Tanaka and Dr. Reiji Masuda on “linking the study of the land and the sea”

Meet two Japanese scientists we spoke to at the Larval Fish Conference in Norway. They spoke of the impacts that the tsunami/earthquake had on the marine life in Japan, but also the new efforts that scientists are making – to make their work more interdisciplinary, and to understand the intimate connection between the land and the sea.

Wrecked and landed vessels in the town of Kesennuma
(May 22, 2011, photo by Dr. Reiji Masuda)

Erica: Could you please tell us what has happened immediately after the Earthquake/Tsunami and how it affected the ocean near Japan?

Dr. Masuda: The entire water mass moved with the earthquake. Unlike a hurricane, in which only the surface water moves, with a tsunami the entire water depth moves, with  a speed of 20-30 km – very fast. So all of the sediment moved towards the land. And all of the sediment from the land was moved into the sea, with debris, both natural and unnatural debris from humans. So at first there was just a lot of debris, both large and small.

Erica: What was it like? I’m imagining sediment covering everything, lots of rubble and garbage in the water. 

Dr. Tanaka: Yes. The influence of the tsunami was mostly in shallow water, but the earthquake occurred 20 km offshore, so the deeper waters were affected more by the earthquake. Our research focuses more on the impacts on shallow waters, so the impact from the tsunami. At first people were concerned with the damage to people, then people were concerned with what happened to the sea. Just one month after the earthquake, our surveys started – to look at the marine environment and the organisms. Dr. Masuda has made a big contribution to this, by taking the photos.

Erica: So what are you finding with those photo surveys now?

Dr. Masuda: Since so many nutrients were transported from the land, plankton has increased a lot. Plankton is prey for bivalves, so the growing speed of cultured oysters is now very fast. Usually it takes 2 years to reach harvesting size, this last year it took only 6 months to reach the harvest size. I tried them, they are delicious.

Erica: Are you worried about radiation in the oysters?

Dr. Masuda: In that area, no. The story about Fukushima is quite different and quite far from our place (Moune). The fishermen near that area are quite concerned, but we are far from there, and the current flows the other way.

Dr. Tanaka: Moune is a small fishing village, but has become quite famous due to the social movement started by Mr. Shigeatsu Hatakeyama who started an oyster culture there. He is quite famous around Japan but was also selected by the United Nations as a “World Forest Hero.”

Spotted gunnel Pholis crassispina in mud-covered Sargassum two months after the tsunami
(May 21, 2011, photo by Dr. Reiji Masuda)

Erica: Can you tell us more about this social movement?

Dr. Tanaka: Before, we studied just marine ecosystems, but now we have a new frontier that was started initially by 6-7 researchers, now we have nearly 22 researchers, where we bring together those that study forests, salt marshes, etc. with those that study the sea. Within this year, an institute will be established for “Headwater to Ocean” (H to O) studies on the entire ecosystem.  In 1989 Mr. Hatakeyama started this project called “The Sea is Longing for the Forest” – he is a very clever person – every Sunday of June he has a tree planting festival that lasts the whole day. This activity is important because it gets a lot of press, but also because it is a great source of environmental education. He says he wants to “plant a tree in children’s hearts,” not only a tree in the mountains. Every year he invites school children, almost 500 students, the total number is around 10,000 people since 1989.

Erica: Is there an ocean equivalent to the tree-planting activity?

Dr. Tanaka: Well, in addition to the tree-planting festival, he also invites the students for a trip to his oyster culture farm.  He teaches them about the oyster and its connection to the forest. The main diet of oysters is phytoplankton, and phytoplankton is influenced by water from the mountain. He has the children sample the plankton – they even drink it – so they can imagine what an urban area would do to the plankton and the oyster fishery. The next day students start to reduce their soap and shampoo use, and begin to influence their parents, then move to their local government.

Shoal of banded gobies Pterogobius elapoides in well-recovered Sargassum
(November 29, 2011, photo by Dr. Reiji Masuda)

Erica: Have you ever been to the tree-planting festival or oyster farm?

Dr. Tanaka: Yes, many times. Previously 700-800 people got together from Japan. This year, 1500 people came.

Erica: So for you personally, what does it mean for you to be involved in this project?

Dr. Tanaka: Mr. Hatakeyama, I have known him for a long time, we are almost the same age. I have three grandchildren, he has four grandchildren. My life is not so long, so how can I contribute to the next generation? I learned so much from this social movement. However, we are researchers. Social movements go ahead of the science; science just follows. But this more integrated science we are starting to do now– including the terrestrial and marine environment –showing the intimate linkage between land and sea, is combining a social movement with science. This means a collaboration between researchers, NGOs, citizens, fishermen, these combinations are very important for our future.

Erica: Do you think the general recovery of Japan will depend upon those kind of collaborations?

Dr. Tanaka: This is becoming more popular. Dr. Masuda lives in a different area where this type of education is becoming very relevant.


Fair sized marbled flounder Pleuronectes yokohamae
(May 27, 2012, photo by Reiji Masuda)

Erica: Dr. Masuda, could you talk a little more about what you’ve seen in terms of the recovery in the marine environment and where you think it will be in the next few years? 

Dr. Masuda: What I’m doing is underwater observations of the fish community. I count fish species and numbers per 100 square meter areas, 10 replicates per station. What I found is that at the beginning, after the tsunami, the bottom was almost bare, with very little vegetation and only small juvenile fish. That means the juveniles spent their lives offshore before the tsunami came. Then in the next few months after the tsunami, the number was dramatically increasing. The reason is that there are so many gobies, because there are no predators of the gobies (like the rockfish). Rockfish is sedimentary and long-lived, so if they were wiped away with the tsunami, it makes a good place for the gobies. But now we are seeing more species and more abundance – and a few rockfish have come back.

From last May to this May, total fish density increased by 20 times; that’s a lot! If you look at terrestrial ecosystems, like after a volcano – first it’s barren, then grasses come in, then trees – it takes up to 50 years to reach a climax community. While in the case of the ocean, the metabolism and the circulation is much faster, so even the longest-lived coastal fish live several years. If that’s the case then only 2-3 years would be needed to fully recover as a system.

Dr. Tanaka: The reason why there is such a difference between primary production in the land and the ocean – the main component in the ocean is phytoplankton, which is quite small, but the turnover rate is quite high. So it can quickly recover, that’s the major reason. Like Dr. Masura said, there has been a big increase in the number of fish. The most exciting finding is that we now have very small clams – before the earthquake there were very few, but now we have more than we did before the earthquake.

Dr. Masuda: There are also more flatfish than before the earthquake. The local people say they have never seen so many flatfish.

Erica: Is there now more discussion about putting in Marine Protected Areas than there was before?

Dr. Masuda: Although I am very interested in putting in marine protected areas, in the context of this earthquake, I am not sure that others are discussing it. But even since the earthquake, there is less fishing pressure since many of the fishing boats were destroyed, which is another reason why we are seeing so many fish.

Erica: What is your hope for the Moune ecosystem? 

Dr. Tanaka: My hope is that now students and graduate students get into this area. There are many challenging research topics, now that this environmental situation is changing so much. For example, predator-prey relationships are changing. We hope that many more students, not only from Japan, but from all over the world, will come to study these dynamics.

Dr. Masuda: I hope that in any decision-making we begin to think more about the long-term, instead of only looking for short-term answers based on economics. I think this is a good opportunity to change our attitude, we have to learn from our experience.

Dr. Tanaka: This is the most important aspect that we have learned from this disaster.  People have really changed their thinking, accepting now that there is such an intimate relationship between the land and the sea.

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