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| The key to recovering the fertility of the seas exists in phytoplanktons. |
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The seas surrounding Japan have experienced substantial changes. The fish catch has been decreasing in the Seto Inland Sea and other seas. The coral reefs are rapidly being lost around Okinawa. Professor Koike studies such extensive environmental changes in the sea, from the viewpoint of microalgae (phytoplankton).
Phytoplankton increase exponentially, and produce various useful components, and are therefore drawing attention for use in health food products and as a fuel source. The most important role of phytoplanktons is to as the bottom base of the food chain in the marine ecosystem.
“The seas where high-quality phytoplanktons are abundant and increasing are fertile, and produce a lot of fish. Coral reefs are well-known candidates to indicate the existence of a fertile sea, and phytoplanktons hold the key to the fertility of coral reefs as well,” says Koike. Recently, coral bleaching has become a global issue. This phenomenon involves zooxanthella, a symbiotic algae with coral, which is also one of the research themes of Professor Koike. |
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Professor Koike’s studies in these fields were first triggered by the sea around Okinawa.
“I started scuba diving in my high school days. While I was a university student, I spent almost all the holidays working part time and diving in Okinawa. In those days, the sea around Okinawa was filled with extremely rich coral reefs.” Subsequently, since around 1990, the coral reefs have continued to decrease. At first, Koike started researching coral bleaching from the perspective of zooxanthella. He worked in Iwate Prefecture, where fisheries were prosperous, before coming to Hiroshima University. This also brought him a sense of urgency regarding the decline of fisheries, and decline of ocean fertility. After coming to Hiroshima University, he was convinced of the decline in fisheries by observing the status of the Seto Inland Sea at the time. “Now, the Seto Inland Sea has become my main field. I will pursue the restoration of the fertility of the sea from the viewpoint of phytoplanktons.” |
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| Koike’s activities, which are contributing to improvement of the marine environment have expanded overseas, in collaboration with people working in the fishing industry. |
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Koike’s research needs to be patiently undertaken over a long period of time. In the meantime, Koike’s concern is that merely identifying the causes will not prevent the fisheries industry from disappearing from the Seto Inland Sea. To avoid this, he has decided to start doing what he can, and has taken several specific actions.
One of these has been “seabed tilling,” which is expected to promote the germination of high-quality phytoplanktons by tilling the seabed and agitating the sediment. Professor Koike has promoted seabed tilling together with fishers. He has also introduced a variety of methods to predict the proliferation of harmful plankton, and has been pursuing their commercialization. Among them, the “red tide prediction” method developed by Koike’s laboratory has been leveraged in many prefectures, and has contributed to reducing damage from the massive deaths of farmed fish caused by red tide. |
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Research on phytoplanktons has also been performed in various locations around Southeast Asia. Over the past five years, Koike has conducted the first research study in the world concerning the coastal environment and marine production in Myanmar. This research has suggested a concern that, contrary to the traditional assumption of fertility in the Myanmarese coastal area, marine productivity has been declining, because excessive forest development has caused turbid flows into the sea, which has blocked light required for the photosynthesis of phytoplanktons.
Based on this research finding, an environment-friendly bivalve farming project was started this year, as a joint project by Hiroshima University, a Japanese governmental research agency, the Myanmarese government, and a local university.
In the meantime, Professor Koike says that research concerning zooxanthella has drawn much attention in Western countries, because coral bleaching has become a serious issue in the Caribbean Sea and around Australia. “Why does coral discharge zooxanthella? My publication concerning its mechanism in an American journal created an extensive reaction,” says Koike. |
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According to his publication, a coral inherently has mechanisms to digest and discharge zooxanthella through its body. However, when the water temperature rises, the amount of zooxanthella increases, and digestion by the coral does not catch up with the speed of increase. As a result, the coral starts to discharge weakened zooxanthella without digesting them.
“This can be said to be a sign that leads to bleaching. Corals are doing their best to adapt to changes.”
His research has had another effect: an innovation in the method for proliferating giant clams (Tridacna), which are also symbiotic with zooxanthella, just like coral. “It had been difficult to artificially infect juvenile clams with zooxanthella. Our research achievements have led to remarkable improvement in the survival rate of juvenile clams, by infecting them with zooxanthella of types that match the development stages of the clams.” |
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| Feeling joy in sampling activities and in greater public recognition, and seeking to shift the focus of activities to Southeast Asia in the future |
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Professor Koike loves going to the sea, and says with a smile, “I love doing sampling work together with my students, among other activities.” He also adds, “If I could identify crises of the seas through these activities, and relieve such crises in collaboration with local people, that would be the most wonderful joy for me.”
While he is engaged in research activities, Koike also focuses on activities to disseminate the importance of phytoplanktons. “I keep making efforts to explain our research achievements to fishers as well as to children in an understandable way.”
As a prospect for the future, Koike says, “I would like to shift my research base in full scale from the Seto Inland Sea to Southeast Asia.”
“In that region, fertile coral reefs and mangrove forests expanded in the past, but they are now rapidly decreasing. From the mountains occupied by plantations, muddy water gushes into the sea in the rainy season, turning the coastal sea into a pool of muddy water just like miso soup. These factors are contributing not only to the deaths of coral, but also to the decreased production of phytoplanktons and poor fish catches. I would like to research the present status first, and then indicate the results to the relevant countries so that people will have a sense of urgency. It is also extremely important to provide appropriate education to children in those countries. I hope that the local children will recognize the wonderful marine environment of their countries to begin with. I also want people in Japan, as a consuming country of palm oil produced in plantations, to better understand the conditions.”
In conclusion, Professor Koike extended the following message to prospective researchers:
“I did not become a researcher under any strong desire to do so, but ended up being a researcher without knowing it, while I was enjoying my favorite activities in the sea, and had a growing sense of urgency as I learned about the status of the sea environment. In my opinion, to be a researcher is to ‘find a problem, motivate oneself toward resolving the problem, and make steady and persistent efforts toward its resolution, without being defeated by 90% failures.’ I think enthusiasm for the process is the most important thing to have. The more enthusiastic you are, the more spontaneous will be the outcomes that follow. I sincerely hope that you not only learn what you like, but also acquire a variety of cultures and knowledge, and observe people around you with an open mind. Visit sites by yourself, and listen to various people. In this way, a problem (i.e. treasure) that has yet to be explored will reveal itself to you.” |
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| Kazuhiko Koike |
| Professor, Laboratory of Marine Ecosystem Dynamics
April 1, 1994 to December 31, 2006 Associate Professor, Department of Fisheries Sciences, Kitasato University
January 1, 2007 to March 31, 2016 Associate Professor, School of Applied Biological Science, Hiroshima University
Since April 1, 2016 Professor, School of Applied Biological Science, Hiroshima University
Posted on Feb 24, 2017 |
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