Case studies > Dr.Joji Ishizaka Interview

Interview with Dr.Joji Ishizaka
Photo of Ishizaka Dr.Joji Ishizaka
Texas A&M University Ph.D
Nagasaki University, Faculty of Fisheries
and Institute for East China Sea Research
<Major research themes>
Red tides of Ariake Sea
Primary production of the East China Sea
Primary production of the Japan Sea
Q What kind of topics are you investigating using satellite remote sensing?
Q Remote sensing with satellites currently allows for the measurement of various items. I am particularly interested in a sensor that detects, via the color of the ocean, a pigment called chlorophyll a, which is an indicator of phytoplankton. Phytoplankton is minute organisms that can only be seen with a microscope. However, in sufficient quantity, they change the color of ocean water and from this color it is possible to estimate the amount of phytoplankton in the water.

Q What is phytoplankton’s relationship to mankind?
Q Phytoplankton is food for fish or food for food of fish. From the perspective of the productivity of the ocean, phytoplankton is crucial and its function of producing organic matter via photosynthesis has been called the primary production. Moreover, phytoplankton also play a role of major importance in the global environment as it takes carbon dioxide and other inorganic materials and change them into organic materials which sink deep in the ocean. Conversely, in coastal areas phytoplankton can adversely affect the environment because when phytoplankton become too much amount they generate a red tide, killing fish, creating anoxic water.

Q What can you learn about phytoplankton from satellite remote sensing?
Q Satellite remote sensing allows you to view a broad area of ocean so it makes it easy to understand where phytoplankton is abundant or not. For example, it can also tell us to what an extent a river is having an effect on the ocean. In addition, it can show changes in the ocean that occur with the seasons, such as around Japan in spring and fall when phytoplankton increases. In English this is called a bloom, a phrase taken from the blooming of a flower. Like the cherry blossom front that moves across Japan, there is a “bloom phenomenon” that moves from south to north that can be seen with the help of satellites. Moreover, satellite remote sensing is a comparatively new means of obtaining data, but we have already accumulated close to 10 years of data. With 10 years worth of information, the changes that are occurring become visible and we should be able to know what is the major factor, for example, El Nino, or longer-time scale global warming.

Q Recently what kind of research are you conducting?
Q One topic that I am interesting is that why red tides occur in the Ariake Sea. Recently more red tides are happening in the Ariake Sea and, through the continued monitoring by satellites, we start to understand the relationship between red tides and precipitation. We are also interested in the East China Sea. There are reports that nutrients from an inflow of freshwater from the Yangtze River are causing massive red tide algal blooms, and also there is a large possibility that the construction of a dam on the Changjian River could dramatically change the environment of the East China Sea.
(Interview date: March 14, 2005)

Student interview
Taishi Morita M2
Kyushu Tokai University Department of Engineering graduate
Nagasaki University Graduate School of Science and Technology, Fisheries Science major
Ishizaka Research Team
Q What was your motivation for joining Professor Ishizaka’s research group?
Q While I was a student in the Kyushu Tokai University’s Engineering Department I learned that satellite data can be used to study the inter-annual changes in plants for (Mt.) Aso and earthquake induced changes in the earth’s crust. That was where and how I learned that such satellite data could be used and what piqued my interest in satellites.
Another reason for my interest is that I was born and raised in an area of Kumamoto Prefecture that faces the Ariake Sea, and through fishing and other activities I came to love the ocean.
So all of this led me to want to use satellite imagery to see the local Ariake Sea and, as a result, I found and joined to the research team of Prof. Ishizaka.

Q Please tell us about your current research themes.
Q I am studying about the relation between suspended sediments and phytoplankton in the Ariake Sea using satellite remote sensing.
It has been noticed that in a shallow area of the Ariake Sea, there is strong relationship between tidal motion and suspended sediments and it seems to be influenced to concentration of phytoplankton.
This is where my research comes in, as I work to see if remote sensing by satellite can provide information about this phenomenon for large area.

Q Please tell us about difficult part of your research.
Q One hurdle is that even satellite data covering wide area with frequent observation, ocean data may be missing for a while with cloud. Also, in reviewing satellite data, there is a need to compare it with field data, but in the case of the Ariake Sea, the effect of the tides is incredibly large and the condition of the water can change dramatically in a very short time. As a result, we are struggling to find a way to coordinate the time for satellite and field data for comparisons. This is a topic that we have to work out.
(Interview date: March 14, 2006 )