| Co-Investigator(Kenkyū-buntansha) |
TOGASHI Tatsuya Chiba Univ., Marine Biosystems Res. Ctr., Assist. Prof., 海洋バイオシステム研究センター, 助手 (70345007)
YOSHIMURA Jin Shizuoka Univ., Fac. of Engineering, Professor, 創造科学技術大学院, 教授 (10291957)
|
|---|
| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
|
|---|
| Research Abstract |
In this project, we studied mechanisms of phytoplankton coexistence, experimentally and theoretically.
(1) Culture experiments: Using continuous cultures of phytoplanktonic species, we examined coexistence and competition under various concentration of nutrients and flow speed of culture medium. Competition and exclusion of the green alga Scenedesmus quadricauda and the cyanobacterium Microcystis novacekii depended on nutrient concentration and flow speed of supply culture medium. Since experiments with varying supply modes of the medium, especially, has not been tried to date, the present results on the effects of the supply mode were new.
(2) Theoretical analysis: Competition in the low flow continuous culture, the paradox of plankton and the paradox of enrichment were examined. Dominant species in homogeneous environments is considered to be one or a few. Phytoplankton species diversity is usually high, though water environments seems homogeneous. This high diversity has been called "
… More
the paradox of plankton." In the higher nutrient conditions, diversity is considered to increase. However, diversity in the field observation of many water environments, this is not the case. This diversity change along nutrient gradient is called "the paradox of enrichment."
In the low nutrient and low flow continuous cultures, phytoplankton species were not necessarily under nominative concentration of nutrients, but were in reality under lower nutrient concentrations. This relation was species-specific and explained the lower diversity low in lower nutrient conditions. In the lattice model, we assumed slight differences in growth of ten species. We introduced "ecological time scale" that means it is long ecologically, but in the time scales the system is not in stable conditions. In this theoretical framework, we examined changes in the number of species. This growth rate depended on nutrient concentrations in the ecological time scale. Phytoplankton species grew more locally than it is generally considered. The local growth explained "the paradox of plankton". In higher nutrients, each species grew more globally, and some species became excluded. This means "the paradox of enrichment." Less
|
