11:50 AM - 12:10 PM
[MIS15-11] Has geodiversity contributed on diatom biodiversity in subalpine ponds on the northern Japanese Alps?
★Invited Papers
Keywords:diatom, biodiversity, ubiquitous distribution, geodiversity, the northern Japanese Alps, subalpine ponds
Diatoms are unicellular primary producers that are widely distributed in any water bodies, such as oceans, lakes, ponds, rivers, marshes and soils. Because of their widespread distribution, habitats of each diatom species are often understood to be controlled by environmental factors like salinity, acidity, nutrient concentrations and pollution. We unconsciously assume ubiquitous distribution that diatoms have the ability to rapidly expand their distribution and can grow anywhere as long as the environment is suitable. On the other hand, the dispersal of diatoms between water bodies is not fully understood, and the mechanisms that maintain their ubiquitous distribution are unknown. It has also been suggested that long distance limit the ubiquitous distribution of freshwater diatoms, as implied by the extremely low diversity of diatoms on oceanic islands, which are geographically isolated from other freshwater bodies. In fact, significant number of relic species and lineages in ancient lakes with exceptionally long histories are known to have limited geographical distributions. Time and geographic scales of diatom dispersal should be demonstrated to shape local diatom diversity.
The aim of this study, therefore, is to reveal restricted diatom dispersal in a subalpine region where slope collapses and mass movements frequently create ponds or fill them up. Diatom flora of subalpine ponds in the Northern Alps, are tested to be influenced not only by environmental factors such as water quality but also by geodiversity (origin of landforms, microclimate or hydrological settings caused by landforms). We have collected surface sediments from more than 50 ponds and identified more than 75 diatom taxa from the sediments based on morphological observations of their frustules. Some of these taxa are difficult to identify to species under a light microscope and can only be classified to genera, while others cannot be identified to known species. Although there are still some taxonomic problems to be solved, the results of the diatom flora were statistically tested to evaluate the diversity and similarity between the flora of the ponds. The results show that the diversity is high in the low elevation ponds along the Azusa River and low in the high elevation ponds on the mountain ridge. In addition, the diatom flora of ponds in the same mountain massif or drainage basin, which are geographically close to each other, show similarities. Factors explaining these diatom distributions are further discussed and perspectives on how geodiversity influences diatom diversity will be presented.
The aim of this study, therefore, is to reveal restricted diatom dispersal in a subalpine region where slope collapses and mass movements frequently create ponds or fill them up. Diatom flora of subalpine ponds in the Northern Alps, are tested to be influenced not only by environmental factors such as water quality but also by geodiversity (origin of landforms, microclimate or hydrological settings caused by landforms). We have collected surface sediments from more than 50 ponds and identified more than 75 diatom taxa from the sediments based on morphological observations of their frustules. Some of these taxa are difficult to identify to species under a light microscope and can only be classified to genera, while others cannot be identified to known species. Although there are still some taxonomic problems to be solved, the results of the diatom flora were statistically tested to evaluate the diversity and similarity between the flora of the ponds. The results show that the diversity is high in the low elevation ponds along the Azusa River and low in the high elevation ponds on the mountain ridge. In addition, the diatom flora of ponds in the same mountain massif or drainage basin, which are geographically close to each other, show similarities. Factors explaining these diatom distributions are further discussed and perspectives on how geodiversity influences diatom diversity will be presented.