Microbial ecology and environmental monitoring in micro-habitat in streams

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We have developed a new sampling method for collecting microorganisms living on pebbles in streams to minimize the loss of microorganisms. Cell densities of bacteria, heterotrophic nanoflagellates and ciliates collected by the new method tended to be higher than those obtained by the conventional method. Significant correlations between concentration of chlorophyll α and cell densities of heterotrophic microorganisms, and among heterotrophic microorganisms suggest the presence of active microbial food webs in streams. As a next step, benthic bacterial cell densities and production rates together with chlorophyll concentration and primary production of periphyton on biofilm pebbles in a stream were analyzed to examine whether primary production supports bacterial production in this natural aquatic biofilm. Percentages of bacterial production to net primary production were calculated as 61 to 435% with the assumption of bacterial growth yield as 30%. Thus, it is likely that both autochthonous and allochthonous supplies of organic matter are important for production of bacteria in the pebble biofilms that develop in fresh water streams. Abundance and composition of microorganisms are susceptible to subtle environmental changes. Hence, we tried to detect the changes in biofilms using Microsensors (Unisense). The Microsensors could determine vertical profiles of current velocity and dissolved oxygen concentration in biofilms. These profiles were different, depending on biofilms. This is attributable to abundance and composition of dominant periphyton algae in biofilms.