Linkage between microbial loop and grazing food chain in benthic environments of streams

1. 我们利用微电极测定了人工基质和天然基质上生物膜流速和溶解氧饱和度的垂直变化。流速随深度的垂直剖面显示存在粘性亚层。我们的研究结果还表明，基材表面的光滑度与DO饱和度的垂直分布有关。一年来，我们几乎每月都对河床卵石生物膜中微生物生产力的各种测量结果进行分析，以量化初级生产作为有机物质的原生来源的重要性，这些有机物质用于支持这种天然微生物栖息地动态食物网中异养细菌的生产。很可能原生和外来的有机物供应对于在快速流动的淡水溪流中形成的卵石生物膜中的细菌的产生都是重要的。2004年7 - 8月，我们在以富营养化水库为主要水源的爱himme市Hiji Steram进行了水生昆虫对微藻的食物选择性研究。我们的研究结果表明，Cheumatopsyche在微囊藻的群体规模较小时选择性地吃草，并且这种昆虫对一些真核微藻如Pediastrum和synedra3表现出选择性吃草。为了验证关于周围植物和食草动物之间线索交流的假设，我们用带壳的食虱（Glossosoma spp.）和微藻进行了两种实验室通道实验。虽然对颗粒线索（即化学气味和视觉漂移微藻）的选择性高于溶解线索（仅化学气味），但颗粒和溶解线索之间的选择性也没有显著差异。由此得出结论，舌藻幼虫既能探测到视觉信号（即漂浮的微藻），也能探测到化学信号。

1. We determined vertical changes in flow velocity and dissolved oxygen saturation in biofilms on artificial and natural substrates using microelectrodes. Vertical profile of current velocity versus depth indicated a presence of viscous sublayer. Our results also suggest smoothness of substrate surface is related to vertical profile of DO saturation.2. Various measurements of microbial productivity in streambed pebble biofilms were analyzed almost monthly for one year to quantify the importance of primary production as an autochthonous source of organic matter utilized to support heterotrophic bacterial production in the dynamic food web within this natural microbial habitat. 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 rapidly flowing fresh water streams.3. We examined food selectivity on microalgae by aquatic insects in Hiji Steram, Ehime, whose main water source is a eutrophic reservoir, from July to August 2004. Our results suggest that Cheumatopsyche selectively grazes on Microcystis when the size of the colony is small, and that the insect shows selective grazing on some eukaryotic microalgae such as Pediastrum and Synedra.4. To test hypotheses relating the cue communication between periphyton and grazers, we performed two kinds of laboratory channel experiments using case-bearing caddisfly grazer (Glossosoma spp.) and microalgal cue. Although the selectivity to the particle cue (i.e., chemical scent and visual drifting microalgae) was higher than that of the dissolved cue (only chemical scent), the selectivity was also not significantly different between the particle and the dissolved cues. Thus, it was concluded that Glossosoma larvae were able to detect both the visual (i.e., drifted microalgae) and the chemical cues.