Microbial assemblages and production in alluvial aquifers of the Flathead River, Montana, USA
Microbial assemblages and production in alluvial aquifers of the Flathead River, Montana, USA
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DOI：
10.2307/1468361
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发表时间：
1998-12-01
影响因子：
--
通讯作者：
Ward, JV
中科院分区：
文献类型：
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作者：
Ellis, BK;Stanford, JA;Ward, JV
微生物群落的冲积洪泛区含水层的第5和第6阶达到平头河，蒙大拿州，进行了量化采样威尔斯井钻沿着断面（500-5100米）垂直的渠道。在两个河段，细胞密度随着离河流的距离而逐渐降低。在河流水柱中测得的总微生物密度（3.1 x 10（5）个细胞/mL）中，只有2-3%出现在离河流最远的威尔斯井中（9.0 x 10（3）个细胞/mL）。细菌密度的快速下降可能是床沉积物的过滤作用的结果。多元回归分析表明，从河道的站点距离是唯一的变量，解释了大量的细菌密度在下降流区的断面的方差。溶解有机碳（DOC）的生物有效性也可能是重要的细菌的分布，但没有空间相关性，观察使用DOC。然而，连续低的细菌密度在威尔斯远离河流表明，DOC在潜水沃茨主要是耐火材料。在少数威尔斯孔中真菌生物量超过细菌生物量，在许多孔样品中菌丝很常见（高达89个/mL），表明与表面环境有很强的连通性。低真菌密度的河流和高密度的威尔斯位于downgradient的流动路径表明，垂直移民通过渗透和渗透的水从表层土壤，这是典型的高真菌，可能是一个重要的过程影响含水层群落和生产力。在所有地点均观察到原生动物，河流中的密度范围为0 - 64/mL，威尔斯中的密度范围为0 - 213/mL。24个属的藻类的发现以及距离河流4公里处含叶绿素细胞的存在提供了强有力的证据，表明河流微生物群被远距离携带在这些高传输含水层中。在威尔斯井中对小岩石进行培养，结果显示，与间隙沃茨中的稀疏种群相比，石上微生物群落广泛;石上细菌的平均密度为6.3 x 10（6）个细胞/cm（2），而真菌和原生动物的平均密度分别为134个/cm（2）和350个/cm（2）。通过H-3胸苷掺入DNA的速率估计，石缘细菌的产量范围为0.4 - 6.9 μ g Cm（-2）h（-1）。缺乏更高的石生生物量和代谢附近的河流威尔斯表明，非常原始的沃茨的平头河并没有刺激生产。然而，零星增加DOC在春季径流，风暴事件，地下湿润的不饱和区，垂直渗透的雨和雪融化的微生物群落可以非常有效地使用。需要进行更多的研究，将这些冲积含水层的水文地貌过程与源-汇背景下碳和营养物质的时空分布联系起来，以充分阐明对这些贫营养地下水系统中微生物群落的控制。
Microbial communities of alluvial floodplain aquifers of 5th- and 6th-order reaches of the Flathead River, Montana, were quantified by sampling wells drilled along transects (500-5100 m) perpendicular to the channels. Cell densities decreased progressively with distance from the river at both reaches. Only 2-3% of the total microbial densities measured in the river water column (3.1 x 10(5) cells/mL) occurred in wells most distant from the river (9.0 x 10(3) cells/mL). The rapid decline in bacterial densities could be a result of the filtering effect of the bed sediments. Multiple regression analysis indicated that site distance from the river channel was the only variable examined that explained a significant amount of the variance in bacterial densities in the transects in the downwelling region. Bioavailability of dissolved organic carbon (DOC) also may have been important in the distribution of bacteria, but no spatial correlation was observed using DOC. However, continuously low bacterial densities in wells far from the river suggested that DOC in phreatic waters was primarily refractory. Fungal biovolume exceeded bacterial biovolume in a few wells and hyphae were common in many well samples (up to 89/mL), suggesting strong connectivity with the surface environment. Low fungal densities in the river and elevated densities observed in wells located downgradient in the flow path suggested that vertical immigration through infiltration and percolation of water from surface soils, which were typically high in fungi, may have been an important process influencing aquifer communities and productivity. Protozoa were observed at all sites with densities ranging from 0 to 64/mL in the river and 0 to 213/mL in wells. The discovery of 24 genera of algae and the presence of chlorophyll-containing cells 4 km from the river provided strong evidence that riverine microbiota were entrained great distances in these highly transmissive aquifers. Incubation of small rocks in wells revealed an extensive epilithic microbial community compared to sparse populations in interstitial waters; mean density of epilithic bacteria was 6.3 x 10(6) cells/cm(2), whereas fungi and protozoa averaged 134/cm(2) and 350/cm(2), respectively. Epilithic bacterial production estimated by the rate of H-3 thymidine incorporation into DNA, ranged from 0.4 to 6.9 mu g C m(-2) h(-1). Lack of higher epilithic biovolume and metabolism in wells near the river suggested that the very pristine waters of the Flathead River did not stimulate production. However, sporadic increases in DOC during spring runoff, storm events, subsurface wetting of the unsaturated zone, and vertical percolation of rain and snow melt may be used very efficiently by the microbial community. Additional study linking hydrogeomorphic processes in these alluvial aquifers to temporal and spatial distribution of carbon and nutrients in a source-sink context is needed to fully elucidate controls on the microbial communities in these very oligotrophic groundwater systems.