Stratification and dynamics of microbial loop communities in Lake Fryxell, Antarctica
Stratification and dynamics of microbial loop communities in Lake Fryxell, Antarctica
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DOI：
10.1046/j.1365-2427.2000.00612.x
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发表时间：
2000-08-01
影响因子：
2.7
通讯作者：
Novarino, G
中科院分区：
文献类型：
--
作者：
Roberts, EC;Laybourn-Parry, J;Novarino, G
1.弗莱克塞尔湖位于南极洲麦克默多干燥河谷，在没有甲壳类浮游动物和其他高等生物的情况下，提供了研究微生物循环过程的机会。这是首次对弗莱克塞尔湖进行的研究，提供了微生物环状生物体的详细的时间和垂直变化。原生动物群落集中在弗莱克塞尔湖的化跃层(9-10米)周围。光养纳米鞭毛虫、异养纳米鞭毛虫和纤毛虫分别形成14580、694和58个细胞的最大值。虽然化跃层的丰度和生物量较高，但原生动物多样性较低，纤毛虫生物量占纤毛虫总数的80%。在混合层(4.5-8m)中，原生动物数量较少，但种类较多，在该水柱区域内鉴定出24种纤毛虫形态类型。原生动物生物量和丰度的年际变化在混合层中比在化学跃层中大，这是因为营养物质和猎物的浓度变化较大。弗莱克塞尔湖的物理化学梯度非常稳定，因为常年的冰盖减少了风力驱动的洋流。因此，纤毛虫物种分布在不同的深度地层中，单甲虫最多，Askenasia在8m处最多，斜纹藻在化斜层的纤毛虫生物量占主导地位。缺乏垂直混合减少了PNAN和纤毛虫物种的季节演替。PNAN群落一直以三种隐芽植物为主(占总生物量的79%)。
1. Lake Fryxell, situated in the McMurdo Dry Valleys, Antarctica, offers the opportunity to study microbial loop processes in the absence of crustacean zooplankton and other higher organisms. This is the first study of Lake Fryxell to provide detailed temporal and vertical variations of microbial loop organisms.2. Protozoan communities are concentrated around the chemocline (9-10 m) in Lake Fryxell. Phototrophic nanoflagellates (PNAN), heterotrophic nanoflagellates (HNAN) and ciliates formed deep maxima of 14580, 694 and 58 cells mL(-1) respectively. Although abundance and biomass at the chemocline was high, diversity of protozoa was low, Plagiacampa accounting for > 80% of the total ciliate biomass.3. In the mixolimnion (4.5-8 m), protozoa were less abundant, but more diverse, with 24 ciliate morphotypes being identified within this region of the water column. Interannual variability of protozoan biomass and abundance was greater in the mixolimnion than at the chemocline due to more variable nutrient and prey concentrations.4. Physicochemical gradients in Lake Fryxell were very stable because the perennial ice cover reduced wind driven currents. As a consequence, ciliate species occurred in distinct depth strata, Monodinium being most abundant directly beneath the ice cover, Askenasia having maximum abundance at 8 m and Plagiocampa dominating ciliate biomass at the chemocline. The lack of vertical mixing reduced seasonal successions of PNAN and ciliate species. Three cryptophyte species dominated the PNAN community at all times (> 79% of total biomass).