Importance of pigmented and colourless nano-sized protists as grazers on nanoplankton in a phosphate-depleted Norwegian fjord and in enclosures
Importance of pigmented and colourless nano-sized protists as grazers on nanoplankton in a phosphate-depleted Norwegian fjord and in enclosures
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在磷酸盐耗尽的挪威峡湾和围栏中，有色和无色纳米级原生生物作为纳米浮游生物的食草者的重要性
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
Hansen As
中科院分区：
文献类型：
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作者：
H. Havskum;Hansen As
研究了纳米级无色鞭毛虫、纤毛虫和兼养甲藻的颗粒食物大小以及兼养和严格异养原生生物之间的竞争。1995年7月，从挪威Hylsfjord的磷酸盐耗尽的表层和营养操纵的外壳在1周期间收集样品。在研究期的最后一天，使用荧光标记的藻类（弗拉）和细菌（FLB）进行的放牧实验表明，大小为10-20 μ m的食食性原生生物对微型浮游生物有相当大的放牧影响，但对微型浮游生物没有影响。相比之下，较小的无色鞭毛虫，大小为5-10 μ m。FLB显著增加。在富磷围隔中，严格的光合原生生物和异养细菌的生长受到刺激。在研究期结束时，无色鞭毛虫和纤毛虫的生物量也远远高于在非富磷的外壳和峡湾的表层，在富磷的外壳。与此相反，混合营养甲藻有一个类似的生物量，无论磷酸盐富集。在非富磷环境中，混合营养型的原生动物对FL大小的2-5 μ m猎物的摄食份额平均为34%，在富磷环境中为12%。额外的光养模式的营养可能给的mixotrophs更好的手段，严格的异养原生生物在环境中的猎物密度或生产是低的竞争。这一发现，色素和无色nanoprotists有相当大的放牧影响2-5 μ m原生生物（纳米尺寸部分的一部分）是重要的微生物食物网的有机体之间的关系的理解。
Particulate food sizes of nano-sized colourless flagellates, ciliates, and mixotrophic dinoflagellates were investigated as well as the competition between mixotrophic and strictly heterotrophic protists. Samples were collected during 1 wk in July 1995 from the phosphate-depleted surface layer of the Hylsfjord, Norway, and from nutrient-manipulated enclosures. Grazing experiments conducted on the last day of the study period, using fluorescently labelled algae (FLA) and bacteria (FLB), suggested that phagotrophic protists, 10-20 pm in size, had a considerable grazing unpact on nanoplankton, but not on picoplankton. In contrast, smaller colourless flagellates, 5-10 pm in size. ingested FLB significantly. In phosphate-enriched enclosures, the growth of strictly phototrophic protists and of heterotrophic bacteria was stimulated. At the end of the study period, the biomass of colourless flagellates and ciliates was also much higher in phosphate-enriched enclosures than in nonphosphate-enriched enclosures and the surface layer of the fjord. In contrast, mixotrophc dinoflagellates had a similar biomass regardless of phosphate enrichment. Mixotroph share of protist grazing on FLA-sized, 2-5 pm prey was on average 34 % in non-phosphate-enriched environments and 12% in phosphate-enriched enclosures. The additional phototrophic mode of nutrition probably gave the mixotrophs better means to compete with strictly heterotrophic protists in environments where the prey density or production was low. The finding that both pigmented and colourless nanoprotists had a considerable grazing impact on 2-5 Ilm protists (part of the nano size fraction) is important for the understanding of the relationships between organisms of the microbial food web.