Prochlorophytes as secondary prey for heterotrophic nanoflagellates in the deep chlorophyll maximum layer of the (sub)tropical North Atlantic
Prochlorophytes as secondary prey for heterotrophic nanoflagellates in the deep chlorophyll maximum layer of the (sub)tropical North Atlantic
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DOI：
10.3354/meps204053
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发表时间：
2000-01-01
影响因子：
2.5
通讯作者：
Witte, HJ
中科院分区：
文献类型：
--
作者：
Kuipers, BR;Witte, HJ
利用稀释技术研究了北大西洋（亚热带）热带低光带原绿藻的生长速率及其在放牧作用下的损失率。在“深叶绿素最大值”（DCM）正上方，原叶绿素生长速率约为0.3 d(-1)，放牧速率约为0.4 d(-1)；这两个比率在DCM内和直接低于DCM。3个孔径过滤器对放牧的影响较弱，表明异养纳米鞭毛虫是主要的食草动物。白天和夜间的区分表明，DCM以上的原绿藻在白天分裂，在3 d以上翻倍，而在更深的地方，分裂发生在夜间。相比之下，放牧总是局限于白天，放牧率与原绿藻丰度、生长速度或分裂时间无关。然而，原绿藻的掠食率与同一层中更丰富的异养细菌的损失率相关。因此，我们得出结论，原藻类是异养纳米鞭毛虫捕食异养细菌的次要猎物。
Growth rates in prochlorophytes and their loss rates to grazing were investigated by the dilution technique in the lower euphotic zone of the (sub)tropical North Atlantic. Directly above the 'deep chlorophyll maximum' (DCM), prochlorophyte growth rates were approximately 0.3 d(-1) and grazing rates 0.4 d(-1); both rates were considerably lower in and directly below the DCM. Grazing was only weakly affected by filtration through 3 mum pore-size filters, indicating heterotrophic nanoflagellates as the main grazers. Discrimination between day and night revealed that the prochlorophytes above the DCM, with doubling times of 3 d or more, divided during the day whereas at greater depth division occurred during the night. In contrast, grazing was always restricted to the daylight period and grazing rate was independent of prochlorophyte abundance, growth rate or time of division. Prochlorophyte grazing rates were, however, correlated with the loss rates in the much more abundant heterotrophic bacteria in the same layers. We conclude therefore that prochlorophytes are consumed as a secondary prey by heterotrophic nanoflagellates grazing on heterotrophic bacteria.