Duan Yingbo, Sen Biswarup, Xie Ningdong, Paterson James S, Chen Zixi, Wang Guangyi
Center for Marine Environmental Ecology, School of Environmental Science and Engineering, Tianjin University.
School of Biological Sciences, Flinders University.
Microbes Environ. 2018 Jul 4;33(2):195-204. doi: 10.1264/jsme2.ME17162. Epub 2018 Jun 16.
Marine fungus-like eukaryotic unicellular protists (thraustochytrids) are considered to play an important role in the marine microbial food web. However, their abundance, distribution, and relative biomass in coastal waters have not yet been examined in detail. By using a flow cytometry method (FCM) for the rapid enumeration of thraustochytrids in nearshore and offshore stations along the Gulf of Bohai, China, we herein expanded current knowledge on their ecological significance. The FCM method allows for the rapid detection and quantification of prokaryotic and eukaryotic cells, but is rarely applied to the enumeration of small eukaryotic protists. Epifluorescence microscopy (EpiM) has been commonly used for the direct detection and enumeration of thraustochytrids; however, this method is time-consuming and inapplicable to a large-scale analysis of complex seawater samples. There is no available FCM method to track the abundance and biomass of thraustochytrids in marine habitats. The FCM enumeration of thraustochytrids in seawater samples ranged between 400 and 4,080 cells mL with a biomass range of 8.15-83.96 μg C L. The thraustochytrid biomass contributed 10.9% to 98.1% of the total biomass of the heterotrophic microbial community comprising bacterioplankton and thraustochytrids. Their overall abundance in nearshore stations was significantly different from that in offshore stations (P<0.5). The present results provide an optimized method for the rapid detection and enumeration of thraustochytrids in seawater and facilitate large-scale studies of the ecological role of thraustochytrids in the microbial food web of coastal waters.
海洋类真菌真核单细胞原生生物（破囊壶菌）被认为在海洋微生物食物网中发挥着重要作用。然而，它们在沿海水域的丰度、分布和相对生物量尚未得到详细研究。通过使用流式细胞术（FCM）方法快速计数中国渤海湾近岸和离岸站点的破囊壶菌，我们在此扩展了关于它们生态意义的现有知识。FCM方法可用于快速检测和定量原核和真核细胞，但很少应用于小型真核原生生物的计数。落射荧光显微镜（EpiM）通常用于直接检测和计数破囊壶菌；然而，这种方法耗时且不适用于对复杂海水样本的大规模分析。目前没有可用的FCM方法来追踪海洋生境中破囊壶菌的丰度和生物量。海水样本中破囊壶菌的FCM计数范围为400至4080个细胞/毫升，生物量范围为8.15 - 83.96微克碳/升。破囊壶菌生物量占由浮游细菌和破囊壶菌组成的异养微生物群落总生物量的10.9%至98.1%。它们在近岸站点的总体丰度与离岸站点的显著不同（P<0.5）。本研究结果提供了一种优化的方法，用于快速检测和计数海水中的破囊壶菌，并有助于大规模研究破囊壶菌在沿海水域微生物食物网中的生态作用。
