Microbial Sampling from Shark River Slough and Taylor Slough, Everglades National Park, South Florida (FCE) from January 2001 to Present

We collected monthly observations of water microbial characteristics from each of the FCE LTER sites beginning in February 2001. Bacteria counts using DAPI epifluorescence, heterotrophic bacteria production with tritiated Thymidine uptake, and algal energetics and chl a using the PAM fluorometer were determined from each of the water samples. Bacteria counts in Shark River Slough in the freshwater end of the transect revealed highest bacteria numbers upon marsh rewetting after the dry down. The highest overall count of bacteria was found at the most freshwater point adjacent to the perimeter of the water conservation area but only in March of 2001. Peak numbers of bacteria in the saline end of Shark River transect occurred in December and July. There is some evidence that these higher bacteria numbers in the SR transect are associated with higher salinities. Highest bacteria counts along the Taylor slough transect were observed at the mouth of the Taylor River with peak counts in the wet season in October. Bacteria densities also increased from the eastern to western end of the transect in Florida Bay. Heterotrophic bacterial production did not relate closely bacteria numbers and exhibited highest numbers in the dry season. There was no discernible relationship between salinity and bacteria production as seen in bacteria numbers. Monthly observations using PAM fluorometry revealed that brown algae was the greatest contribution to the algal chal a pool and this relationship was consistent across all FCE LTER sites. Converse to the pattern of bacteria abundance along the Shark River transect, there was evidence that algal biomass decreases from freshwater to estuary. In the Shark River, algal energetics increased from marsh to estuary as well as in the panhandle region of the Taylor River transect. From these observations we conclude the behavior of the microbial loop and interactions generated between functional guilds is highly variable along individual transects and between the Shark River and Taylor River transect. Wet dry season dynamics partially explain temporal variability in microbial dynamics along the individual transects yet responses were unique for each section of the transect as freshwater versus estuarine versus Bay. Relationships between salinity and microbial parameters in this case, were not easily discerned but were more consistent within the two river transects than between river transects.

本研究自2001年2月起，对FCE LTER（Florida Coastal Everglades Long Term Ecological Research）站点的水体微生物特征开展月度观测。研究对所有水体样本均完成了以下检测：采用DAPI荧光染色荧光显微术进行细菌计数，以氚标记胸苷摄入法测定异养细菌生产力，通过PAM荧光仪（Pulse Amplitude Modulation fluorometer）测定藻类能量代谢与叶绿素a（chlorophyll a, chl a）含量。对样带淡水端的鲨鱼河沼泽（Shark River Slough）的细菌计数结果显示，干旱期后沼泽复湿阶段的细菌数量达到峰值。2001年3月，紧邻水源保护区边界的最淡水点位的细菌总数为所有采样点中的最高值。鲨鱼河槽样带咸水端的细菌数量峰值出现在12月与7月，有证据表明该样带内较高的细菌数量与更高盐度存在关联。泰勒河槽样带的最高细菌计数出现在泰勒河河口，湿季10月达到数量峰值；佛罗里达湾（Florida Bay）样带的细菌密度同样从东向西逐渐升高。异养细菌生产力与细菌数量并未呈现显著关联，其峰值出现在旱季，且与细菌数量的规律不同，盐度与细菌生产力之间未发现可辨识的关联。通过PAM荧光仪开展的月度观测结果显示，褐藻对藻类叶绿素a库的贡献最大，且这一规律在所有FCE LTER站点中均保持一致。与鲨鱼河槽样带的细菌丰度模式相反，有证据表明藻类生物量从淡水区向河口区逐渐降低；在鲨鱼河与泰勒河槽样带的狭长地带段，藻类能量代谢均从沼泽区向河口区逐渐升高。基于上述观测结果，本研究认为：微生物环（microbial loop）的动态变化以及功能群（functional guilds）之间的相互作用，在单个样带内部以及鲨鱼河槽与泰勒河槽样带之间均存在显著差异。干湿季动态能够部分解释单个样带内微生物动态的时间变异性，但不同区段（淡水区、河口区与海湾区）的响应特征各不相同。本研究中盐度与微生物参数之间的关联并不容易辨识，但相较于两条河槽样带之间的关联，两条样带内部的关联更为一致。