Microbial Sampling from Shark River Slough and Taylor Slough, Everglades National Park, South Florida from January 2001 to April 2012

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.

本研究于2001年2月起，对佛罗里达海岸大沼泽地长期生态研究（Florida Coastal Everglades Long Term Ecological Research, FCE LTER）各监测站点的水体微生物特征开展月度观测。针对每份水体样本，均采用DAPI落射荧光法进行细菌计数、采用氚标记胸苷摄取法测定异养细菌生产力，并借助脉冲振幅调制（Pulse-Amplitude-Modulation, PAM）荧光仪分析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开展的细菌计数结果显示，沼泽经历干旱干涸后复湿时，细菌数量达到峰值。2001年3月，紧邻水源保护区边界的淡水端站点细菌总数为所有观测中的最高值。鲨鱼河样带咸水端的细菌数量峰值出现在12月与7月，现有证据表明该样带内较高的细菌丰度与更高盐度存在关联。泰勒河沼泽样带的最高细菌计数出现在泰勒河河口，且峰值位于10月的湿季；佛罗里达湾样带的细菌密度则从样带东端向西端逐步升高。异养细菌生产力与细菌数量的相关性较弱，且其峰值出现在旱季；与细菌数量的变化规律不同，盐度与异养细菌生产力之间未发现显著关联。借助PAM荧光仪开展的月度观测结果显示，褐藻是藻类叶绿素a库的最主要贡献组分，该规律在所有FCE LTER站点均保持一致。与鲨鱼河样带内细菌丰度的变化模式相反，藻类生物量从淡水端向河口端逐渐降低。在鲨鱼河样带与泰勒河样带的锅柄状狭长区段，藻类能量代谢均呈现从沼泽向河口逐步升高的趋势。基于上述观测结果，本研究认为：微生物食物环的动态特征以及不同功能群之间的相互作用，在单条样带内部以及鲨鱼河与泰勒河样带之间均存在显著差异。干湿季动态可以部分解释单条样带内微生物动态的时间变异性，但不同样带区段（淡水区、河口区与海湾区）的响应模式各具特色。本研究中盐度与微生物参数之间的关联并不明确，但相较于不同河流样带之间，该关联在两条河流样带内部的一致性更强。