Effects of Larval Mosquitoes (Aedes triseriatus) and Stemflow on Microbial Community Dynamics in Container Habitats

The dynamics of the microbial food sources for Aedes triseriatus larvae in microcosms were found to be strongly influenced by larval presence. The total abundance of bacteria in water samples generally increased in response to larvae, including populations of cultivable, facultatively anaerobic bacteria. Additionally, a portion of the community shifted from Pseudomonaceae to Enterobacteriaceae. Bacterial abundance on leaf material was significantly reduced in the presence of actively feeding larvae. Principle-component analysis of whole community fatty acid methyl ester (FAME) profiles showed that larvae changed the microbial community structure in both the water column and the leaf material. Cyclopropyl FAMEs, typically associated with bacteria, were reduced in microcosms containing larvae; however, other bacterial fatty acids showed no consistent response. Long-chain polyunsaturated fatty acids characteristic of microeukaryotes (protozoans and meiofauna) declined in abundance when larvae were present, indicating that larval feeding reduced the densities of these microorganisms. However, presumed fungal lipid markers either increased or were unchanged in response to larvae. Larval presence also affected microbial nitrogen metabolism through modification of the physiochemical conditions or by grazing on populations of bacteria involved in nitrification-denitrification. Stemflow primarily influenced inorganic ion and organic compound concentrations in the microcosms and had less-pronounced effects on microbial community parameters than did larval presence. Stemflow treatments diluted concentrations of all inorganic ions (chloride, sulfate, and ammonium) and organic compounds (total dissolved organic carbon, soluble carbohydrates, and total protein) measured, with the exceptions of nitrite and nitrate. Stemflow addition did not measurably affect larval biomass in the microcosms but did enhance development rates and early emergence patterns of adults.

本研究发现，微宇宙（microcosms）系统内三带伊蚊（Aedes triseriatus）幼虫的微生物食物源动态，受幼虫存在与否的影响极为显著。水体样本中的细菌总丰度通常随幼虫的存在而升高，其中包括可培养兼性厌氧菌的种群。此外，群落中的部分类群从假单胞菌科（Pseudomonaceae）向肠杆菌科（Enterobacteriaceae）发生演替。在活跃取食的幼虫存在时，叶片基质上的细菌丰度会显著降低。对全群落脂肪酸甲酯（fatty acid methyl ester, FAME）谱图进行主成分分析后发现，幼虫会改变水体及叶片基质中的微生物群落结构。通常与细菌相关的环丙烷型脂肪酸甲酯，在含幼虫的微宇宙系统中丰度有所降低，但其他细菌源脂肪酸并未表现出一致的响应规律。当幼虫存在时，作为微型真核生物（原生动物（protozoans）与小型后生动物（meiofauna））特征标志物的长链多不饱和脂肪酸丰度出现下降，表明幼虫的取食行为降低了这类微生物的种群密度。但被认为是真菌脂质标志物的成分，其丰度随幼虫存在而升高或保持不变。幼虫的存在还可通过改变系统理化环境，或是捕食参与硝化-反硝化（nitrification-denitrification）作用的细菌种群，来影响微生物的氮代谢过程。茎流（Stemflow）主要影响微宇宙系统中的无机离子与有机化合物浓度，其对微生物群落参数的影响程度显著弱于幼虫的存在。茎流处理会稀释所有被检测的无机离子（氯离子、硫酸根离子与铵根离子）及有机化合物（总溶解有机碳、可溶性碳水化合物与总蛋白）的浓度，亚硝酸盐（nitrite）与硝酸盐（nitrate）除外。施加茎流未对微宇宙系统中的幼虫生物量产生可检测的影响，但确实提升了成虫的发育速率，并改变了其早期羽化规律。