PDF(Pubmed)
Abstract：
Small lentic water bodies are important emitters of methane (CH4) and carbon dioxide (CO2), but the processes regulating their dynamics and susceptibility to human-induced stressors are not fully understood. Bioturbation by chironomid larvae has been proposed as a potentially important factor controlling the dynamics of both gases in aquatic sediments. Chironomid abundance can be affected by the application of biocides for mosquito control, such as Bti (Bacillus thuringiensis var. israelensis). Previous research has attributed increases in CH4 and CO2 emissions after Bti application to reduced bioturbation by chironomids. In this study, we separately tested the effect of chironomid bioturbation and Bti addition on CH4 production and emission from natural sediments. In a set of 15 microcosms, we compared CH4 and CO2 emission and production rates with high and low densities of chironomid larvae at the bioturbating stage, and standard and five times (5x) standard Bti dose, with control sediments that contained neither chironomid larvae nor Bti. Regardless of larvae density, chironomid larvae did not affect CH4 nor CO2 emission and production of the sediment, although both rates were more variable in the treatments with organisms. 5xBti dosage, however, led to a more than three-fold increase in CH4 and CO2 production rates, likely stimulated by bioavailable dissolved carbon in the Bti excipient and priming effects. Our results suggest weak effects of bioturbating chironomid larvae on the CH4 and CO2 dynamics in aquatic ecosystems. Furthermore, our results point out towards potential functional implications of Bti for carbon cycling beyond those mediated by changes in the macroinvertebrate community.
摘要：
小实体水体是甲烷（CH4）和二氧化碳（CO2）的重要排放者，但是调节其动力学和对人为应激源的敏感性的过程尚未完全了解。已提出摇蚊幼虫的生物扰动是控制水生沉积物中两种气体动力学的潜在重要因素。摇蚊的丰度可能会受到杀虫剂用于控制蚊子的应用的影响，例如Bti（苏云金芽孢杆菌var。以色列）。先前的研究将Bti应用后CH4和CO2排放量的增加归因于减少了chironomids的生物扰动。在这项研究中,我们分别测试了摇蚊生物扰动和Bti添加对天然沉积物中CH4产生和排放的影响。在一组15个缩影中，我们比较了CH4和CO2的排放和生产率与高和低密度的摇蚊幼虫在生物扰动阶段，和标准和五倍（5倍）标准Bti剂量，对照沉积物既不包含摇蚊幼虫也不包含Bti。不管幼虫密度如何,摇蚊幼虫不影响CH4或CO2排放和沉积物的产生，尽管在使用生物体的治疗中这两种比率差异更大。5xBti剂量，然而,导致CH4和CO2生产率增加了三倍以上，可能受到Bti赋形剂中生物可利用的溶解碳和引发效应的刺激。我们的结果表明，生物扰动摇蚊幼虫对水生生态系统中CH4和CO2动力学的影响较弱。此外，我们的结果指出了Bti对碳循环的潜在功能影响，超出了大型无脊椎动物群落变化所介导的功能。
