Savannah River Ecology Laboratory, University of Georgia, P. O. Drawer E, Aiken, SC, 29802, USA.
Environ Pollut. 2022 May 1;300:118976. doi: 10.1016/j.envpol.2022.118976. Epub 2022 Feb 9.
Dragonfly adults and their aquatic immature stages are important parts of food webs and provide a link between aquatic and terrestrial components. During emergence, contaminants can be exported into terrestrial food webs as immature adults fly away or be shed with their exuviae and remain in the wetland. Our previous work established metals accumulating in dragonfly nymphs throughout a contaminated constructed wetland designed to regulate pH and sequester trace metals from an industrial effluent line. Here, we evaluated the concentration and mass of metals leaving the wetland in flying emergents versus remaining in the wetland with the shed exuviae in 10 species of dragonflies belonging to 8 genera. Nine elements (Cu, Zn, Cd, Mn, V, Mg, Fe, Al, Pb) were evaluated that include essential and nonessential elements as well as trace and major metals. Metal concentrations in the emergent body and exuviae can differ by orders of magnitude. Aluminum, Fe, Mn, and Pb were largely shed in the exuviae. Vanadium and Cd were more variable among species but also tended to be shed with the exuviae. In contrast, Cu, Zn, and Mg showed a higher tendency to leave the wetland with an emerging dragonfly. Metals shed in dragonfly exuviae can moderate the transport of metals from contaminated wetlands. Taxonomic- and metal-specific variability in daily metal flux from the wetland depended upon concentration accumulated, individual body mass, and number of individuals emerging, with each factor's relative importance often differing among species. This illustrates the importance of evaluating the mass of metals in an individual and not only concentrations. Furthermore, differences in numbers of each species emerging will magnify differences in individual metal flux when calculating community metal flux. A better understanding of the variability of metal accumulation in nymphs/larvae and metal shedding during metamorphosis among both metals and species is needed.
蜻蜓成虫及其水生若虫是食物网的重要组成部分，它们在水生和陆地成分之间提供了联系。在羽化过程中，污染物可以随着不成熟的成虫飞走或随着它们的蜕壳而被排出到陆地食物网中，并留在湿地中。我们之前的工作已经确定，在一个设计用来调节 pH 值并从工业废水线中隔离痕量金属的受污染的人工湿地中，金属在蜻蜓若虫体内积累。在这里，我们评估了在 10 种属于 8 个属的蜻蜓中，飞走的成虫与留在湿地中带有蜕壳的成虫之间，离开湿地的金属浓度和质量。评估了 9 种元素（Cu、Zn、Cd、Mn、V、Mg、Fe、Al、Pb），包括必需和非必需元素以及痕量和主要金属。成虫体和蜕壳中的金属浓度可以相差几个数量级。铝、铁、锰和铅主要在蜕壳中被排出。钒和镉在物种间变化较大，但也倾向于随蜕壳排出。相比之下，Cu、Zn 和 Mg 更倾向于随成虫离开湿地。在蜻蜓蜕壳中排出的金属可以调节受污染湿地中金属的传输。来自湿地的每日金属通量的分类和金属特异性变化取决于积累的浓度、个体体重和成虫数量，每个因素的相对重要性在物种之间往往不同。这说明了评估个体金属质量而不仅仅是浓度的重要性。此外，在计算群落金属通量时，由于每种物种的成虫数量不同，金属通量的个体差异会放大。需要更好地了解金属在若虫/幼虫中的积累和金属在变态过程中的排出的变异性，以及金属和物种之间的差异。
