Data from: Pollution-tolerant invertebrates enhance greenhouse gas flux in urban wetlands

One of the goals of urban ecology is to link community structure to ecosystem function in urban habitats. Pollution-tolerant wetland invertebrates have been shown to enhance greenhouse gas (GHG) flux in controlled laboratory experiments, suggesting that they may influence urban wetland roles as sources or sinks of GHG. However, it is unclear if their effects can be detected in highly variable conditions in a field setting. Here we use an extensive dataset on carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) flux in sediment cores (n = 103) collected from ten urban wetlands in Melbourne, Australia during summer and winter in order to test for invertebrate enhancement of GHG flux. We detected significant multiplicative enhancement effects of temperature, sediment carbon content, and invertebrate density on CH4 and CO2 flux. Each doubling in density of oligochaete worms or large benthic invertebrates (oligochaete worms and midge larvae) corresponded to ~42% and ~15% increases in average CH4 and CO2 flux, respectively. However, despite exceptionally high densities, invertebrates did not appear to enhance N2O flux. This was likely due to fairly high organic carbon content in sediments (range: 2.1-12.6%), and relatively low nitrate availability (median 1.96 μM NO3--N), which highlights the context-dependent nature of community structural effects on ecosystem function. The invertebrates enhancing GHG flux in this study are ubiquitous, and frequently dominate faunal communities in impaired aquatic ecosystems. Therefore, invertebrate effects on CO2 and CH4 flux may be common in wetlands impacted by urbanization, and urban wetlands may make greater contributions to the total GHG budgets of cities if the negative impacts of urbanization on wetlands are left unchecked.

城市生态学的核心目标之一，是将城市生境中的群落结构与生态系统功能建立关联。已有研究表明，耐污染湿地无脊椎动物可在受控实验室实验中提升温室气体（Greenhouse Gas, GHG）通量，这提示它们可能会影响城市湿地作为温室气体源或汇的功能角色。然而，目前尚不清楚在野外环境的高度可变条件下，是否仍可观测到这类动物的调控效应。本研究依托一套涵盖二氧化碳（Carbon Dioxide, CO₂）、甲烷（Methane, CH₄）与氧化亚氮（Nitrous Oxide, N₂O）通量的大型数据集，数据采自澳大利亚墨尔本10处城市湿地的沉积物岩芯（n=103），采样时段覆盖夏季与冬季，旨在验证无脊椎动物对温室气体通量的增强效应。研究团队观测到温度、沉积物碳含量与无脊椎动物密度对CH₄与CO₂通量存在显著的倍增增强效应。寡毛类蠕虫或大型底栖无脊椎动物（含寡毛类蠕虫与摇蚊幼虫）的密度每提升一倍，其对应的平均CH₄与CO₂通量分别提升约42%与15%。但即便无脊椎动物密度极高，其并未对N₂O通量表现出显著增强效应。这一现象可能与沉积物中较高的有机碳含量（范围：2.1%~12.6%）以及相对较低的硝酸盐有效性（中位数为1.96 μM NO₃⁻-N）有关，该结果凸显了群落结构对生态系统功能的调控效应具有情境依赖性。本研究中增强温室气体通量的无脊椎动物类群分布广泛，且在受损水生生态系统的动物群落中常占据优势地位。因此，无脊椎动物对CO₂与CH₄通量的调控效应可能普遍存在于受城市化影响的湿地中；若不对城市化对湿地的负面影响加以管控，城市湿地可能会对城市总温室气体预算做出更大贡献。