Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, 92093, USA.
Water Studies Center, School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia.
Ecol Appl. 2017 Sep;27(6):1852-1861. doi: 10.1002/eap.1572. Epub 2017 Jul 12.
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 data set on carbon dioxide (CO ), methane (CH ), and nitrous oxide (N O) flux in sediment cores (n = 103) collected from 10 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 CH and CO 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 CH and CO flux, respectively. However, despite exceptionally high densities, invertebrates did not appear to enhance N O 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 μmol/L NO -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 CO and CH 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.
城市生态学的目标之一是将群落结构与城市生境中的生态系统功能联系起来。已表明耐受污染的湿地无脊椎动物能够增强温室气体（GHG）在受控实验室实验中的通量，这表明它们可能影响城市湿地作为 GHG 源或汇的作用。然而，在野外高度变化的条件下，它们的影响是否能够被检测到还不清楚。在这里，我们使用了澳大利亚墨尔本 10 个城市湿地在夏季和冬季采集的 103 个沉积物芯中二氧化碳（CO ）、甲烷（CH ）和氧化亚氮（N O）通量的大量数据集，以测试无脊椎动物对 GHG 通量的增强作用。我们检测到温度、沉积物碳含量和无脊椎动物密度对 CH 和 CO 通量的显著倍增增强效应。无脊椎动物密度每增加一倍，CH 和 CO 通量的平均增长率分别约为 42%和 15%。然而，尽管密度异常高，但无脊椎动物似乎并没有增强 N O通量。这可能是由于沉积物中有机碳含量较高（范围为 2.1-12.6%），硝酸盐供应相对较低（中位数为 1.96 μmol/L 的 NO -N），这突出了群落结构对生态系统功能的影响具有情境依赖性。在本研究中增强 GHG 通量的无脊椎动物是普遍存在的，并且经常在受损水生生态系统中占动物群落的主导地位。因此，如果不对城市化对湿地的负面影响加以控制，那么受城市化影响的湿地中 CO 和 CH 通量的无脊椎动物效应可能很常见，并且城市湿地可能会对城市的总 GHG 预算做出更大的贡献。
