Supplementary Information files for: Differential responses of macroinvertebrate ionomes across experimental N:P gradients in detritus-based headwater streams

Supplementary Information files for: Differential responses of macroinvertebrate ionomes across experimental N:P gradients in detritus-based headwater streams Diverse global change processes are reshaping the biogeochemistry of stream ecosystems. Nutrient enrichment is a common stressor that can modify flows of biologically important elements such as carbon (C), nitrogen (N), and phosphorus (P) through stream foodwebs by altering the stoichiometric composition of stream organisms. However, enrichment effects on concentrations of other important essential and trace elements in stream taxa are less understood. We investigated shifts in macroinvertebrate ionomes in response to changes in coarse benthic organic matter (CBOM) stoichiometry following N and P enrichment of five detritus-based headwater streams. Concentrations of most elements (17/19) differed among three insect genera (Maccaffertium sp., Pycnopsyche spp., and Tallaperla spp.) prior to enrichment. Genus-specific changes in the body content of: P, magnesium, and sodium (Na) in Tallaperla; P, Na, and cadmium in Pycnopsyche; and P in Maccaffertium were also found across CBOM N:P gradients. These elements increased in Tallaperla but decreased in the other two taxa due to growth dilution at larger body sizes. Multivariate elemental differences were found across all taxa, and ionome-wide shifts with dietary N and P enrichment were also observed in Tallaperla and Pycnopsyche. Our results show that macroinvertebrates exhibit distinct differences in elemental composition beyond C, N, and P and that the ionomic composition of common stream taxa can vary with body size and N and P enrichment. Thus, bottom-up changes in N and P supplies could potentially influence the cycling of lesser studied biologically essential elements in aquatic environments by altering their relative proportions in animal tissues.附属信息文件：基于碎屑的源头溪流中实验性氮磷梯度下大型无脊椎动物（macroinvertebrate）离子组（ionome）的差异响应 多样的全球变化过程正在重塑溪流生态系统的生物地球化学循环。营养富集是一种常见的胁迫因子，可通过改变溪流生物的化学计量组成，调控碳（C）、氮（N）、磷（P）等生物必需元素在溪流食物网中的流动路径。然而，目前学界对营养富集如何影响溪流类群中其他重要必需元素与微量元素的浓度仍知之甚少。 本研究针对5条基于碎屑的源头溪流开展氮磷富集实验，探究了粗底栖有机质（coarse benthic organic matter, CBOM）化学计量组成变化对大型无脊椎动物离子组的调控效应。实验前，3个昆虫属（Maccaffertium sp.、Pycnopsyche spp.与Tallaperla spp.）体内的多数元素（17/19）浓度存在显著差异。随着CBOM氮磷比的变化，各属昆虫的体内元素含量亦呈现属特异性变化：Tallaperla属的磷（P）、镁（Mg）与钠（Na），Pycnopsyche属的磷（P）、钠（Na）与镉（Cd），以及Maccaffertium属的磷（P）均存在显著改变。受个体体型增大带来的生长稀释（growth dilution）效应影响，Tallaperla属体内上述元素浓度呈上升趋势，而另外两个类群则呈下降趋势。所有类群的多变量元素组成均存在显著差异；此外，Tallaperla属与Pycnopsyche属的离子组也随日粮氮磷富集发生了全局性变化。 本研究结果表明，大型无脊椎动物的元素组成不仅局限于碳、氮、磷，还存在显著的类间差异；同时，常见溪流类群的离子组组成可随个体体型与氮磷富集程度发生变化。因此，氮磷供给的上行调控变化，可通过改变动物组织内元素的相对占比，潜在地影响水生环境中尚未被充分研究的生物必需元素的循环过程。