School of Biological Sciences, Southern Illinois University, Carbondale, Illinois, United States of America.
United States Fish and Wildlife Service, Fairbanks Fish and Wildlife Field Office, Fairbanks, Alaska, United States of America.
PLoS One. 2023 May 26;18(5):e0286368. doi: 10.1371/journal.pone.0286368. eCollection 2023.
Arctic lowland tundra is often dominated by wetlands. As numbers and types of these wetlands change with climate warming, their invertebrate biomass and assemblages may also be affected. Increased influx of nutrients and dissolved organic matter (DOM) from thawing peat may alter the relative availability of organic matter (OM) sources, differentially affecting taxa with disparate dependence on those sources. In five shallow wetland types (<40 to 110 cm deep) and in littoral zones of deeper lakes (>150 cm), we used stable isotopes (δ13C, δ15N) to compare contributions of four OM sources (periphytic microalgae, cyanobacteria, macrophytes, peat) to the diets of nine macroinvertebrate taxa. Living macrophytes were not distinguishable isotopically from peat that likely contributed most DOM. Within invertebrate taxa, relative OM contributions were similar among all wetland types except deeper lakes. Physidae snails consumed substantial amounts of OM from cyanobacteria. However, for all other taxa examined, microalgae were the dominant or a major OM source (39-82%, mean 59%) in all wetland types except deeper lakes (20‒62%, mean 31%). Macrophytes and macrophyte-derived peat, likely consumed mostly indirectly as DOM-supported bacteria, ranged from 18‒61% (mean 41%) of ultimate OM sources in all wetland types except deeper lakes (38-80%, mean 69%). Invertebrate consumption of microalgal C may often have involved bacterial intermediates, or a mix of algae with bacteria consuming peat-derived OM. High production of periphyton with very low δ13C values were favored by continuous daylight illuminating shallow depths, high N and P levels, and high CO2 concentrations from bacterial respiration of peat-derived DOM. Although relative OM sources were similar across wetland types except deeper lakes, total invertebrate biomass was much higher in shallow wetlands with emergent vegetation. Impacts of warming on the availability of invertebrate prey to waterbirds will likely depend not on shifts in OM sources, but more on changes in overall number or area of shallow emergent wetlands.
北极低地苔原通常以湿地为主。随着这些湿地数量和类型随着气候变暖而变化，它们的无脊椎动物生物量和群落也可能受到影响。随着泥炭解冻，营养物质和溶解有机物质 (DOM) 的大量涌入可能会改变有机物质 (OM) 来源的相对可用性，从而对依赖这些来源的不同类群产生不同的影响。在五种浅层湿地类型（<40 至 110 厘米深）和较深湖泊的滨岸区（>150 厘米深）中，我们使用稳定同位素（δ13C，δ15N）比较了四种 OM 来源（附生微藻、蓝藻、大型植物、泥炭）对九种大型无脊椎动物类群的饮食的贡献。活的大型植物在同位素上与可能提供大部分 DOM 的泥炭无法区分。在无脊椎动物类群中，除了较深的湖泊外，所有湿地类型的相对 OM 贡献都相似。Physidae 蜗牛从蓝藻中消耗大量 OM。然而，对于所有其他检查的类群，微藻是所有湿地类型（除了较深的湖泊）中主要或主要的 OM 来源（39-82%，平均值为 59%）。除了较深的湖泊（20-62%，平均值为 69%）外，在所有湿地类型中，大型植物和大型植物衍生的泥炭，可能主要作为 DOM 支持的细菌间接消耗，范围从最终 OM 来源的 18-61%（平均值为 41%）。无脊椎动物对微藻 C 的消耗可能经常涉及细菌中间产物，或者是藻类与细菌混合消耗泥炭衍生的 OM。在连续光照照亮浅水区、高氮和磷水平以及细菌对泥炭衍生 DOM 的呼吸产生高二氧化碳浓度的情况下，具有非常低 δ13C 值的后生生物的高产量受到青睐。尽管除了较深的湖泊外，不同湿地类型的相对 OM 来源相似，但具有挺水植被的浅层湿地的总无脊椎动物生物量要高得多。变暖对水鸟无脊椎动物猎物可利用性的影响可能不取决于 OM 来源的变化，而更多地取决于浅水挺水湿地的总体数量或面积的变化。
