Human activities have led to 1–2% of coastal wetlands lost per year globally, with subsequent losses in ecosystem services such as nutrient filtering and carbon sequestration. Wetland construction is used to mitigate losses of marsh cover and services resulting from human impacts in coastal areas. Though marsh structure can recover relatively quickly (i.e., <10 years) after construction, there are often long-term lags in the recovery of ecosystem functions in constructed marshes. We conducted a year-long study comparing seasonal plant productivity, ecosystem respiration (), denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) between two 33-year-old constructed marshes (CON-1, CON-2) and a nearby natural reference marsh (NAT). We found that CON-1 and CON-2 were structurally similar to NAT (i.e., plant aboveground and belowground biomass did not differ). Likewise, gross ecosystem productivity (GEP), , and net ecosystem exchange (NEE) were similar across all marshes. Further, DNRA and denitrification were similar across marshes, with the exception of greater denitrification rates at CON-2 than at the other two sites. While pore-water ammonium concentrations were similar across all marshes, organic matter (OM) content, pore-water phosphate, nitrate + nitrite, and hydrogen sulfide concentrations were greater in NAT than CON-1 and CON-2. Collectively, this work suggests that current marsh construction practices could be a suitable tool for recovering plant structure and some ecosystem functions. However, the lag in recovery of pore-water nutrient stocks and OM content also suggests that some biogeochemical functions may take longer than a few decades to fully recover in constructed marshes.

中文翻译：

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两个具有 33 年历史的人工盐沼的生态系统碳交换和氮去除率与附近天然沼泽的相似

人类活动导致全球每年 1% 至 2% 的沿海湿地丧失，随之而来的是营养过滤和碳固存等生态系统服务的丧失。湿地建设用于减轻沿海地区人类影响造成的沼泽覆盖和服务损失。虽然湿地结构在建成后可以相对较快地恢复（即<10年），但人工湿地生态系统功能的恢复往往存在长期滞后。我们进行了一项为期一年的研究，比较了季节性植物生产力、生态系统呼吸（)、反硝化作用和在两个 33 年历史的人工沼泽 (CON-1、CON-2) 和附近的自然参考沼泽 (NAT) 之间将硝酸盐异化还原为铵 (DNRA)。我们发现 CON-1 和 CON-2 在结构上与 NAT 相似（即植物地上和地下生物量没有差异）。同样，生态系统总生产力 (GEP)、和净生态系统交换 (NEE) 在所有沼泽中都相似。此外，沼泽地的 DNRA 和反硝化作用相似，除了 CON-2 的反硝化率高于其他两个地点。虽然所有沼泽的孔隙水铵浓度相似，但有机质 (OM) 含量、孔隙水磷酸盐、硝酸盐 + 亚硝酸盐和硫化氢浓度在 NAT 中高于 CON-1 和 CON-2。总的来说，这项工作表明，目前的沼泽建设实践可能是恢复植物结构和某些生态系统功能的合适工具。然而，孔隙水营养储备和有机质含量恢复的滞后也表明，某些生物地球化学功能可能需要几十年以上的时间才能在人工沼泽中完全恢复。