Despite considerable efforts to restore coastal wetlands, the ecological mechanisms contributing to the success or failure of restoration are rarely assessed. Accumulation of hydrogen sulfide in sediments may accelerate rates of marsh loss in eutrophic estuaries and is likely driven by complex feedbacks between wetland plant growth and microbial redox reactions. We used a chronosequence of restored marshes in urbanized and eutrophic Jamaica Bay (New York City, USA) to assess how sediment redox conditions change among seasons and over the lifetime of restored marshes. We also compared a stable extant marsh to one that has deteriorated over the past 50 years. We collected seasonal sediment cores from each marsh, and used a motorized microprofiling system to measure the vertical distribution of oxygen and sulfide. We fit a logistic function to each profile to estimate (1) maximum concentrations, (2) rates of increase/decline, and (3) depths of maximum increase/decline. We quantified sediment density, porosity, organic content, and belowground plant biomass, and estimated differences in daily tidal inundation among sites using water-level loggers. We found that minimum oxygen and maximum sulfide concentrations occur during summer. Sulfide concentrations were highest in sites that experienced the longest daily tidal inundation, including the degraded extant marsh and the oldest restored marsh. Spatial patterns in oxygen and sulfide were related to belowground plant biomass, supporting our hypothesis that root growth increases sediment oxygen and partially alleviates sulfide stress. Our data support the growing body of evidence that belowground plant growth may enhance the resilience of marshes to sea-level rise by increasing marsh elevation and facilitating oxygen diffusion into marsh sediments.

中文翻译：

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沼泽植物通过改变城市富营养化河口的沉积物氧气和硫化物浓度来增强沿海沼泽的复原力

尽管为恢复沿海湿地付出了巨大的努力，但很少评估有助于恢复成败的生态机制。沉积物中硫化氢的积累可能会加速富营养化河口湿地的流失速度，并且可能是由于湿地植物生长与微生物氧化还原反应之间的复杂反馈所致。我们使用了在城市化和富营养化的牙买加湾（美国纽约）中恢复的沼泽的时间序列，以评估在恢复的沼泽的整个季节和整个生命周期中沉积物氧化还原条件如何变化。我们还比较了稳定的现存沼泽与过去50年中恶化的沼泽。我们收集了每个沼泽的季节性沉积物核心，并使用了电动微轮廓分析系统来测量氧气和硫化物的垂直分布。我们将逻辑函数拟合到每个轮廓，以估计（1）最大浓度，（2）增/减速率和（3）最大增/减深度。我们使用水位记录仪对沉积物密度，孔隙度，有机物含量和地下植物生物量进行了定量，并估计了站点之间每日潮汐淹没的差异。我们发现最小的氧气和最大的硫化物浓度发生在夏季。在每天潮汐淹没时间最长的地点（包括退化的现存沼泽和恢复最旧的沼泽）中，硫化物的浓度最高。氧气和硫化物的空间格局与地下植物的生物量有关，支持了我们的假说，即根生长会增加沉积物的氧气并部分缓解硫化物的胁迫。