OLAR：铁元素驱动的海草生态恢复新策略

海草草甸作为重要的“蓝碳”生态系统，在全球范围内因富营养化等因素导致的退化正迅速加剧。本文探讨了沉积物中铁和硫的形态变化对海草恢复能力的影响，特别是在富硫化物环境中的表现。研究表明，尽管硫化物浓度有所降低，铁矿物（尤其是氧化铁）的耗竭可能阻碍海草的再生。通过增加沉积物中活性铁的含量，能够显著提高海草的存活率和恢复潜力。这一研究为应对全球海草退化问题提供了新的策略，特别是针对富营养化严重地区的海草生态系统恢复具有重要意义。

海草草甸作为碳汇受到广泛关注，但其在富营养地区的退化问题日益严重。硫化物被证明是导致海草死亡的关键因素，而沉积物中的铁氧化物能够与硫化物结合，形成硫化铁（FeS）或黄铁矿（FeS₂），从而减少硫化物毒性。本文对美国马萨诸塞州West Falmouth港口三个不同富营养化程度区域的沉积物进行研究，揭示了铁和硫形态的长期变化，评估了富营养化对铁矿物形态的影响。

图 1 调查区域及研究方法

研究分析了不同营养水平下沉积物中总铁、硫化物、铁氧化物和硫化铁的含量与比例。为评估活性氧化铁（FeOOH）对海草存活率的影响，实验组向沉积物中添加了氧化铁，而对照组未进行处理。六周的实验中定期测量沉积物孔隙水中的铁和硫化物浓度，并监测海草的存活情况。

结果表明，在铁氧化物含量较低的沉积物中，海草的存活率显著降低。而在添加活性铁后，海草的存活率得到了提高。这表明增加沉积物中的活性铁能有效减少硫化物毒性，为海草提供更适宜的生存环境。此外，沉积物中的铁硫比（Fe/S）与海草的恢复能力密切相关。

图2 整个实验中每个治疗组的存活率

本研究揭示了富营养化条件下铁氧化物耗竭对海草复苏的阻碍作用，建议未来的海草恢复项目可通过增加沉积物中的氧化铁含量来促进生态系统的修复。

文章标题：

The Potential Role of Sediment Iron and Sulfur Speciation in Seagrass Meadow Loss and Recovery

文章作者 ：

Katherine A. Haviland, Robert W. Howarth, Anne E. Giblin, Roxanne Marino

文章摘要：

Oxidized iron (Fe) can reduce seagrass dieback when present in sufficient quantities in the sediment to fix sulfide as pyrite (FeS ₂ ) or iron monosulfide (FeS). However, the oxidized Fe pool may become depleted over time as Fe is reduced and precipitated with sulfides. In this study, we estimated long-term variations in the speciation of solid forms of reduced and oxidized Fe along a eutrophication gradient in West Falmouth Harbor (WFH) (a temperate lagoon with substantial seagrass meadows) and conducted a 6-week microcosm study to assess the role of oxidized Fe in supporting seagrass recovery. We planted seagrass in sediments obtained from 2 WFH regions with differing Fe speciation. We found depletion of oxidized Fe over a decade following a seagrass dieback, even when the soluble sulfide levels decreased to concentrations unlikely to cause toxicity in seagrass. The continued absence of large concentrations of available oxidized Fe minerals in sediments, where most Fe was bound in FeS ₂ , could impede the recovery of seagrass in formerly vegetated regions. Seagrass grown in sediments with low Fe:S ratios exhibited an increased probability of survival after 4 weeks. Field and laboratory results indicated that even when the soluble sulfide levels decrease after seagrass dieback, sediments may not be able to support seagrass recovery due to the legacy effects of eutrophication on the sediment Fe pool. However, we observed signs of reoxidation in the Fe pool within a few years of seagrass dieback, including a decrease in the total sediment S concentration, which could help spur recolonization.

文章引用：

Katherine A. Haviland, Robert W. Howarth, Anne E. Giblin, Roxanne Marino. The Potential Role of Sediment Iron and Sulfur Speciation in Seagrass Meadow Loss and Recovery. Ocean-Land-Atmos Res . 2024;3:0069.DOI:10.34133/olar.0069

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