Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone
Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone
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DOI：
10.4319/lo.2012.57.3.0851
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发表时间：
2012-05
影响因子：
4.5
通讯作者：
A. Noffke;C. Hensen;S. Sommer;F. Scholz;L. Bohlen;T. Mosch;M. Graco;K. Wallmann
中科院分区：
文献类型：
--
作者：
A. Noffke;C. Hensen;S. Sommer;F. Scholz;L. Bohlen;T. Mosch;M. Graco;K. Wallmann
溶解亚铁 (Fe2+) 和磷酸盐 (TPO4) 的底栖通量通过原位底栖室孵化和沿秘鲁最低氧区 (OMZ) 深度横断面 (11°S, 80-1000 m) 的孔隙水剖面进行量化。到 500 米水深时，底水 O2 水平< 2 µmol L−1，并在 1000 米处增加至 ∼ 40 µmol L−1。 Fe2+ 通量在浅陆架最高（最大 316 mmol m−2 yr−1），在 250 m 至 600 m 之间中等（15.4 mmol m−2 yr−1），在较深的站可以忽略不计。在持久性 OMZ 岩心中，Fe 羟基氧化物的持续减少导致沉积物 Fe : Al 比率的消耗。整个陆架和 OMZ 核心的 TPO4 通量很高（最大 292 mmol m−2 yr−1），与高有机碳降解率相关。有机碳降解与 TPO4 通量之间的比率表明，与 Redfield 化学计量相比，P 释放量超过 C 释放量。最有可能的是，这是由于有机物优先释放磷、鱼残骸溶解和/或微生物垫群落磷释放造成的，而氢氧化铁只能被推断为浅层陆架的主要磷源。这里呈现的底栖通量是类似缺氧环境中报道的最高通量之一，突显了缺氧水体下面的沉积物作为海洋营养源的重要性。陆架尤其重要，因为沿海困波的周期性通过和相关的底层水氧化事件预计会引起短暂的生物地球化学环境，其中 Fe2+ 和 TPO4 的释放变化很大。
Benthic fluxes of dissolved ferrous iron (Fe2+) and phosphate (TPO4) were quantified by in situ benthic chamber incubations and pore‐water profiles along a depth transect (11°S, 80‐1000 m) across the Peruvian oxygen minimum zone (OMZ). Bottom‐water O2 levels were < 2 µmol L−1 down to 500‐m water depth, and increased to ∼ 40 µmol L−1 at 1000 m. Fe2+ fluxes were highest on the shallow shelf (maximum 316 mmol m−2 yr−1), moderate (15.4 mmol m−2 yr−1) between 250 m and 600 m, and negligible at deeper stations. In the persistent OMZ core, continuous reduction of Fe oxyhydroxides results in depletion of sedimentary Fe : Al ratios. TPO4 fluxes were high (maximum 292 mmol m−2 yr−1) throughout the shelf and the OMZ core in association with high organic carbon degradation rates. Ratios between organic carbon degradation and TPO4 flux indicate excess release of P over C when compared to Redfield stoichiometry. Most likely, this is caused by preferential P release from organic matter, dissolution of fish debris, and/or P release from microbial mat communities, while Fe oxyhydroxides can only be inferred as a major P source on the shallow shelf. The benthic fluxes presented here are among the highest reported from similar, oxygen‐depleted environments and highlight the importance of sediments underlying anoxic water bodies as nutrient sources to the ocean. The shelf is particularly important as the periodic passage of coastal trapped waves and associated bottom‐water oxygenation events can be expected to induce a transient biogeochemical environment with highly variable release of Fe2+ and TPO4.