ABSTRACT: We investigated the effects of Manila clam aquaculture on the rates and pathways of anaerobic organic carbon (OC) oxidation in highly bioturbated (HB) and poorly bioturbated (PB) sediment in Keunso Bay, Yellow Sea. Due to the labile organic matter supply via sediment reworking by Manila clams, the anaerobic OC oxidation rate in HB sediment (38.8 mmol m^-2 d^-1) was ~1.5 times higher than that in PB sediment (26.8 mmol m^-2 d^-1). Microbial Fe(III) reduction (FeR) dominated OC oxidation pathways in HB sediment, comprising 55 to 76% of anaerobic OC oxidation, whereas sulfate reduction (SR) was the dominant oxidation pathway in PB sediment, accounting for up to 92% of anaerobic OC oxidation. Despite higher anaerobic respiration rates at the HB site, concentrations of NH₄⁺, PO₄^3-, oxalate-extractable iron (Fe(II)_(oxal)), and total reduced inorganic sulfur were 2 to 3 times lower in HB than in PB sediment. Conversely, the concentration of reactive Fe(III)_(oxal) at the HB site (2243 mmol m^-2) exceeded that at the PB site (1127 mmol m^-2) by a factor of 2. These results indicate that bioturbation by Manila clams enhances the re-oxidation processes of reduced metabolites in the sediment, thereby prohibiting SR and promoting FeR. Overall, the results suggest that aquaculture activities of Manila clams shift the dominant OC oxidation pathways in sediment from SR to FeR, which generates relatively oxidized and less sulfidic environments.

中文翻译：

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马尼拉蛤养殖对黄海克恩索湾沉积物中有机碳氧化速率和分配的影响

摘要：我们调查了马尼拉蛤类养殖对黄海基恩索湾高度生物扰动（HB）和生物扰动差（PB）沉积物中厌氧有机碳（OC）氧化速率和途径的影响。由于马尼拉蛤re通过沉积物再加工提供的有机物不稳定，HB沉积物（38.8 mmol m ^-2 d ^-1）的厌氧OC氧化速率是PB沉积物（26.8 mmol m ^-2 d-）的〜1.5倍^{。 1个}）。HB沉积物中微生物的Fe（III）还原（FeR）主导OC氧化途径，占厌氧OC氧化的55％至76％，而PB沉积物中硫酸盐还原（SR）是主要的氧化途径，占厌氧性的92％ OC氧化。尽管HB部位的无氧呼吸速率较高，但HB的NH ₄ ⁺，PO ₄ ^3-，草酸盐可萃取铁（Fe（II）_（草酸））和总还原无机硫的_浓度比HBs低2至3倍。 PB沉积物。相反，HB位点的反应性Fe（III）_（草酸）浓度（2243 mmol m ^-2）超过PB位点的反应性Fe（III）（1127 mmol m ^-2））的2倍。这些结果表明，马尼拉蛤bio引起的生物扰动增强了沉积物中代谢物还原的再氧化过程，从而阻止了SR并促进了FeR。总体而言，结果表明，马尼拉蛤的水产养殖活动将沉积物中主要的OC氧化途径从SR转移到FeR，从而产生了相对氧化和较少硫化的环境。