There exists a substantial amount of research on abiotic (e.g. photochemical) degradation pertaining to organic matter (OM) in the marine realm. While recent research has shown its importance in the degradation of terrestrial particulate OM (TPOM), the mechanisms involved in the induction of autoxidation in estuaries remain unclear. In this study, we propose for the first time the involvement of lipoxygenase (LOX) activity in the induction of autoxidation in mixed waters. The observation of unusual profiles of palmitoleic acid oxidation products and the presence of jasmonic acid in suspended particulate matter (SPM) collected close to the Rhone River, as well as in samples from the Mackenzie and Amazon rivers, is attributed to strong LOX activity. We show the role played by salinity in the induction of this LOX activity and provide an explanation for the differences in estuarine autoxidation level. At high latitude, lower temperatures and irradiance favor photooxidative damage to higher plant debris and, consequently, hydroperoxide production. High hydroperoxide content strongly contributes to LOX activation in mixed waters. The high resulting LOX activity enhances alkoxyl radical production and thus autoxidation. On the contrary, at low latitude, photooxidative effects are limited, and riverine autoxidation is favored. The higher hydroperoxide content of TPOM may, as a consequence, thereby also contribute to a high level of LOX activity and autoxidation in estuaries. In temperate zones, land and riverine photooxidative and autoxidative damage is limited, unlike estuaries where we observed significant LOX-induced and autox-idative damage. .

中文翻译：

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脂肪氧化酶诱导的河口陆地颗粒有机物的自氧化降解：在高纬度和低纬度增强的广泛过程

有大量关于海洋领域有机物 (OM) 的非生物（例如光化学）降解研究。虽然最近的研究表明其在降解陆地颗粒物 OM (TPOM) 中的重要性，但诱导河口自氧化的机制仍不清楚。在这项研究中，我们首次提出脂氧合酶 (LOX) 活性参与诱导混合水中的自氧化。观察到棕榈油酸氧化产物的异常特征和在罗纳河附近收集的悬浮颗粒物 (SPM) 以及来自麦肯齐河和亚马逊河的样本中存在茉莉酸，这归因于强 LOX 活性。我们展示了盐度在诱导这种 LOX 活动中的作用，并解释了河口自氧化水平的差异。在高纬度地区，较低的温度和辐照度有利于对高等植物残骸的光氧化损伤，从而产生过氧化氢。高氢过氧化物含量强烈有助于混合水中的 LOX 活化。产生的高 LOX 活性增强了烷氧基自由基的产生，从而增强了自氧化。相反，在低纬度地区，光氧化作用有限，有利于河流自氧化。因此，TPOM 中较高的氢过氧化物含量也可能有助于河口中高水平的 LOX 活性和自氧化。在温带地区，陆地和河流的光氧化和自氧化损伤是有限的，与我们观察到显着 LOX 诱导和自氧化损伤的河口不同。.