Abstract Degradation of palmitoleic acid (C 16:1ω7 ), the main fatty acid component of sea ice-associated (sympagic) diatoms, was monitored in Arctic sea ice at the beginning of ice melting and in the underlying sinking particles and superficial bottom sediments. In sea ice, degradation of sympagic algae involved biotic oxidation induced by 10 S -DOX-like lipoxygenase of unknown salinity-stressed attached bacteria, while photo- and autoxidation were limited. In the water column, strong hydratase and Z / E isomerase activity were observed. Hydration of unsaturated fatty acids seems to be a detoxification strategy, which is essential for bacterial survival when associated with free fatty acid-rich environments such as ice algae. In contrast, Z / E isomerisation of palmitoleic acid was attributed to the release of Fe 2+ ions during radical-induced damage of the active site of the bacterial 10 S -DOX-like lipoxygenase and Z / E isomerases. Due to the poor physiological state of their attached bacteria resulting from salinity stress in brine channels or toxicity of free ice algae fatty acids, sympagic algae appeared to be only very weakly biotically degraded within the water column. In bottom sediments, free radicals resulting from 10 S -DOX-like lipoxygenase activity induced a strong autoxidation of the ice algal material. The presence in bottom sediments of a significant proportion of oxidation products resulting from 10 S -DOX-like lipoxygenase activity attested to the strong contribution of sea ice-derived OM released during the early stages of ice melt prior to deposition in the sediments. However, on the basis of the highest fatty acid photooxidation state observed in these sediments, an additional contribution of highly photooxidized material (ice algal material released at the end of ice melting or open water phytoplankton) seems likely. The degradation of hydroperoxides, resulting from biotic and abiotic degradation of palmitoleic acid, appeared to involve: (i) homolytic cleavage of the peroxyl group affording the corresponding hydroxy- and oxoacids, (ii) reduction to the corresponding hydroxyacids by peroxygenases, (iii) heterolytic proton-catalysed cleavage and (iv) conversion to allylic 1,4-diols by diol synthases and hydroperoxide isomerases.

中文翻译：

---

使用棕榈油酸及其氧化产物监测北极水域和底部沉积物中冰藻的降解

摘要 在冰融化开始时的北极海冰中以及下沉颗粒和浅表底部沉积物中监测了棕榈油酸 (C 16:1ω7 ) 的降解，这是海冰相关（共生）硅藻的主要脂肪酸成分。在海冰中，交感藻类的降解涉及由未知盐度胁迫的附着细菌的 10 S -DOX 样脂氧合酶诱导的生物氧化，而光氧化和自氧化是有限的。在水柱中，观察到很强的水合酶和Z/E异构酶活性。不饱和脂肪酸的水合作用似乎是一种解毒策略，当与富含游离脂肪酸的环境（如冰藻）相关时，这对细菌的生存至关重要。相比之下，棕榈油酸的 Z/E 异构化归因于在自由基诱导的细菌 10 S -DOX 样脂氧合酶和 Z/E 异构酶活性位点损伤期间释放 Fe 2+ 离子。由于盐水通道中的盐度胁迫或游离冰藻脂肪酸的毒性导致其附着细菌的生理状态不佳，交游藻类似乎在水柱内仅进行了非常微弱的生物降解。在底部沉积物中，由 10 S-DOX 样脂氧合酶活性产生的自由基诱导了冰藻材料的强烈自动氧化。由 10 S-DOX 样脂肪氧化酶活性产生的大量氧化产物存在于底部沉积物中，证明了在沉积物沉积之前冰融化的早期阶段释放的海冰衍生 OM 的强烈贡献。然而，根据在这些沉积物中观察到的最高脂肪酸光氧化状态，高度光氧化物质（在冰融化或开放水域浮游植物结束时释放的冰藻物质）的额外贡献似乎是可能的。由棕榈油酸的生物和非生物降解引起的氢过氧化物的降解似乎涉及：（i）过氧基的均裂裂解，提供相应的羟基和含氧酸，（ii）通过过氧化酶还原为相应的羟基酸，