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首页> 外文期刊>Marine ecology progress series >Bioconversion of fatty acids at the basis of marine food webs: insights from a compound-specific stable isotope analysis
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Bioconversion of fatty acids at the basis of marine food webs: insights from a compound-specific stable isotope analysis

机译：以海洋食物网为基础的脂肪酸的生物转化：化合物特异性稳定同位素分析的见解

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ABSTRACT: Polyunsaturated fatty acids (PUFA) are essential compounds that can limit the productivity of primary consumers in aquatic food webs, where the efficiency in energy transfer at the plant–animal interface has been related to food quality in terms of fatty acids (FA). At this interface, copepods play a pivotal role both as consumers of primary production and as a food source for higher trophic levels. Understanding the role of grazing copepods in the transfer of FA is therefore essential for our knowledge on the overall functioning of marine ecosystems. The harpacticoid copepod Microarthridion littorale grazed for 9 d on 13C labelled diatoms and bacteria in the laboratory and was then subjected to FA-specific stable isotope analysis. The objective of this analysis was to inspect the copepod’s ability to bioconvert short-chain FA (SC-PUFA, 20 carbons) into long-chain PUFA (LC-PUFA, ≥20 carbons) and the FA involved in the potential bioconversion pathways. Diatoms and bacteria were chosen as test diets because of their different FA composition, i.e. docosahexaenoic acid (DHA; 22:6ω3) was absent in the bacteria, and eicosapentaenoic acid (EPA; 20:5ω3) was 5% of the total FA weight of bacteria. The presence of labelled DHA in copepods feeding on bacteria showed that this PUFA must have been converted from other FA, possibly EPA. The FA composition of copepods in the laboratory was different from that of field copepods, which suggests the availability of more food sources in the field than those offered in the experiment. The weight proportion of C18 FA decreased in copepods feeding on either bacteria or diatoms relative to field copepods, while the proportion of both EPA and DHA increased. In contrast to planktonic calanoid copepods that have limited ability to bioconvert FA, benthic harpacticoid copepods apparently developed the ability to elongate FA and to exploit niches with poor quality food. Moreover, by improving the quality of the food they graze upon, especially in terms of EPA and DHA, harpacticoid copepods upgrade the nutritive value of food available to the higher trophic levels in marine food webs.
机译：摘要：多不饱和脂肪酸（PUFA）是必不可少的化合物，它们会限制水生食物网中主要消费者的生产力，而植物与动物之间的能量传递效率与脂肪酸（FA）的食品质量有关。在这个界面上，co足类动物既是初级生产的消费者，又是较高营养水平的食物来源，起着举足轻重的作用。因此，对于我们关于海洋生态系统整体功能的知识，了解放牧co足类动物在FA转移中的作用至关重要。实验室中的类拟co足类足类小棚立虫在 13 标记的硅藻和细菌上放牧9 d，然后进行FA特异性稳定同位素分析。这项分析的目的是检验pe足动物将短链FA（SC-PUFA，碳数小于20）转化为长链PUFA（LC-PUFA，碳数≥20）的能力以及涉及潜在生物转化途径的FA。选择硅藻和细菌作为测试饮食，因为它们的FA组成不同，即细菌中不存在二十二碳六烯酸（DHA; 22：6ω3），而二十碳五烯酸（EPA; 20：5ω3）小于FA总重量的5％细菌。以细菌为食的co足类动物中存在标记的DHA，这表明该PUFA必须已经从其他FA（可能是EPA）转化而来。实验室中co足类动物的FA组成与田间co足类动物的FA组成不同，这表明田野中可获得的食物来源远多于实验提供的食物来源。相对于田间di足类，以细菌或硅藻为食的co足纲中C18 FA的重量比例相对降低，而EPA和DHA的比例均增加。与浮游性cal足类co足动物的生物转化能力有限相反，底栖类立足类拟足足co足类动物显然具有拉长FA和利用劣质食品开发壁ni的能力。此外，通过改善吃草的食物的质量，特别是在EPA和DHA方面，类拟co足类pe足类可将食物的营养价值提升到海洋食物网中较高的营养水平。

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