Abstract Tropical estuaries are characterised by high spatial and temporal variability in the conditions they provide for living organisms, which in turn may affect their biochemical composition. Anthropogenic contaminants such as nutrients, antibiotics, pesticides and trace metals may also affect the biochemical composition of these coastal organisms, notably with regard to fatty acids (FA), of which optimal species-specific polyunsaturated FA ratios are required to maintain living species in healthy conditions. The objective of this study was to evidence changes in the FA profile of four ubiquist benthic species in relation to the salinity gradient of a human impacted and mangrove dominated tropical estuary (Can Gio, Southern Vietnam). Among the four benthic species studied, two exhibited spatial and seasonal changes in their FA composition: the varunid crab Metaplax elegans and the predatory mangrove murex snail Chicoreus capucinus. Proportions of the FA 16:1ω7, proportions of highly unsaturated FA and ratios of eicosapentanoic acid/arachidonic acid in the tissues of both species seemed related to upstream inputs. Different relative abundances of benthic microalgae affected both claw muscle and hepatopancreas FA composition of M. elegans, while the FA composition of C. capucinus shows that the influence of prey's diet might be transferred within trophic chains. Finally, some species, such as Nerita balteata and Metapenaeus ensis might have more adaptive capacities, because of their mobility, or because of their specific metabolic pathways, minimizing the potential impact of spatial and/or temporal changes in food resources quality. A starvation experiment involving N. balteata actually revealed the metabolic synthesis of non-methylene interrupted FA that may confer cell membranes a higher resistance to external stressors than common polyunsaturated FA. Our study highlights the future possibility of using the FA composition of sentinel organisms (i.e. feeding on specific food resources and/or especially subject to environmental stresses) as a bioindicator tool to assess mangrove ecosystems health.

中文翻译：

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沿人类受影响和红树林主导的热带河口的盐度梯度的四种底栖物种的脂肪酸组成（Can Gio，越南）

摘要 热带河口的特点是它们为生物体提供的条件在空间和时间上具有很大的变异性，这反过来又可能影响它们的生化成分。诸如营养素、抗生素、杀虫剂和微量金属等人为污染物也可能影响这些沿海生物的生化成分，特别是脂肪酸 (FA)，其中需要最佳的物种特异性多不饱和脂肪酸比率来维持生物物种的健康使适应。本研究的目的是证明四种普遍存在的底栖物种的 FA 分布与人类受影响和红树林主导的热带河口（越南南部 Can Gio）的盐度梯度有关的变化。在研究的四种底栖物种中，两种表现出其 FA 组成的空间和季节性变化：varunid 蟹 Metaplax elegans 和掠食性红树林骨螺蜗牛 Chicoreus capucinus。两个物种组织中 FA 16:1ω7 的比例、高度不饱和 FA 的比例和二十碳五烯酸/花生四烯酸的比例似乎与上游输入有关。底栖微藻的不同相对丰度影响了秀丽隐杆线虫的爪肌和肝胰腺 FA 组成，而 C. capucinus 的 FA 组成表明猎物饮食的影响可能在营养链内转移。最后，一些物种，如 Nerita balteata 和 Metapenaeus ensis，可能具有更强的适应能力，因为它们的流动性，或者因为它们特定的代谢途径，最大限度地减少了食物资源质量空间和/或时间变化的潜在影响。一项涉及 N 的饥饿实验。balteata 实际上揭示了非亚甲基间断 FA 的代谢合成，与常见的多不饱和 FA 相比，这可能使细胞膜对外部压力源具有更高的抵抗力。我们的研究强调了使用哨兵生物的 FA 组成（即以特定食物资源为食和/或特别受到环境压力）作为评估红树林生态系统健康的生物指标工具的未来可能性。