Data from: Trophic dynamics of filter feeding bivalves in the Yangtze Estuarine Intertidal Marsh: stable isotope and fatty acid analyses

Benthic bivalves are important links between primary production and consumers, and are essential intermediates in the flow of energy through estuarine systems. However, information on the diet of filter feeding bivalves in estuarine ecosystems is uncertain, as estuarine waters contain particulate matter from a range of sources and as bivalves are opportunistic feeders. We surveyed bivalves at different distances from the creek mouth at the Yangtze estuarine marsh in winter and summer, and analyzed trophic dynamics using stable isotope (SI) and fatty acid (FA) techniques. Different bivalve species had different spatial distributions in the estuary. Glauconome chinensis mainly occurred in marshes near the creek mouth, while Sinonovacula constricta preferred the creek. Differences were found in the diets of different species. S. constricta consumed more diatoms and bacteria than G. chinensis, while G. chinensis assimilated more macrophyte material. FA markers showed that plants contributed the most (38.86 ± 4.25%) to particular organic matter (POM) in summer, while diatoms contributed the most (12.68 ± 1.17%) during winter. Diatoms made the largest contribution to the diet of S. constricta in both summer (24.73 ± 0.44%) and winter (25.51 ± 0.59%), and plants contributed no more than 4%. This inconsistency indicates seasonal changes in food availability and the active feeding habits of the bivalve. Similar FA profiles for S. constricta indicated that the bivalve had a similar diet composition at different sites, while different δ13C results suggested the diet was derived from different carbon sources (C4 plant Spartina alterniflora and C3 plant Phragmites australis and Scirpus mariqueter) at different sites. Species-specific and temporal and/or spatial variability in bivalve feeding may affect their ecological functions in intertidal marshes, which should be considered in the study of food webs and material flows in estuarine ecosystems.

底栖双壳类（Benthic bivalves）是初级生产与消费者之间的重要纽带，也是河口系统能量流动过程中的关键中间环节。然而，由于河口水体中存在多种来源的颗粒物，且双壳类为机会性摄食者，目前学界对河口生态系统中滤食性双壳类的食性认知仍存在不确定性。本研究于冬季和夏季在长江口湿地开展调查，按距溪口的不同距离梯度采集双壳类样本，并通过稳定同位素（stable isotope, SI）与脂肪酸（fatty acid, FA）技术分析其营养动力学特征。
不同双壳类物种在河口的空间分布存在显著差异。中国绿螂（Glauconome chinensis）主要分布于溪口附近的潮间湿地，而缢蛏（Sinonovacula constricta）则更偏好溪口生境。不同物种的食性亦存在明显分化：缢蛏摄食的硅藻与细菌比例高于中国绿螂，而中国绿螂则更多同化大型植物有机质。
脂肪酸标志物分析显示，夏季颗粒有机物（particular organic matter, POM）的主要贡献来源为大型植物（占比38.86 ± 4.25%），冬季则以硅藻为主要贡献来源（占比12.68 ± 1.17%）。无论夏季（24.73 ± 0.44%）还是冬季（25.51 ± 0.59%），硅藻均为缢蛏食性的最大贡献组分，而大型植物的贡献占比均不超过4%。这种食性差异反映了食物资源可获得性的季节变化，以及双壳类的主动摄食习性。
缢蛏的脂肪酸谱特征表明，其不同采样点的食性组成较为相似，但碳同位素δ¹³C结果显示，不同采样点的缢蛏食性碳源存在差异，分别为C4植物互花米草（Spartina alterniflora）以及C3植物芦苇（Phragmites australis）和海三棱藨草（Scirpus mariqueter）。
双壳类食性的物种特异性以及时间、空间变异可能会影响其在潮间带湿地中的生态功能，这一点在河口生态系统食物网与物质流动研究中应予以充分重视。