Data from: Detrital shadows: estuarine food web connectivity depends on fluvial influence and consumer feeding mode

We measured the influence of landscape setting on estuarine food web connectivity in five macrotidal Pacific Northwest estuaries across a gradient of freshwater influence. We used stable isotopes (δ13C, δ15N, δ34S) in combination with a Bayesian mixing model to trace primary producer contributions to suspension- and deposit-feeding bivalve consumers (Mytilus trossulus and Macoma nasuta) transplanted into three estuarine vegetation zones: emergent marsh, mudflat, Japanese eelgrass (Zostera japonica), and native eelgrass (Zostera marina). Fluvial discharge and consumer feeding mode strongly influenced the strength and spatial scale of observed food web linkages, while season played a secondary role. Mussels displayed strong cross-ecosystem connectivity in all estuaries, with decreasing marine influence in the more fluvial estuaries. Mussel diets indicated homogenization of detrital sources within the water column of each estuary. In contrast, the diets of benthic deposit-feeding clams indicated stronger compartmentalization in food web connectivity, especially in the largest river delta where clam diets were trophically disconnected from marsh sources of detritus. This suggests detritus deposition is patchy across space, and less homogenous than the suspended detritus pool. In addition to fluvial setting, other estuary-specific environmental drivers, such as marsh area or particle transport speed, influenced the degree of food web linkages across space and time, often accounting for unexpected patterns in food web connectivity. Transformations of the estuarine landscape that alter river hydrology or availability of detritus sources can thus potentially disrupt natural food web connectivity at the landscape scale, especially for sedentary organisms which cannot track their food sources through space.本研究针对太平洋西北岸的5个大潮河口（横跨淡水影响梯度），探究了景观背景对河口食物网连通性的影响。研究采用稳定同位素（stable isotopes，δ¹³C、δ¹⁵N、δ³⁴S）结合贝叶斯混合模型（Bayesian mixing model），追踪初级生产者对滤食性与沉积食性双壳类消费者——紫贻贝（Mytilus trossulus）与Macoma nasuta——的营养贡献，这些双壳类被移植至3类河口植被生境：挺水沼泽、潮间带泥滩、日本鳗草（Zostera japonica）群落与本土鳗草（Zostera marina）群落。结果显示，河流径流与消费者摄食模式对观测到的食物网联系强度与空间尺度具有显著调控作用，而季节仅起到次要影响。贻贝在所有河口均表现出较强的跨生态系统连通性，且在淡水占比更高的河口，其海洋影响信号呈减弱趋势；贻贝的食性表明，各河口水柱内的碎屑源呈现均质化特征。与之相对，底栖沉积食性蛤类的食性则表现出更强的食物网连通性分隔化特征，尤其在最大的河流三角洲区域，蛤类的食性与沼泽碎屑源在营养层面完全脱节。这说明碎屑沉积在空间上呈斑块状分布，其异质性高于悬浮碎屑库。除河流背景外，其他河口特异性环境驱动因子（如沼泽面积、颗粒物传输速率）也会影响食物网联系的时空分布特征，往往能解释部分非常规的食物网连通性模式。因此，改变河流水文或碎屑源可获得性的河口景观改造活动，可能会破坏景观尺度下的自然食物网连通性，对于无法随空间追踪食物源的定居生物而言，这一影响尤为显著。