Sturbois A, Riera P, Desroy N, Brébant T, Carpentier A, Ponsero A, Schaal G
Vivarmor Nature, 18 C rue du Sabot, 22440, Ploufragan, France; Réserve naturelle nationale de la Baie de Saint-Brieuc, site de l'étoile, 22120, Hillion, France; Ifremer, Laboratoire Environnement et Ressources Bretagne nord, 38 rue du Port Blanc, 35800, Dinard, France; Laboratoire des Sciences de l'Environnement Marin (LEMAR), UMR 6539 CNRS/UBO/IRD/IFREMER, BP 70, 29280, Plouzané, France.
Sorbonne Université, CNRS, Station Biologique de Roscoff, UMR7144, Place Georges Teissier, CS90074, 29688, Roscoff Cedex, France.
Mar Environ Res. 2022 Mar;175:105572. doi: 10.1016/j.marenvres.2022.105572. Epub 2022 Feb 2.
Assessing fluxes of matter and energy in food webs within and across benthic habitats is important to understand the ecological functioning in bays and estuaries, where the productivity is favoured by a wide diversity of primary producers. The temporal variability (March vs September 2019) in the carbon and nitrogen stable isotope composition of primary food sources and benthic invertebrates consumers was investigated in a large intertidal area (Western English-Channel, France). The study area is influenced by megatidal conditions and characterised by salt marshes in the sheltered part, and seasonal Ulva spp. blooms. The spatio-temporal variability in the structure of the benthic food web was analysed at the scales of both the whole bay and the different assemblages, which constitute the mosaic of habitats. Inferences on potential sources fuelling the food web were supported by spatio-temporal patterns based on covariations and stable isotope trajectory analysis. Results highlighted that phytoplankton, microphytobenthos and SOM were, most likely, the main food sources. The trophic connectivity between salt marsh and benthic habitats within the bay was limited to some macrofauna species inhabiting muddy creeks within the salt marsh. Unexpectedly, the influence of Ulva spp. blooms appeared also limited. Spatial patterns illustrates the constancy of the spatial variability in the benthic pelagic coupling, with a higher influence of microphytobenthos in the upper shore compared to low shore assemblages. This first attempt to characterize intertidal benthic food web constitutes a relevant baseline for the conservation of the bay of Saint-Brieuc where a national Nature Reserve has been created in 1998 for the conservation of overwintering birds. The spatial and temporal patterns of the benthic food web observed in this study (1) confirm the importance to consider food web variability at spatial and temporal scales from sampling designs to data analysis, and (2) demonstrate the ability of the stable isotope trajectory analysis framework to highlight food web dynamics.
评估底栖生境内部和之间食物网中的物质和能量通量，对于理解海湾和河口的生态功能很重要，因为这些地方的生产力得益于多种多样的初级生产者。在法国英吉利海峡西部的一个大型潮间带区域，研究了初级食物来源和底栖无脊椎动物消费者的碳和氮稳定同位素组成的时间变异性（2019年3月与9月）。研究区域受大潮条件影响，在受庇护的部分有盐沼，还有季节性的石莼属藻类大量繁殖。在整个海湾和构成栖息地镶嵌体的不同群落这两个尺度上，分析了底栖食物网结构的时空变异性。基于协变和稳定同位素轨迹分析的时空模式，为为食物网提供能量的潜在来源提供了推断依据。结果表明，浮游植物、微型底栖藻类和土壤有机质很可能是主要食物来源。海湾内盐沼和底栖生境之间的营养连通性仅限于一些生活在盐沼内泥质溪流中的大型动物物种。出乎意料的是，石莼属藻类大量繁殖的影响似乎也有限。空间模式说明了底栖 - 水层耦合中空间变异性的稳定性，与低潮位群落相比，微型底栖藻类在上岸带的影响更大。这首次对潮间带底栖食物网进行特征描述的尝试，为圣布里厄湾的保护构成了一个相关的基线，该湾于1998年设立了国家自然保护区以保护越冬鸟类。本研究中观察到的底栖食物网的时空模式：（1）证实了从采样设计到数据分析在时空尺度上考虑食物网变异性的重要性；（2）证明了稳定同位素轨迹分析框架突出食物网动态的能力。
