Galván David Edgardo, Funes Manuela, Paparazzo Flavio Emiliano, Alonso Roldán Virginia, Derisio Carla, Pisoni Juan Pablo, Temperoni Brenda, Del Valle Daniela Alejandra, Segura Valeria, Newsome Seth D
Centro para el Estudio de Sistemas Marinos (CESIMAR-CONICET), Boulevard Brown 2915, Puerto Madryn U9120ACD, Argentina.
Instituto de Investigaciones Marinas y Costeras (IIMyC, UNMdP-CONICET), Juan B. Justo 2550, Mar del Plata B7608FBY, Argentina.
Biology (Basel). 2024 Nov 29;13(12):990. doi: 10.3390/biology13120990.
Maps of (baseline) δC and δN values of primary producers or consumers near the base of food webs provide crucial information for interpreting patterns in the isotopic composition of consumers that occupy higher trophic levels. In marine systems, understanding how oceanographic variables influence these values enables the creation of dynamic isoscapes across time and space, providing insights into how ecosystems function. The San Jorge Gulf (SJG) in the southwest Atlantic Ocean (45° S-47° S) is an area of particular importance, as it is located on one of the most productive continental shelves in the world, supporting large fisheries and marine mammal and seabird populations. We reconstructed spatial variation in zooplankton δC and δN values across SJG and investigated their relationship with physical and chemical oceanographic conditions. During cruises in the austral spring of 2016 and 2017, we collected medium-sized copepods whose isotopic composition integrate short-term (days to weeks) variation in oceanographic conditions recorded by phytoplankton at the base of the food web. We also collected data on water column depth, surface and bottom temperatures, water column stability, and macronutrient (nitrate, phosphate, and silicic acid) concentrations. The results revealed significant variation in both δC and δN values of up to 7-8‱ over a relatively small spatial scale (200-300 km). Copepod δC values were lower at the center of the SJG, showing an inverse correlation with water column stability, surface nitrate concentration, and water column depth. δN values showed a strong and negative relationship with surface nitrate concentration and water column stability, increasing from south to north in the SJG. δN values also showed a positive relationship with surface silicic acid concentration. These spatial patterns in nutrient dynamics and copepod carbon and nitrogen isotope values are interpreted in the context of the dominant northward current and temporal development of the frontal systems in the SJG.
食物网底部附近初级生产者或消费者的（基线）δC和δN值地图，为解释处于较高营养级的消费者同位素组成模式提供了关键信息。在海洋系统中，了解海洋学变量如何影响这些值有助于创建跨时空的动态等距线图，从而深入了解生态系统的功能。西南大西洋（南纬45°-47°）的圣豪尔赫湾（SJG）尤为重要，因为它位于世界上生产力最高的大陆架之一，支撑着大型渔业以及大量的海洋哺乳动物和海鸟种群。我们重建了圣豪尔赫湾浮游动物δC和δN值的空间变化，并研究了它们与物理和化学海洋学条件的关系。在2016年和2017年南半球春季的巡航期间，我们收集了中型桡足类动物，其同位素组成整合了食物网底部浮游植物记录的海洋学条件的短期（数天至数周）变化。我们还收集了有关水柱深度、表层和底层温度、水柱稳定性以及大量营养素（硝酸盐、磷酸盐和硅酸）浓度的数据。结果显示，在相对较小的空间尺度（200-300公里）内，δC和δN值均有高达7-8‱的显著变化。圣豪尔赫湾中心的桡足类动物δC值较低，与水柱稳定性、表层硝酸盐浓度和水柱深度呈负相关。δN值与表层硝酸盐浓度和水柱稳定性呈强烈负相关，在圣豪尔赫湾从南向北增加。δN值还与表层硅酸浓度呈正相关。这些营养动态以及桡足类动物碳和氮同位素值的空间模式，是在圣豪尔赫湾主要向北的洋流和锋面系统的时间发展背景下进行解释的。
