Centro de Investigación y Gestión de Los Recursos Naturales (CIGREN), Universidad de Valparaíso, Valparaíso, Chile; Facultad de Ciencias Del Mar y Recursos Naturales, Universidad de Valparaíso, Viña Del Mar, Chile; Núcleo Milenio de Salmónidos Invasores (INVASAL), Universidad de Concepción, Concepción, Chile.
Núcleo Milenio de Salmónidos Invasores (INVASAL), Universidad de Concepción, Concepción, Chile; Instituto de Ciencias Naturales Alexander von Humboldt, Universidad de Antofagasta, Antofagasta, Chile; Universidad de Antofagasta Stable Isotope Facility (UASIF), Instituto Antofagasta, Universidad de Antofagasta, Chile; Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, UK.
Mar Environ Res. 2024 Nov;202:106732. doi: 10.1016/j.marenvres.2024.106732. Epub 2024 Sep 3.
Spatial differences in the isotope values of widely distributed marine apex consumers may reflect geographical differences in the isotopic composition of basal resources (e.g., phytoplankton) fueling food webs (bottom-up effects) or spatial differences in the trophic ecology of the taxon of interest (top-down effects). We examined spatial variation in δC and δN values from 264 South American sea lions (SASL, Otaria flavescens) of different age classes (adults, subadults and juveniles), their putative prey consisting of pelagic and benthic coastal fishes, and particulate organic matter (POM) measured from locations situated across >2300 km of the Chilean coast (between 18°42' and 39°17' S). We used generalized least squares (GLS) models to compare the form of the relationship between δC and δN and latitude between the three functional groups. Our results show that SASL from northern, central, and southern areas were isotopically distinct, with individuals from the north having lower δC and higher δN values in comparison to individuals from the south. When the relationship for each functional group was modelled individually using GLS, results indicated that for each degree of increasing latitude δN decreased on average by 0.12‰ (POM), 0.15‰ (prey), and 0.14‰ (SASL), while δC increased by 0.06‰ (POM) and 0.05‰ in both prey and SASL. We suggest that the latitudinal differences observed in SASL δC and δN values reflect baseline isotopic variation rather than marked differences in trophic ecology of these widely distributed consumers.
广泛分布的海洋顶级消费者的同位素值的空间差异可能反映了基础资源（例如浮游植物）的同位素组成在地理上的差异，这些差异为食物网提供了燃料（自上而下的影响），或者是感兴趣的分类群的营养生态在空间上的差异（自下而上的影响）。我们研究了来自不同年龄组（成年、亚成年和幼年）的 264 只南美的海狮（Otaria flavescens）的 δC 和 δN 值的空间变化，它们的假定猎物由远洋和近岸沿海鱼类以及从位于智利海岸 2300 多公里范围内的地点测量的颗粒有机物质（POM）组成（在 18°42' 和 39°17' S 之间）。我们使用广义最小二乘法（GLS）模型比较了三个功能组之间 δC 和 δN 与纬度之间的关系形式。我们的结果表明，来自北部、中部和南部地区的 SASL 在同位素上存在明显差异，与来自南部的个体相比，来自北部的个体的 δC 更低，δN 更高。当使用 GLS 分别对每个功能组的关系进行建模时，结果表明，对于每度增加的纬度，δN 平均减少 0.12‰（POM）、0.15‰（猎物）和 0.14‰（SASL），而 δC 在猎物和 SASL 中分别增加 0.06‰ 和 0.05‰。我们认为，在 SASL 的 δC 和 δN 值中观察到的纬度差异反映了基线同位素的变化，而不是这些广泛分布的消费者在营养生态上的显著差异。
