Characterizing the patterns of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes at the base of the food webs (baseline) is essential in ecological studies for assessing the feeding habits and migration patterns of marine predators. We analysed δ¹³C and δ¹⁵N in zooplankton samples collected in spring and autumn (2012–2015), along the south (SCM) and southeast (NCSM) Brazilian oceanic waters. An increase in δ¹³C from the shelf break towards the offshore was associated with the influence of continental water input and upwellings along the shelf break, which introduce ¹³C-depleted inorganic carbon to the surface, where it will be incorporated into the biological system through phytoplankton growth. An opposite trend was observed in δ¹⁵N, with higher values along the shelf break related to the intrusion of upwelled deep-water nutrients, contrasting with the oligotrophic offshore waters where N₂ fixation takes place, resulting in primary and secondary production that is relatively more depleted in ¹⁵N. A latitudinal (north-south) decrease in δ¹³C along the offshore area coincided with known isotopic patterns in inorganic carbon, which were more ¹³C-depleted towards higher latitudes. On the other hand, an increase in δ¹⁵N was observed towards the south, reflecting the contrast between the N₂ fixation in the more oligotrophic waters in the NCSM and the higher nutrient availability in the SCM. Additionally, δ¹³C was significantly higher in autumn and δ¹⁵N was higher in spring. Although inter-annual differences in δ¹⁵N were non-significant, δ¹³C was significantly lower in 2012 than in the later years. This study provides novel information regarding the patterns of baseline δ¹³C and δ¹⁵N in the southwestern Atlantic Ocean, which will be useful for future investigation of the ecology of higher trophic-level organisms occurring in this area.

表征稳定的碳（δ的图案¹³ C）和氮（δ ¹⁵ N）在食物网（基线）的基同位素是用于评估食性和海洋食肉动物的迁移模式在生态研究必不可少的。我们分析δ ¹³ C和δ ¹⁵在春季和秋季（2012- 2015年）收集的浮游动物样本中N，沿南（SCM）和东南（NCSM）巴西海洋水域。在δ的增加¹³从朝向近海搁板断裂溶液用陆地水输入和上升流的沿着搁板断裂影响力，这引入相关联的¹³碳贫化的无机碳到达表面，然后通过浮游植物的生长将其掺入生物系统。在δ观察到相反的趋势¹⁵ N，具有较高值的沿与上涌深水营养物质的侵入的架子断裂，与其中N贫营养近海水域对比₂固定发生，导致初级和次级生产是相对更贫¹⁵ N的纬度（北-南）减少δ ¹³ ç沿着与无机碳同位素已知图案，这是更近海区域正好¹³朝更高纬度C-耗尽。在另一方面，增加δ ¹⁵观察到向南的氮，这反映了NCSM中营养较弱的水中N ₂固定与SCM中较高的养分利用率之间的对比。此外，δ ¹³下在秋季是显著更高和δ ¹⁵ n为在弹簧更高。虽然δ年度间的差异¹⁵ ň是非显著，δ ¹³下，在2012被显著低于在以后的岁月里。这项研究提供了关于基线δ模式新颖的信息，¹³ C和δ ¹⁵ N的西南大西洋，这将是这一领域出现的高营养级生物生态学将来的调查是有用的。