Bode Antonio, García-Seoane Rita, Varela Zulema, Viana Inés G
Centro Oceanográfico de A Coruña, Instituto Español de Oceanografía (IEO-CSIC), A Coruña, Spain.
CRETUS, Ecology Unit, Department of Functional Biology, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.
PLoS One. 2025 Jul 1;20(7):e0327159. doi: 10.1371/journal.pone.0327159. eCollection 2025.
Upwelling is one of the major mechanisms responsible for the input of nutrients sustaining high levels of marine primary production. As a consequence of global change, variations in upwelling intensity may affect nutrient supply thus impacting marine food webs. In this study, we examine the effects of decadal variability of upwelling strength on nitrate supply and its influence on the nitrogen stable isotope composition at the base of the marine food web at the northern boundary of the Canary Current upwelling system (NW Spain) between 1989 and 2023. The study focused on the early upwelling season each year (March-June) to minimize the effects of nitrogen remineralization. Intertidal macroalgae (Phaeophyceae) and mussels (Mytilus galloprovincialis) were used as proxies for temporally integrated isotopic signals of nitrogen sources (δ15N). While no significant temporal trends for either upwelling strength, nitrate concentrations, or stable isotopes were found, three periods with characteristic upwelling and nutrient regimes were identified. A linear increase in δ15N, particularly in Fucus spp., associated with a decreasing contribution of upwelling-derived nitrogen suggest the influence of additional sources, likely of anthropogenic origin. Thus, no net change in productivity would be expected in this region despite quasi-decadal shifts in upwelling dynamics. Further insights on the origin and relevance of these sources can be gained through the investigation of river and runoff inputs and the use of more sensitive tracers, such as amino acid δ15N analysis in mussels.
上升流是维持高水平海洋初级生产力的营养物质输入的主要机制之一。由于全球变化，上升流强度的变化可能会影响营养物质供应，从而影响海洋食物网。在本研究中，我们考察了1989年至2023年期间，加那利洋流上升流系统（西班牙西北部）北部边界处上升流强度的年代际变化对硝酸盐供应的影响及其对海洋食物网底部氮稳定同位素组成的影响。该研究聚焦于每年的早期上升流季节（3月至6月），以尽量减少氮再矿化的影响。潮间带大型藻类（褐藻纲）和贻贝（地中海贻贝）被用作氮源（δ15N）时间积分同位素信号的替代物。虽然未发现上升流强度、硝酸盐浓度或稳定同位素的显著时间趋势，但确定了三个具有特征性上升流和营养状况的时期。δ15N的线性增加，特别是在墨角藻属中，与上升流衍生氮的贡献减少相关，这表明可能存在人为来源的其他来源的影响。因此，尽管上升流动态存在准十年变化，但预计该区域的生产力不会有净变化。通过调查河流和径流输入以及使用更敏感的示踪剂，如贻贝中氨基酸δ15N分析，可以进一步了解这些来源的起源和相关性。
