Cornejo-D'Ottone Marcela, Silva Nelson, Contreras Esteban
Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Chile; Núcleo Milenio para el estudio de la Desoxigenación del Océano Pacífico Sur oriental (DEOXS), Pontificia Universidad Católica de Valparaíso, Chile.
Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Chile.
Sci Total Environ. 2025 Aug 25;992:179953. doi: 10.1016/j.scitotenv.2025.179953. Epub 2025 Jun 26.
Fjords are subject to significant variability not only spatially, seasonally, and interannually but also on a daily scale due to the influence of tides and climatic events and terrestrial contributions that modify the water column and, therefore, the contribution of nutrients and waters of different temperatures and salinity. In the present study, we compare the daily variability of oceanographic and biogeochemical characteristics at two stations in northern Chilean Patagonia, one in the Reloncaví fjord, the northernmost Chilean fjord, with a strong terrestrial influence and anthropogenic activities, and the second in Ancud, east of the Chacao channel, with a direct influence of the Pacific Ocean. The sampling at each station was conducted in July 2013 (austral winter), a period typically characterized by high precipitation and river discharge, but low solar radiation and primary productivity. The study offers a snapshot of winter conditions with high-frequency sampling (1-3 h) for two days. The analysis shows two contrasting stations: i) a station with a high stratification and riverine influence in Reloncaví fjord driving the surface biogeochemistry, with stoichiometry indicators suggesting phosphorus deficiency and high silicic acid levels that could support diatom proliferation, while a deeper layer driven by tidal cycle with a lag of 6-10 h from the Puerto Montt station (69 km west) and ii) a quasi-homogeneous station at Ancud, with low influence of freshwater, lower silicic acid and higher N:P ratios, while the vertical oceanographic and nutrients distribution seems to be driven by tidal cycle with a lag of 2-3 h. Based on short-term oxygen level and nutrient ratios, both stations showed no immediate signs of eutrophication. However, this observation reflects only a snapshot, and seasonal variability or eutrophication cannot be ruled out without long-term monitoring. The oxygen and nutrient concentration differences between both stations reflect the biogeochemical processes during the water mass transportation. These results highlight the different drivers of the oceanographic and biogeochemical dynamic along the water column in the northern Patagonia ecosystems. However, as the study represents a short-term winter condition, it does not rule out the occurrence of seasonal or episodic oxygen depletion events. This emphasizes the importance of high-frequency studying and monitoring of the ecosystem.
峡湾不仅在空间、季节和年际尺度上存在显著变化，而且由于潮汐、气候事件以及陆地因素的影响，导致水柱发生改变，进而影响不同温度和盐度的营养物质及水体的贡献，因此在日尺度上也存在显著变化。在本研究中，我们比较了智利巴塔哥尼亚北部两个站点海洋学和生物地球化学特征的日变化情况。一个站点位于智利最北部的雷隆卡维峡湾，受到强烈的陆地影响和人为活动干扰；另一个站点位于查科海峡以东的安库德，直接受太平洋影响。每个站点的采样于2013年7月（南半球冬季）进行，这一时期通常降水和河流流量较高，但太阳辐射和初级生产力较低。该研究通过为期两天的高频采样（1 - 3小时），呈现了冬季状况的一个快照。分析显示了两个形成对比的站点：i）雷隆卡维峡湾的一个站点具有高度分层和河流影响，驱动着表层生物地球化学过程，化学计量指标表明磷缺乏且硅酸水平较高，这可能支持硅藻大量繁殖，而深层受潮汐周期驱动，与蒙特港站（以西69公里）存在6 - 10小时的时间滞后；ii）安库德的一个近乎均匀的站点，淡水影响较小，硅酸含量较低，氮磷比更高，而垂直海洋学和营养物质分布似乎受潮汐周期驱动，滞后2 - 3小时。基于短期的氧含量水平和营养物质比例，两个站点均未显示出富营养化的直接迹象。然而，这一观察结果仅反映了一个快照，若无长期监测，无法排除季节性变化或富营养化的可能性。两个站点之间的氧和营养物质浓度差异反映了水体输送过程中的生物地球化学过程。这些结果突出了巴塔哥尼亚北部生态系统水柱中海洋学和生物地球化学动态的不同驱动因素。然而，由于该研究代表的是短期冬季状况，并不排除季节性或偶发性氧耗尽事件的发生。这强调了对生态系统进行高频研究和监测的重要性。
