Biogeochemical features along the northern and central Patagonian shelf during a spring cruise: implications for biological productivity

•We report biogeochemical patterns across the Patagonian continental shelf.•Three macrozones were identified by nutrient concentration and hydrological gradients.•Highest nitrate uptake and new primary production occurred in northern oceanic waters.•Southern shelf waters were dominated by ammonium u...

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Veröffentlicht in:Progress in oceanography Jg. 236; S. 103511
Hauptverfasser: Valdés-Castro, Valentina, Narváez, Diego A., Gutiérrez, Marcelo H., Pantoja-Gutiérrez, Silvio, Fernández, Camila
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Elsevier Ltd 01.08.2025
Elsevier
Schlagworte:
ammonium
anthropogenic activities
biogeochemistry
C and N biogeochemical cycles
carbon
Chile
chlorophyll
climate change
continental shelf
Environmental Sciences
hydrology
N assimilation
nitrates
oceanography
organic matter
oxygen
Pacific Ocean
Patagonian fjords
Primary production
primary productivity
salinity
silicic acid
snowmelt
spring
temperature
Chile
Pacific Ocean
N assimilation
Patagonian fjords
C and N biogeochemical cycles
Primary production
ISSN:0079-6611
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Zusammenfassung:•We report biogeochemical patterns across the Patagonian continental shelf.•Three macrozones were identified by nutrient concentration and hydrological gradients.•Highest nitrate uptake and new primary production occurred in northern oceanic waters.•Southern shelf waters were dominated by ammonium uptake and recycled production. The Patagonian fjords, channels, and glacial meltwater plays a key role in shaping the hydrography and biogeochemistry of the Southeastern Pacific Ocean, through substantial exchanges with open ocean waters. However, the continental shelf between 46°S and 48°S remains less explored, leaving critical gaps in our understanding of nutrient dynamics and productivity patterns. This study investigates latitudinal gradients in water column biogeochemistry and productivity in northern and central Chilean Patagonia during the austral spring of 2018. We identified three distinct zones: a northern area (41°S and 46°S) with higher temperature, salinity, dissolved oxygen, and chlorophyll-a concentrations; an exchange zone between Guafo entrance and Moraleda Channel, characterized by elevated inorganic nutrient concentrations; and a southern area (46°S and 48°S) with increased ammonium concentrations and the lowest silicic acid levels. Offshore stations in the northern area exhibited the highest integrated primary production rates (up to 6.3 g C m−2 d−1), primarily sustained by nitrate uptake (ƒ ratios up to 0.98). In contrast, the southern area showed a preference for ammonium assimilation, with lower ƒ ratios (0.1–0.3). These findings suggest that the northern area supports a high proportion of new primary production, which likely enhances organic matter export and the efficiency of the biological pump, whereas regenerated production in the southern area may limit carbon export potential. Our study provides the first large-scale description of the biogeochemical features of the Patagonian continental shelf, particularly around the Taitao Peninsula, offering a critical baseline for understanding biogeochemical processes in this region and its potential responses to climate change and anthropogenic pressure.
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ISSN:0079-6611
DOI:10.1016/j.pocean.2025.103511