Abstract
The biogeochemical consequences of extreme thermal events in coastal upwelling systems remain poorly characterized across temporal scales, although, these events are increasingly recognized for their capacity to disrupt ecosystems functioning. Here, we integrate a four-decade temperature satellite-based analysis (1982–2022), a coastal time series, and targeted in situ observations during a short-term heat spike to assess the physical and biogeochemical signatures of thermal extremes. Specifically, we examine marine heat waves (MHWs) and marine cold spells (MCS) in a seasonal mid-latitude coastal upwelling region in central-southern Chile. MCSs were more frequent and intense than MHWs, particularly near upwelling centers, and were associated with enhanced vertical mixing and greater surface nutrient availability. In contrast, MHWs promoted stratification and surface nutrient depletion, consistent during the Coliumo Bay heat spike, when elevated temperatures coincided with declines in nitrate, phosphate, and silicate. This event was also accompanied by short-term increases in carbon and ammonium assimilation, highlighting the role of recycled production under warmer, stratified conditions. Together, these thermal extremes drive distinct and rapid biogeochemical responses, that can alter productivity, nutrient cycling, and coastal ecosystem resilience under climate change. These findings underscore the critical need for sustained time series and event-based observations to capture short/lived yet ecologically significant processes that are often overlooked by remote sensing.
Acknowledgements
We thank the crew of the R/V Kay Kay II and the staff at the Dichato Marine Station (University of Concepción) for their valuable support during fieldwork. We also acknowledge the contributions of all colleagues involved in the operation and maintenance of the Station 18 time series. Special thanks to Juan Faundez, who led the logistical coordination of sampling during the COVID-19 pandemic.
Funding
This research was supported by the National Agency for Research and Development (ANID, Chile) through a Postdoctoral grant 3210481and the Center for Oceanographic Research in the eastern South Pacific COPAS Coastal FB210021. R. A. Quiñones was funded by grant ANID-INCAR 1523A0007 and INCAR2-CIA 250009. Data set compilation and data analysis were funded by FONDECYT 1211977 and 1241067. Time series study from 2002 to 2015 was supported by COPAS Center (FONDAP No. AFB170006). From 2016 to 2022, the time series study was supported by the following grants: ANID-FONDECYT grants 1161138 (LF; 2016–2020); FONDECYT 12008861 (LF; 2020–2023); and INCAR-ANID 15110027. Laura Farias coordinated time series sampling for the period 2016–2022.
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Valdés-Castro, V., Narváez, D.A., Farías, L. et al. Biogeochemical signal from marine heatwaves, cold spells, and transient warming events in a coastal upwelling system.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-62941-1
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DOI: https://doi.org/10.1038/s41598-026-62941-1
Keywords
- Marine heat waves
- Marine cold spells
- Heat spike events
- Coastal upwelling
- Nutrient cycling
- Carbon-nitrogen assimilation
Source: Ecology - nature.com
