Coastal upwelling generates cryptic temperature refugia

Area of Science:

• Marine ecology
• Oceanography
• Climate change biology

Background:

• Organismal distribution is influenced by climate-driven environmental changes.
• Understanding spatiotemporal patterns in environmental conditions is crucial for predicting species' responses to global change.
• Intertidal zones are sensitive indicators of climate impacts.

Purpose of the Study:

• To investigate the role of upwelling in creating spatiotemporal thermal refugia.
• To quantify the effects of upwelling intensity on water temperature variation.
• To predict how these thermal refugia influence organismal performance and distribution.

Main Methods:

• Wavelet analysis was employed to examine daily water temperature variation.
• Spatiotemporal (co)variation was analyzed across 16 intertidal sites along the European Atlantic Coast.
• Upwelling intensity was categorized as 'no', 'weak', or 'strong'.

Main Results:

• Weak upwelling sites showed high temperature synchrony but low co-variability at monthly to weekly scales.
• Strong upwelling sites exhibited the opposite pattern, with lower synchrony and higher co-variability.
• Wavelet coherence and correlograms indicated scale-dependent temperature fluctuations, with rapid spatial decay in strong upwelling areas.

Conclusions:

• Upwelling generates both temporal and spatial thermal refugia, mitigating heat stress and reducing extreme temperature durations.
• These refugia can enhance organismal performance by providing cooler waters and promoting fine-scale temperature fluctuations.
• Identifying cryptic spatiotemporal refugia is essential for mapping potential organismal distribution patterns under climate change.