Arctic Coralline Algae Elevate Surface pH and Carbonate in the Dark

Area of Science:

• Marine Biology
• Oceanography
• Biogeochemistry

Background:

• Red coralline algae are vital ecosystem engineers in polar regions.
• Ocean acidification poses a significant threat to marine calcifiers, especially in Arctic environments.
• Understanding carbon acquisition is key to predicting coralline algae's response to changing ocean chemistry.

Purpose of the Study:

• To investigate the localized carbonate chemistry at the surface of Arctic coralline algae.
• To determine if Arctic coralline algae possess mechanisms to cope with ocean acidification.
• To assess the implications for future Arctic marine ecosystems.

Main Methods:

• Utilized microsensors to measure pH and carbonate ion concentration ([CO32-]) at the algal surface.
• Investigated three species of Arctic coralline algae.
• Analyzed carbon concentrating mechanisms, including bicarbonate uptake and carbonic anhydrase activity.

Main Results:

• Surface pH and [CO32-] were elevated compared to bulk seawater, both in light and after dark incubation.
• Arctic coralline algae demonstrated efficient carbon concentrating mechanisms, utilizing bicarbonate directly and indirectly.
• No net dissolution was observed in the dark, suggesting active biological control over surface chemistry.

Conclusions:

• Arctic coralline algae exhibit strong biological control over their microenvironment's carbonate chemistry.
• Light-independent carbon fixation may mitigate respiratory CO2 release, potentially aiding adaptation to ocean acidification.
• These findings have significant implications for the resilience of Arctic marine ecosystems under future climate change scenarios.