Blue carbon: past, present and future, with emphasis on macroalgae.

Area of Science:

• Marine Biology
• Carbon Sequestration Studies
• Paleoceanography

Background:

• Blue carbon initially excluded macroalgal ecosystems, focusing on seagrasses, salt marshes, and mangroves.
• Growing evidence indicates macroalgal ecosystems are crucial for marine carbon sequestration.
• Marine macroalgae contribute significantly to Net Primary Productivity (NPP), particularly haptophytic algae on eroding shores.

Purpose of the Study:

• To investigate the role of macroalgal ecosystems in marine carbon sequestration.
• To explore the historical and potential future contributions of macroalgae to carbon storage.
• To assess the impact of environmental changes, such as ocean warming and acidification, on macroalgal carbon sequestration.

Main Methods:

• Review of existing scientific literature on marine macroalgae and carbon cycling.
• Analysis of the processes involved in macroalgal biomass production, export, and sedimentation.
• Consideration of paleoceanographic data and future climate change projections.

Main Results:

• Long-term storage of particulate organic carbon by haptophytic algae may have begun as early as 1.6 billion years ago.
• Storage by rhizophytic macroalgae, seagrasses, tidal marshes, and mangroves initiated at least 209 million years ago.
• Ocean warming may cause poleward migration of temperate macroalgae and stress tropical species, while increased CO2 favors uncalcified algae, potentially reducing sedimentation.

Conclusions:

• Macroalgal ecosystems play a significant, though historically overlooked, role in marine organic carbon storage.
• Understanding macroalgal contributions is vital for accurate marine carbon budget assessments.
• Future climate change may alter the capacity of macroalgal ecosystems for carbon sequestration.