Kelp carbon sink potential decreases with warming due to accelerating decomposition

Area of Science:

• Marine ecology
• Biogeochemistry
• Climate change science

Background:

• Oceanic organic carbon cycling is crucial for climate regulation.
• Environmental factors controlling coastal carbon flux remain poorly understood.
• Kelp forests are significant primary producers in coastal ecosystems.

Purpose of the Study:

• To investigate the decomposition rates of kelp detritus.
• To determine the influence of environmental factors, particularly temperature and latitude, on decomposition.
• To model the potential impact of ocean warming on kelp carbon sequestration.

Main Methods:

• A field experiment across 28° latitude using two dominant Northern Hemisphere kelp species.
• Measurement of kelp detritus decomposition rates on the seafloor.
• Analysis of relationships between decomposition, ocean temperature, and initial carbon content.
• Modeling of coastal residence times and carbon transport to marine sinks.

Main Results:

• Kelp detritus decomposition rates were strongly correlated with ocean temperature and initial carbon content.
• Higher decomposition rates were observed at lower, warmer latitudes.
• Slow decomposition suggests kelp detritus can reach deep marine sinks.
• Ocean warming may increase remineralization at low latitudes, reducing carbon sink potential by 9-42% under RCP4.5 and RCP8.5 scenarios.
• Slow decomposition at high latitudes indicates potential for increased carbon sinks in expanding kelp forests.

Conclusions:

• A significant latitudinal gradient exists in coastal ecosystem function regarding carbon cycling.
• Ocean warming will likely alter kelp detritus decomposition and carbon sequestration potential.
• Findings improve predictions of ocean warming impacts on coastal carbon cycling and identify potential carbon sequestration hotspots.