By Sharon Atieno

Despite kelp forests- a type of seaweed forests found along temperate and polar coastlines- being able to capture and store large amounts of carbon from the atmosphere, ocean warming could reduce this capacity, thus increasing the effects of climate change.

This is according to a recent study by Karen Filbee-Dexter at the University of Western Australia and the Institute of Marine Research and others, published in the open-access journal PLOS Biology.

The study notes that changes in the abundance of kelp, and the environmental conditions they experience, may have consequences for the global carbon cycle. This is because the slower the decomposition of kelp waste in the ocean, the greater chance it has for long-term storage in the deep ocean and the longer it takes to reenter the atmosphere as carbon.

The study which investigated kelp decomposition from 35 locations across the Northern Hemisphere found that sea temperature had a strong influence on the rate of decomposition, with kelp fragments in cooler waters degrading more slowly.

Modeling showed that kelp decomposition is slow enough that a significant proportion can reach deep ocean carbon sinks. But ongoing sea temperature rises due to climate change could accelerate decomposition, reducing the amount of carbon that is stored for the long-term.

Notably, the study found that a projected increase in sea temperature of 0.4 degrees Celsius by 2050 could reduce the carbon capturing and storing potential of decomposing kelp by 9%.

However, kelp forests are likely to expand in higher latitude waters as the climate warms, and here slower decomposition rates could make these forests a major contributor to long-term ocean carbon stores, the authors say.

Filbee-Dexter adds, “Our experiment measured kelp carbon turnover across twelve regions throughout the northern hemisphere and found that carbon breakdown was strongly linked to ocean temperature. This suggests that kelp carbon storage could be reduced as the ocean warms and that kelp forests in cool polar environments have potential to be important blue carbon ecosystems.”