New Study Suggests Warmer Oceans May Limit Kelp Forests’ Ability To Store Carbon for Long Periods of Time

Kelp generates enormous seaweed forests along temperate coastlines, sequestering large amounts of atmospheric carbon.

However, warming oceans, according to a study published in the open-access journal PLOS Biology by Karen Filbee-Dexter of the University of Western Australia and the Institute of Marine Research and colleagues, could reduce the capacity of kelp forests to trap carbon in deep ocean stores for long periods, exacerbating the effects of climate change.

Reduction of kelp forest due to climate change

(Photo : J Cruikshank/Unsplash)

Kelp carbon can either feed other organisms during decomposition or be trapped in the deep ocean for hundreds or thousands of years, as per ScienceDaily.

Researchers studied kelp decomposition rates in 35 locations across the Northern Hemisphere to better understand how the capacity of kelp forests to build long-term carbon stores will change as the climate warms.

They collected fresh kelp fragments and tied them to the sea floor for four to 18 weeks in a mesh bag within a plastic cage, allowing water and bacteria to flow through but inhibiting larger herbivores.

They discovered that sea temperature had a major influence on the pace of decomposition, with kelp fragments decomposing more slowly in cooler waters.

According to modeling, kelp breakdown is slow enough that a large amount of it can reach deep ocean carbon sinks.

However, continuous water temperature changes caused by climate change may hasten decomposition, lowering the amount of carbon retained in the long run.

A 0.4 degree Celsius increase in sea temperature by 2050 could diminish the carbon sequestration capability of decaying kelp by 9%.

However, as the climate warms, kelp forests are expected to spread in higher latitude regions, where slower decomposition rates might make these forests a key source of long-term ocean carbon reserves, according to scientists.

According to Filbee-Dexter, the experiment evaluated kelp carbon turnover across twelve areas in the northern hemisphere and discovered that carbon breakdown was substantially related to ocean temperature.

This shows that as the ocean warms, kelp carbon storage may decrease, and that kelp forests in cool polar regions have the potential to be key blue carbon ecosystems.

Also Read: Consequences of Climate Change: Kelp! Australia's Underwater Forest Wiped Out by Marine Heatwave

The value of kelp forests to nature and society

Kelp forests are frequently referred to as "underwater rainforests."

They form a three-dimensional habitat and a highly productive system as a result of the dense growth of multiple kelp species, as per Maco Bios.

Kelps are giant brown algae that stick to the seafloor (benthic) and are typically found in water temperatures below 20 °C.

They can grow incredibly fast in the right conditions, up to 30 cm per day, and can reach 45 m in length for the giant kelp.

They not only provide plenty of surfaces and nooks and crannies for other species to settle and live on, but they also protect coasts from storms and help sequester or absorb carbon from the atmosphere, making them extremely valuable social resources.

Kelp forests provide habitat for a wide range of animals, including other benthic algae, invertebrates, fish, and marine mammals.

Investigations along the Norwegian coast have revealed that a maximum of about 100 000 small invertebrates are linked to a single stipe (main stem) of the species Laminaria hyperborea.

With an average of 10 plants per m2, this results in a very high diversity and abundance of animals that form the foundation of food webs all the way up to fish and mammals.

Many of these fish are then caught for human consumption.

Related article: Urchins Turn Kelp Forests into Barren Wasteland