Image: Marine Research Institute / FIS

Norwegian algae forests are a large carbon store - but are threatened by climate change

NORWAY
Thursday, March 30, 2023, 07:00 (GMT + 9)

Norway have around 10,000 km2 of blue forest along our coast. New research indicates that the marine forests have an important role in sequestering and storing carbon, but we do not know enough about what the blue forest means in the fight against climate change. New status report points to gaps in knowledge.

Marine algae (Laminaria hyperborea, left) form dense forests on rocky bottoms in areas exposed to waves (photo: Marine Research Institute). Marine algae (several species, center) grow in the intertidal zone and can withstand both wave exposure and dry laying (photo: NIVA). Seaweeds (Zostera marina, right) are among the few flowering plants that live in the sea, where they can form large underwater beds (photo: NIVA).

Beneath the water crust along the Norwegian coast, we have huge forest areas.

The blue forest consists of seaweed, kelp and eel grass - and hides a secret. Because the ocean's forest stores carbon.

And in Norway, the warehouse is full.

"We believe that almost half of all carbon that is stored long-term from blue forests in the Nordics originates from Norwegian kelp forests", says researcher Kjell Magnus Norderhaug at the Institute of Marine Research (HI).

CO2 is bound in seaweed, kelp, grass and plankton - and stored in the seabed itself

How does it happen? The ocean absorbs about a quarter of all the carbon we humans release into the atmosphere through physical, chemical and biological processes.

Part of the carbon is tied up in standing biomass of seaweed, kelp, eelgrass and phytoplankton through photosynthesis.

A proportion sinks to the seabed at greater depths, as dead algae. This only applies to a very small part of the plankton, while an unknown and presumably large part of the organic material from the blue forest sinks to deep water and is permanently stored in the sediments. Sediment is the various layers the seabed consists of.

When carbon is stored in this way, it is no longer part of the carbon cycle - and thus CO2 is pumped from the atmosphere into the seabed. In this way, the forests in the sea can have an important climate role.

The carbon cycle in the ocean (from the Norwegian Environment Agency (2019), graphics: Tibe T).

New report from the Monitoring Group reveals gaps in knowledge

For the first time, the monitoring group has provided a joint assessment of the state and development of the environment in all Norwegian sea areas.

A separate chapter has been devoted to what we know about blue carbon in the management plan areas for the Barents Sea, the Norwegian Sea and the North Sea with Skagerrak.

"This is a new field of research, and there is still much we do not know and understand", says Norderhaug.

For example, it is not known how much carbon from blue forests is stored in Norwegian waters each year.

"But new research shows that the carbon stock in the uppermost meter of the sediments inside eelgrass beds is high in the North Sea and Skagerrak if we compare it to other sea areas."

Another knowledge gap pointed out in the report is how the carbon store possibly counteracts climate change.

Kelp forests in good condition in Norwegian waters - but threatened by climate change in the long term

The report also includes a recent "health status" for our kelp forest.

"Over large areas in western and central Norway, the kelp forest is in good condition. In northern parts of the Norwegian Sea and in the Barents Sea, most of the kelp forest has been grazed by sea urchins, probably due to overfishing of predatory fish that eat the sea urchins, until the 1970s", explains the HI researcher.

"We expect that this situation will slowly improve in the years to come, due to global warming. The green sea urchin is a cold-water species."

<-- Source Wiki / FIS

However, due to the increased rate of decomposition in warmer water, the researchers also believe that the carbon storage capacity is reduced with global warming.

In the North Sea and Skagerrak, the sugar kelp forests face major threats.

"The frequency and intensity of heat waves is increasing, and combined with nutrient salts, darkening and siltation of runoff from land, conditions are getting worse."

"It is crucial that we put in place more comprehensive monitoring of our blue forests, and that we can conduct further research into how large the carbon storage in Norwegian sea areas really is - and what role it plays in the fight against climate change" says Norderhaug.

Source: Institute of Marine Research (traducido del original en noruego) 

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