Does seabed soil hold secret to supreme carbon storage?
Interest in natural carbon storage in the ocean has, to date, focused on mangrove forests, salt marshes, and seagrass meadows. However, a new study from Canadian researchers implores us to take a closer look at the very soil beneath us: the sediment on the seafloor.
For life in the ocean, the effectiveness of established marine protected areas in providing benefits to the environment’s spectrum of biodiversity has been well proven. So too, has the positive impact on elements of the wider blue economy – such as sustainably-managed fisheries. But what if there was yet another perk? One so far, less extensively covered? What if using marine protected areas also provided us with one of the most effective tools for natural carbon storage on the seafloor, too?
To date, interest in natural carbon storage within the ocean – often referred to as ‘blue carbon’ has typically focused on mangrove forests, salt marshes, and seagrass meadows. However, a new study – led by researchers at the University of Victoria – implores us to take one more environment into consideration: seabed sediment.
In fact, University of Victoria postdoctoral fellow, Graham Epstein argues that while the soils on the ocean floor may seem empty and unimportant, “they may hold even greater potential for carbon storage” and should therefore be considered for ‘greater protection’.
“Seabed sediments actually contain a unique, diverse, and often fragile group of species vital to marine ecosystems,” said Epstein, a member of Blue Carbon Canada, a national research coalition led by the University of Victoria established to evaluate the current and future capacity of natural carbon storage across Canada’s marine habitats.
“Seafloor sediments are the final point in the marine carbon cycle, and since they cover the majority of the ocean floor, they make up one of the planet’s largest stores of carbon, dwarfing mangroves, seagrass meadows, and salt marshes.”
The new study – published this month in FACETS – estimates that Canada’s current MPA network encompasses just 11% of the carbon contained in the seafloor, down to depths of 2,500 metres, and only around 13% of the carbon hotspots.
Working alongside his colleagues Julia Baum, a special advisor in climate for the University of Victoria and an expert in marine ecology and conservation, as well as partners at Oceans North and Fisheries and Oceans Canada, Epstein found that under Canada’s current proposal to expand its marine protected area (MPA) network, protection would be provided to an additional 9% of the total seafloor carbon and 6% of the carbon hotspots.

It’s true that while MPAs were initially created to conserve and recover declining, depleted, rare, or fragile species or habitats – there is now a growing interest in their ability to provide climate mitigation benefits, too.
In fact, Canada’ marine governing body has stated that climate change mitigation is an aim of their MPA network development. While Canada has currently designated 15.5% of its seas as MPAs and has joined global commitments to designate 25% by 2025 and 30% by 2030, there are, to date, no MPAs designated explicitly for the protection of carbon storage.
Researchers hope that this latest study may go some way to changing this.
“It’s becoming increasingly apparent that industrial marine activities, such as bottom fishing, deep sea mining, marine energy development processes, oil and gas extraction, and marine construction can disrupt the carbon found in seabed sediments,” said Susanna Fuller, vice president of conservation and projects at Oceans North.
“Protecting important areas of seabed sediment will help to ensure that the carbon stays buried, rather than re-entering the carbon cycle and contributing to climate change.”
Through his research, Epstein has identified and ranked some 247 priority areas for future study and potential future spatial protection. These areas have all been ranked based n the estimated amount of carbon, the potential vulnerability of the carbon, and the ecological and biological significance of the area.
In British Columbia, the highest priority areas included the Queen Charlotte Strait and northern Salish Sea, as well as many of the fjords and inlets on the west coast of Vancouver Island and mainland BC. In the Atlantic, highest priority areas include Placentia, Mahone, and Trinity bays, as well as parts of the Laurentian Channel and Scotian Shelf.

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