Blue Carbon: Uncovering the Ocean's Significant Role in Climate Action
Researchers find that UK seabed habitats have a surprisingly high capacity as carbon sinks in marine protected areas
Breaking the Ice:
A newly published report titled The United Kingdom's Blue Carbon Inventory reveals the immense potential for carbon storage and sequestration within the UK's seas, focusing on blue carbon habitats such as seabed sediments, salt marshes, and kelp forests. The report by the Scottish Association for Marine Sciences (SAMS) provides an in-depth assessment of the marine carbon sinks across UK waters, highlighting their crucial role in mitigating climate change by capturing and storing carbon for the long term. The report also emphasizes the role of Marine Protected Areas (MPAs) in safeguarding these valuable blue carbon habitats.
The study highlights that seabed sediments are the largest carbon stores in UK seas, holding an estimated 240 million tonnes of organic carbon within the top 10 cm of sediment alone. This sediment storage capacity is much higher than previously assumed (and may be higher still considering ocean mud and silt can be hundreds of meters thick), underscoring the importance of safeguarding these habitats to maximize the ocean's natural ability to absorb carbon dioxide and help stabilize the climate.
(Editor’s Note: If you don’t understand blue carbon sequestration, don’t worry! AccumulationZone explains this in “The Thaw” below.)
Quick Melt:
The SAMS study sheds light on the critical need to protect and restore blue carbon habitats. Seabed sediments, particularly in protected areas, are highly effective at locking away carbon and preventing its release into the atmosphere. However, these vital carbon stores face significant threats from human activities such as demersal fishing, installation of offshore infrastructure, and climate change-induced ocean acidification. Protecting these habitats is not only about biodiversity but also about climate action.
The report also emphasizes the potential role of MPAs in enhancing carbon sequestration. MPAs currently cover 38% of the UK's Exclusive Economic Zone; these areas are estimated to hold 43% of the total organic carbon in long-term stores. To protect blue carbon stores and support global climate goals, policymakers, and conservation groups should focus on expanding and effectively managing these areas.
The Thaw:
How Does Sequestration of Blue Carbon Work? AccumulationZone Explains.
Blue carbon refers to the carbon captured and stored by ocean and coastal ecosystems. During this process, marine plants such as seagrass and macroalgae absorb carbon dioxide (CO2) from the atmosphere during photosynthesis. Once these organisms die, they sink to the ocean floor, taking the carbon they have absorbed with them. This process is described in more detail in last week’s post about the biological carbon pump.
Seabed sediments are particularly important for long-term carbon storage. These sediments, composed of organic particles from dead marine life, accumulate over time and store vast amounts of carbon. Coastal vegetated habitats like salt marshes, mangroves, and seagrass beds also play a crucial role in carbon sequestration. These ecosystems are highly productive and can store carbon not only in their plant biomass but also in the soil beneath them, which can accumulate carbon for centuries.
The efficiency of blue carbon ecosystems in capturing and storing carbon is largely dependent on water temperature, nutrient availability, and ocean acidity. Warmer temperatures enhance the growth of marine plants, thereby increasing carbon uptake; however, excessively high temperatures can lead to die-offs in sensitive species. Nutrient availability is equally critical, as excessive nutrient runoff from agricultural or urban areas can lead to harmful algal blooms that disrupt these ecosystems. Increased ocean acidity, a consequence of higher CO2 levels, poses another challenge, as it hinders the growth of calcifying organisms (i.e. corals and shellfish) which are important components of marine carbon storage.
Final Thoughts
Human activities, such as coastal development, pollution, and destructive fishing practices, pose the greatest threat to these blue carbon ecosystems. Protecting and restoring these habitats is essential for maintaining their ability to sequester carbon and help mitigate climate change. MPAs can play a key role in this effort by reducing human impacts and allowing blue carbon habitats to thrive, ultimately enhancing their carbon sequestration capacity.