Sea grass as an ally in the fight against climate change

Seagrasses are widespread in shallow coastal regions of both temperate and tropical seas, covering up to 600,000 square kilometers, which is roughly the area of France. They form the basis of an entire ecosystem, which is home to thousands of marine species and a nursery ground for many economically important fish species. But they are under many threats including pollution, run-off from agricultural land and sewage works, physical disruption from motor boats and inshore fishing and many more. Vast areas of sea grass meadow have been lost, damaged or degraded with many detrimental effects on our environment. Potentially about 90% of UK sea grass meadows have been lost and yet Sea grass as an ally in the fight against climate change is the most potent marine.

Sea grass as an ally in the fight against climate change

Seagrass meadows are vital marine habitats for many reasons but perhaps in the current context, most important for carbon sequestration – namely they are plants absorbing carbon dioxide into their leaves and “fixing” it as organic matter by photosynthesis just like land plants – they also have roots just like land plants and pass carbon into the marine “soil” they are growing in. They also :

stabilize sediment
protect coastlines from erosion by storm surges
capture carbon at a rate greater than that of tropical forests.
are home to thousands of species species of fish, invertebrates, birds, reptiles and mammals
sequester millions of tons of carbon dioxide every year, which is stored in the ecosystem as so-called “blue carbon” for long periods of time.
produce more oxygen than all of the rain forest and grasslands combined
occupy only 0.1% of the seafloor, yet are responsible for 11% of the organic carbon buried in the ocean
are found around the coast of the UK in sheltered areas such as harbours, estuaries, lagoons and bays.
occupy 8,493 hectares of UK coastal seabed but may have once covered 82,000 hectares of seabed (The Conversation 2021 – reporting ).
are one of the world’s most efficient sinks of carbon and support 20% of the world’s biggest fisheries. They once stored 11.5 million tonnes of carbon, equivalent to the annual emissions of 7.7 million cars. With the destruction of the seagrass, much of that carbon has been added to the atmosphere and needs to be returned. These huge meadows could also have sheltered 400 million fish, and annually filtered pollution equivalent to the amount of urine produced by the entire population of Liverpool each year. (research by University College, London)

Watch this you-tube video on Seagrass : meadows of the sea

The habitat of many seagrasses is poor in nutrients, such as nitrogen, for much of the year. Although nitrogen is abundant in the sea in its elemental form (N₂), seagrasses cannot use it in this form. Latest research has shown that seagrass operates in symbiosis with nitrogen fixing bacteria that lives inside seagrass root tissue, where it provides ammonia and amino acids to its host in exchange for sugars

Seagrass around Anglesey

Marine Character Areas MCA 9 HOLY ISLAND WEST & PENRHOS BAY

The relative shelter of Rhoscolyn Bay and Penrhos Bay support a subtidal seagrass community with many species of algae, crustaceans, molluscs, fish, sponges and anemones.

(Porth Dinllaen is another area of sea grass)

Seagrass conservation / restoration

The newly published [Nov 2021] Seagrass Restoration Handbook provides foundational and practical guidance on the restoration and conservation of seagrasses and seagrass beds in the UK and Ireland with a focus on the Zostera species Z. marina and Z. noltei. It recognises Sea grass as an ally in the fight against climate change. The guidance outlined is also relevant to restoration projects across the biogeographic range of these seagrass species. To restore seagrass habitats will require a combination of approaches depending on the location, surrounding landscape and extent of degradation or loss. This handbook aims to shed light on these different approaches, and to support small-scale projects but ultimately with an ambition to facilitate larger seagrass seascape restoration efforts. Anglesey has large areas of potential seagrass meadow but these need careful management and protection from damage [pollution, run-off from agricultural land and sewage works, physical disruption from motor boats and inshore fishing…]

A companion volume, Saltmarsh Restoration Handbook has also been published -this is also an important habitat for carbon sequestration, both primary carbon sequestration from the plants growing in previously barren marine sediments, but also secondary carbon in trapped organic debris. Anglesey has large areas of saltmarsh but these are threatened with drowning by rising sea levels, turning them back into barren marine sediment.

Project Seagrass is an marine conservation charity dedicated to ensuring that seagrass meadows are protected globally, for the biodiversity and people that depend on them. Since 1980, we’ve lost over 35% of our seagrass meadows. That equates to about 1.5% per year, or 2 football fields each hour. This rate of loss is equal to that of coral reefs and rainforests, yet seagrass receives no attention and we’re here to change that!

Project Seagrass is committed to the conservation of seagrass ecosystems and ensuring that the benefits they provide communities are sustained now and for the future. Through education, influence, research and action, we can save seagrass!