Seagrass Meadows – a critical part of the ecosystem

Seagrass meadow
Source: GRID-Arendal (via Flickr)
Why Seagrass could be a vital "hidden weapon" in the fight against climate change

By Jemma Powell | Science Editor

Since the industrial revolution, the ocean has absorbed 1/3 of the carbon man-kind has emitted. This is due to the aquatic ‘blue carbon’ (marine carbon sinks) such as mangroves, salt marshes, and sea grass.

What is sea grass?

Sea grass is a hidden weapon against climate change. There is estimated 16-27 million hectares of sea grass meadows globally. However, we have lost around 6 million of those due to human activity. With other 80 different species worldwide, it used to be common place on the ocean floor from Jamaica to Scotland. Shockingly, it’s such a good carbon sink that some species of sea grass are 35 times more effective at absorbing carbon dioxide than the rainforest.

Why is it so effective?

Sea grasses are effective at storing carbon, partially because they have such a high leaf turnover rate. Multiple times a month (instead of just in autumn), new leaves will grow and the old ones will fall and sink to the sediment.

However, unlike with leaves from trees, these leaves don’t rot away. Instead, they become part of the sediment on the ocean floor, trapping the carbon they absorbed indefinitely. This action is similar to the peat bogs on land, which are some of the most effective carbon sinks in the terrestrial hemisphere.

They’re also incredibly effective as they trap carbon in multiple different ways. Whilst CO2 is used for photosynthesis like in most plants, sea grasses also extract extra carbon from the passing water via particle trapping. As the water flows over sea grass, the meadows increase the friction on the water, slowing it down. This leads to heavier particles being carried in the water falling, and also becoming trapped in the sediment. Sea grass removed particles such as carbon from organic waste and heavy metals from pollution are taken out of the currents. It traps the carbon twice!

Sea Grass Restoration:

Researches at Cardiff University are investigating how we can restore grass meadows to the sea around the UK. Sea grass used to be common, but through ecosystem damaging fishing techniques such as trawling, pollution, and heavy methyl mining, its occurrence is reduced.

Field sites in north-west Wales and Pembrokeshire are planting (by hand) over a million seeds a month. They’re hoping to emulate and expand on work done by US researches, who have planted and successfully grown over 30 km of sea grass in Chesapeake bay.

Apart from the positives of carbon absorption, sea grass meadows provide a load of other environmental benefits. They’re key ecosystems for numerous aquatic life, invertebrates, and birds.

A climate change game changer?

By itself, the impact sea grass will have on carbon emissions is not very dramatic. However, if we aid the restoration of multiple blue carbon storage sites, they’re predicted to act as a sink for 0.2% of global carbon output. If we add other sustainable operations and lifestyle choices, that small number grows to have a significant impact.

Jemma Powell Science and Technology

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