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Green seaweed (not seagrass)

Blue Planet recently showcased seagrass beds in tropical waters, but did you know we have seagrass right here in the Solent?

This autumn Blue Planet II has captured the nation’s imagination. Episode five – entitled Green Seas – saw green turtles grazing on seagrass meadows off Western Australia. But you don’t need to travel to tropical waters to see this amazing plant for yourself; it grows right here in the Solent.

Seagrass is not algae or seaweed; it is in fact the only type of flowering plant able to live under the sea. Seagrass has long, narrow leaves just like terrestrial grasses. It depends on photosynthesis, so is only found in shallow water where high levels of light can reach. Four varieties of seagrass grow in sheltered areas around the UK coast – and the natural harbours, estuaries and bays of the Solent are ideal.

Seagrass supports a diverse and productive ecosystem. In areas of dense growth it helps to stabilise the coastline and defend against erosion. In addition, it shelters many varieties of sea life, from tiny invertebrates and crustaceans to octopuses and fish, including bass and even seahorses. The young fish that mature in the safety of the seagrass meadows contribute to the fish stocks that our fishing industry relies on. The leaves can be colonised by algae and provide attachment points for creatures like anemones and stalked jellyfish. The roots help oxygen to penetrate the mud below making it more favourable for invertebrates and other organisms that live there.

Seagrass is a key food source at low tide for wildfowl such as brent geese and wigeon. They particularly like rotting seagrass as it is rich in invertebrates. The extensive seagrass beds on the north coast of the Isle of Wight, and in Langstone and Portsmouth Harbours are especially important for overwintering birds.

Seagrasses meadows are able to capture and store carbon at rates up to 100 times greater than rainforests. One hectare (two football pitches) of seagrass can produce 1000,000 litres of oxygen per day. They literally make the air we breathe and are helping us battle against climate change.

But despite all this hard work seagrass still suffers from being a hidden hero, threats to seagrass are much less reported on than damage to rainforests or tropical coral reefs. It is estimated one hectare of seagrass is lost globally every hour. However, seagrass beds have been nationally identified as a priority habitat in the UK Biodiversity Action Plan, and are protected locally under Sites of Special Scientific Interest (SSSI) designation. Additional protection is also provided locally under the “Solent Maritime” Special Area of Conservation (SAC).

Next time you see overwintering birds feeding at low tide, spare a thought for seagrass – the unsung hero that doesn’t just benefit overwintering birds, but our local environment and the world as a whole.