The Rainforest of the Sea: The Importance of Seagrass and its Conservation
What is seagrass? Seagrass is surely just grass that’s found in the sea? Or maybe it’s a type of seaweed?
Although it looks very similar to terrestrial grass, with its long emerald fronds, closer investigation reveals that seagrass is a flowering plant – the only flowering plant found in the ocean. This is where it also differs from seaweed, which is classed as an algae rather than a flowering plant. There are 70 species of seagrass, and meadows of this underwater rainforest are found in shallow, sheltered areas on every continent except for Antarctica.
Illustration by Nathalie Dickson.
Why is seagrass important?
Despite its unexceptional appearance, seagrass provides a multitude of benefits which are vital for both the health of the ocean as well as our planet at large.
Firstly, because seagrass is sensitive and rapidly responds to change, it is an important indicator species. This means it can help monitor the state of the environment as a whole and give insight into issues such as water pollution and overfishing.
Arguably one of the most important roles of seagrass is in combating climate change. As a plant, they photosynthesise meaning they produce oxygen and absorb carbon dioxide. Since the carbon is absorbed and trapped underwater it is referred to as “Blue Carbon”. Are you ready for the figures proving how badass this plant is? Seagrass meadows only make up 0.1% of the ocean floor and yet they account for 10% of global carbon absorption, and are thought to be more efficient in carbon absorption than a rainforest! Huge quantities of oxygen are produced in exchange for all this CO2 absorption and so often seagrass is given the title of “lungs of the sea”.
Seagrass also has important implications for biodiversity. The meadows provide a habitat for sea creatures, as well as forming the base of marine food webs making it very desirable real-estate for critters including cuttlefish, turtles, seahorses and manatees. In fact, 30 times more animals live in seagrass meadows compared to the more barren sandy habitats. Commercial fish stock also take shelter in seagrass meaning these underwater pastures also have a vital role to play in food security and poverty alleviation. In short, without seagrass we wouldn’t be able to feed the 1 billion people who depend on fish for protein.
A recent study has even found that some species of seagrass can help in the fight against plastic pollution! The rather quirkily named “Neptune’s balls” are the key to this. These are created when the motion of the current shreds seagrass leaves, which still remain attached at the base of the plant to the rhizome (the part of a plant that creates roots and shoots). As this leaf debris then gets buried by sediment, the fibres twist together into a ball and collect plastic in the process. Neat!
The rhizome roots of seagrass have another important role; this time in helping to stabilise the seabed. Long seagrass leaves help to soften the impact of waves and slow the current down which allows the sediment suspended in the water to settle on to the seabed. Then the rhizome root structure helps to “knit” the layers of sediment together. By aiding this accumulation of sediment, seagrass assists in the prevention of coastal erosion and ultimately protects our infrastructure built near the sea.
The threats
Despite all its superpowers, seagrass sadly cannot withstand the continued pressure of human activity. As a result, seagrass is declining at a rate of 7% a year globally – that’s more than 2 football pitches an hour. This makes its disappearance even faster than that of rainforests. Pollution and habitat destruction are the main threats contributing to the dreaded “critically endangered” label of seagrass.
Intense agriculture practices can contribute to water pollution by causing eutrophication. This is when rain causes fertilisers, often used in farming, to run off the land into rivers and oceans. The high levels of nutrients found in fertilisers, such as nitrates, cause rapid and excessive growth of algae which will block out the sunlight that seagrass needs in order to photosynthesise. Therefore, it is important for seagrass to have clean waters.
Coastal development often goes hand-in-hand with the destruction of seagrass habitats. For example, resorts often remove seagrass for the aesthetic purposes of a sandy seabed. Of course, the irony is that by removing the seagrass from its natural habitat close to the shore, resorts are also removing a natural and sustainable defence to coastal erosion. Clearly seagrass is valuable in terms of the longevity of the resort and what’s more is that it’s removal would only need to be replaced with expensive, man-made alternatives!
Bad fishing practices can also contribute to habitat destruction of seagrass meadows, this includes the mooring of boats in shallow waters and throwing of anchors into the sea, which then drag along the seabed.
Conservation work
In the UK, we have lost 92% of seagrass due to threats such as these. Even though humans are responsible for the decline in seagrass, we can also play a large part in its recovery. So, what is being done to help conserve seagrass?
The Community Seagrass Initiative, led by the National Marine Aquarium, is a citizen science project based in the South West of England which aims to raise awareness about seagrass. It has brought together 450 dive volunteers to survey 500 hectares of seabed, providing much needed insight into the state of UK seabeds and seagrass meadows. Surveys like this are a vital starting point for conservation efforts – seagrass can recover on its own but only if we are aware of the current impacts we are having.
Collaborations between local organisations are also helping to provide new data on seagrass meadows. This is the case in Looe, Cornwall, where a surveying project involving Looe Marine Conservation Group, Cornwall Wildlife Trust and the University of Plymouth revealed that seagrass beds in Looe are up to 10 times bigger than those found in Plymouth, Falmouth and Torbay and the equivalent of 157 football pitches! Without this collaborative survey these beds might not have been discovered and we could have lost a hugely important area of seagrass. Now further investigations with underwater cameras are being carried out to continue mapping and monitoring the area to safeguard this habitat.
As part of some surveys, seeds are also collected and taken back to a lab and grown, out of harms way. Wild Planet Trust, a conservation charity with two zoos in the South West, collaborated with the Community Seagrass Initiative and now leads their own “Save our Seagrass” project to do exactly this. The seagrass seeds harvested by local dive volunteers on monitoring surveys are taken back to the lab and firstly examined to determine the likelihood of germination. Those deemed in good shape are planted in tanks to be used in research to understand the conditions seagrass needs to thrive. It is hoped that in the future the matured seagrass can be transplanted back into the seagrass meadows from whence it came in Torbay. So, not only are we conserving the seagrass that is left in the ocean but also actively helping to increase existing numbers through ex-situ conservation (ie, conservation of a species outside of its native habitat).
The LIFE Recreation ReMEDIES project is an amazing example of a large-scale habitat conservation project. Led by Natural England, and with £2.5 million in funding, it aims to reduce and mitigate the impacts of erosion and disturbance on the seabed of five Special Areas of Conservation in southern England. This will be achieved through firstly, raising awareness and inspiring others to take care of underwater habitats. Additionally, environmentally friendly moorings, known as advanced mooring systems, will be provided. These are more gentle as they do not drag along the seabed, thus allowing seagrass growth. And finally, there will be large-scale seed collection and replanting into areas of seagrass loss in order to restore the habitat. To illustrate the scale of what the project hopes to achieve, the Ocean Conservation Trust, one of the ReMEDIES project partners, is growing 25,000 seagrass plants a year with the aim of restoring the 4 hectares of seagrass lost in the Plymouth Sound marine area! Although ReMEDIES is a UK based project, it has implications for seagrass conservation worldwide as findings and successful conservation methods will be shared with places managing similar seagrass habitats.
So there is hope for seagrass yet! And next time you go to the beach, don’t just look out for the typical charismatic seashore creatures, but take a moment to appreciate the often unsung hero that is seagrass.
To find out more about seagrass you can visit Project Seagrass.
Maddy Simmonds
Maddy is a Zoology graduate from the University of Exeter and her passions include conservation, anthrozoology and science communication. She often draws inspiration from connecting with nature in everyday life and hopes to encourage people to also be just as excited by local conservation stories as international ones. She enjoys how writing not only allows her to share information with others, but that she is also able to learn new things for herself in the process
You can follow Maddy on her nature-based Instagram account @nature_nutter.