Project Manaia

Seagrass and the replantation project in the Mediterranean Sea

What is seagrass?

Seagrass in the mediterranean Sea

Seagrasses are flowering underwater plants with grass like leaves that evolved around 100 million years ago. They reproduce in two ways, cloning meaning they repeatedly make genetically identical shoots and through sexual reproduction by growing seeds. Seagrasses, such as the Posidonia oceanica in the Mediterranean Sea, spread all across the ocean floor with new shoots emerging through the sediment and can become so big they can be seen from space.

Recently, in June 2022, a seagrass called Posidonia Australis was found in Australia’s Shark Bay that is 4,500 years old, covers 180 square kilometres, but is just one single plant. This is now believed to be the largest plant in the world. 

Why is seagrass so important?

There are 72 different types of seagrass that can be found all around the world from tropical to temperate and even arctic waters. The leaves act to slow the flow of water, which makes it a safe habitat and breeding ground for a myriad of species from seahorses to manatees and sea turtles as well as commercial fish like plaice and pollock. 

Seagrass is a safe habitat and breeding ground for a myriad of species

Through photosynthesis, seagrass absorbs 11% of the world’s carbon, 35% more than a typical rainforest, making it a vital tool in the fight against climate change. It also produces more oxygen than all the rainforests combined. For this reason, it quite literally helps us to breathe and has been given the nickname ‘the lungs of the ocean’. 

What causes the damage to seagrass?

Pollution in the water, usually from macroplastics, reduces the clarity of the water, which means the seagrasses capacity to photosynthesise is impaired. Also dissolved nutrients from sewage runoff or industrial waste causes algae blooms which also impacts the clarity of the water. If a plant cannot photosynthesise it cannot eat and will die. 

Human activity in the water can disturb the seabed and damage seagrass meadows. This is usually caused by swimming, kayaking or any boating activity with a propeller, but damage can also come from mooring over a meadow and cutting off light to the seagrass or dropping and dragging an anchor along the seabed. There are some really simple rules you can follow to help protect seagrass meadows when using the water, with the most effective tool being an understanding of where seagrass meadows are located. You can find out more at the Clean Sailors website who support Project Seagrass, creators of the ’Seagrass Spotter’ app that allows users to track the locations of seagrass meadows and help keep them safe. 

What can we do to reduce our impact on seagrass?

Protecting and planting is a huge focus for the work we do at Project Manaia and a particular passion of our founder, Manuel Marinelli. With his team, he is currently sailing the Mediterranean coast to understand what changes are happening in the water and where we can help. He took some time out to explain why protecting seagrass is so vital. 

‘Right now we are a small team of 6 people total, Pinar and myself are on board the entire season and the rest of the crew changes every 2-4 weeks. What we currently focus on is habitat mapping in the entire Mediterranean, which means every morning we jump in the, currently not so cool, water and physically measure seagrass meadows and other growth in the bays around us. This enables us to see changes from year to year more clearly. We also try to find as many species as possible in every spot we stop and estimate the amount, again with the idea of being able to observe changes over the years.’ 

As well as documenting species the Project Manaia team map the locations where macroplastics have built up and in what quantities in an attempt to identify hotspots of pollution and where they can focus their clean up efforts in the future. One of the changes that the team have spotted this year has been the increase in the temperature of the water, which leads to subtle changes like the slow creep of invasive species into new territory or more obvious algae blooms which can be deadly for seagrass. 

‘Last year the sea was 30 degrees in August, while this year we are already above 30 degrees in July. This triggers rapid growth of phytoplankton and therefore causes the infamous sea snot, basically suffocating many organisms that are grown on the bottom of the sea.’ 

Manuel explains that with seagrass at risk from climate change and pollution, there are things we can do to help protect seagrass from damage 

‘Seagrass grows incredibly slowly. The leaf itself can be fast, but the meadows only extend by about 1cm per year, so a full grown meadow takes centuries to develop. And they only give their seeds, on average, every seven years, and not all of them synchronised, so it is very difficult to say where one will be able to collect seeds and in what year. There are some easy things we can do to protect it. Don’t anchor in seagrass, don’t support bottom trawling (a fishing method that destroys big seagrass meadows in the blink of an eye). Try to minimise your impact on the ocean. 

‘You can also collect seeds and drop them off at one of our partner dive centres who will plant them. Same is true for washed up seagrass plants that have another chance if put back in the water in a secure spot, but once floating around freely without help they will die off. And one big thing is to start a conversation. Explain to people how important seagrass is and why. If we loose seagrass we loose a good third of all marine species in the area and with that the complete loss of all marine life will follow soon after. We don’t have reefs in the Mediterranean Sea, not the kind you know from tropical areas, but the seagrass is just as full of life. All it takes is a closer look and some patience.’ 

What is Project Manaia doing to help?

Manuel’s team have been particularly busy this year working at a local level to build a community of people who can help with seagrass replanting and protection. 

‘Right now we are working on establishing a network of participants who help us set up a safety net for Posidonia. People can drop off ripped out plants, seeds etc, in different locations and we make sure they find their way back into the sea and get a second chance. We’ve already managed to get 12 participating dive centres on our side, who will plant and observe with us and we are growing this network all the time with the latest figures on our website. Already more than 300 seeds have been planted, all of which have the potential to grow their own little meadow within a few years. We also already sailed the entire west coast of Italy, mapping meadows in 40 different locations for comparison in the following years and a lot more – but for all the updates, it’s best to follow us on Instagram or Facebook and you can see what we are up to in real time.’ 

Diving for the conservation of seagrass

Manuel explains that seagrass is such a huge focus for the team this and every year, because it is just so key to the survival of the oceans and all life on the planet 

‘I think what it really boils down to for me is that lack of informed choices. IF we were all aware of the importance of a healthy marine eco system we would never treat it the way we do. IF we knew how important seagrass is for the balance we would never anchor in it. There is a lot of IFs in this, but consider this: No seagrass, no healthy sea in the Mediterranean. No healthy sea, no fisheries, no jobs, no nice water, no tourism and the list continues. And of course, my personal favourite. Take a deep breath and breath out… have another breath. And now think about the fact that all the oxygen comes from the sea. More than 50% of the air we breathe every minute of every day is produced by plankton in the sea. We are directly linked to this big blue patch on the globe. So we really should not gamble with it.’ 

It’s really important that everyone is involved in helping to protect seagrass and our oceans and people can help in many different ways. 

‘So one of the big steps is for us to scale things up a bit. We want to get more done, be able to involve more people, host more workshops, invite school groups etc. We do have a lot of information packed directly on our website, about seagrass, but also many other projects we are working on and how people can get involved. We invite citizen scientists to submit sightings of changes in seagrass distribution they see, but also to submit pictures of invasive species and much more. If you want to get a better idea of the work we do, there is also a chance to join us on board our research sailboat in the Mediterranean Sea!’

‘As an NGO we are dependent on donations from individuals, who believe in our cause and we are currently looking into the best options to expand and grow. so that in the future we can work even more efficiently towards the protection of our oceans.’ 

Writer – Caroline Anderson for Project Manaia, August 2022

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