What is seagrass?
“Seagrass emerged out of terrestrial plants that at some point started to grow on the seabed. In the past it was used for building dikes, and as a mattress stuffing. But its real value lies in the way it contributes to its own habitat, and the benefits it brings to many other plant and animal species. For example, it provides a breeding ground for fish, and a food source for other aquatic animals. It also sequesters huge volumes of CO2, and by anchoring its roots in the seabed it creates stability and protects the coastline. Seagrasses are found all over the world. But the species as a whole is going downhill, and that applies to seagrass in the Netherlands too.”
And can you eat it?
“No, but apparently there’s a restaurant where they serve seagrass seeds as a delicacy. I’m not sure how damaging the harvest of those seeds is to seagrass.”
Why is seagrass in trouble?
“Globally, there are a variety of underlying causes. These include eutrophication (an excess of nutrients), damage to food webs caused by fisheries, disease, and disturbances caused by tourism and boat traffic. In Lake Grevelingen policy changes have led to significant changes in water salinity, and it’s likely that this has played a really important role. The lake has also been closed off by the Delta Works, and that has probably had a big impact on its fauna too.”
“Rijkswaterstaat has launched a project to restore seagrass in Lake Grevelingen, and one of its main aims is to improve the water quality of the lake. We’ve been working on this for the past four years.”
Four years on, have there been improvements to the seagrass in Lake Grevelingen?
“My colleagues and I have looked at various sowing and transplantation strategies. At one point we discovered that introducing the common periwinkle alongside seagrass plants is very effective. Periwinkles are snails and they protect the seagrass by eating the algae and worms that otherwise tend to damage the plants in Lake Grevelingen. When we tried this, we observed a huge improvement in the survival rates of the plants. For the first time in twenty years, seagrass plants have been present in the lake for a full year. That’s a big step forward.”
So, periwinkles to the rescue. Job done?
“We’ve made great progress, but we’ll need to see the seagrass expanding over several years before we can declare a successful recovery. A new team will be taking over the project and developing it further. I’m now focusing on writing up the results, and hopefully I will be publishing them sometime soon.”
An overview of the fieldwork conducted in 2021 in Lake Grevelingen is available here
More information about seagrass research at Radboud University
Photo: Wikimedia Commons