© P. Schubert
MEKUN: Interview with Philipp Schubert, Seagrass Researcher
What seagrass, sailors and the T-Rex have to do with each other
Hi, I'm Rolf Karez, I'm a marine biologist and have been working at the State Office for the Environment in Schleswig-Holstein (LfU) for over 20 years. I am responsible for seagrass and large marine algae, and I am sitting here with Philipp Schubert from GEOMAR, with whom the LfU has been collaborating on seagrass beds for 15 years.
Philipp Schubert
Seagrass Researcher at GEOMAR Helmholtz Centre for Ocean Research, Kiel
Philipp Schubert: Yes, exactly, I am a seagrass researcher at the GEOMAR Helmholtz Centre for Ocean Research here in Kiel and I study seagrass.
What exactly is seagrass and how does it differ from algae?
In evolutionary terms, seagrass couldn't be further away from algae. There are brown, red, and green algae, and land plants evolved from green algae. Some of these land plants, which also gave rise to flowering plants, migrated back to the sea 65 million years ago, when T-Rex was roaming the earth. They adapted to the difficult conditions and sea grasses developed. These are the only flowering plants in the sea and there are only about 60 species worldwide.
In my memory, seagrass didn't used to have such a great reputation, but now everyone is talking about it. What is so important about seagrass?
Seagrass is a very good CO2 store – keyword climate change. Seagrass beds are similar to moors on land and store biomass in the absence of oxygen, whose carbon is then no longer available to the atmosphere for a long time.
At the same time, seagrass is extremely important as a habitat for animals and plants. It increases biodiversity and is an important nursery for almost all of our fish species. They feed on seagrass, live there for part of their lives, or spawn there.
It also acts as a filter for nutrients, of which we have too many in the water. Even bacteria that are dangerous to humans are filtered out – our working group has just discovered this.
“Before World War II, seaweed was found at depths of up to 14 meters. Back then, the water was much clearer. Then the green revolution took place and agriculture began using artificial fertilizers.”
Philipp Schubert
Host City Local Partner
The Ocean Race Europe 2025
Speaking of health, how is the seaweed itself doing? What threats might it be facing?
Here on the coast of Schleswig-Holstein and also in Mecklenburg-Western Pomerania, seagrass in the North Sea and Baltic Sea is increasingly doing better. And yet there are areas where seagrass is unfortunately declining, as is the case worldwide, for example in the Flensburg Fjord.
Before World War II, seaweed was found at depths of up to 14 meters. Back then, the water was much clearer. Then the green revolution took place and agriculture began using artificial fertilizers. In addition, domestic wastewater was not yet being properly treated, while the population continued to grow. This led to an oversupply of nutrients in the sea. This causes more plankton to grow, including more filamentous algae. These overgrow the sea, suffocate it, and block its access to light. This plankton reduces visibility in the sea. As a result, seaweed can no longer grow at such depths.
© C.Howe
“We are currently researching the best methods for replanting seagrass.”
Philipp Schubert
© C.Howe
And what could we do to protect the seagrass?
We are currently researching the best methods for replanting seagrass. This involves really simple questions, such as what is the best time to plant seagrass? What is the best depth? Do we do it with seeds? Where do we get the seeds from? Do we do it with individual plants, i.e. with sprouts? How do they grow best? We are currently trying to find out in research projects.
And as a normal citizen, is there anything I can do?
If you are a diver yourself: interested seagrass planters are specially trained for this.
On the other hand, we can move away from this intensive farming, which is very bad for nutrient inputs.
Or as a swimmer, for example, you can swim and no longer walk as soon as the seagrass is there.
Now we're talking about the Ocean Race, a sailing event. What do sailors have to do with seagrass?
You shouldn't anchor in seagrass beds, because every anchor causes great damage. Sailors should simply make sure to anchor only on sandy areas or in front of sea grass beds. Seagrass beds only occur in water depths of six to seven meters in our area. If you anchor deeper, you are usually on the safe side.
And now, the Ocean Race and seagrass — do they have anything to do with each other?
Perhaps more negatively, due to drifting seagrass fields when the seagrass sheds its leaves in August and September. The leaves can wrap around the foils and hinder smaller foilers such as wing foilers, kite foilers, or pump foilers.
Okay, thank you very much. Do you have any tips for anyone who is particularly interested in seagrass or would like to find out more?
We actually have a great website, seegraswiesen.de, where you can find out more. And otherwise, I would always recommend that everyone grab a snorkel and goggles and take a look at how life explodes in the meadows.
All right, thank you very much, Philipp.
You're welcome.
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