Baltic Sea Day
September has been a busy month for us, but there is one August walk we still wanted to come back to.
On 27 August, we marked Baltic Sea Day with a slightly different Kaupunki Kaverit walk. Together with the Finnish non-profit Oceanry, we took a group to Suomenlinna to talk about the sea that is so much a part of everyday life in Helsinki.
For those who are new to Kaupunki Kaverit, the idea behind the project is quite simple. Our volunteers organise small walks and activities where they introduce others to places and topics they know or care about. Sometimes it is history or architecture, sometimes culture or a particular neighbourhood. The aim is to help people who have recently moved to Finland get to know their new home from different perspectives and build a stronger sense of belonging here.
This time we wanted to add nature to that list.
When you live in Helsinki, the Baltic Sea is almost impossible to avoid. You see it from the tram, walk beside it, take ferries across it and spend summer days on its shores. But seeing the sea every day does not necessarily mean knowing much about what is happening below the surface.
That was our starting point.
For the walk, the Oceanry founders, Tomi and Melina, joined us and took our group to Suomenlinna. Along the way, we talked about Suomenlinna itself, but most of the afternoon was about the water around us and how unusual the Baltic Sea actually is.
Melina Pinomaa
Oceanry Co-Founder
Tomi Nyman
Oveanry Co-Founder
Too much here, too little elsewhere
One of the most interesting parts of the walk was comparing the Baltic Sea with the open ocean.
The Baltic has a serious problem with too many nutrients, particularly nitrogen and phosphorus. Much of this reaches the sea from land through rivers and runoff, with agriculture among the important sources. The result is eutrophication: more algae and cyanobacteria, murkier water and, when all that organic material decomposes, less oxygen available near the seabed.
We also learned more about the algae that many people in Finland hear about every summer. Despite the familiar name, these blooms are actually caused by cyanobacteria. During the walk we talked about how to recognise a possible bloom and why swimming should be avoided when cyanobacteria are present.
There is another reason why changes in the Baltic can stay with us for a long time. It is an almost enclosed sea, connected to the North Sea only through narrow Danish straits. According to HELCOM, a full exchange of Baltic Sea water takes roughly 30 years.
Then Tomi and Melina turned the story around.
In parts of the open ocean, the problem can be almost the opposite. There may be plenty of other major nutrients, but too little of a tiny trace element needed by phytoplankton: iron.
The true lunges of our planet
This brought us to Oceanry's own work.
Oceanry is a Finnish non-profit working to advance research, discussion and responsible regulation around Ocean Iron Replenishment. The basic idea starts with phytoplankton, microscopic organisms that photosynthesise in the ocean and form the base of marine food webs. In some open-ocean regions, their growth is limited by the availability of iron. Oceanry is interested in whether carefully replenishing iron in such iron-limited areas could strengthen natural processes that capture carbon and support marine ecosystems.
The scale of phytoplankton's role was probably one of the facts that stayed with us most. Roughly half of the oxygen produced on Earth comes from the ocean, mainly through photosynthetic plankton. They also take up carbon dioxide and sit at the very beginning of most marine food webs.
Oceanry also introduced us to another part of the iron story. The organisation cites research estimating that commercial marine harvest removes unintentionally approximately 25,000 tonnes of iron from ocean ecosystems each year, iron that would otherwise continue circulating through the marine food web.
And there was one more connection that surprised many of us: ocean biology does not stop at the surface of the water. Some phytoplankton-related compounds, including dimethyl sulfide (DMS), can contribute to particles around which cloud droplets form. Scientists are still studying exactly how these ocean-atmosphere processes affect clouds and climate, but the connection itself is a good reminder of how closely the ocean and atmosphere are linked.
By the end of the walk, we had talked about two very different seas. In the Baltic, too much nitrogen and phosphorus contributes to eutrophication. In some areas of the open ocean, a shortage of iron can limit phytoplankton growth. The same word, “nutrients”, can therefore describe very different environmental problems depending on where you are.
And perhaps that was the most useful thing to take home from the day: there is no single story about what an ocean needs.
For Kaupunki Kaverit, this was also a small experiment in what getting to know your new home can mean. Moving to Finland involves learning a language, finding work or studies and understanding how society works. But it can also mean learning why the sea outside your window sometimes turns green in summer, why the water here is different from the Atlantic, or what is happening in an ecosystem you pass every day.
Thank you to Tomi, Melina and the whole Oceanry team for sharing your knowledge with us, and to everyone who spent Baltic Sea Day with us in Suomenlinna.
We definitely came back knowing more about the water around Helsinki than when we left.
Comments