Finland’s national treasure the Archipelago Sea is in danger

Jaakko Ruola,
Content Director,
Operation Archipelago Sea,

Kari Veijonen,
Project Director,
Operation Archipelago Sea,

The globally unique Archipelago Sea is in great danger due to eutrophication which has lasted for several decades.

It is the reason why Operation Archipelago Sea has been founded. By means of communications and marketing, we aim to enhance awareness and appreciation of the region both in Finland and elsewhere in the world.

Our goal is to influence political decision-makers and ordinary citizens in Finland and at the EU level in order to save a natural and cultural entity that is unique even on a global scale.

As part of the Operation, Professor and Rector Emeritus of the University of Turku Kalervo Väänänen has drawn up a three-part action plan, based on circular economy solutions, for starting the purification of the waters.

In our view, the nutrient recycling model presented in the action plan by Professor Väänänen offers a feasible concept that can be implemented also globally in other marine regions suffering from eutrophication.

What makes nature in the Archipelago Sea so unique, and why is it important to save it for future generations?

The Archipelago Sea is situated in the northern part of the Baltic Sea in Southwest Finland, stretching out in front of the City of Turku. Many areas of the Archipelago Sea belong to the World Network of UNESCO Biosphere Reserves.

The world’s largest archipelago measured by the number of islands

The Archipelago Sea is a unique natural formation by any standards. It is the largest archipelago in the Baltic Sea consisting of as many as 41,255 islands and countless islets, tiny skerries and reefs.

Some of the islands are tightly clustered, some stand alone in the open sea. The fragmented topography has resulted in various kinds of marine areas: narrow gulfs, different types of bays and vast open seas.

The Archipelago Sea has the highest biodiversity in Finland

The diversity of nature in the Archipelago Sea is one of its kind in Finland.

It is where the north, south and southwest meet. It is home to an exceptionally large number of endangered species and biotopes.

There are over 40 biotopes in the Archipelago Sea that are particularly valuable for the biodiversity in the region, and significant in the whole of Europe. Underwater rocky reefs, sandbanks and sand-based ridges as well as the islands and islets of the outer archipelago are among the most valuable biotopes. Fragmented topography, various archipelago zones and variability of the soil and the seabed further increase the biodiversity in the region.

Bedrock of almost 2 billion years of age

The Archipelago Sea is a peculiar formation on the Fennoscandian Shield. It belongs to the oldest and most stable bedrock in Europe. The whalebacks of the open seas and the massive rocks of the archipelago are the steadfast roots of the Svecofennian mountain belt that was created about 1,900 million years ago.

About 200 million years later rapakivi granites were formed in the depth of several kilometres, and they became the bedrock of the Åland Islands and the north-western part of the Archipelago Sea. What is extraordinary on a global scale is that the surface of the bedrock is widely visible around the region.

Signs of the latest Ice Age are visible everywhere

While the bedrock is ancient, the Archipelago Sea of today is young when measured by a geologic time scale. The series of Ice Ages that began more than two million years ago swiped off practically all signs of life from the area which is now Finland. As the ice spread, it pushed aside any loose soil and organic material.

At its most wide-spread stage, the glacier was 5.6 million square kilometres in size, which is seventeen times bigger than the area of Finland today. In some parts, the ice was three kilometres thick.

The pressure of the ice sheet created depressions on the ground that still exist. As it moved, the massive glacier dislodged pieces of the eroded land, even huge rocks. The hard pieces of material mixed inside the spreading ice scoured the bedrock which lay beneath the ice sheet. It became round in shape, and glacial grooves were formed on its surface, indicating the direction of ice movement.

The Archipelago Sea and its brackish water

As a living environment, brackish water is physiologically very challenging for aquatic animals. While for the marine species the major cause of stress is the low salinity level, for the freshwater species it is the too high level of salinity.

The Baltic Sea is a young sea, and all its species were spread out in the region after the last Ice Age. For example, there are only about 60 species of bottom fauna visibly detectable in the Archipelago Sea, while in the North Sea there are over 1,500 species.

The Archipelago Sea has plenty of shoreline – more than any other region of equivalent size – and many shallow, biologically productive water areas. Even though there are not many species, there is an abundance of individuals.

In addition to the long shoreline, another typical feature of the Archipelago Sea is strong deviations in the shapes of the seabed. That is why different organisms may live side by side, even mixed together – just another example of the exceptional character of the Archipelago Sea.

The Archipelago Sea is home for several hundreds of endangered plant species and invertebrate animals

The tidal zones in the shorelines of large seas offer a highly productive habitat for many different species. The Archipelago Sea is productive in a different way: there are few species, but many individuals.

The high level of basic production creates and maintains huge amounts of biomass. The biological productivity of the Archipelago Sea is the result of the long shoreline and vast shallow water areas.

The number of biotopes and level of biodiversity vary greatly from area to area: from the coastline to the outer archipelago, from rocky islands to shingles, from soft seabed to rocky seabed, from shallow waters to deep basins.

There are many species in the Archipelago Sea that exist nowhere else in Finland’s coastline. Large eelgrass meadows in the sandy seafloor in the outer archipelago and ­algae growing in various depths under water form together stunning communities that are hard to find in other parts of the country.

One can experience the changing of the seasons in the Archipelago Sea

The climate of the Archipelago Sea is mild and marine compared to mainland Finland. The Gulf Stream warms up Northwest Europe and has a dominant effect on the climate of the whole Baltic Sea region.

Daily temperature variation in the Archipelago Sea is smaller than in the mainland. The water masses of the sea have a strong influence also on the changing of the seasons. Winter in the Archipelago Sea is short. In the outer archipelago, for example, it is often not until late February that the sea freezes, and the ice season lasts around twenty days on average. In the inner archipelago the ice season is usually about one and a half months, but in some winters the sea does not freeze at all. Yet there are winters when fast ice stretches far out to the open sea, covering it for several months.

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