Shallow bays to wetlands

As a result of the land uplift, shallow bays will eventually be cut off from the sea, and they eventually become freshwater lakes. The first stage is called a flad. Flads are still in contact with the sea, but they have a clear underwater sill at the mouth. They are shallow, on average only 1 m deep; and therefore it is common that the water freezes all the way to the bottom during winter. Both plants and animals thrive here in spring and summer. The water gets warm quickly, there are plenty of nutrients, and it is a protected environment. Flads are good spawning areas for fish, and birds use these calm bays as nesting sites. The vegetation can differ much from flad to flad, but underwater vascular plants, charales and common reed are common. The bottom of the bay is almost always composed of soft mud and silt, while the sill in the mouth of the bay consists of stone and gravel.

Image 1: Flads at Norra Lappören

As land uplift continues, flads eventually become gloes. Unlike flads, there is an inflow of saltwater into gloes only at high tide or during autumn storms. Gloes therefore have more freshwater than flads. Here freshwater plants (such as duckweed and floating pondweed) thrive, but fennel pondweed is also common. Around the lagoon common reed often grows in a thick belt, which offers excellent protected environments for nesting birds.

Image 2: Gloe with rich water vegetation, Haggisgrund in Revöfjärden.

When salty seawater no longer flows into the gloe, it slowly turns into a freshwater lake. Many lakes have brown water with only a little vegetation. However, different species of water lilies and aquatic mosses thrive here. Eventually the lakes might become overgrown by vegetation and form wetlands. Sphagnum species, or peat moss, start to spread from the lakeshore towards the middle; and mire vegetation (such as sedge, bog-bean, and marsh calla and marsh bedstraw) become lusher.

Image 3: Peat moss, sedge and marsh cinquefoil are common vegetation on wetlands

In Kvarken you can see the progression from flad to lake, or wetland, in many places. For example, flad-gloe-lake series can clearly be seen at Lappörarna, but individual flads and gloes are found all over the World Heritage area.

Image 4: Flad-gloe-lake series at Norra Lappören

Some wetlands and mires can be wooded. Swampy forests of willow, downy birch, alder and spruce can be found between the hills and closer to the beaches. In other places, where the ground is composed of a thicker layer of peat moss, pine thrives together with marsh ledum, crowberry and heather. Most of the marshes in Kvarken are quite small, but they can be found here and there. You can find them on Björkö, Slåttskär, Storskär (Valsörarna), Villskär (Mickelsörarna), and in the south on Halsön in the Korsnäs archipelago.


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