Korpoström

Under the sea

On the surface we can explore nature and admire different species as carefully as we wish to, but the world under the surface of water is a lot harder for us to approach. However, it’s teeming with life beneath the waves!

Some species provide food and shelter for other species and are therefore especially important. One such key species in the Baltic Sea is bladder wrack. You have probably come across it as you’ve explored the sea. It has gotten its name by the bladders that support its stems. On open areas bladder wracks tend to have less bladders because it is supported by the currents of water and can do without so many bladders. The plant need a solid base to grown on and can’t survive on soft surfaces covered by algae or clay.

Bladder wracks tend to branch over large areas and form under-water forests that provide a shelter, a nursery and a pantry for tens of different species, such as isopods, amphipods, snails, blue mussels, fishes and their spawn. Even embankments of washed-up bladder wrack serve as a habitat for many species and are used by for example grass snakes to lay their eggs on.

The propagation of bladder wrack is an interesting event. In summer, just before full moon or new moon, the parent plant releases its spores. Female spores are heavy and drop close to the parent plant. Male spores swim to the female spores and together they form a beginning of a new plant.

Embark on an expedition to the underwater world!

Carefully shake a bladder wrack growth over a container so that the creatures that dwell among it, fall into your container. Bladder wrack dies if it is removed from its surface so handle it with great care. Explore the animals that you found and try to determine their species.

Did you know, that algae are vital even for us people? Up to 75% of oxygen is produced by algae.

Can you find the big dock ring?