The Sunshell sculpture is a shell of a mud snail[1], of the family Hydrobiidae – a commonly occurring species in the Baltic Sea – enlarged to a thousand times its natural size. It is a tiny snail that can be found in numbers up to 10,000 on a single square meter of seabed. But despite its diminutive size, it is vital to the ecological balance along the Baltic shores, where it devours rotting plant fibres and serves as food for fish and seabirds.

Bigert & Bergström’s snail consumes the energy of the sun, reflecting it from its mirror-like copper shell as multiple spots of light thrown in different directions onto the people moving on the square. The shell is also a sundial, its tall spiral shape forming the central obelisk on the city of Norrtälje’s new square, Sjötullstorget. Its shadow moves around the square during the day and you can tell the time by looking at where the shadow falls.

The interior of the shell appears as an organic spiral of mother of pearl, striving towards the open top, where currents of air flow in. Light also shines in through the top of the shell, and from the inside of it the sun is always at its zenith. At the top is a heliostat – a mirror that follows the path of the sun thanks to computerized motors, reflecting the sun’s rays to the inner core of the shell.

Photo: Ulf Lundin

The inside is made of steel with an iridescent coating, giving the surface a shimmering quality like mother of pearl. A snail’s shell is built up of various minerals in the sea. Calcium and magnesium are two of the most important building blocks, and climate researchers are studying how snails build up their shells over time and what the chemical composition of the layers consists of. A snail builds its shell with a tiny layer every day. These “day rings” can provide a great deal of information, including the day’s temperature, which can be determined by measuring the magnesium content of the ring.

If we want to really gain insight into prehistoric climatology, the time rings of ancient sea snails take us significantly further back than ice cores and tree rings. By studying snails of the phylum Foraminifera, researchers have gazed into the biological event horizon more than 200 million years ago.


[1] Mud snail: Measures up to 6–7 mm. Description: The shell can vary from the horn-colored to a light bark brown, sometimes slightly transparent. At a distance, live mud snails often look like tiny black or grey dots. The soft tissue is white with dark spots or stripes. Depth: 0–20 m. Habitat: Mud snails prefer to live in soft seabeds, but in the Baltic they are also found on hard seabeds. Some mud snails can live in freshwater. Other: Mud snails tend to be noticeable because they (especially in muddy seabeds) can occur in huge numbers (tens of thousands per square meter). Taxonomy: It is often very difficult or even impossible to determine the species of mud snails. You have to look at the shape of the shell, pigmentation of the tentacles and mouth, the appearance of the radula and the shape of the reproductive organs. Mud snails are in the subclass Prosobranchia (meaning gills in front of the heart), class Gastropoda (meaning stomach-footed), phylum Mollusca.
Photo: Ulf Lundin
Photo: Ulf Lundin


Artists' sketch
Peringia ulvae (mud snail). ©Wikimedia




Photos: Studio Bigert & Bergström

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