Different seabeds
When you swim in a lake or in the sea, the bottom can be completely different. It might be muddy, fine sand, pebbly or rocky, which can hurt your feet. The pebbly and rocky bottoms make a hard seabed. Hard seabeds have steep rock faces, caves and many different kinds of rock.
Hard seabeds make up a small proportion of the world’s oceans, but about 80% of marine species live here. Hard seabeds are a more varied habitat than soft seabeds. Many different species of corals, moss animals, molluscs, crustaceans, algae, sponges, echinoderms, sea-urchins and tubeworms attach themselves to the rocks, cliffs and inside crevices.
On the left is Måkläppen, a place in southern Skåne with soft seabed. On the right is Kullaberg, a rocky area in north-western Skåne.
Photo: Henrik-Jönsson-CC-BY-SA och Davidstolt-CC-BY-SA
The coral Dead man's fingers builds its colonies on hard and rocky seabeds.
Photo: heartypanther-CC-PDM
Blue mussels also build its colonies on hard surfaces.
Photo: Michael-Palmgren-Marint-Kunskapscenter
The lobster finds its best hiding spots on hard seabeds, among cliffs and rocks.
Photo: wislonhk-CC-BY-NC
Hard seabeds in shallow waters is a perfect spot for forests of algae to grow, on hard rocks and cliffs.
Photo: Ellika-Nordström-Malmö-Museer
Sea urchins, which are also related to starfish, look like small hedgehogs. They live on rocky walls and often hide in cavities and on gravel beds at the bottom as protection against predators.
Photo: Bengt-Littorin-CC-BY
The Ballan wrasse thrives in rocky areas, and places its eggs in crevices among the sea cliffs.
Photo: Johanna-Rylander-Malmö-Museer
Soft seabeds
Soft seabeds consist mostly of clay and sand. They make up the vast majority of the world’s ocean floor. The species that live here are mainly sea snails, worms, crustaceans, soft-shell clams, starfish and developing insect larvae. Many species found on soft seabeds are buried. Many of the plant species on soft seabeds have root systems.
You've probably seen worm-shaped sand piles on the beach at some point? It's poop from a bottom-dwelling worm called a sandworm. It eats sand to catch tiny animals that live in the sand, then the excess sand is pooped out into winding piles.
Photo: Auguste-Le-Roux-CC-BY
The sand shrimp is well camouflaged against the surface on soft and sandy seabeds.
Photo: Lamiot-CC-BY-SA
Soft shell clams live most of their lives buried in sandy and soft seabeds.
Photo: Ecomare-CC-BY-SA
A large colony of bristle stars waves for food with their arms, while their bodies ar buried in the soft seabed.
Photo: Ken-ichi-Ueda-CC-BY
The brill, lives its life on the bottom just like other flatfish. It is well camouflaged when it partially or completely digs into the soft bottom material.
Photo: Roberto-Pillon-CC-BY
The common goby thrives on soft seabeds, and easily hides in the muddy or sandy sediments.
Photo: Ove-Glenjen-CC-BY-SA
Burrow for protection
There are many different species that live close to the bottom and like to burrow. They can use this strategy either to hide, or to hunt by being partially buried. There are about 500 species of flatfish that burrow into the material on the bottom. The eyes are located on the upper side of the adult fish’s body, while the lower side lies buried or flat against the bottom. The common goby, a type of small fish, lives off the southern half of the Swedish coast. It also buries itself completely in the sand for long periods to protect itself.