Sand beach

They are wonderful

Small organism´s food web

Small particles and soluble organic material are filtered out of the sea water when they pass through the bottom sediment. Microalgae exploit this source of food and produce new organic material. Both the newly produced and the imported material support the food web that is made up of bottom-living micro-organisms.
    Bacteria and fungi further break down organic material and themselves eat single celled creatures (protozoas). Bakteria, fungi and protozoas are then eaten by small creatures, many of which are less than one millimetre in size. These specie are then in turn eaten by other small specie.
    On most sand beaches, the links in the food chain between the smaller and larger animals are quite vague, because many of the larger animals have the ability to filter their food out of the water. The flow between the different food webs is believed to be larger in more protected beach environments.

Variations in quantity and specie

It is common to find different organisms on different beaches that are close to each other and where composition and populations vary from year to year and with the seasons.
    Many of the larger animals that live on the beach as adults have eggs and larvae that drift in the sea. One explanation of these differences can be that the larvae of different specie arrive on the sand bottoms in varying numbers.

Magnified larvae of a polychaete, periwinkle and a crab.

Pervious page

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Waves, bottoms and construction

Sand movement and erosion

Sand bottoms as living environments

The art of digging

Sand beach organisms

Food web

Change and variation

Swedish beach life

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Bo Johannesson | Martin Larsvik | Lars-Ove Loo | Helena Samuelsson