sjöbotten

Sjöbotten refers to the bottom substrate of a lake or sea, comprising the sediment and solid material that accumulates on the bed. It forms the physical foundation for aquatic ecosystems and differs from the overlying water column in chemistry, oxygen content, and biological communities. The term is used in limnology and marine science to describe the habitat where benthic organisms live.

The material that makes up the sjöbotten varies with location and energy conditions. In freshwater lakes it can range from fine clays and silts to sand and gravel, with organic-rich muds forming under low-energy conditions and peat possible in waterlogged, nutrient-rich areas. In marine environments, sediments may include sand, silt, clay, and calcareous or siliceous layers. The uppermost layer is often mixed by organisms and physical processes, a phenomenon known as bioturbation and sediment resuspension.

Ecologically, the sjöbotten is crucial for nutrient cycling, carbon storage, and habitat structure. Benthic communities—including worms, crustaceans, mollusks, and small fish—depend on the sediment type and oxygen availability. Oxygen depletion in deeper sediments during stratified periods can lead to chemical changes and shifts in community composition.

Human activities and natural changes affect sjöbotten. Sedimentation from erosion, pollution, dredging, and bottom-trawling can alter sediment structure and contaminant distribution. Studying sediment cores and conducting benthic surveys help scientists understand historical environmental conditions and current ecosystem health.