softbottomed

Softbottomed (also written as soft-bottomed) is an adjective used in ecology and geoscience to describe substrates composed of unconsolidated sediments, including mud, silt, and fine sands, rather than solid, cohesive materials like rock or coral. The term is commonly applied to benthic habitats in rivers, estuaries, lakes, and coastal seas where sediment softness shapes physical conditions and biological communities.

Physical and chemical characteristics include high porosity, low shear strength, and substantial water content. Soft bottoms often exhibit limited pore-water exchange, leading to varying redox conditions with depth, a zone of microbial and chemical activity, and pronounced bioturbation by infauna that rework sediments and influence oxygen penetration.

Ecologically, soft-bottom habitats support a distinctive assemblage of organisms, including burrowing polychaete worms, bivalves, crustaceans, and grazing microalgae. Primary production is contributed by microphytobenthos on the surface, while detrital pathways drive much of the energy flow. These habitats play a role in sediment stabilization and nutrient cycling, and they can store substantial organic carbon.

Environmental pressures such as dredging, trawling, dredged material disposal, urban runoff, and sedimentation can drastically alter soft-bottom ecosystems, reducing habitat complexity and biodiversity. Recovery from disturbance is variable and depends on sediment properties and connectivity with surrounding habitats. Conservation and management often emphasize reducing sediment pollution, controlling dredging activity, and preserving the integrity of the soft-bottom substrate.