Benthic boundary layer

The benthic boundary layer (BBL) is the layer of water directly above the sediment at the bottom of a body of water (river, lake, or sea, etc.).^[1] Through specific sedimentation processes, certain organisms are able to live in this deep layer of water. The BBL is generated by the friction of the water moving over the surface of the substrate, which decrease the water current significantly in this layer.^[2] The thickness of this zone is determined by many factors, including the Coriolis force. The benthic organisms and processes in this boundary layer echo the water column above them.^[2]

The BBL serves as a transitional zone between the water column and the sediment layer by regulating biogeochemical processes and the flux of nutrients and organic materials.^[2] This zone also serves as the main layer of resistance for the shift of mass, heat, and nutrients from the sediment to the water, or vice versa.^[1] It is this area of interaction between the two environments that is important in many species' reproductive strategies, particularly larvae dispersal. The benthic boundary layer also contains nutrients important in fisheries, a wide array of microscopic life, a variety of suspended materials, and sharp energy gradients. It is also the sink for many anthropogenic substances released into the environment as the substances commonly sink to the bottom of the water column.^[2]