The Development of a Benthic Chamber (BelcI) for Benthic Boundary Layer Studies

Abstract

We have developed an in-situ benthic chamber (BelcI) for use in coastal studies that can be deployed from a small boat. It is expected that BelcI will be useful in studying the benthic boundary layer because of its flexibility. BelcI is divided into three main areas: 1) frame and body chamber, 2) water sampler, and 3) stirring devices, electric controller, and data acquisition technology. To maximize in-situ use, the frame is constructed from two layers that consist of square cells. All electronic parts (motor controller, pA meter, data acquisition, etc.) are low-power consumers so that the external power supply can be safely removed from the system. The hydrodynamics of BelcI, measured by PIV (particle image velocimetry), show a typical radial-flow impeller pattern. Mixing time of water in the chamber is about 30 s, and shear velocity () near the bottom layer was calculated at . Measurements of diffusivity boundary layer thickness showed a range of . Sediment oxygen consumption rate, measured in-situ，was , more than two times higher than on-board incubation results. Benthic fluxes assessed from in-situ incubation were estimated as follows: nitrate + nitrite = ammonium phosphate = and silicate = .