Flumes for benthic ecologists: theory, construction and practice

Although the utility of laboratory flumes in benthic ecological research has been demonstrated by numerous studies there are no general references on the technique, and the details of flume design have often been neglected in published work. Details of boundary-layer flow relevant to benthic processes and their study in flumes are presented, using a newly constructed flume at Dalhousie as an example. The Dalhousie flume is a straight flow-through channel 3 m long, with a corewell for sediment samples and adjustable exit weirs to control flow rate and water depth. This design is suitable to assess the stress imposed on organisms and sediments by the motion of fluid near the bottom. The important criteria for channel design, flow visualization and measurement are presented for this and more complex recirculating designs. We report various means of measuring concentrations of suspended particles, allowing calculation of the horizontal flux of organic matter at the bed. Controlled flow experiments are essential to determine the effect of organisms on sediment stability through biofilms or roughening of the sea-bed. The role of the horizontal transport of detrital organic material will become clearer as this technique is more frequently applied in quantitative benthic ecology.