Nutrient fluxes measured by two types of benthic chamber

Abstract

Comparisons were made between benthic nutrient fluxes in a shallow marine embayment measured by a sophisticated automated benthic chamber device and a much simpler design. Both devices have similar chamber dimensions. The sophisticated design can be deployed by line from a vessel, incorporates an sealed waterproof computer, uses one chamber and all operations are fully programmable; dissolved oxygen concentrations are electronically monitored every 6 min and stored by the computer. The simpler design incorporates three opaque and three clear chambers per site to investigate small-scale sediment differences and the effect of benthic photosynthetic production on fluxes; dissolved oxygen concentrations are electronically monitored every 10 min. within all chambers and stored in a data logger; the deployment and recovery and sampling operations other than for DO require the use of divers. Except where sediments differ greatly over a few metres, both chamber devices deliver similar results and indicate the consistency of the technique regardless of the design. The simpler design is limited by the need for diver deployment and sampling. An automated chamber array is recommended as the best way of measuring ‘patchy’ sediments