Benthic chamber for metabolic measurements of underwater flora: a new realization

Benthic chambers are widely used in studies concerning both marine sediments and flow of solutes through them up to high depth. Benthic chambers were used also for studies on metabolism of coral reefs and vegetable biomasses; these studies can be carried out for use up to a few meters of depth because the data acquisition instruments can be placed above the water surface. Difficulties arise when these measurements have to be made to depths of several tens of meters. In these cases, the instruments should be waterproof for pressures up to several bar. For a study, in collaboration with the Department of Biology - University of Pisa, a benthic chamber was designed and built. The chamber is able to carry out metabolic measurements of underwater flora at depths between 0 and 50 m. The chamber is large enough to contain several plants and provides a reasonable compromise with chamber handling. Parameters which can be measured are underwater solar radiation (global, red, green, blue), depth, temperature, pH, conductivity, dissolved oxygen. In the Chamber there are two operation phases: measurement of water physical-chemical parameters, altered by biological activity of plants and a water exchange with external water. A pump system avoids the water stratification and allows the water renewal. Results of several tests confirm full compliance of the benthic chamber with respect to the requirements of marine biologists and to the project data.