Flow-through chamber method for clearance rate measurements in bivalves: design and validation of individual chambers and mesocosm

Abstract

There is an ongoing discussion in the scientific literature about methodological aspects of clearance rate (CR) measurement with regard to bivalves, especially when the CR is measured by flow-through chamber method. In the present paper, an experimental chamber, a mesocosm system, and a validation protocol have been developed for determining the CR using the flow-through method. The procedure consisted of a preliminary analysis of the fluid dynamics in the interior of the chamber and a statistical analysis of the CR measurement in the mussel Mytilus galloprovincialis L at different water inflows. This allowed the performance of the chamber for each flow to be identified. The performance of the chamber for all the flows studied was also modeled simultaneously by means of Ivlev curve. The protocol, applied to an individual cylindrical experimental chamber (ICEC) (radius 71 mm, height 76 mm, volume 1200 mL), established that the ICEC complies with all the requirements for CR measurement using the flow-through chamber method, provided that the percentage of particles cleared is approximately 20% (minimum 13%, maximum 25%). In agreement with the allometric relationship between length and volume of Mytilus galloprovincialis, 3 types of ICEC were designed for CR measurement on individuals of 20 to 85 mm length. After validation of the ICEC, the performance of a mesocosm system used regularly by our group (box raft experimental chamber or BREC) was evaluated. Three comparative measurements were carried out for the ICEC and BREC, two in situ and one in the laboratory. No statistically significant differences were observed between the experimental systems for the CR determinations, which validates the BREC for CR measurement using the flow-through chamber method.