A 'semi-closed' recirculating system for the in situ study of feeding and respiration of benthic suspension feeders

Suspension feeding is one of the most widespread feeding strategies among b enthic organisms. However, natural feeding ecology and energetics of benthi c suspension feeders are poorly known. The scarcity of field methods, appar atus and protocols that facilitate obtention of reliable in situ data has c ontributed to this lack of knowledge. A detailed description of an improved semi-closed recirculating system as well as the experimental set up is pro vided for the study of energetics in benthic suspension feeders. The system , completely submersible and surface-independent, allows us to assess oxyge n concentration changes and feeding rates under natural conditions. Methodo logical examinations are conducted to investigate: a) the circulation of th e water within the chamber; b) the time required for the flushing pump to e ntirely renew the volume of water of the incubation chambers; c) the behavi or of the species within the chambers; d) the time of acclimation to the ch amber conditions for the different species; e) the maximum decrease in oxyg en concentration without affecting respiration rate; f) the time required t o detect changes in concentration of the natural food sources. The system a nd experimental protocol is tested with species from three representative p hyla, Porifera, Cnidaria and Tunicata.