Incubation chambers system for in situ studies of benthic suspension feeders
Channel: Encontro Recifal Brasileiro
Date: 2020-07-01

Derviche Patrick; Lana Paulo

Suspension feeding is one of the most common feeding strategies in hard-bottom benthic communities. Enclosure experiments are often used to assess variables related to suspension-feeding in underwater habitats, but due to logistical restrictions they often lack adequate sampling design and sampling effort. To overcome these challenges, we have developed an innovative incubation chambers system to assess variations in feeding rates, diet composition, and clearance rates of benthic suspension feeders in a reliable and repeatable way. The system, operated by two SCUBA divers, consists of nine connected 2,590 ml dome-shaped transparent acrylic chambers, 12 cm in diameter, uniformly arranged on a 90 x 120 cm acrylic plate. Seawater flows independently in each chamber, which may be treated as replicates for experimental designs. The system may be switched from open (continuous entry of seawater from outside) to closed circulation (seawater only inside the chamber). To avoid an uneven input of suspended particles among the chambers during the open circulation operation, seawater entry is restricted to a single point. Nine 120 l.h-1 pumps powered by a sealed 6V 12Ah battery allows for turbulent flow and the maintenance of suspended particles within each chamber. Underwater sampling can occur at varying times, depending on the research problems and hypotheses being tested, through a set of valves that traps the seawater in bottles. Feeding rates and variations in the density or abundance of preys may be calculated from the decrease in the number and nature of particles from the initial to the final samples. Our system provides consistent estimates of the feeding performance of benthic suspension feeders under natural or experimental conditions. As such, it can be widely applied to experimental ecology, allowing for a better understanding of ecological relationships between benthic species, bentho-pelagic coupling, and the biogeochemical cycles of shallow benthic marine habitats.