Meeting Abstract

P3.39  Tuesday, Jan. 6  In situ filtration rates of pelagic tunicates: results from morphometric measurements RAKOW SUTHERLAND, K*; MADIN, L; MIT/WHOI Joint Program in Oceanography; Woods Hole Oceanographic Institution krakow@whoi.edu

Salps are suspension-feeding pelagic tunicates that filter higher volumes of seawater than almost any other planktonic grazer. Oral and atrial siphons are at opposite ends of the barrel shaped body and a unidirectional feeding current is produced by rhythmically contracting circular muscle bands. Seawater and associated small particles (0.1 m-1mm) are filtered through a mucous mesh that fills the mostly hollow pharyngeal cavity. Accurately measuring filtration rates poses a challenge because salps are delicate, difficult to collect and maintain, and may not behave normally in the laboratory. Morphometric analysis of salps swimming in situ provided a way to measure the volume of fluid passing through the mucous filtering mesh. High definition video sequences were collected by SCUBA divers and then video frames were digitized to measure time-varying swimming kinematics and body volume over a pulse cycle. This in situ technique has been applied to several species of salps and compares reasonably to results from other methods. Differences in filtering efficiency between Salpa cylindrica, Pegea confoederata and Cyclosalpa sp. will be presented.