Marine Biology 86, 47-54 (1985)

Marine Biology

Clearance rates of the salp Thalia democratica fed naturally occurring particles

D. Deibel

Skidaway Institute of Oceanography; P.O. Box 13687, Savannah, Georgia 31406, USA


Abstract

Net-captured aggregate stages of the salp Thalia democratica were fed naturally occurring particles in 2-liter bottles onboard ship. The goal was to compare clearance rates of net-captured T. democratica fed natural particles to clearance rates previously determined in laboratory born T. democratica fed monocultures of phytoplankton. On a cruise from 19-29 April, 1979, clearance rates were estimated by monitoring the decrease in concentration of particles with a multi-channel Coulter Counter TA II over a particle size range of 2 to 32 µm equivalent spherical diameter (E.S.D.). Clearance rates were slightly lower than those measured in the laboratory, decreasing 3-fold over an 18-fold increase in the initial food concentration. Ingestion rates were slightly higher than those measured in the laboratory, increasing about 6-fold over the same range of food concentration. Within the particle concentration range examined (0.08 to 1.34 mm l¬¹), there was no lower threshold of food concentration below which clearance of particles ceased. There was no effect of the concentration of T. democratica on clearance rate over a range of 2.5 to 11.5 salps l¬¹. The mean hourly ration was 2.0% of body carbon.