Fate of particle-bound bacteria ingested by Calanus pacificus

Abstract

Adult female copepods were fed on freeze-thawed diatoms (Cylindrotheca fusiformis and Chaetoceros sp.) which had been colonized by natural populations of seawater bacteria labeled with 3H-leucine. The copepods retained 26-31% of the label 43 h after ingestion and subsequent gut clearance, indicating that a substantial fraction of bacterial boimass bound to particulates of appropriate size can be directly available to this copepod as a source of material and energy. Bacteria were present at very high concentrations (109 to 1010 ml-1) in the fecal pellets of copepod fed on bacterized food, but were absent in the fecal pellets of copepods fed axenic food. Feeding of these copepods on attached bacteria not only serves to link the microbial loop with the grazing food chain but, because of the passage of viable bacteria into the fecal pellet, may also influence fecal pellet degradation. -from Authors