Egestion of non-pellet-bound fecal material from the copepod Acartia tonsa: implication for vertical flux and degradation

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 293:131-142 (2005) - doi:10.3354/meps293131 Egestion of non-pellet-bound fecal material from the copepod Acartia tonsa: implication for vertical flux and degradation Michael Olesen1,*, Solvita Strake2, Andris Andrushaitis2 1Marine Biological Laboratory, University of Copenhagen, 3000 Helsingør, Denmark2Institute of Aquatic Ecology, University of Latvia, 2169 Riga, Latvia *Email: molesen@bi.ku.dk ABSTRACT: Only a minor fraction of copepod defecation appears to leave the upper water column as fast-sinking fecal pellets in coastal waters. This study suggests that most egested matter from copepods is retained in the water column because (1) >50% of fecal matter is released as small, slowsinking particles that are not surrounded by a peritrophic membrane and (2) small fecal pellets sink slowly and are degraded rapidly. The production, appearance and fate of fecal material from the calanoid copepod Acartia tonsa (fed on 2 different phytoplankton species, the cryptophyte Rhodomonas salina and the diatom Skeletonema costatum) was followed in association with the grazing activity of the copepod in a laboratory experiment. For both diets, >50% of the defecation was released as dispersed small (<10 mm) non-pellet-bound particles. The diatom was less suitable as a food item than the flagellate and led to a 3 times higher rate of grazing and egestion. Nevertheless, specific assimilation and egg production per female were 2 times higher for the Rhodomonas diet versus the Skeletonema diet. As a result, the total egestion comprised 18% of the ingestion of Rhodomonas and 27% of the Skeletonema ingestion. In terms of vertical loss, sinking rates for both types of fecal pellets were ca. 5 m d–1 and, in terms of degradation, ca. 0.5 d–1 (18°C) in the absence of copepods. Transferring these findings to similar neritic conditions suggests that 60% of the fecal pellets from copepods will be recycled within a 15 m deep mixed layer and that >80% of the total fecal matter can be expected to be retained when the unbound fecal material is also included. KEY WORDS: Zooplankton · Grazing · Chlorophyll · Fecal pellets · Egestion · Assimilation · Degradation · Vertical flux Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 293. Online publication date: June 02, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.