Grazing of two common appendicularians on the natural prey assemblage of a tropical coastal ecosystem

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 294:201-212 (2005) - doi:10.3354/meps294201 Grazing of two common appendicularians on the natural prey assemblage of a tropical coastal ecosystem R. D. Scheinberg1,*, M. R. Landry2, A. Calbet3 1Department of Oceanography, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA2Integrative Oceanography Division, Scripps Institution of Oceanography, La Jolla, California 92093-0227, USA3Institut de Ciències del Mar, CMIMA (CSIC), P. Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain *Email: scheinbe@hawaii.edu ABSTRACT: The clearance rates of co-occurring appendicularian species, Oikopleura longicauda and O. fusiformis, in Kaneohe Bay, Hawaii, were investigated to evaluate and compare their roles in a tropical food web. Individual appendicularians were captured in situ and allowed to feed on the natural plankton assemblage for 60 to 180 min. Feeding rate estimates were based on flow-cytometry analyses of cell-density changes for heterotrophic bacteria (Hbact), Synechococcus spp. (Syn) and <13.0 µm autotrophic eukaryotes (Aeuks). Despite morphological differences, O. longicauda and O. fusiformis cleared the largest prey size-fraction at statistically indistinguishable rates. For the 3 prey categories (Hbact, Syn and Aeuks), mean clearance rates (±95% CI) were 12 ± 7, 27 ± 6 and 34 ± 18 ml individual (ind.)–1 h–1 and 25 ± 12, 26 ± 15 and 38 ± 20 ml ind.–1 h–1 for O. longicauda and O. fusiformis, respectively. The mean clearance rates of these 2 species on total sub-micron cells in Kaneohe Bay were not significantly different; however, O. fusiformis cleared Hbact at a marginally higher rate (p = 0.07). Only O. longicauda exhibited significantly different retention efficiencies as a function of prey size, clearing the smallest prey (Hbact) at approximately 36% the rate of the largest (Aeuks) (p < 0.01). Despite reduced efficiencies on the smallest prey categories, at high abundances in Kaneohe Bay (often 2 ind. l–1), O. longicauda is capable of removing >60% of the picoplankton standing stock from the water column daily. While generally much less abundant, during occasional peaks of 1 ind. l–1, O. fusiformis can remove an almost equivalent amount (> 50%). Nevertheless, the consistently higher abundances of O. longicauda make this species a more significant link between picoplankton production and higher-level consumers (chaetognaths and fishes) in this coastal tropical embayment. KEY WORDS: Appendicularian · Grazing · Clearance rates · Oikopleura spp. Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 294. Online publication date: June 09, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.