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Filtration of submicrometer particles by pelagic tunicates

Sutherland, Kelly R. and Madin, Laurence P. and Stocker, Roman (2010) Filtration of submicrometer particles by pelagic tunicates. Proceedings of the National Academy of Sciences of the United States of America, 107 (34). pp. 15129-15134. ISSN 0027-8424. PMCID PMC2930554.

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Salps are common in oceanic waters and have higher per-individual filtration rates than any other zooplankton filter feeder. Although salps are centimeters in length, feeding via particle capture occurs on a fine, mucous mesh (fiber diameter d ~0.1 μm) at low velocity (U = 1.6 ± 0.6 cm•s^(−1), mean ± SD) and is thus a low Reynolds-number (Re ~10^(−3)) process. In contrast to the current view that particle encounter is dictated by simple sieving of particles larger than the mesh spacing, a low-Re mathematical model of encounter rates by the salp feeding apparatus for realistic oceanic particle-size distributions shows that submicron particles, due to their higher abundances, are encountered at higher rates (particles per time) than larger particles. Data from feeding experiments with 0.5-, 1-, and 3-μm diameter polystyrene spheres corroborate these findings. Although particles larger than 1 μm (e.g., flagellates, small diatoms) represent a larger carbon pool, smaller particles in the 0.1- to 1-μm range (e.g., bacteria, Prochlorococcus) may be more quickly digestible because they present more surface area, and we find that particles smaller than the mesh size (1.4 μm) can fully satisfy salp energetic needs. Furthermore, by packaging submicrometer particles into rapidly sinking fecal pellets, pelagic tunicates can substantially change particle-size spectra and increase downward fluxes in the ocean.

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Additional Information:© 2010 by the National Academy of Sciences. Edited by Mimi A. R. Koehl, University of California, Berkeley, CA, and approved July 14, 2010 (received for review March 17, 2010). Published online before print August 9, 2010. We thank those who facilitated our work at the Liquid Jungle Lab, Panama, especially Ellen Bailey, Luis Camilli, and numerous SCUBA divers. Mark Wells, Hugh Ducklow, and Dariusz Stramski, as well as two anonymous reviewers, provided insightful comments relating to the manuscript. This work was supported by National Science Foundation Grants OCE-0647723 (to L.P.M.) and OCE-074464-CAREER (to R.S.) and the Woods Hole Oceanographic Institution Ocean Life Institute. Author contributions: K.R.S, L.P.M., and R.S. designed research; K.R.S., L.P.M., and R.S. performed research; K.R.S. analyzed data; and K.R.S, L.P.M., and R.S. wrote the paper.
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Woods Hole Oceanographic InstitutionUNSPECIFIED
Subject Keywords:biofiltration; low Reynolds number; salps; colloids; carbon cycle
Issue or Number:34
PubMed Central ID:PMC2930554
Record Number:CaltechAUTHORS:20100913-113946215
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19909
Deposited By: Tony Diaz
Deposited On:15 Sep 2010 19:32
Last Modified:02 Jun 2020 21:08

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