期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：34
页码：15129-15134
DOI：10.1073/pnas.1003599107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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 {micro}m) at low velocity (U = 1.6 {+/-} 0.6 cm{middle dot}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-{micro}m diameter polystyrene spheres corroborate these findings. Although particles larger than 1 {micro}m (e.g., flagellates, small diatoms) represent a larger carbon pool, smaller particles in the 0.1- to 1-{micro}m 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 {micro}m) 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.
