Journal
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
Volume 94, Issue -, Pages 72-86Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.dsr.2014.09.001
Keywords
Vertical flux; Euphausiid; Fecal pellets; Retention efficiency
Categories
Funding
- National Science Foundation (NSF) [OCE-0927863, OCE-0928139, OCE-0928425]
- Directorate For Geosciences [0927863] Funding Source: National Science Foundation
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We sampled zooplankton and fecal pellets in the upper 200 m of Monterey Bay and nearby coastal regions in California, USA. On several occasions, we observed high concentrations of large pellets that appeared to be produced during night-time by dielly migrating euphausiids. High concentrations of pellets were found in near-surface waters only when euphausiids co-occurred with high concentrations of large (> 10 mu m) phytoplankton. Peak concentrations of pellets at mid-depth (100 or 150 m) during the day were consistent with the calculated sinking speeds of pellets produced near the surface at night. At these high flux locations (HI group), pellet concentrations declined below mid-depth. In contrast, at locations where the phytoplankton assemblage was dominated by small phytoplankton cells (< 10 mu m), pellet production and flux were low (LO group) whether or not euphausiid populations were high. Protozooplankton concentrations did not affect this pattern. We concluded that the day and night differences in pellet concentration and flux in the HI profiles were mostly due to sinking of dielly-pulsed inputs in the surface layer, and that small zooplankton (Oithona, Oncaea), heterotrophic dinoflagellates, and bacterial activity probably caused some pellet degradation or consumption below 100 m. We estimated that consumption of sinking pellets by large copepods was insignificant. High fluxes of pellets were episodic because they required both high concentrations of large phytoplankton and large stocks of euphausiids. Under these conditions, flux events overwhelmed retention mechanisms, resulting in large exports of organic matter from the upper 200 m. (C) 2014 The Authors. Published by Elsevier Ltd.
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