Deep-Sea Research I 47 (2000) 277}294 A comparison of the quantity and composition of material caught in a neutrally buoyant versus surface-tethered sediment trap Ken O. Buesseler*, Deborah K. Steinberg, Anthony F. Michaels, Rodney J. Johnson, John E. Andrews, James R. Valdes, James F. Price Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Clark Building 447, Woods Hole, MA 02543-1541, USA Bermuda Biological Station for Research, Inc., Ferry Reach, St. George's, GE01, Bermuda Wrigley Institute for Environmental Studies, University of Southern California, AHF 232, Los Angeles, CA 90089-0371, USA Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543-1541, USA Received 1 October 1998; received in revised form 26 February 1999; accepted 26 February 1999 Abstract The #ux and composition of material caught using two di!erent upper ocean sediment trap designs was compared at the Bermuda Atlantic Time-series Study site (BATS). The standard surface-tethered trap array at BATS was compared to a newly designed neutrally buoyant sediment trap (NBST). Both traps used identical cylindrical collection tubes. Of particular concern was the e!ect of horizontal #ow on trap collection e$ciency. In one experiment, mass, particulate organic carbon (POC) and particulate organic nitrogen (PON) #uxes were slightly lower (20}30%) in the NBST than in the standard BATS trap. In contrast, Th and fecal pellet #uxes were up to a factor of two to three lower in the NBST. In a second experiment, mass and POC #uxes decreased signi"cantly with depth in the BATS surface-tethered trap, but not in the NBST. Di!erent brine treatments had no measurable e!ect on collection e$ciencies. A striking observation was that the swimmer `#uxa was much larger in the standard BATS traps than in the NBST. Overall, these results show that di!erent components of the sinking #ux can be collected with di!ering e$ciencies, depending upon how traps are deployed in the ambient environment.  1999 Elsevier Science Ltd. All rights reserved. Keywords: Sediment trap; Thorium-234; Bermuda * Corresponding author. Tel.: 001-508-289-2309; fax: 001-508-457-2193. E-mail address: kbuesseler@whoi.edu (K.O. Buesseler) 0967-0637/99/$ - see front matter  1999 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 7 - 0 6 3 7 ( 9 9 ) 0 0 0 5 6 - 4