Fecal pellet flux summary from samples collected during CCE LTER process cruises in the California Current system, 2007 – present.

The collection and enumeration of sinking fecal pellets on CCE LTER Process cruises has been led by Mike Stukel since 2007. Sinking particles are collected in VERTEX-style particle interceptor traps (PIT) with an 8:1 aspect ratio, 70-mm diameter, and a baffle on top comprised of 13 smaller beveled tubes with a similar 8:1 aspect ratio. Tubes are deployed with a formalin-brine for a duration of 2-5 days. After recovery, samples are gently split on a Folsom splitter and typically 3/8 to 1/2 of two separate tubes are utilized for fecal pellet enumeration. After the cruise, samples for fecal pellet enumeration are placed in a settling chamber to allow fecal pellets to settle out. Overlying water is then strained through a 60-um filter to collect any pellets that may have remained in the water. Pellets were then placed on a gridded Petri dish and analyzed using a Zeiss Discovery stereomicroscope. Pellets were separated from other particles and photographed with a dedicated camera. Image processing was then conducted using either Image J or Image Pro to extract area and maximum feret length for each fecal pellet. Pellets were classified by shape and shape-appropriate equations were used to determine the volume of each fecal pellet. Volume was converted to mass using the equations in Stukel et al. (2013). Fecal pellet mass flux is the sum of the mass of all fecal pellets for a sample multiplied by a conversion factor that takes into account the proportion of the gridded petri dish that was enumerated, the fraction of the PIT tube that was used for fecal pellet enumeration, the cross-sectional area of the PIT tube, and the deployment duration. Standard error of the mean is determined from the two samples enumerated for each sediment trap deployment. For more details please see Stukel et al. (2013) or Morrow et al. (submitted). Knauer, G. A., J. H. Martin and K. W. Bruland (1979). "Fluxes of particulate carbon, nitrogen, and phosphorus in the upper water column of the Northeast Pacific." Deep-Sea Research 26(1): 97-108. Morrow, R. M., M. D. Ohman, R. Goericke, T. B. Kelly, M. R. Landry, B. M. Stephens and M. R. Stukel (submitted). "Primary Productivity, Mesozooplankton Grazing, and the Biological Pump in the California Current Ecosystem: Variability and Response to El Niño." Deep-Sea Research I. Stukel, M. R., M. D. Ohman, C. R. Benitez-Nelson and M. R. Landry (2013). "Contributions of mesozooplankton to vertical carbon export in a coastal upwelling system." Marine Ecology Progress Series 491: 47-65.