Comparison of vertical distributionof suspended fecal pellets and production of copepod fecal pellets in the Ulleung Basin between 2005 and 2006

Abstract

Vertical distribution of suspended fecal pellets (SFP) in water column and production rates of fecal pellets by copepod community was studied in the Ulleung Basin, Japan/East Sea in July 2005 and April 2006. An anticyclonic eddy existed in the center of the basin in 2005 and 2006. The eddy was stratified with a seasonal thermocline and in the center of the eddy a strong subsurface chlorophyll maximum was developed at 40-50m depth in 2005. The seasonal thermocline in 2006, however, showed different pattern between stations. Experiments were made at two stations: D2 (at the periphery of the eddy) and D4 (inside the eddy). The SFP at D2 and D4 peaked at 30-50m depth with no clear difference between the day and night sampling in 2005. The SFP in 2006 showed different pattern between stations: D2 (no difference between the day and night sampling and SFP distributed through the water column until 100m depth) and D4 (SFP peaked at 10-30m depth at night and at 100m depth at day sampling). The production rates of fecal pellets by copepod community were estimated 0.57 mgC m-3 day-1 (or 115 mgC m-2 day-1 in the upper 200m) in July 2005 and 0.43 mgC m-3 day-1 (or 96.2 mgC m-2 day-1) in April 2006. The major controlling factors for the variability of mesozooplankton fecal pellets are discussed in the context of the potential role of fecal pellets in carbon flux in the Ulleung Basin in summer and spring.