Time series of vertical flux of zooplankton fecal pellets on the continental shelf of the Western Antarctic Peninsula

Zooplankton fecal pellet contribution to particulate organic carbon (POC) flux over the continental shelf of the Western Antarctic Peninsula (WAP) was investigated to better understand the possible effects of changes in zooplankton community structure, due to climate change, on fecal pellet export. Fecal pellets were collected at 170 m depth in a moored sediment trap from Jan. 2004 - Jan. 2009. Fecal pellet shape and size (i.e., carbon content) were quantified to assess flux of pellets from different zooplankton taxa, and compared between seasons and years. Fecal pellet POC constituted the dominant proportion of total POC flux, with summer (Nov. – Apr.) pellet POC flux (67%) significantly higher than winter (May – Oct.; 34%), and phytodetritus or fecal ‘fluff’ constituting the remainder. Cylindrical euphausiid pellets contributed to a monthly mean of 72% of total fecal pellet flux; ovoid copepod and tabular salp pellets contributed significantly less (22% and 6%, respectively). Cylindrical and ovoid pellet export was significantly higher in summer, while 48% of tabular pellet flux occurred in the winter. Tabular pellets had the highest carbon content (median = 1.0 µgC pellet^-1, largest 134.9 µgC pellet^-1), followed by cylindrical (0.2 µgC pellet^-1), and ovoid (0.04 µgC pellet^-1) pellets. As krill fecal pellets are the dominant component of particle export in the WAP, we predict a decrease in krill and increase in salps in the region could alter export of POC to the deep sea.