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

The contribution of zooplankton fecal pellets to particulate organic carbon (POC) flux in the Western Antarctic Peninsula (WAP) was investigated to predict the effect of changes in the zooplankton community due to rapid climate change on flux of fecal pellets to the deep sea. Fecal pellets were collected in a moored sediment trap from 2005 to 2009, along the continental shelf of the WAP. Fecal pellet shape, size, and color were quantified to assess flux of pellets from different zooplankton taxa, and compared between seasons and years. Fecal pellet POC flux constituted a significant proportion of total POC flux, with summer pellet C flux (68% of total) significantly higher than in winter (36%) (n = 11,270). Cylindrical pellets, produced by euphausiids, contributed to a monthly mean of 79% of fecal pellet flux, with copepod and salp pellets contributing significantly less (15% and 6%, respectively, of total fecal pellet flux). Cylindrical and ovoid pellets were significantly higher in summer samples, while 90% of tabular pellet flux occurred in the winter. Tabular pellets were the largest (median size = 0.8 �gC/fecal pellet), followed by cylindrical pellets (0.2 �gC/fecal pellet), with ovoid pellets the smallest (0.02 �gC/fecal pellet). The largest tabular pellets contained up to 3-orders of magnitude more carbon than cylindrical pellets. Most fecal pellets were dark or light brown in color (suggesting an herbivorous or omnivorous diet), and <1% of pellets were white or red (detritivorous/ carnivorous diet). Zooplankton fecal pellets, especially from krill, are a significant component of carbon flux in the WAP. Loss of sea-ice due to climate change is making this region less suitable for krill, and more suitable for salp populations. Loss of krill and increase in salps could significantly change export of POC to the deep sea in this region, resulting in enhanced, but highly variable flux, with a possible increase in phytodetritus contribution to flux.