Fig. 2: Potential faecal pellet (FP) flux and export efficiency of krill and salp FP.

The potential flux of FP of krill in the upper 200 m accounted on average for 396.3 mg C m⁻² d⁻¹, incl. the presence of dense krill swarms, resulting in an export efficiency of krill FP of 72% to 300 m. The flux of salp FP in the upper 170 m accounted for 59.6 mg C m⁻² d⁻¹ for FP produced from feeding on phytoplankton (type 1), resulting in an export efficiency of 20% to 300 m. The carbon-specific microbial respiration accounted for only 0.3% of the carbon loss per day for salp FP, and for 1.2% d⁻¹ for krill FP. Consequently, other remineralisation processes and zooplankton-mediated processes, such as feeding and loosening of the pellets must account for the retention of about 80% of salp FP, and 27% of krill FP in the top 200 m. The dashed arrow depicts the production of type 2 FP at the surface after feeding on krill FP at depth and the unknown contribution to the export flux of carbon.