Impact of submarine hydrothermal vents on the metal composition of krill and its excretion products

We have measured the metal composition and estimated the excretion rate of trace elements (Ag, Cd, Co, Cu, Ni, Pb, V and Zn) by Antarctic krill (Euphausia superba) in three locations (two located within a submarine hydrothermal vent field and one away from it) along the Antarctic Peninsula region of the Southern Ocean. Results indicated that krill excreted large amounts of Ag, Cu, Pb and Zn, (range: 1.9-41.2 pmol Ag g DW^{- 1} h^{- 1}, 15.3-26.8 nmol Cu g DW^{- 1} h^{- 1}, 308.7-1118.3 pmol Pb g DW^{- 1} h^{- 1} and 24.4-76.5 nmol Zn g DW^{- 1} h^{- 1}), compared with the non-significant or undetectable release rates of Cd, Co, Ni and V. The metal composition of the excreted material from krill collected in the area of hydrothermal activity was similar to the metal composition reported for suspended particles emitted from those vents. Our results suggest that krill recycling of Ag, Cu, Pb and Zn could potentially influence trace metal concentrations in the water column of the Bransfield region of the Southern Ocean, and that the original source of metals to these waters may be hydrothermal vents.