Teira, Eva, Hendrik van Aken, Cornelis Veth, and Gerhard J. Herndl
Limnol. Oceanogr., 51(1), 2006, 60–69
We determined the contribution of the three major prokaryotic groups (Bacteria, Crenarchaeota, and Euryarchaeota) on the uptake of D- and L-aspartic acid (Asp) in the major water masses of the North Atlantic (from 100- to 4,000-m depth) with the use of microautoradiography combined with catalyzed reporter deposition fluorescence in situ hybridization (MICRO-CARD-FISH). The percentage of prokaryotic cells that assimilated D- and L-Asp ranged from <5% to 25%. In the meso- and bathypelagic waters of the North Atlantic, Archaea are more abundant (42% ± 2% of 49,69-diamino-2-phenylindole [DAPI]–stained cells) than Bacteria (30% ± 1% of DAPI-stained cells), and more archaeal than bacterial cells are actively incorporating D-Asp (62% ± 2% vs. 38% ± 2% of total D-Asp active cells). In contrast, Bacteria and Archaea almost equally contribute to L-Asp use in the deep waters of the North Atlantic (47% ± 2% vs. 53% ± 2% of total L-Asp active cells). The increase in the D-Asp : L-Asp uptake ratio in the prokaryotic community with depth appears to be driven by the efficient uptake of D-Asp by, especially, the Crenarchaeota in the deep waters. Because Archaea, and particularly Crenarchaeota, commonly dominate the prokaryotic communities in the ocean’s interior, we suggest that they represent a previously unrecognized sink of D–amino acids in the deep ocean.