TY - JOUR
T1 - Rapid, oxygen-dependent microbial Mn(II) oxidation kinetics at sub-micromolar oxygen concentrations in the Black Sea suboxic zone
AU - Clement, Brian G.
AU - Luther, George W.
AU - Tebo, Bradley M.
N1 - Funding Information:
The authors thank co-chief scientist, J. Murray for facilitating the cruise and constructive discussions, the captain and crew of the R/V Knorr for assistance in obtaining samples, Woods Hole Oceanographic Institute for extensive help with radioisotope logistics, G. Dick, M. Griffith and C. Sheehan for Mn determinations, and B. Glazer and R. Trouwborst for sharing their concurrent Black Sea work. We also thank Allen Shiller and two anonymous reviewers for their critical comments on the manuscript. This research was supported by National Science Foundation Grants OCE-0096365 (GWL) and OCE-0221500 (BMT). B.G.C. was also supported by a National Defense Science and Engineering Fellowship.
PY - 2009/4/1
Y1 - 2009/4/1
N2 - Microbial Mn(II) oxidation kinetics in response to oxygen concentration were assessed in suboxic zone water at six sites throughout the Black Sea. Mn(II) oxidation rates increased asymptotically with increasing oxygen concentration, consistent with Michaelis-Menten enzyme kinetics. The environmental half-saturation constant, KE, of Mn(II) removal (oxidation) varied from 0.30 to 10.5 μM dissolved oxygen while the maximal environmental rate, VE-max, ranged from 4 to 50 nM h-1. These parameters varied spatially and temporally, consistent with a diverse population of enzymes catalyzing Mn oxide production in the Black Sea. Coastally-influenced sites produced lower KE and higher VE-max constants relative to the Western and Eastern Gyre sites. In the Bosporus Region, the Mn(II) residence time calculated using our KE and VE-max values with 0.1 μM oxygen was 4 days, 25-fold less than previous estimates. Our results (i) indicate that rapid Mn(II) oxidation to solid phase Mn oxides in the Black Sea's suboxic zone is stimulated by oxygen concentrations well below the 3-5 μM concentration reliably detected by current oceanographic methods, (ii) suggest the existence of multiple, diverse Mn(II)-oxidizing enzymes, (iii) are consistent with shorter residence times than previously calculated for Mn(II) in the suboxic zone and (iv) cast further doubt on the existence of proposed reactions coupling solid phase Mn oxide production to electron acceptors other than oxygen.
AB - Microbial Mn(II) oxidation kinetics in response to oxygen concentration were assessed in suboxic zone water at six sites throughout the Black Sea. Mn(II) oxidation rates increased asymptotically with increasing oxygen concentration, consistent with Michaelis-Menten enzyme kinetics. The environmental half-saturation constant, KE, of Mn(II) removal (oxidation) varied from 0.30 to 10.5 μM dissolved oxygen while the maximal environmental rate, VE-max, ranged from 4 to 50 nM h-1. These parameters varied spatially and temporally, consistent with a diverse population of enzymes catalyzing Mn oxide production in the Black Sea. Coastally-influenced sites produced lower KE and higher VE-max constants relative to the Western and Eastern Gyre sites. In the Bosporus Region, the Mn(II) residence time calculated using our KE and VE-max values with 0.1 μM oxygen was 4 days, 25-fold less than previous estimates. Our results (i) indicate that rapid Mn(II) oxidation to solid phase Mn oxides in the Black Sea's suboxic zone is stimulated by oxygen concentrations well below the 3-5 μM concentration reliably detected by current oceanographic methods, (ii) suggest the existence of multiple, diverse Mn(II)-oxidizing enzymes, (iii) are consistent with shorter residence times than previously calculated for Mn(II) in the suboxic zone and (iv) cast further doubt on the existence of proposed reactions coupling solid phase Mn oxide production to electron acceptors other than oxygen.
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U2 - 10.1016/j.gca.2008.12.023
DO - 10.1016/j.gca.2008.12.023
M3 - Article
AN - SCOPUS:61849097845
SN - 0016-7037
VL - 73
SP - 1878
EP - 1889
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 7
ER -