MEPS 290:1-14 (2005)  -  doi:10.3354/meps290001

ABSTRACT: Microbial consumption is the dominant sink of oceanic carbon monoxide (CO), one of the major carbon-containing photoproducts of chromophoric dissolved organic matter in marine waters. This study presents first-order microbial CO consumption rate constants (k_CO) determined using whole-water dark incubations in summer and fall in diverse marine ecosystems covering the Delaware Bay, NW Atlantic, and Beaufort Sea. The microbial CO consumption rate constant, k_CO (mean ± SD) was 1.11 ± 0.76 h^–1 in the Delaware Bay, 0.33 ± 0.26 h^–1 in the coastal Atlantic, 0.099 ± 0.054 h^–1 in the open Atlantic, 0.040 ± 0.012 h^–1 in the coastal Beaufort Sea and 0.020 ± 0.0060 h^–1 in the offshore Beaufort Sea. The k_CO in the Delaware Bay covaried with chlorophyll a concentration ([chl a]), rising with increasing salinity in the range 0 to 19 and diminishing with further increasing salinity. The k_CO in the Beaufort Sea is significantly positively correlated with [chl a]. Both the Atlantic and cross-system data sets showed significant positive correlations between k_CO and the product of [chl a] and water temperature, suggesting that [chl a] can be used as an indicator of CO-consuming bacterial activity in the areas and seasons sampled in this study. Microbial CO consumption was shown to follow Wright-Hobbie kinetics, with variable but low half-saturation concentrations: ~1 nM in the Beaufort Sea and Gulf Stream and 2 to 18 nM in the coastal NW Atlantic. These low half-saturation concentrations suggest that microbial CO consumption in seawater is at times partly saturated, and that some previous microbial CO consumption rates determined with the commonly used ¹⁴CO method could be underestimates due to the addition of ¹⁴CO as a tracer substrate. The present study provides valuable data for coastal and Arctic waters whose k_CO values are poorly or not constrained, including extensive data on the dependence of k_CO on the concentration of CO.

KEY WORDS: Carbon monoxide · Microbial consumption · Wright-Hobbie kinetics · Marine waters