Aspects of carbon monoxide production and oxidation by marine macroalgae

Rates of macroalgal carbon monoxide (CO) production were compared among 5 taxa representing 3 major phylogenetic groups (Phaeophyta, Chlorophyta, Rhodophyta). CO production varied substantially from a minimum of about 20 ng CO gdw–1 h–1 for Fucus vesiculosus to >4000 ng CO gdw–1 h–1 for Laminaria saccharina. None of the macroalgae examined contained significantly elevated CO concentrations within their pneumatocysts (float bladders), so the variability among taxa reflects other intrinsic properties. An in vitro evaluation of Ascophyllum nodosum indicated that CO production varied as a function of temperature, desiccation and illumination. CO production increased strongly for live fronds over an ecologically relevant range (5 to 23°C), but decreased at 45°C. For non-living desiccated wrack, CO production increased consistently from 5 to 47°C. Shortterm desiccation of living algae decreased CO production substantially, but long-term changes in water content appeared not to markedly alter CO production relative to fresh material. Illumination strongly increased CO production relative to dark incubations, with similar responses for living and non-living material. CO oxidation (presumably bacterial) was observed for most living algae during incubations with exogenous CO at concentrations of 100 ppm, suggesting that a microbe-alga association might limit in part CO fluxes. Extrapolation of CO production rates indicates that macroalgae likely contribute only a minor fraction (<1%) of global marine CO emissions to the atmosphere (about 10 Tg yr–1).