Aerobic hydrogen production and dinitrogen fixation in the marine cyanobacterium Trichodesmium erythraeum IMS101

Abstract

Rates of hydrogen production and acetylene reduction were measured in aerobic cultures of the marine cyanobacterium Trichodesmium erythraeum IMS101 grown in a supplemented seawater medium low in combined inorganic nitrogen. Both hydrogen production and acetylene reduction conformed to a circadian pattern with maximum activity in the afternoon. Normalized hydrogen production rates ranged from 0.06 to 0.71 nmol H-2 mu g chlorophyll a (Chl a)(-1) h(-1), while nitrogen fixation rates, calculated using an assumed ratio of 4 mol acetylene to 1 mol dinitrogen, ranged from 0.12 to 4.71 nmol N-2 Chl a(-1) h(-1). Yields of hydrogen from nitrogen fixation were in the range 0.15-0.48 mol H-2 evolved per mol N2 reduced. A comparatively low net rate of H2 uptake was observed in one culture during the dark period (-0.01 nmol H-2 mu g Chl a(-1) h(-1)). These measurements suggest that T. erythraeum is potentially a net source of hydrogen to the low-latitude surface ocean.