It has been recently demonstrated that the diazotrophic cyanobacterium Trichodesmium can produce methane by utilizing methylphosphonate (MPn). However, little is known how changed levels of light and temperature affect such methane production and its relationship with carbon, nitrogen, and phosphorus assimilation in Trichodesmium. By growing this diazotroph with MPn, we found that increasing levels of light (up to 220 μmol photons m^-2 s^-1) or temperatures (up to 31°C) promote its methane production along with enhanced rates of growth carbon, nitrogen and phosphorus assimilations. The highly positive correlations between methane production and carbon, nitrogen and phosphorus assimilations indicate that one mole CH₄ produced required 227-494 mole CO₂ fixed, 26-128mole N₂ fixed and 1.3-3.4 mole MPn assimilated. The combined effects of light levels and temperatures showed that the impact of temperature is dependent on light levels. Under ample light at 110 μmol photons m^-2 s^-1, rising temperatures showed positive effects. In contrast, under insufficient light at 30 μmol photons m^-2 s^-1, a temperature rise within the range of 23-31°C reduced methane production, phosphorus assimilation and specific growth rate, while carbon and nitrogen assimilation rates remain largely unchanged, disrupting their synergy.
 

light, methane, temperature, Trichodesmium