Molybdenum enrichment increases production by the cyanobacterium, Nostoc commune, in the short grass prairie of Southern Colorado

Since molybdenum is a cofactor for the nitrogen fixing enzyme nitrogenase, we hypothesize that soil enrichment with Mo will result in increased vegetative tissue production (thalli) by the terrestrial cyanobacterium, Nostoc commune.  In June 2006, all thalli were quantified and removed from belt transects with seven 1 m² quadrats per transect.  One transect was inoculated with 0.10 g dried ground thalli of N. commune/m² and enriched with Mo and Fe (1 L/m² of Bold’s basal media).  Another transect was inoculated with the same amount of N. commune in distilled water.  A control transect received the same volume of distilled water alone, and a reference control transect (nothing added, nothing removed) was quantified for evaluation of thalli movement by wind.  In June 2010, an additional transect was enriched with 0.10 g molybdate/m².  No thalli were removed at the start of this study.  The results of the 2006-2010 study showed that Mo/Fe enrichment resulted in a significant increase in thalli (p=0.003, t-test).  Inoculation with N. commune did not cause a significant difference (p=0.12, t-test).  The reference control had a significantly higher mass of thalli (p=.011, t-test) when compared to the control. This indicates that wind dispersal of thalli did not compromise the field study. The 2010-2011 study showed a significant increase with Mo enrichment without Fe (p=0.015, t-test).  Our conclusion is that soil enrichment with as little as 0.039g of Mo/m² greatly increases N. commune production.  This study has potential implications for climate change mitigation in semi-arid regions via increased carbon sequestration.