ATP as a biomass indicator for closed ecosystems.

Nucleotide measurements have been used as biomass indicators in microbial ecology. We report the use of this metric in materially closed, energetically open microbial ecosystems. Our results indicate that: (i) both ATP concentrations and pO2 show an increase from time of closure; (ii) ATP concentrations (0.2 1.2 ng/ml) are approximately 2 3 times higher than open ocean water; (iii) there is an apparent oscillation of ATP concentrations on the order of 50 days; and (iv) within experimental limitations the ratios of ATP concentrations to observed total cell counts is constant.