Proper estimation of marine gross O 2 production with 17 O/ 16 O and 18 O/ 16 O ratios of dissolved O 2

Recently, the method for estimation of marine gross production from measurements of 17 O/ 16 O and 18 O/ 16 O of dissolved O 2 has been improved by obtaining a rigorous equation for evaluation of gross production, and it has been suggested that small errors associated with approximations resulted in significant underestimation of gross production rates. The new equation requires accurate knowledge of the isotopic composition of photosynthetic and atmospheric oxygen. While the values for the latter have been determined very precisely, those of the former have never been measured. Here we present the first experimentally derived values of δ 17 O p and δ 18 O p of marine photosynthetic O 2 (−10.126 and −20.014 ‰). Based on these, we show that the suggested underestimation was not the result of approximation errors, rather it was caused by inaccurate estimated values of δ 17 O p and δ 18 O p .