Laboratory experiments under controlled chemical conditions have found that phytoplankton biomass will conform to the Redfield Ratio even when environmental nutrient levels exceed them, suggesting that ecological adaptation to oceanic nutrient ratios is not the only governing mechanism (contrary to one of the mechanisms initially proposed by Redfield). However, subsequent modeling of feedback mechanisms, specifically nitrate-phosphorus coupling fluxes, do support his proposed mechanism of biotic feedback equilibrium, though these results are confounded by limitations in our current understanding of nutrient fluxes.