Ocean acidification decreases the light-use efficiency in an Antarctic diatom under dynamic but not constant light

摘要

- There is increasing evidence that different light intensities strongly modulate the effects ofudocean acidification (OA) on marine phytoplankton. The aim of the present study was to investigateudinteractive effects of OA and dynamic light, mimicking natural mixing regimes.ud- The Antarctic diatom Chaetoceros debilis was grown under two pCO2 (390 andud1000 latm) and light conditions (constant and dynamic), the latter yielding the same integratedudirradiance over the day. To characterize interactive effects between treatments,udgrowth, elemental composition, primary production and photophysiology were investigated.ud- Dynamic light reduced growth and strongly altered the effects of OA on primary production,udbeing unaffected by elevated pCO2 under constant light, yet significantly reduced underuddynamic light. Interactive effects between OA and light were also observed for Chl productionudand particulate organic carbon quotas.ud- Response patterns can be explained by changes in the cellular energetic balance. While theudenergy transfer efficiency from photochemistry to biomass production (Φe,C) was not affectedudby OA under constant light, it was drastically reduced under dynamic light. Contrastingudresponses under different light conditions need to be considered when making predictionsudregarding a more stratified and acidified future ocean.