The fate of photons absorbed by phytoplankton in the global ocean

Abstract

Solar radiation absorbed by marine phytoplankton can follow three possible paths. By simultaneously measuring the quantum yields of photochemistry and chlorophyll fluorescence in situ, we calculate that, on average, ~60% of absorbed photons are converted to heat, only 35% are directed toward photochemical water splitting, and the rest are reemitted as fluorescence. The spatial pattern of fluorescence yields and lifetimes strongly suggests that photochemical energy conversion is physiologically limited by nutrients. Comparison of in situ fluorescence lifetimes with satellite retrievals of solar-induced fluorescence yields suggests that the mean values of the latter are generally representative of the photophysiological state of phytoplankton; however, the signal-to-noise ratio is unacceptably low in extremely oligotrophic regions, which constitute 30% of the open ocean.

Seasonal development of iron limitation in the sub-Antarctic zone

“…3c, d). This is in agreement with similar observations made in the Ross Sea, the high-latitude North Atlantic and the equato- rial Pacific (Behrenfeld et al, 2006;Lin et al, 2016;Macey et al, 2014;Ryan-Keogh et al, 2017a), all regions where the phytoplankton communities are subject to iron limitation. Elevated ratios of F m Chl −1 are potentially indicative of an energetically decoupled pool of chlorophyll that possesses a higher fluorescence yield than PSII at F m (Macey et al, 2014;Ryan-Keogh et al, 2012, 2017aSchrader et al, 2011).…”

“…Shown are averages with ±standard deviations, where n = 6 − 12 for Chl a and n = 6 − 7 for nitrate (see Table S1 for specific details). Lin et al, 2016;Macey et al, 2014;RyanKeogh et al, 2017a). To determine these relative changes in photophysiology, the absolute difference in F v / F m between the control and iron addition bottles was calculated at 24 h, (F v / F m ) (Ryan-Keogh et al, 2013).…”

Enhancement of Non-photochemical Quenching as an Adaptive Strategy under Phosphorus Deprivation in the Dinoflagellate Karlodinium veneficum

“…It was estimated that as high as 75% of the absorbed light energy could be eliminated by this thermal dissipation (Demmig-Adams et al, 1996; Niyogi, 1999). In the global ocean, about 60% of photons absorbed by marine phytoplankton are converted to heat (Lin H. et al, 2016). …”

The influence of phytoplankton pigments composition and dominant cell size on fluorescence-derived photophysiological parameters and implications for primary production rates

“…σPSII was negatively correlated to the proportions of Zeaxanthin and Lutein (Table 3) (Bibby et al 2008); Southern Ocean waters (Holeton et al 2005;Suggett et al 2009;Lin et al 2016); tropical and subtropical Pacific and Atlantic waters (e.g. Behrenfeld et al 2006;Moore et al 2008;Browning et al 2014, Lin et al 2016; shelf and coastal waters Suggett et al 2009). The variability found in these results encourages the search for patterns and for better interpretations of photo-physiology.…”

“…However, the relationship between chlorophyll fluorescence and photochemistry becomes non-linear as a suite of heat losses mechanisms will come into play when cells are exposed to high light (Papageorgiou and Govindjee 2004;Lin et al 2016). Three competing pathways of the absorbed photons by the PSII: photosynthesis (ØP), fluorescence (ØF) and heat dissipation (ØH).…”