English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

. Understanding the dynamics of marine phytoplankton productivity requiresmechanistic insight into the non-linear coupling of light absorption,photosynthetic electron transport and carbon fixation in response toenvironmental variability. In the present study, we examined the variabilityof phytoplankton light absorption characteristics, light-dependent electrontransport and 14C -uptake rates over a 48 h period in the coastalsubarctic north-east (NE) Pacific. We observed an intricately coordinatedresponse of the different components of the photosynthetic process to diurnalirradiance cycles, which acted to maximize carbon fixation, whilesimultaneously preventing damage by excess absorbed light energy. Inparticular, we found diurnal adjustments in pigment ratios, excitation energytransfer to reaction centre II (RCII), the capacity for non-photochemicalquenching (NPQ), and the light efficiency ( α ) and maximum rates( Pmax ) of RCII electron transport (ETR RCII ) and 14C uptake. Comparison of these results from coastal waters toprevious observations in offshore waters of the subarctic NE Pacific providesinsight into the effects of iron limitation on the optimization ofphotosynthesis. Under iron-limited, low-biomass conditions, there was asignificant reduction of iron-rich photosynthetic units per chlorophyll  a ,which was partly offset by higher light absorption and electron transport perphotosystem II (PSII). Iron deficiency limited the capacity of phytoplanktonto utilize peak midday irradiance for carbon fixation and caused anupregulation of photoprotective mechanisms, including NPQ, and the decouplingof light absorption, electron transport and carbon fixation. Such decouplingresulted in an increased electron requirement ( Φe,C ) anddecreased quantum efficiency ( ΦC ) of carbon fixation at theiron-limited station. In both coastal and offshore waters, Φe,C and ΦC correlated strongly to NPQ, albeitwith a significantly different slope. We discuss the implications of ourresults for the interpretation of bio-optical data and the parameterizationof numerical productivity models, both of which are vital tools in monitoringmarine photosynthesis over large temporal and spatial scales.

Diurnal regulation of photosynthetic light absorption, electron transport and carbon fixation in two contrasting oceanic environments