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Light absorption by phytoplankton in the North Pacific Subtropical Gyre
Author(s) -
Letelier Ricardo M.,
White Angelicque E.,
Bidigare Robert R.,
Barone Benedetto,
Church Matthew J.,
Karl David M.
Publication year - 2017
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10515
Subject(s) - ocean gyre , photosynthesis , chlorophyll a , phytoplankton , photic zone , absorption (acoustics) , chlorophyll , mixed layer , oceanography , photosynthetic pigment , pigment , chlorophyll c , fucoxanthin , subtropics , chemistry , atmospheric sciences , botany , chlorophyll fluorescence , biology , nutrient , carotenoid , physics , ecology , geology , optics , organic chemistry
To constrain the energy fueling photosynthesis in the North Pacific Subtropical Gyre (NPSG) we characterize the variability of phytoplankton absorption spectra in conjunction with that of the light field at Station ALOHA (22 ° 45′N, 158 ° 00′W). Furthermore, we decompose the phytoplankton absorption into photosynthetic and photoprotective components based on high‐performance liquid chromatography pigment analysis. Between January 2006 and December 2012 the variability in chlorophyll‐specific absorption (a ϕ ∗) above the deep chlorophyll maximum (DCM) layer was driven by changes in photoprotective carotenoid concentrations while the chlorophyll‐specific absorption of photosynthetic pigments (a ϕ ( P S P ) ∗) remained nearly constant with a mean (± SD) value of 0.008 ± 0.001 m 2 (mg chl a ) −1 . In contrast, below the DCM layer changes ina ϕ ∗resulted from increases in the relative contribution of photosynthetic pigments with depth, suggesting that the constancy ina ϕ ( P S P ) ∗above the DCM layer is controlled by nutrient limitation. While the daily photon fluxes absorbed by photosynthetic pigments in the upper 45 m did not vary at a seasonal scale, averaging 0.45 ± 0.12 mol quanta m −2 d −1 in winter and 0.46 ± 0.10 mol quanta m −2 d −1 in summer, when integrated over the upper 200 m these fluxes ranged from 0.64 ± 0.16 to 0.79 ± 0.19 mol quanta m −2 d −1 in winter and summer, respectively. Based on the rate of photons trapped by the photosynthetic pigments and on the seasonal euphotic zone depth integrated gross O 2 evolution rates derived fromH 2 18O in situ incubations we estimate a mean photosynthetic yield of ∼0.1 mol O 2 evolved per mol quanta absorbed by photosynthetic pigments.