Variability in spectral and nonspectral measurements of photosynthetic light utilization efficiencies

Abstract

The aim of this study was to quantify the variability in and differences between spectral and nonspectral measurements: of light utilization efficiencies for natural phytoplankton communities, in order to evaluate possible consequences for blo-opt~cal models of in s j t~l p]-1ma1-y production (P). Field samples were collected at 4 coastal stations durlng a 1 d transect (July 23, 1988) and productivity P(AA,,z) were derived. Significant spatial variability in all bio-optical parameters was noted for communities in the surface waters and the chlorophyll maximum. For surface waters, there was significant variability in the 525 to 600 nm region of the spectral signatures of dl[dA,,z) and P(AA,,z) which was attributable to phycobilins not resolved In absorption spectra. The importance of light absorption by photosynthetic pigments other than chlorophyll a (chl), and thcir assoc~ated Impact upon absorption-based production parameters, increased w~t h light depth. One consequence was a close correspondence between AQ,, and P(AA,,z) at depth w h~c h was not evident in surface waters A second consequence was that while spectrally weighted and whlte l~g h t estimates of quantum yield were occasionally sim~lar In surface waters, spectral estimates for all chlorophyll maximum communities were 4-to 6-fold higher than white light measurements. Results confirm previous observations that white light measures of quantum yield can significantly underestimate quantum yield for subsurface communities of phytoplankton (Prezelin e t al. 1989) a n d provide a conceptual base on which to improve existing and future spectral models of in situ photosynthetic quantum yield.

Chromoprotein- and pigment-dependent modeling of spectral light absorption in two dinoflagellates, Prorocentrum minimum and Heterocapsa pygmaea

“…Our data can also be used as basic information for the interpretation of in situ sensed bio-optical data from multi-wavelength transmissometers and from remote sensing of ocean color (cf. I r k 1983, Pr6zelin & Boczar 1986, Mitchell & Kiefer 1988, Schofield et al 1991, Johnsen et al 1994). …”

“…Both models can in addition be used as a tool to understand and to model/ reconstruct photosynthetic efficiency (aB) with and without the impact of photoprotective pigments (aB = @ , , . amph; Bidigare et al 1989, Sakshaug et al 1991, Schofield et al 1991.…”

Darkness at the break of noon: Phytoplankton production in the Lower Mississippi River

“…Measurements of the photosynthesis-irradiance (P-I) relationship were made in the laboratory using a Lewis et al 1985;Schofield et al 1991). This instrument consisted of an aluminum block bored to hold 20 mL scintillation vials at 21 irradiances from 0 mmol photon m 22 s 21 to 700 mmol photon m 22 s 21 .…”

Photosynthesis–irradiance parameters of marine phytoplankton: synthesis of a global data set

“…Samples where incubation temperatures differed from in situ temperatures by more than 2 • C were removed from the database. It is well known that the light spectrum has a significant effect on the magnitude of light-limited photosynthesis (α B ) and the derived light saturation parameter (E k ) (Kyewalyanga et al, 1997;Schofield et al, 1991). We have included in the database quality flags indicating whether a correction factor for the spectrum of the lamp was applied to obtain a readily intercomparable broadband (white light) value (e.g.…”