Determination of the cross‐section absorption coeffcient of individual phytoplankton cells by analytical flow cytometry

Abstract

An empirical relationship between the cellular cross-section absorption coefficient (a) and the Chl a fluorescence of individual plankton cells was established. Chl a fluorescence of single cells was measured in a flow cytometer with 488-nm argon-ion laser excitation. Absorption by dilute suspensions of cells was measured spectrophotometrically and normalized to cell number for computation of (r(488) (m2 cell-l). At the high excitation irradiances characteristic of lasers, a constant proportion of photons absorbed by photosynthetic pigments was re-emitted as Chl a fluorescence; a strong correlation was observed between absorption at 488 nm and Chl a fluorescence (r2 = 0.93; P << 0.00 1). The regression predicted the total phytoplankton absorption coefficient [a,,,,(488) (m-l)] at 488 nm for mixtures of five monospecific cultures with <9% error. For field samples, discrepancies between the flow cytometric method and the filter pad spectrophotometric method for estimating a,,,,(488) were greater. Relatively large, rare phytoplankton cells accounted for a disproportionate percentage of total a,,,,(488). The coherence between absorption at 488 nm and at other wavelengths was high and provides a basis for extrapolating from (r(488) to single-cell absorption coefficients at all visible wavelengths. The single-cell spectral absorption coefficients can be used to compute total in situ photon absorption for modeling light-limited photosynthetic rates of individual phytoplankton cells in the ocean.

Modeling in situ phytoplankton absorption from total absorption spectra in productive inland marine waters

“…UTEX 1652, Peridinium triquetrum), prymnesiophytes (Isochrysis galbana, Pavlava lutheri), diatoms (Chaeotoceros gracilis, Cylindrotheca fusiformis, Nitzschia closterium, Phaeodactylum tricornium, SkeIetonema costatum, Thalassiosira weisflogii), prasinophyte (Pyramimona parkerae), and chlorophytes (Ilunaliella euchlora, Nannochloris sp.) (from Perry and Porter 1989). Each spectrum is normalized to its respective spectrally averaged absorption coefficient to remove the effects of concentration and major packaging.…”

“…The second approach is direct measurement of individual cells by microspectrophotometry (Iturriaga et al 1988;Iturriaga and Siegel 1988) or by flow cytometry (Perry and Porter 1989). The third approach consists of filtering total particulates from a water sample (Yentsch 1962;Kiefer and SooHoo 1982;Kiefer 1984, 1988) and then separating the phytoplankton from the detrital component chemically, statistically, or by modeling (Kishino et al 1985;Morrow et al 1989;Cleveland and Perry in prep.).…”

Contributions of phytoplankton and bacteria to the optical backscattering coefficient over the Mid-Atlantic Ridge

“…To aid in the understanding of bulk optical properties of the ocean, flow cytometry has been used for studies of the absorption coefficient (Perry & Porter 1989). Other studies have combined flow cytometric counts of the marine pico-and nanoplankton communities with attenuation and scattering (Durand & Olson 1996, Chung et al 1998, Claustre et al 1999, Green et al 2003a, Oubelkheir et al 2005, Grob et al 2007, Montes-Hugo et al 2009).…”

Contributions of phytoplankton and other particles to inherent optical properties in New England continental shelf waters

“…Flow cytometry has been used to enumerate and distinguish specific groups of particles, and advances have been made toward determining distributions of particle D, n, and nЈ with application to determining particle contributions to IOPs (Ackleson and Spinrad 1988;Olson et al 1989;Perry and Porter 1989;Olson et al 1993;Marie et al 1997;DuRand and Olson 1998;Claustre et al 1999;Green et al 2003).…”