The Effect of Nitrogen Limitation on the Absorption and Scattering Properties of the Marine Diatom Thalassiosira pseudonana,
Abstract
Optical properties of the marine diatom thalassiosira pseudonana were examined in nitrate-limited semicontinuous cultures at four rates of growth. Two experiments were conducted at each growth rate in which sampling of the culture was done at either the dark-to-light (D-L) or light-to-dark (L-D) transition of a 12 h photoperiod. Optical cross-sections and efficiency factors for absorption, scattering, and attenuation were calculated from measurements of the spectral absorption and beam attenuation coefficients, cell concentration, and the size distribution of cells in suspension. The refractive index of cells was calculated from this data using an inverse method. Nitrogen limitation strongly influences the optical properties of this species. Absorption cross-sections increased more than twofold with increasing growth rate, predominantly caused by increases in the imaginary part of the refractive index, n'. Variability in n(1) was strongly correlated with intracellular chlorophyll alpha concentration. In contrast; to absorption, scattering cross-sections were not a strong function of growth rate but exhibited significant differences between D-L and L-D experiments at any given growth rate. Variability in the real part of the refractive index was correlated with intracellular carbon concentration. The chlorophyll alpha-specific absorption coefficient decreased with increasing growth rate in response to decreases in the carotenoid to chlorophyll alpha ratio and increased pigment packaging. The chlorophyll alpha-specific scattering coefficient also decreased with increasing growth rate, and was correlated with the cellular carbon to chlorophyll alpha ratio. Our results suggest that the optical properties of phytoplankton populations in nitrogen-limited surface waters may be significantly altered from those in deeper portions of the water column.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1996
- Accession Number
- ADA324832
Entities
People
- Daiusz Stramski
- Dale A. Kiefer
- Rick A. Reynolds
Organizations
- University of Southern California