Deriving in situ phytoplankton absorption for bio‐optical productivity models in turbid waters

Abstract

As part of Hyperspectral Coupled Ocean Dynamics Experiment, a high-resolution hydrographic and bio-optical data set was collected from two cabled profilers at the Long-Term Ecosystem Observatory (LEO). Upwelling-and downwelling-favorable winds and a buoyant plume from the Hudson River induced large changes in hydrographic and optical structure of the water column. An absorption inversion model estimated the relative abundance of phytoplankton, colored dissolved organic matter (CDOM) and detritus, as well as the spectral exponential slopes of CDOM and detritus from in situ WET Labs nine-wavelength absorption/attenuation meter (ac-9) absorption data. Derived optical weights were proportional to the parameter concentrations and allowed for their absorptions to be calculated. Spectrally weighted phytoplankton absorption was estimated using modeled spectral irradiances and the phytoplankton absorption spectra inverted from an ac-9. Derived mean spectral absorption of phytoplankton was used in a bio-optical model estimating photosynthetic rates. Measured radiocarbon uptake productivity rates extrapolated with water mass analysis and the bio-optical modeled results agreed within 20%. This approach is impacted by variability in the maximum quantum yield (Ф) and the irradiance light-saturation parameter (Ek (PAR)). An analysis of available data shows that Фmax variability is relatively constrained in temperate waters. The variability of Ek(PAR) is greater in temperate waters, but based on a sensitivity analysis, has an overall smaller impact on water-column-integrated productivity rates because of the exponential decay of light. This inversion approach illustrates the utility of bio-optical models in turbid coastal waters given the measurements of the bulk inherent optical properties.

Variations in Spectral Absorption Properties of Phytoplankton, Non-algal Particles and Chromophoric Dissolved Organic Matter in Lake Qiandaohu

“…The IOPs of the specific OACs present play a vital role in determining underwater light distribution, photosynthetic process and remote sensing reflectance [1]. For example, the spectral absorption properties of the three OAC types and the specific light absorption by phytoplankton have been well documented in the literature, which illustrates that the dynamics controlling the distribution of OACs are important for determining the light attenuation and primary production in open oceans and productive inland waters [2][3][4][5][6][7][8].…”

A Novel Statistical Approach for Ocean Colour Estimation of Inherent Optical Properties and Cyanobacteria Abundance in Optically Complex Waters

“…An example of the a ph spectra measured (black), modelled with the fixed number of EOF modes (green), and modelled with EOF modes selected with a stepwise fit (blue) for one data set. Knowledge of the shape of the phytoplankton absorption spectra is needed in models that estimate phytoplankton chlorophyll concentrations [64,65], or as an input into bio-optical models that predict carbon fixation rates for the global ocean [66][67][68]. The shape and the magnitude of the phytoplankton absorption spectra is controlled primarily by the concentration of various photosynthetic and photoprotective pigments and by the level of the pigment package effect within the cells.…”

Density dependent expression of a diatom retrotransposon

“…This is because the growth rates and nutrient kinetics of diatoms favor these types of environments (Tozzi et al, 2004). In the Mid-Atlantic, the near shore coastal environment is turbulent due to interactions of synoptic wind patterns with bathymetry and continental boundaries (Gong et al, 2010;Malone, 1976;Oliver et al, 2004) and are nutrient rich due to coastal upwelling and coastally trapped river plumes . These physical interactions predict that the physical geography of coastal environments is predictive of dense populations of diatoms (Fig.…”