Relationships between vertical mixing and photoadaptation of phytoplankton: similarity criteria

Abstract

In their natural environment, phytoplankton are exposed to fluctuations in incident irradiance due to vertical displacements in the water column induced by turbulent fluid motion. Physiological adaptation to these fluctuations results in variation in a number of measurable quantities (e.g. parameters of P-I curves, fluorescence yield, chemical composition), each of which have different time-scales of adaptation. A reaction-diffusion model is analyzed to determine the physical conditions under which a given physiological adaptation would be of ecological importance and thus may show variation in the photoadaptive variable with depth in a mixing layer. Two non-dimensional numbers control the dynamics. KJP2y expresses the ratio of the mixing rate to the photoadaptation rate (K, is the eddy diffusion coefficient, l' is the mixing length, and y is the photoadaptation rate constant for given variable). k,t' is the ratio of the mixing length scale to the optical length scale (k, is the attenuation coefficient for scalar irradiance). When KJP2y is low and k,P is high, photoadaptation proceeds fast enough to create variations in depth in the photoadaptive variable and conversely, when &/P&( is high and k,t' is low, turbulent fluid motion dissipates any depth variation. By observing the variation in depth of several photoadaptive variables, each with a different photoadaptation time-scale, the mixing rate of the water can be estimated. Data from laboratory and field experiments are used to illustrate applications.

Interactive effects of increased pCO2, temperature and irradiance on the marine coccolithophoreEmiliania huxleyi(Prymnesiophyceae)

“…Rijssel & Gieskes, 2002). Cells of E. huxleyi are known to adjust chlorophyll content faster than many other species, which may minimize photo-damage (Lewis et al, 1984). This type of photoadaptation may be an adaptive trait under changing future stratification regimes.…”

An in vivo fluorescence method for the continuous in situ estimation of phytoplankton photosynthetic characteristics

“…The instantaneous in situ estimation of the fluorescence ratio FA/FB eliminates this source of error and allows the continuous in situ measurement of photosynthetic characteristics on either the vertical or the horizontal axis. Since it is well known that vertical mixing is an important parameter affecting phytoplankton photosynthesis (Falkowski 1983), the possibility of measuring a photosynthetic response on a continuous basis may prove to be valuable in deriving models of vertical mixing such as the one proposed by Lewis et al (1984).…”

Pigments, size, and distributions of Synechococcus in the North Atlantic and Pacific Oceans

“…The large squares represent data from the coastal stations used as examples in panel A. The regression equation was y = 0.094 + 0.013x; r2 = 0.50, y1 = 130, P < 0.005. be used to calculate mixing rates in surface Distribution of mean cell size forward light waters in the same way as proposed for oth-scatter) -Light scattering by particles is not er photoadaptive processes (Harris 1980; simple to interpret; its angular intensity dis- Lewis et al 1984; Welschmeyer and Hoepff-tribution at a given wavelength is deterner 1986; Cullen and Lewis 1988). We have mined by a complex interaction between done simple laboratory experiments de-size, shape, and refractive index (Van de signed to put a time scale on photoaccliHulst 1957; Ackleson and Spinrad 1988).…”

“…The absorptive properties of these high-plhycourobilin strains are not very different from those of the eucaryotic phytoplankton because they have a strong absorption peak at about 495 nm in addition to the 545-nm absorption peak of phycoerythrobilin. This pigment complement could explain why photosynthetic action spectra measured in oceanic waters do not yield the patterns one would expect from cells containing mainly phycoerythrobilin (Lewis et al 1987). …”