A high resolution bio-optical model of microalgal growth: Tests using sea-ice algal community time-series data

Abstract

A high resolution, two-dimensional (z, t) time-dependent model of microalgal growth has been developed in which simulated physiological responses arc determined by ambient temperature, spectral irradiance, nutrient concentration, and salinity. The model is based on the concept ofa maximum temperaturedependent growth rate that is subsequently reduced by limitations imposed from insufficient light or nutrients, as well as sub-or supraoptimal salinity. Limitation terms for these variables are derived from studies of nutrient-, light-, and salinity-dependent algal growth (or photosynthetic) rates that have been normalized to maximum observed rates with respect to each variable. Particular emphasis was placed on developing the formulation for light limitation, which includes the effects of diel changes in spectral irradiance, seasonal changes in photoperiod, and related adjustments in biochemical C : Chl a ratios. This level of detail was needed because the importance of light limitation has been demonstrated on diurnal, seasonal, and annual time scales in polar regions. The model was tested by comparing simulation results to a sea-ice microalgal bloom in McMurdo Sound, Antarctica, in 1982. Environmental information from 1982 and biological coefftcients derived from sea-ice communities were used as model input. Model results showed excellent agreement with microalgal bloom dynamics observed in 1982 under a variety of environmental conditions. Predicted Chl a standing crops were consistently within 15% of observations for the congelation ice and platelet ice, regardless of snow thickness (snow-free, 5-cm, and IO-cm snowcover scenarios were tested), and predicted vertical distributions of Chl a exhibited the same depthdependent pattern as observations. Microalgae living in many aquatic ecosystems experience widely fluctuating environmental conditions which profoundly influence rates of photosynthesis and growth. For example, in upwelling regions, ambient irradiance and temperature may change on time scales of hours as seawater from depth is advected to the surface. Similarly, estuarine and sea-ice algal assemblages may experience rapid diel and seasonal shifts in salinity and temperature. Accurate assessments of primary AcknowledgmentsWe thank Mike Lizotte, Steve Ackley, Jim Kremer, Dale Kiefer, John Cullen, and an anonymous reviewer for comments on earlier versions of this manuscript. We are also grateful to Dale Robinson and Mike Lizotte for helpful insights during the formulation of this model. We are particularly appreciative of the manner in which Susan Kilham handled all facets of the publication of this manuscript.

Parameterization of vertical chlorophyll <i>a</i> in the Arctic Ocean: impact of the subsurface chlorophyll maximum on regional, seasonal, and annual primary production estimates

“…More recently, it was suggested that Arctic phytoplankton are sufficiently acclimated to existing light conditions for maintaining saturated rates of carbon fixation during the course of a bloom as well as during the deepening of the SCM (Martin et al, 2010;Palmer et al, 2011). In addition, Huot et al (2013) showed that the Beaufort Sea phytoplankton communities are more "shade acclimated" than previously reported for high-latitude regions (Arrigo and Sullivan, 1994;Arrigo et al, 1998). It is especially critical to adopt appropriate photosynthetic parameters for the performance of our depth-integrated PP algorithm, taking into account the photoacclimation/adaptation of Arctic phytoplankton communities.…”

Impact of chromophoric dissolved organic matter on UV inhibition of primary productivity in the sea

“…Details of the model used in the present analysis can be found in Arrigo (1994); for convenience, the basic formulations are listed in Table 1. Diffuse attenuation by CDOM, not modeled by Arrigo (1994), has been described by the equation where KCDOM(h) and acDoM(h) are the diffuse attenuation and absorption coefficients (m-'), respectively, for CDOM, and p (dimensionless) is the mean cosine of the angular distribution of the downwelling light field.…”

“…Diffuse attenuation by CDOM, not modeled by Arrigo (1994), has been described by the equation where KCDOM(h) and acDoM(h) are the diffuse attenuation and absorption coefficients (m-'), respectively, for CDOM, and p (dimensionless) is the mean cosine of the angular distribution of the downwelling light field. It has been shown that dcDoM(h) takes the form…”

“…The l-dimensional model of Arrigo (1994) was used to compute the depth-dependent variation in primary production as a function of the spectral distribution of incoming solar radiation (280 to 700 nm). Included in the model were separate components for calculating the flux of atmospheric radiation, in-water bio-optics, and primary production.…”

“…Holm-Hansen et al (1993b) measured total partic'ulate absorption coefficients at 300 nm as ranging from 0.1 to 0.3 m-' in Southern Ocean waters. Specific absorption coefficients for Antarctic phytoplankton have been reported to exceed 0.1 m2 (mg chl a)-' within the UV range (Mitchell et al 1989, Arrigo 1994. Kopelevich et al (1987) showed that bacterial attenuation at 390 nm ranged from 0.002 m-' for Micrococcus sp.…”