Bio-optical properties of the subtropical North Atlantic. I. Vertical variability

Abstract

Studies of the physiological and optical properties of phytoplankton of the subtropical open ocean are rare. Yet, assessing the spatial and temporal variation in t h e photo-physiological parameters and chlorophyll-specific absorption coefficients of marine phytoplankton is essential if we are to account for the relative importance of pelagic systems in the global carbon economy. As a contribution to this general goal, the photosynthetic and bio-optical properties of phytoplankton were measured at 5 stations across a broad swath of the subtropical North Atlantic Ocean. Similar vertical patterns in pigment composition, chlorophyll-specific absorption coefficients and the photosynthesis-. irradiance parameters were observed at all 5 stations. A considerable proportion of the vertical variation in the chlorophyll-specific absorption coefficients was caused by vertical changes in the proportion of the non-photosynthetic pigment (NPP) zeaxanthin relative to chlorophyll a. On the other hand, pigment packaging appeared to'have a minor influence on the optical characteristics of .the picoplankton-dominated region: chlorophyll-specific absorption coefficients observed at the red peak frequently exceeded 0.02 m2 (mg chl a)-'. Multiple, linear-regression analysis was used to examine the value of some commonly-measured environmental variables as potential predictors of the photosynthetic parameters aB and P : . The results showed that indices of ambient irradiance, nutrient flux or nutrient concentration, separately or in combination, account for a significant fraction of the total variance in the photosynthetic parameters. The stability in the distribution patterns of both the photosynthetic parameters and absorptive characteristics of subtropical phytoplankton assemblages and in the principal factors governing the variability in these properties may facilitate the selection of appropriate input parameters for use in models of primary production for this hydrographic region.

Photosynthesis–irradiance parameters of marine phytoplankton: synthesis of a global data set

“…Establishing relationships between taxonomic composition and phytoplankton photophysiology will require simultaneous measurements of community structure alongside photosynthesis-irradiance experiments. The high range of photosynthetic parameters recorded at lower latitudes is largely caused by depth-dependent changes due to photoacclimation and photoadaptation (Babin et al, 1996;Bouman et al, 2000b;Huot et al, 2007) in highly stratified waters. Strong vertical gradients in nutrient supply and growth irradiance lead to a vertical layering of ecological niches, resulting in strong vertical gradients in species composition, and in the case of marine picocyanobacteria, high-light and low-light ecotypes are observed (Johnson et al, 2006;Zwirglmaier et al, 2007).…”

“…Although depth-dependent variability in the photosynthetic parameters can be examined in the MAPPS data set, in particular E k (Fig. 10), it has been argued that optical depth may be a more useful predictor of changes in the P-E parameters resulting from vertical changes in the photoacclimatory status of phytoplankton cells (Babin et al, 1996;Bouman et al, 2000b). In highly stratified and stable seas such as the oligotrophic gyres this may be the case, yet in more dynamic ocean conditions such as the Beaufort Sea, optical depth has been shown to have no more predictive skill, and sometimes less, than using depth alone (Huot et al, 2013).…”

Bio-optical modelling of primary production in the SW Finnish coastal zone, Baltic Sea: fast repetition rate fluorometry in Case 2 waters

“…(A, B) P M1 and E o (z); (C-H) P M1 , P M2 , P M3 as % of P M1 frequent sampling. Consequently, the interpolation of bio-optical parameters over seasons and/or depth intervals that are sparsely sampled -considered a weakness in PP modelling - (Bouman et al 2000), introduces greater error in the results from such hydrodynamically labile areas compared to results from (e.g.) the central basins of the oceans.…”

Absorption of light by phytoplankton, detritus, and dissolved organic substances in the coastal region of the Black Sea (July–August 2002)

“…In relatively calm waters characterized by the formation of a layer of elevated values of C a + p at depths of 16-20 m, the vertical distributions of the spectral characteristics a ph * ( ) λ and R were nonuniform and the indicated quantities decreased with depth as a result of changes in the degree of packing of pigments in the cells and the fraction of nonphotosynthetic photoprotector caroteinoids (Figs. 3 and 4) [10]. The other possible type of vertical profile corresponds to the constant distribution of a ph * ( ) λ in depth.…”