Variability of phytoplankton light absorption in Canadian Arctic seas

Abstract

Phytoplankton light absorption spectra (aϕ(λ)) were measured in the Canadian Arctic (i.e., the Amundsen Gulf, Canadian Arctic Archipelago, northern Baffin Bay and the Hudson Bay system) to improve algorithms used in remote‐sensing models of primary production. The absorption by algae, dominated by picophytoplankton (<5 μm), was not the major light absorption factor in the four provinces; the colored dissolved organic matter (CDOM) contributed up to 70% of total light absorption. During the fall, the low total chlorophyll a‐specific aϕ*(443) (aϕ(443)/TChl a) coefficients of the Canadian High Arctic were associated with photoacclimation processes (i.e., the package effect) occurring in light‐limited environments. Low light availability and high proportion of CDOM (absorbing strongly the ultraviolet) seem to allow the growth of phytoplankton with accessory pigments absorbing light at longer wavelengths. The ratio of photoprotective and photosynthetic carotenoids (PPC:PSC) was inversely proportional with the salinity and the cell size, and mostly decreases throughout the Canadian High Arctic during fall. In return, the highest TChla‐specific phytoplankton light absorption coefficients at the blue peak (aϕ*(443)) were observed in the Hudson Bay system from September to October (i.e., fall) as well as in the Amundsen Gulf from May to July (i.e., spring/summer). These results will ultimately allow the accurate monitoring of phytoplankton biomass and productivity evolution that is likely to take place as a result of the fast‐changing Arctic environment.

Nutritive and photosynthetic ecology of subsurface chlorophyll maxima in Canadian Arctic waters

“…± < 0.001 µg C (µg chl a) −1 h −1 (µmol quanta m −2 s −1 ) −1 ) over the depth interval that separates surface and SCM samples in our study. Such a shift is similar to the statistical error attached to α estimates obtained with the 13 C method (here ± 11 % for a mean value of 0.027) and one order of magnitude smaller than the observed range of α values (0.027 ± 0.014; see also Brunelle et al, 2012) SCM communities located in a strongly stratified environment would benefit by acclimating to low irradiance. For C uptake, this expectation is consistent with the contrast between the data of Platt et al (1982), who found no vertical differences in uptake-irradiance parameters in weakly stratified waters (Baffin Bay), and our data set, where α was higher at the SCM than at the surface.…”

Assessment of ocean color data records from MODIS-Aqua in the western Arctic Ocean

“…In the western Arctic, we do not expect a dg (λ) to covary with C a as it does in lower latitude and oligotrophic oceans . High levels of CDOM in Arctic Ocean waters have been widely documented (e.g., Brunelle et al, 2012;Granskog et al, 2012;Guéguen et al, 2005;Matsuoka et al, 2013aMatsuoka et al, , 2011Matsuoka et al, , 2007Pegau, 2002;Stedmon et al, 2011). The basin as a whole receives the largest dissolved organic carbon input (and hence CDOM input) from rivers, relative to its size, than any other ocean basin (Rachold et al, 2004).…”

“…In the Labrador Sea, the OC4 algorithm was found to underestimate C a by 50% over most of its dynamic range , while in the western Arctic Ocean (i.e., Beaufort and Chukchi seas) and the Arctic region of the Atlantic, the bias has been consistently towards overestimation (Ben Mustapha et al, 2012;Matsuoka et al, 2007;Stramska et al, 2003;Wang and Cota, 2003). Atypically high absorption by chromophoric dissolved organic matter (CDOM) from river inputs to this Arctic region has been suggested as the main cause for C a overestimation from satellite radiometry (Brunelle et al, 2012;Matsuoka et al, 2007). Attempts at developing regionally tuned C a for the Arctic (Cota et al, 2004;Wang and Cota, 2003) have had mixed successes (Ben Mustapha et al, 2012;Matsuoka et al, 2007).…”

Apparent optical properties of the Canadian Beaufort Sea – Part 1: Observational overview and water column relationships

“…Historical observations were complemented only much more recently by measurements made in ice-free waters (Wang and Cota, 2003;Matsuoka et al, 2007Matsuoka et al, , 2009Matsuoka et al, , 2011Hill, 2008;Ben Mustapha et al, 2012;Brunelle et al, 2012), and no other measurements have been reported in between in the open literature, at least to our knowledge. Therefore, attenuation and reflectance properties of Arctic waters are still poorly known.…”