Taxon-specific differences in photoacclimation to fluctuating irradiance in an Antarctic diatom and a green flagellate

Abstract

Photoacclimation towards rapid changes in irradiance was studied in 2 Antarctic microalgae, the diatom Chaetoceros brevis (Bacillariophyceae) and the flagellate Pyramimonas sp. (Prasinophyceae). Both species were subjected to 3 different light regimes. Two regimes of vertical mixing (1:1 h and 3:3 h high light:low light) were superimposed on a diurnal light cycle mimicking the solar sine. For both species, maximum growth was recorded at the fastest rates of light fluctuation (1:1 h). The light regimes had a minor effect on growth rates of the flagellate but growth in the diatom was reduced significantly at moderate rates of mixing (3:3 h). While xanthophyll cycling was active in both species, fluorescence analysis with a dual-modulated fluorometer showed that down-regulation of photosynthetic efficiency was more pronounced in Pyramimonas sp. (ca. 50%) than in C. brevis (ca. 30%). The ratio of photoprotectors to chlorophyll a was not significantly affected by the light regime, neither in the flagellate nor in the diatom. In the flagellate, state transition offered an additional means of energy dissipation during the periods of high irradiance. The diatom apparently acclimated to the average light intensity received and not to the maximum irradiance. It can be reasoned that this strategy led to photodamage during the 3:3 h cycling. It is argued that enhanced maintenance costs associated with necessary repair processes can explain the reduced growth rate that was observed. The ecological consequences for large bloom-forming diatom species are briefly discussed.

The spectral sensitivity of phytoplankton communities to ultraviolet radiation‐induced photoinhibition differs among clear and humic temperate lakes

“…3) and potential diurnal variation in the vertical distribution of phytoplankton due to phototactic motility (Tilzer 1973) introduces additional uncertainty into estimates of the spectral irradiance history of the epilimnetic communities we sampled. Alternatively, if the differences in e k we determined reflect acclimation of phytoplankton to the maximum rather than mean irradiance experienced (van Leeuwe et al 2005), then it would not be surprising that DOC was a better predictor of e k values than Ē % UVR .…”

Temperature and photoperiod effects on phytoplankton growing under simulated mixed layer light fluctuations

“…However, our results showed that S. minutulus, N. acicularis, and L. redekei did change their P-I curves under fluctuating light to compensate for this. Enhanced rates of photosynthesis would also lead to higher maintenance costs (van Leeuwe et al 2005;Dimier et al 2009), which could also contribute to a decrease in growth rates. Accordingly, the reason that some authors found no change in growth rates under fluctuating light compared to a constant or sinusoidal regime of the same average irradiance and photoperiod (Litchman 2000;HavelkovaDousova et al 2004;Dimier et al 2009) may have been that the degree of saturation of photosynthesis was similar in the respective regimes.…”

“…Eluent B consisted of acetonitrile and acetone (45 : 55). Sixty microliters of extract was injected with a water packing of 20 mL before and 10 mL after the sample (Wright et al 1997;van Leeuwe et al 2006). Chl a from Anacystis nidulans (Sigma-Aldrich) was used as a standard.…”

Microalgal community structure and primary production in Arctic and Antarctic sea ice: A synthesis

“…Early in the season, irradiance levels below sea ice are low, due to the low angle of incoming solar radiation and as snow cover may attenuate irradiance (Palmisano et al, 1987). Microalgae can acclimate to low irradiance levels by expansion of the light-harvesting complexes and adjustment of the pigment composition (Van Leeuwe et al, 2005;Van Leeuwe and Stefels, 2007;AlouFont et al, 2013). Changes in the structure of the photosynthetic units may be accompanied by a decrease in their numbers (Barlow et al, 1988;Thomas et al, 1992).…”