Comparison of Photoacclimation in Twelve Freshwater Photoautotrophs (Chlorophyte, Bacillaryophyte, Cryptophyte and Cyanophyte) Isolated from a Natural Community

Abstract

Different representative of algae and cyanobacteria were isolated from a freshwater habitat and cultivated in laboratory to compare their photoacclimation capacity when exposed to a wide range of light intensity and to understand if this factor may modify natural community dominance. All species successfully acclimated to all light intensities and the response of phytoplankton to increased light intensity was similar and included a decrease of most photosynthetic pigments accompanied by an increase in photoprotective pigment content relative to Chl a. Most species also decreased their light absorption efficiency on a biovolume basis. This decrease not only resulted in a lower fraction of energy absorbed by the cell, but also to a lower transfer of energy to PSII and PSI. Furthermore, energy funnelled to PSII or PSI was also rearranged in favour of PSII. High light acclimated organisms also corresponded to high non-photochemical quenching and photosynthetic electron transport reduction state and to a low Φ'M. Thus photoacclimation processes work toward reducing the excitation pressure in high light environment through a reduction of light absorption efficiency, but also by lowering conversion efficiency. Interestingly, all species of our study followed that tendency despite being of different functional groups (colonial, flagellated, different sizes) and of different phylogeny demonstrating the great plasticity and adaptation ability of freshwater phytoplankton to their light environment. These adjustments may explain the decoupling between growth rate and photosynthesis observed above photosynthesis light saturation point for all species. Even if some species did reach higher growth rate in our conditions and thus, should dominate in natural environment with respect to light intensity, we cannot exclude that other environmental factors also influence the population dynamic and make the outcome harder to predict.

Vertical patterns of metabolism in three contrasting stratified lakes

“…There are two explanations for an increase in a in metalimnion. Either it can be due to physiological acclimation in the phytoplankton (Grobbelaar et al 1995;MacIntyre et al 2002;Deblois et al 2013) or it can be due to an increase in biomass of phytoplankton in this zone (Amand and Carpenter 1993;Hamilton et al 2010). To explore whether the higher metalimnetic a values were dictated by higher levels of phytoplankton biomass with depth, we examined daily profiles of Chl a fluorescence measured in Vedsted Lake.…”

Characterizing the Absorption Properties for Remote Sensing of Three Small Optically-Diverse South African Reservoirs

“…A similar effect is observed in Hartbeespoort for accessory pigments allophycocyanin (AP C = 11.2 × chla 0.59 , r 2 = 0.68, N = 34) and pheophytin (P heo = 0.16×chla 0.9522 , r 2 = 0.95, N = 38). Accessory pigments are modulated either by high light and nutrient exposure (e.g., [63]) or through other physiological processes reflected by changes in gross biomass. The equations for the PC:chl-a ratio versus chl-a were derived mathematically from the power-law function and are, therefore, not a result of "spurious correlation" [64].…”

“…This effect might be related to nitrogen limitation as cell abundance increases [65]; however, nutrient data acquired simultaneously reveal no shortage of total nitrogen (or other nutrients) associated with reduced PC:chl-a ratios ( Figure 17C). An alternative explanation is that phycobilipigment production is reduced in high light, shallow mixed surface scum layers [63,66] or in fast growth scenarios. While a precise explanation for this effect remains somewhat unknown, the observation has some important implications for extremely high biomass and surface scum scenarios.…”

Effects of Small-Scale Gold Mining Tailings on the Underwater Light Field in the Tapajós River Basin, Brazilian Amazon

“…To calculate Z c , we adopted E c (PAR) based on the freshwater phytoplankton minimum light requirement described by Deblois et al [47]. The authors reported that Chlamydomonas sp.…”

“…(Chlorophyta) (identified in this study) shows a growth rate close to zero when exposed to irradiance of 14 µEm −2 s −1 , whereas other species, such as Aulacoseira granulate (diatom) and Cryptomonas obovata (Cryptophyta), present a growth rate of up to 0.2 divisions/day when exposed to the same light regime. For freshwater phytoplankton communities, a minimum E c of 14 µEm −2 s −1 was defined as a general compensation irradiance as described in Deblois et al [47] and therefore used as input to calculate Z c in Equation (9). Furthermore, analyses of critical depth must take into account the depth of the mixing layer (Z m ).…”