Photosynthesis and photoprotection characteristics related to ROS production in three Chattonella (Raphidophyceae) species

Abstract

The toxic potential of Chattonella is associated with a high production of reactive oxygen species (ROS). Chattonella species can tolerate high irradiance levels but seems not to be efficient in the induction of nonphotochemical chl a fluorescence (NPQ) under light stress conditions. Therefore, we postulated that high ROS production of this microalgal group is related to the lack of effective photoprotection mechanisms. We compared the NPQ induction, xanthophyll cycle interconversion (XC), and the production of the ion superoxide (O2−) in Chattonella marina var. antiqua, Chattonella sp., and C. marina acclimated to 43 (LL) and 300 µmol photons · m2 · s−1 (HL). We also evaluated the photosynthetic characteristics of the three strains. Photosynthesis saturated at relative high irradiances (above 500 µmol photons · m2 · s−1) in LL and HL Chattonella strains. For the first time, we documented the conversion of diadinoxanthin into diatoxanthin in microalgae that have violaxanthin as the major XC carotenoid. The slow NPQ induction indicated that qE (fast component of NPQ) was not present, and this process was related to the interconversion of XC pigments. However, the quenching efficiency (QE) of deepoxidated xanthophylls was low in the three Chattonella strains. The strain with the lowest QE produced the highest amount of a O2−. Therefore, ROS production in Chattonella seems to be related to a low expression of XC‐related thermal PSII dissipation.

Hemolytic Activity in Relation to the Photosynthetic System in Chattonella marina and Chattonella ovata

“…Similarly, low growth (max. 0.46 d −1 , Figure 4d) was observed at the strain of C. ovata, compared to the isolates from Japan (0.8~1.4 d −1 ) under the similar condition, indicating the strain genetic difference and/or potential biological stress, such as co-existing bacteria [52,53]. The non-axenic C. marina and C. ovata culture in the present study were established at 2002 and 2003 [54,55], with no significant changes on growth rate and HA at 2015 [56].…”

“…Irradiance and iron are essential for most phytoplankton, especially phototrophic phytoplankters. Saturation light of C. marina was reported at 30~110 µmol m −2 s −1 under the suitable temperature (20~30 • C), salinity (20-35 psu) and nutritional condition, with the growth rate ranging from 0.3 to 1.4 d −1 [52,53]. The maximum growth rate of C. marina, our Hong Kong isolate, reached 0.41 d −1 (Figure 4c), located at the lower range of all the reported C. marina strains.…”

“…The maximum quantum yield (F v /F m ) is an essential indicator of algal cell health status. Changes in F v /F m have been observed when algae are exposed to endogenous or exogenous stressors, such as light [52,70,71], temperature [71], salinity [72], iron and algistat addition [73][74][75][76]. A significant decline in F v /F m of C. marina and C. ovata was shown in the present study under high light (Figure 3), in the dark (Figure 7), under iron depleted conditions (Figure 9) and the presence of PSII inhibitors (Figure 11), suggesting inactivation of PSII reaction center (RC) complexes and disruption of the electron transport chain [77,78].…”

“…The xanthophyll cycle consists of xanthophyll, viola, antheraxanthin and zea [89,90]. Similarly, expression of xanthophyll cycle interconversion in Chattonella was most likely related to the production of ion superoxide (O 2− ) [52], which may participate in the C. marina iron-uptake process [32]. High production of C. marina diadinoxanthin or zea would indicate that phototrophs were under stress (Figure 4(e1,f1)), compared to C. ovata (Figure 4(d2,e2)), suggesting that xanthophyll pigments play a role in dissipating excess excitation energy in the PS II of C. marina.…”

Effects of Harmful Algal Blooms on Fish and Shellfish Species: A Case Study of New Zealand in a Changing Environment

“…The higher potency of the Australian blooms (which killed at 66,000 cells L −1 compared to Japan at 500,000 cells L −1 where similar mass fish mortalities have occurred; see [ 199 ]) was attributed to the higher sensitivities of tuna and to the higher ichthyotoxicity of Australian high-light adapted algal strains [ 212 ]. The toxic potential of Chattonella is believed to be associated with a high production of reactive oxygen species [ 213 ]. Early life stages of the Japanese Pearl oyster, Pinctada fucata martensii have been shown to be sensitive to C. marina with negative effects observed on sperm swimming velocity [ 124 ] and on the umbo and pre-settling larval stages [ 125 ].…”