Regulation of inorganic carbon acquisition in a red tide alga (&amp;lt;i&amp;gt;Skeletonema costatum&amp;lt;/i&amp;gt;): the importance of phosphorus availability

Gao, Guang R.; Xia, Jianrong; Yu, Jin; Fan, Jiale; Zeng, Xiaopeng

doi:10.5194/bg-2017-475

Cited by 1 publication

(3 citation statements)

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“…Therefore, changes in CA activity have been considered as a signal of regulation of CCMs. Lowered CO 2 availability usually induces CA activity to different extents under different levels of nutrients ( Gao et al, 2018a , b ). While it is known that decreased CO 2 concentration and increased levels of light can trigger higher CA activity in S. costatum ( Chen and Gao, 2003 ; Giordano et al, 2005 ), only limited knowledge has been documented on effects of UVR on it ( Wu and Gao, 2009 ).…”

Section: Discussionmentioning

confidence: 99%

“…Active uptake of HCO 3 − is another pathway of algal CCMs ( Giordano et al, 2005 ). A pH compensation point over 9.2 has been deemed as a sign of active HCO 3 − uptake for algae because there is hardly any CO 2 available in water with a pH above 9.2 ( Axelsson and Uusitalo, 1988 ; Gao et al, 2018a ). In the present study, the addition of UVA to PAR promoted active uptake and utilization of HCO 3 − , so that pH increased to higher extent ( Figure 3A ).…”

Section: Discussionmentioning

confidence: 99%

“…It was reported that pH level in the surface waters of Mariager Fjord, Denmark, achieved 9.75 during an algal bloom ( Hansen, 2002 ). Algal tolerance to high pH and low CO 2 varies among species, which may be related to the capacity of their CCMs ( Björk et al, 2004 ; Gao et al, 2018a ).…”

Section: Introductionmentioning

confidence: 99%

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Ultraviolet Radiation Stimulates Activity of CO2 Concentrating Mechanisms in a Bloom-Forming Diatom Under Reduced CO2 Availability

Gao

Liu²,

Zhao

et al. 2021

Front. Microbiol.

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The diatom Skeletonema costatum is cosmopolitan and forms algal blooms in coastal waters, being exposed to varying levels of solar UV radiation (UVR) and reduced levels of carbon dioxide (CO2). While reduced CO2 availability is known to enhance CO2 concentrating mechanisms (CCMs) in this diatom and others, little is known on the effects of UV on microalgal CCMs, especially when CO2 levels fluctuate in coastal waters. Here, we show that S. costatum upregulated its CCMs in response to UVR (295–395 nm), especially to UVA (320–395 nm) in the presence and absence of photosynthetically active radiation (PAR). The intensity rise of UVA and/or UVR alone resulted in an increase of the activity of extracellular carbonic anhydrase (CAe); and the addition of UVA enhanced the activity of CCMs-related CAe by 23–27% when PAR levels were low. Such UV-stimulated CCMs activity was only significant at the reduced CO2 level (3.4 μmol L−1). In addition, UVA alone drove active HCO3− uptake although it was not as obvious as CAe activity, another evidence for its role in enhancing CCMs activity. In parallel, the addition of UVA enhanced photosynthetic carbon fixation only at the lower CO2 level compared to PAR alone. In the absence of PAR, carbon fixation increased linearly with increased intensities of UVA or UVR regardless of the CO2 levels. These findings imply that during S. costatum blooming period when CO2 and PAR availability becomes lower, solar UVR (mainly UVA) helps to upregulate its CCMs and thus carbon fixation, enabling its success of frequent algal blooms.

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