Abstract
Photoperiods have an important impact on macroalgae living in the intertidal zone. Ocean acidification also influences the physiology of macroalgae. However, little is known about the interaction between ocean acidification and photoperiod on macroalgae. In this study, a green alga Ulva linza was cultured under three different photoperiods (L: D = 8:16, 12:12, 16:8) and two different CO2 levels (LC, 400 ppm; HC, 1,000 ppm) to investigate their responses. The results showed that relative growth rate of U. linza increased with extended light periods under LC but decreased at HC when exposed to the longest light period of 16 h compared to 12 h. Higher CO2 levels enhanced the relative growth rate at a L: D of 8:16, had no effect at 12:12 but reduced RGR at 16:8. At LC, the L: D of 16:8 significantly stimulated maximum quantum yield (Yield). Higher CO2 levels enhanced Yield at L: D of 12:12 and 8:16, had negative effect at 16:8. Non-photochemical quenching (NPQ) increased with increasing light period. High CO2 levels did not affect respiration rate during shorter light periods but enhanced it at a light period of 16 h. Longer light periods had negative effects on Chl a and Chl b content, and high CO2 level also inhibited the synthesis of these pigments. Our data demonstrate the interactive effects of CO2 and photoperiod on the physiological characteristics of the green tide macroalga Ulva linza and indicate that future ocean acidification may hinder the stimulatory effect of long light periods on growth of Ulva species.
Highlights
Due to the activities of humans, the concentration of atmospheric CO2 has increased to 400 ppm from 278 ppm during the pre-industrial revolution (Gattuso et al, 2015)
The two-way ANOVA showed that elevated CO2 and photoperiod had an interactive effect, and both elevated CO2 levels and the photoperiods had a significant effect on the relative growth rate (RGR) of U. linza (Fig. 1 and Table 3)
At LC, the RGR of adult U. linza increased with the extended light periods, and the highest RGR occurred at a L: D of 16:8
Summary
Due to the activities of humans, the concentration of atmospheric CO2 has increased to 400 ppm from 278 ppm during the pre-industrial revolution (Gattuso et al, 2015). The concentration of atmospheric CO2 has been predicted to reach almost 1,000 ppm by the end of 21st. This would result in the decline of surface ocean pH by 0.3–0.4 units, an increase of hydrogen ion concentration and bicarbonate concentration in seawater, which is termed ocean acidification (OA) (Orr et al, 2005; Koch et al, 2013; Albright, 2016). OA will be maintained for hundreds of years, and could cause a huge change in marine ecosystems (Kroeker et al, 2013; Wittmann & Pörtner, 2013)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
