Response and adaptation of Sargassum muticum to light changes
Sargassum muticum,one of the invasive species of macroalgae,has invaded the European coast and the Mediterranean region along the Pacific coast,causing serious impacts on local ecosystems and leading to a decrease in local algal biodiversity.More seriously,a large number of drifting individuals of S.muticum have been found on the coast of Lanzarote(Canary Islands),which indicates that this species maybe becomes a potential cause of"golden tide".S.muticum is an important component of the seaweed bed of the northern China,naturally growing at 2-4 m depth in the subtidal zone.They will receive stronger light when drifting to the surface of seawater.However,research on the physiological response of S.muticum to strong light stress remains unclear.In this study,a solar simulator was used to provide strong light to simulate the actual light density on seawater surface in different seasons.Three strong light levels(460,920,1 380 μmol photons·m-2·s-1)were set,and photosynthetic physiological characteristics of algae were determined after cultivated under different light conditions,to investigate the effects of different levels of light on the photosynthesis of S.muticum.The results showed that the photosynthetic activity of SS.muticum was significantly inhibited after 120 min of all three strong light treatments.Compared with the initial state,the maximum photochemical quantum yield(Fv/Fm)was reduced by 43.96％,51.15％and 76.93％,respectively.The maximum photosynthetic electron transfer rate(rETRmax)was reduced by 36.93％,54.44％,and 64.84％,respectively.The energy absorbed and dissipated per unit reaction center as well as the energy captured for QA reduction increased significantly with the light level,but electron transfer was hindered.With the light level increasing,the contents of light-trapping pigments reduced,and the inhibition and damage of the reaction center of the PSⅡ system were aggravated in S.muticum.Meanwhile,inhibitions of strong light were alleviated by increasing carotenoid(Car)content and enhancing non-photochemical quenching(NPQ).Car content of S.muticum was elevated by 15.71％,23.81％,and 33.33％respectively,and NPQ was also significantly higher than the initial level.After 240 min of weak light recovery,Fv/Fm,NPQ,rETRmax,and photosynthetic pigments content of thalli cultured under three strong light levels exhibited different degrees of recovery,and even returned to the initial values in the low-light treatment group(460 μmol photons·m-2·s-1).These results indicate that when S.muticum is under strong light stress,multiple protection and recovery pathways could work together to effectively protect or repair the photodamage from light.Therefore,we conservatively speculate that S.muticum may adapt to strong sunlight on sea surface in the daytime,resulting that the drifting population might maintain a rapid growth rate and eventually develop into the golden tide,in case of suitable conditions such as temperature,nutrients,and so on.Our results are expected to provide theoretical and data references for the ecological mechanism research and early warning monitoring work on the golden tide outbreak of Sargassum muticum
万方数据
维普
