Data from: Sensitivity and acclimation of three canopy-forming seaweeds to UVB radiation and warming

Canopy-forming seaweeds, as primary producers and foundation species, provide key ecological services. Their responses to multiple stressors associated with climate change could therefore have important knock-on effects on the functioning of coastal ecosystems. We examined interactive effects of UVB radiation and warming on juveniles of three habitat-forming subtidal seaweeds from Western Australia–Ecklonia radiata, Scytothalia dorycarpa and Sargassum sp. Fronds were incubated for 14 days at 16–30°C with or without UVB radiation and growth, health status, photosynthetic performance, and light absorbance measured. Furthermore, we used empirical models from the metabolic theory of ecology to evaluate the sensitivity of these important seaweeds to ocean warming. Results indicated that responses to UVB and warming were species specific, with Sargassum showing highest tolerance to a broad range of temperatures. Scytothalia was most sensitive to elevated temperature based on the reduced maximum quantum yields of PSII; however, Ecklonia was most sensitive, according to the comparison of activation energy calculated from Arrhenius’ model. UVB radiation caused reduction in the growth, physiological responses and thallus health in all three species. Our findings indicate that Scytothalia was capable of acclimating in response to UVB and increasing its light absorption efficiency in the UV bands, probably by up-regulating synthesis of photoprotective compounds. The other two species did not acclimate over the two weeks of exposure to UVB. Overall, UVB and warming would severely inhibit the growth and photosynthesis of these canopy-forming seaweeds and decrease their coverage. Differences in the sensitivity and acclimation of major seaweed species to temperature and UVB may alter the balance between species in future seaweed communities under climate change.

冠层型海藻（canopy-forming seaweeds）作为初级生产者与基础物种，可提供关键的生态系统服务。因此，它们对气候变化相关多重胁迫因子的响应，会对沿海生态系统的功能产生重要的级联效应。本研究针对西澳大利亚海域3种造栖息地潮下带海藻——Ecklonia radiata、Scytothalia dorycarpa及Sargassum sp.——的幼体，探究了紫外B辐射（UVB）与升温的交互效应。将藻体在16~30℃条件下，分别设置添加与不添加紫外B辐射的处理，进行为期14天的培养，并测定其生长状况、健康状态、光合性能与光吸收特性。此外，本研究借助代谢生态学理论的经验模型，评估了这些重要海藻对海洋升温的敏感性。研究结果显示，海藻对紫外B辐射与升温的响应具有物种特异性：Sargassum sp.对宽泛温度区间的耐受性最强。基于光系统II（PSII）最大量子产率的降幅，Scytothalia dorycarpa对升温最为敏感；而依据阿伦尼乌斯模型计算得到的活化能对比分析，Ecklonia radiata的敏感性最高。紫外B辐射会降低这3种海藻的生长速率、生理响应能力与叶状体健康状态。本研究结果表明，Scytothalia dorycarpa能够通过上调光保护化合物的合成，响应紫外B辐射并提升其在紫外波段的光吸收效率，从而实现生理驯化。另外两种海藻在为期14天的紫外B辐射暴露过程中并未产生驯化效应。整体而言，紫外B辐射与升温会显著抑制这类冠层型海藻的生长与光合能力，并降低其群落盖度。未来气候变化背景下，主要海藻物种对温度与紫外B辐射的敏感性及驯化能力的差异，或会改变未来海藻群落的物种间平衡。