Impact of carbon and nitrogen assimilation in Sargassum fusiforme (Harvey) Setchell due to marine heatwave under global warming - data

Because of the rising global temperatures, Sargassum fusiforme (Harvey) Setchell, a commercially valuable seaweed, has experienced reduced yield and quality due to high temperature from marine heatwave events. However, the mechanisms underlying the effects of heatwave stress on S. fusiforme remain unclear. In this study, the mechanisms of heatwave stress on the carbon and nitrogen assimilation processes in S. fusiforme were analyzed. These results indicated that heatwave stress, especially at 30°C for 12 days, significantly increased the levels of hydrogen peroxide (83%), malondialdehyde (84.7%) and relative conductivity (16.5%) in algae, which suggested an increase in algal damage. Morphologically, heatwave stress damaged the thylakoid structure and reduces the photosynthetic efficiency of algae, and accumulated NADPH, ATP, and α-ketoglutarate significantly, resulting in decreased content of mannitol, the photosynthetic product. Additionally, physiological and transcriptomic results revealed that heatwave stress inhibited the rate of nitrate absorption rate and the activities of the most enzymes associated with nitrogen accumulation, while significantly upregulated glutamate dehydrogenase (GDH), suggesting a crucial role for GDH in S. fusiforme’s adaptation to heatwave stress. In terms of amino acid composition, proline and alanine were the most sensitive to heatwave treatment. Moreover, under natural heatwave environment simulation validation experiment, the algae showed same physiological performance as under laboratory conditions. The results indicated that marine heatwave events increased oxidative damage in S. fusiforme and inhibited carbon and nitrogen absorption and assimilation, ultimately leading to negative effects on growth of algae. Thus, in the context of rapid global warming exacerbating marine heatwave events, our study provides valuable insights for high-temperature-resistant breeding and ecological management in coastal aquaculture.

由于全球气温上升，具有商业价值的羊栖菜（Sargassum fusiforme (Harvey) Setchell）因海洋热浪事件带来的高温，出现了产量与品质双降的情况。然而，海洋热浪胁迫对羊栖菜影响的潜在机制仍不明晰。本研究针对海洋热浪胁迫对羊栖菜碳氮同化过程的作用机制展开分析。结果显示，海洋热浪胁迫（尤其是30℃持续12天的处理）会显著提升藻体中过氧化氢（83%）、丙二醛（84.7%）以及相对电导率（16.5%）的水平，表明藻体受损程度加剧。从形态层面来看，海洋热浪胁迫破坏了类囊体结构，降低了藻体的光合效率，并使烟酰胺腺嘌呤二核苷酸磷酸（NADPH）、三磷酸腺苷（ATP）与α-酮戊二酸发生显著积累，最终导致光合产物甘露醇的含量下降。此外，生理与转录组学分析结果表明，海洋热浪胁迫会抑制硝酸盐吸收速率以及多数与氮积累相关的酶活性，但显著上调谷氨酸脱氢酶（glutamate dehydrogenase, GDH）的表达，这提示GDH在羊栖菜适应海洋热浪胁迫过程中发挥关键作用。在氨基酸组成方面，脯氨酸与丙氨酸是对热浪处理最为敏感的氨基酸。此外，在模拟自然海洋热浪环境的验证实验中，藻体表现出与实验室条件下一致的生理响应。研究结果表明，海洋热浪事件会加剧羊栖菜的氧化损伤，抑制其碳氮吸收与同化过程，最终对藻体生长产生负面影响。综上，在全球变暖加速海洋热浪频发的背景下，本研究为沿海养殖的耐高温育种与生态治理提供了极具价值的参考依据。