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.由于全球气温持续升高，具有较高商业价值的海藻羊栖菜（Sargassum fusiforme (Harvey) Setchell）因海洋热浪事件带来的高温胁迫，出现了产量与品质双降的情况。目前，海洋热浪胁迫对羊栖菜影响的潜在机制仍不明确。本研究解析了海洋热浪胁迫对羊栖菜碳氮同化过程的影响机制。研究结果显示，当羊栖菜暴露于30℃高温环境12天时，其体内过氧化氢（hydrogen peroxide）、丙二醛（malondialdehyde）含量分别提升83%、84.7%，相对电导率（relative conductivity）升高16.5%，表明藻体氧化损伤程度加剧。形态学层面观察发现，海洋热浪胁迫破坏了类囊体（thylakoid）结构，降低了藻类光合效率，且显著积累了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（α-ketoglutarate），最终导致光合产物甘露醇（mannitol）含量下降。此外，生理学与转录组学分析结果表明，海洋热浪胁迫抑制了硝酸盐吸收速率以及多数与氮积累相关的酶活性，但显著上调了谷氨酸脱氢酶（glutamate dehydrogenase, GDH），提示谷氨酸脱氢酶在羊栖菜适应海洋热浪胁迫过程中发挥关键作用。在氨基酸组成层面，脯氨酸（proline）与丙氨酸（alanine）是对高温处理最为敏感的两种氨基酸。另外，在模拟自然海洋热浪环境的验证实验中，羊栖菜表现出与实验室条件下一致的生理响应。本研究结果证实，海洋热浪事件会加剧羊栖菜的氧化损伤，抑制碳氮吸收与同化过程，最终对藻体生长产生负面影响。因此，在全球变暖加速、海洋热浪事件愈发频发的背景下，本研究为沿海养殖的耐高温育种与生态管理提供了宝贵参考。