Haolong Zheng

全球气候变暖及极端热浪事件频发，使高温胁迫逐渐成为制约海藻生长与养殖生产的关键环境因子。长茎葡萄蕨藻（Caulerpa lentillifera）对水温升高较为敏感，进而导致产量与品质波动。为提升其耐热性并提高养殖效益，本研究探讨外源生长素类激素萘乙酸（NAA）在高温胁迫下对长茎葡萄蕨藻的调节作用。实验设定不同浓度（0、50、100、200、400和800 μg·L⁻¹）NAA处理，藻体在常温下培养14天后，进行48小时的急性高温处理。结果表明，NAA对高温胁迫响应具有显著剂量依赖性，总体呈现先促进后回落的变化趋势。高温胁迫后，对照组藻体生长明显受抑并伴随氧化损伤增强。50 μg·L⁻¹处理的缓解效应较弱，与对照组相比无显著差异；100 μg·L⁻¹处理可一定程度改善生长停滞并降低丙二醛（MDA）含量；200 μg·L⁻¹处理对叶绿素水平及超氧化物歧化酶和过氧化物酶活性提升更为显著，且MDA含量最低；400 μg·L⁻¹处理在增重率与特定生长率维持、水溶性糖积累及过氧化氢酶活性提高方面表现最佳，同时组织边界完整性最优；800 μg·L⁻¹处理仍具有一定保护作用，但促进效应减弱。PCA综合评价进一步确定400 μg·L⁻¹为最适处理浓度。综上，适量NAA可通过增强抗氧化防御能力、维持光合功能与碳同化产物积累并稳定组织结构，从而提高长茎葡萄蕨藻对短期高温胁迫的耐受性，为海藻养殖的绿色、低成本调控提供依据。

The escalating impact of human activities has led to the accumulation of microplastics (MPs) and heavy metals in marine environments, posing serious threats to marine ecosystems. As essential components of oceanic ecosystems, large seaweeds such as Caulerpa lentillifera play a crucial role in maintaining ecological balance. This study investigated the effects of MPs and cadmium (Cd) on the growth, physiology, biochemistry, and Cd accumulation in C. lentillifera while elucidating the underlying molecular regulatory mechanisms. The results demonstrated that exposure to MPs alone significantly promoted the growth. In contrast, exposure to Cd either alone or in combination with MPs significantly suppressed growth by reducing stem and stolon length, bud count, weight gain, and specific growth rates. Combined exposure to MPs and Cd exhibited the most pronounced inhibitory effect on growth. MPs had negligible impact while Cd exposure either alone or combined with MPs impaired antioxidant defenses and exacerbated oxidative damage; with combined exposure being the most detrimental. Analysis of Cd content revealed that MPs significantly increased Cd accumulation in algae intensifying its toxic effects. Gene expression analysis revealed that Cd exposure down-regulated key genes involved in photosynthesis, impairing both photosynthetic efficiency and energy conversion. The combined exposure of MPs and Cd further exacerbated these effects. In contrast, MPs alone activated the ribosome pathway, supporting ribosomal stability and protein synthesis. Additionally, both Cd exposure alone or in combination with MPs significantly reduced chlorophyll B and soluble sugar content, negatively impacting photosynthesis and nutrient accumulation. In summary, low concentrations of MPs promoted C. lentillifera growth, but the presence of Cd hindered it by disrupting photosynthesis and antioxidant mechanisms. Furthermore, the coexistence of MPs intensified the toxic effects of Cd. These findings enhance our understanding of how both MPs and Cd impact large seaweed ecosystems and provide crucial insights for assessing their ecological risks.