Ecophysiological measurements from thermal tolerance testing of giant kelp (NESP MaC 1.28)

This record described kelp growth and ecophysiological data relevant to the thermal tolerance of specific warm-tolerant and 'normal' family-lines of giant kelp (Macrocystis pyrifera) from Tasmania, Australia.

For habitat restoration to be effective, the cause of habitat decline must be understood and overcome. But this is problematic when climate change is driving habitat loss, since it cannot be reversed or ameliorated prior to restoration.

A previous NESP project, led by this team, identified warmwater-tolerant strains of giant kelp (Macrocystis pyrifera) from remnant patches in eastern Tasmania, where the species has experienced severe declines over the past half-century due to climate change and ocean-warming. While these strains have high potential to assist with ‘future-proofing’ of kelp forest restoration activities, it is still unclear what the physiological mechanisms are that provide their improved thermal tolerance.

Here we cultivated the warm-tolerant giant kelp strains, along with giant kelp strains of normal tolerance, at both cool (16 °C) and warm temperatures (20 °C). We then harvested the juvenile kelp, and examined a suite of physiological traits that may be responsible for their differences in thermal tolerance, including nutrient usage (carbon and nitrogen content), cellular membrane processes (fatty acid contents), and photosynthesis (PAM fluorometry and photosynthetic pigments).

The cultivation trials again illustrated the improved ability of the warm-tolerant strains to develop at stressful warm temperatures relative to normal giant kelp. For the first time, we also demonstrate that their improved thermal performance may extend to the development and fertilisation of the earlier kelp ‘gametophyte’ life-stage. Despite the clear differences in growth between the two test groups, the physiological assessments illustrated a complex pattern of responses, some of which are contrary to expected based on prior knowledge of thermal performance in kelps. Nonetheless, our results indicate that the warm-tolerant strains of giant kelp have a greater capacity to alter the composition of their fatty acids and may be more efficient users of nitrogen (a key nutrient for growth and development).

This new information will help inform ongoing kelp breeding and selection programs for future-proofing kelp restoration in Australia and globally. This improved understanding of the physiology of kelp thermal tolerance might also help with identifying individuals and populations of Macrocystis, and other kelps, that may be resilient to (or especially threatened by) ocean warming and climate change.

本数据集记录了与澳大利亚塔斯马尼亚州来源的特定耐热型与‘普通’巨藻（Macrocystis pyrifera）家系的热耐受性相关的巨藻生长及生态生理数据。

若要实现有效的栖息地修复，必须先明确并解决栖息地衰退的成因。但在气候变化驱动栖息地丧失的背景下，这一目标难以实现——因为在开展修复前，气候变化带来的负面影响无法被逆转或缓解。

本团队此前牵头的国家环境科学项目（NESP），从塔斯马尼亚东部的残存巨藻种群中筛选出了耐热型巨藻（Macrocystis pyrifera）菌株。过去半个世纪以来，该区域的巨藻因气候变化与海洋变暖出现了严重的种群衰退。尽管这类菌株在为巨藻森林修复活动提供‘未来适配性’方面具备极高潜力，但其提升热耐受性的生理机制仍不明晰。

本研究分别在低温（16℃）与高温（20℃）环境下，对耐热型巨藻菌株与普通耐受型巨藻菌株进行了培养。随后收集幼龄巨藻样本，对一系列可能与其热耐受性差异相关的生理性状展开检测，包括营养利用情况（碳、氮含量）、细胞膜过程（脂肪酸组成）以及光合功能（PAM荧光法与光合色素分析）。

培养试验再次证实，相较于普通巨藻，耐热型巨藻菌株在胁迫性高温环境下的生长能力更强。本研究还首次证明，其优异的热性能优势可延伸至巨藻早期‘配子体’生命阶段的发育与受精过程。尽管两组受试样本的生长差异显著，但生理检测结果呈现出复杂的响应模式，其中部分结果与此前基于巨藻热性能研究得出的预期相悖。尽管如此，本研究结果表明，耐热型巨藻菌株具备更强的脂肪酸组成调控能力，且可能是更高效的氮利用者——氮是巨藻生长与发育的关键营养元素。

这些新发现将为澳大利亚乃至全球范围内的巨藻育种与选育项目提供参考，助力巨藻修复工作的未来适配性提升。此外，对巨藻热耐受性生理机制的深入理解，也有助于识别巨藻属（Macrocystis）及其他藻类中，对海洋变暖和气候变化具备抗性（或尤其脆弱）的个体与种群。