School of Biological and Marine Sciences, University of Plymouth, Drake's Circus, Plymouth, UK.
Ann Bot. 2020 Feb 3;125(2):265-276. doi: 10.1093/aob/mcz042.
The combination of rising sea levels and increased storm frequency and intensity is predicted to increase the severity of oceanic storm surge events and the impact of flooding on coastal ecosystems globally. Understanding how plant communities respond to this threat necessitates experiments involving plant immersion in saline water, but logistical issues and natural variation in seawater composition mean that pure NaCl solutions or marine aquarium salts (MS) are widely used. Nonetheless, their comparative impact on plant ecophysiology, and thus relevance to understanding real-world flooding scenarios, is unknown.
In the first of two experiments, we examined how six ecophysiological responses in white clover (Trifolium repens) varied when plants were subjected to five different inundation treatments: deionized water, natural seawater, an MS solution and two NaCl solutions. In a second experiment, we examined how immersion in deionized water, MS solution and natural seawater affected six European perennial herb species, three native to Spanish sand dunes, and three from British coastal grasslands.
The two NaCl solutions induced exceptional Trifolium mortality, but responses varied little between MS and seawater treatments. In the second experiment, although leaf tissue necrosis and proline concentrations increased, and growth decreased compared with untreated controls, only one response in one species varied between MS and seawater treatments. Chemical speciation modelling revealed major variation in free Na+ and Cl- between NaCl solutions and seawater, but minor differences between MS and seawater.
We show that NaCl solutions are unsuitable surrogates to investigate plant response to elevated environmental salinity. Although responses to natural seawater and MS were consistent within species, there was notable between-species variation. Consequently, the first steps to elucidating how these species-specific responses influence coastal plant community recovery following storm surge can likely be achieved using commercial marine aquarium salts as substitutes for natural seawater.
预计海平面上升、风暴频率和强度增加将加剧海洋风暴潮事件的严重程度，并对全球沿海生态系统的洪水影响。了解植物群落如何应对这一威胁，需要进行植物浸泡在盐水中的实验，但由于物流问题和海水成分的自然变化，广泛使用的是纯净的 NaCl 溶液或海水水族馆盐（MS）。尽管如此，它们对植物生理生态的比较影响，以及对理解现实世界洪水情景的相关性，尚不清楚。
在两个实验中的第一个实验中，我们研究了当植物受到五种不同淹没处理时，白三叶草（Trifolium repens）的六种生理生态反应如何变化：去离子水、天然海水、MS 溶液和两种 NaCl 溶液。在第二个实验中，我们研究了浸泡在去离子水、MS 溶液和天然海水中如何影响六种欧洲多年生草本植物，三种来自西班牙沙丘，三种来自英国沿海草原。
两种 NaCl 溶液引起了异常的三叶草死亡率，但 MS 和海水处理之间的反应差异很小。在第二个实验中，尽管与未处理对照相比，叶片组织坏死和脯氨酸浓度增加，生长减少，但只有一种物种的一种反应在 MS 和海水处理之间有所不同。化学形态建模揭示了 NaCl 溶液与海水之间游离 Na+和 Cl-的主要差异，但 MS 和海水之间的差异较小。
我们表明，NaCl 溶液不适合研究植物对环境盐度升高的反应。尽管海水和 MS 对物种内的反应一致，但物种之间存在明显的差异。因此，阐明这些物种特异性反应如何影响风暴潮后沿海植物群落恢复的第一步，可能可以使用商业海水水族馆盐作为天然海水的替代品。
