Stuart Jacqui, Smith Kirsty F, Miller Matt, Pearman John K, Robinson Natalie, Rhodes Lesley, Thompson Lucy, Challenger Sarah, Parnell Nicole, Ryan Ken G
Victoria University of Wellington, Wellington, New Zealand.
Cawthron Institute, Nelson, New Zealand.
PLoS One. 2025 Jan 16;20(1):e0317044. doi: 10.1371/journal.pone.0317044. eCollection 2025.
Photosynthetic eukaryotic microalgae are key primary producers in the Antarctic sea ice environment. Anticipated changes in sea ice thickness and snow load due to climate change may cause substantial shifts in available light to these ice-associated organisms. This study used a laboratory-based experiment to investigate how light levels, simulating different sea ice and snow thicknesses, affect fatty acid (FA) composition in two ice associated microalgae species, the pennate diatom Nitzschia cf. biundulata and the dinoflagellate Polarella glacialis. FA profiling and transcriptomic analyses were used to compare the impact of three light levels: High (baseline culturing conditions 90 ± 1 μmol photons m-2 s-1), mid (10 ± 1 μmol photons m-2 s-1); and low (1.5 ± 1 μmol photons m-2 s-1) on each isolate. Both microalgal isolates had altered growth rates and shifts in FA composition under different light conditions. Nitzschia cf. biundulata exhibited significant changes in specific saturated and monounsaturated FAs, with a notable increase in energy storage-related FAs under conditions emulating thinner ice or reduced snow cover. Polarella glacialis significantly increased production of polyunsaturated FAs (PUFAs) in mid light conditions, particularly octadecapentaenoic acid (C18:5N-3), indicating enhanced membrane fluidity and synthesis of longer-chain PUFAs. Notably, C18:5N-3 has been identified as an ichthyotoxic molecule, with fish mortalities associated with other high producing marine taxa. High light levels caused down regulation of photosynthetic genes in N. cf. biundulata isolates and up-regulation in P. glacialis isolates. This and the FA composition changes show the variability of acclimation strategies for different taxonomic groups, providing insights into the responses of microalgae to light stress. This variability could impact polar food webs under climate change, particularly through changes in macronutrient availability to higher trophic levels due to species specific acclimation responses. Further research on the broader microalgal community is needed to clarify the extent of these effects.
光合真核微藻是南极海冰环境中的关键初级生产者。气候变化导致的海冰厚度和积雪负荷的预期变化，可能会使这些与冰相关的生物可利用的光照发生显著变化。本研究采用基于实验室的实验，来探究模拟不同海冰和积雪厚度的光照水平，如何影响两种与冰相关的微藻物种——羽纹硅藻近双束菱形藻（Nitzschia cf. biundulata）和甲藻极地波拉藻（Polarella glacialis）——的脂肪酸（FA）组成。利用脂肪酸谱分析和转录组分析，比较了三种光照水平：高光（基线培养条件90±1 μmol光子·m⁻²·s⁻¹）、中光（10±1 μmol光子·m⁻²·s⁻¹）和低光（1.5±1 μmol光子·m⁻²·s⁻¹）对每种分离株的影响。在不同光照条件下，两种微藻分离株的生长速率均发生改变，脂肪酸组成也发生了变化。近双束菱形藻特定的饱和脂肪酸和单不饱和脂肪酸有显著变化，在模拟较薄冰层或积雪减少的条件下，与能量储存相关的脂肪酸显著增加。极地波拉藻在中光条件下多不饱和脂肪酸（PUFA）产量显著增加，尤其是十八碳五烯酸（C18:5N-3），表明膜流动性增强，长链多不饱和脂肪酸的合成增加。值得注意的是，C18:5N-3已被鉴定为一种鱼毒素分子，与其他高产海洋类群相关的鱼类死亡有关。高光水平导致近双束菱形藻分离株中光合基因下调，而极地波拉藻分离株中光合基因上调。这一点以及脂肪酸组成的变化，显示了不同分类群适应策略的变异性，为微藻对光胁迫的响应提供了见解。这种变异性可能会影响气候变化下的极地食物网，特别是由于物种特异性的适应反应，导致向更高营养级提供的大量营养素发生变化。需要对更广泛的微藻群落进行进一步研究，以阐明这些影响的程度。
