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首页> 外文期刊>Diatom Research >EXPOSURE TO SUDDEN LIGHT BURST AFTER PROLONGED DARKNESS - A CASE STUDY ON BENTHIC DIATOMS IN ANTARCTICA
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EXPOSURE TO SUDDEN LIGHT BURST AFTER PROLONGED DARKNESS - A CASE STUDY ON BENTHIC DIATOMS IN ANTARCTICA

机译：长时间黑暗后暴晒暴光-以南极底栖动物为例

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In polar areas, benthic diatoms are regarded to play a major role in supplying energy to the benthic fauna, particularly prior to the release of microalgae from sea ice and the phytoplankton bloom. As phototrophs, benthic polar diatoms have to contend not only with dark polar nights but also with darkness due to sea-ice and snow cover that can prevail in the littoral zone for additional months. Upon sea ice break-tip the autotrophs are suddenly exposed to high light intensities including ultraviolet radiation. The aim Of Our study was to mimic a sudden spring-time sea ice break-up, focusing Oil the ultraviolet part of the solar spectrum. We therefore exposed a semi-natural Community of benthic diatoms to light burst after a period of total darkness. We studied the effects of different spectral qualities: photosynthetically active radiation (PAR, 400-700 nm: P treatment), PAR+ UV-A (UV-A 320-400 nm; PA treatment), and PAR+UV-A+UV-B (UV-B 280-320 nm; PAB treatment) on cell number (growth), species composition and optimum quantum yield (F-v/F-m) in 2 separate experiments where diatoms were kept in darkness for 15 and 64 days, respectively. In both experiments, the most frequently (>50%) observed species were Gyrosigma fasciola and G. obscurum. No growth was observed and no resting spores were found. In both experiments, the initial optimum quantum yield of the PSII prior to dark treatment was comparable (F-n/F-m = 0.70). The F-v/F-m was not affected after 15 days dark incubation but a significant decrease in photosynthetic efficiency was observed after 64 days in the dark (F-v/F-m = 0.39). Exposure to different light treatments (P, PA, PAB) immediately after different dark incubation periods showed higher reduction in F-v/F-m (PAB > PA > P) after the longer dark period. Estimated P-E Curve parameters showed an efficient light harvesting and photosynthetic conversion capacity (alpha= 0.20- rER(max)=14) that was significantly reduced after 64 days ill the dark (alpha= 0.06; rETR(max)=8). The reduction in these photo-physiological indices (alpha and rETR(max)) after dark incubation was compensated with higher saturating irradiance (E-k), which we suspect to be a mechanism to optimize photochemical processes. But the PSII antenna was relatively light-sensitive because photosynthesis was already photoinhibited at half the photon flux density (>= 585 mu mol photons m(-2) s(-1)) relative to light-adapted (>= 972 mu mol photons m(-2) s(-1)) diatoms. We conclude that the benthic diatoms ill our study were able to resume photosynthetic activity after 64 days ill darkness and they were able to cope with relatively high intensities of UV radiation compared with their natural habitat.
机译：在极地地区，底栖硅藻被认为在向底栖动物提供能量方面起着重要作用，特别是在海冰释放微藻和浮游植物开花之前。作为光养生物，底栖极地硅藻不仅要与黑暗的极夜竞争，而且还要与在沿海地区持续数月的海冰和积雪造成的黑暗竞争。在海冰破裂时，自养生物突然暴露于包括紫外线辐射在内的高光强度下。我们的研究目的是模拟春季春季海冰突然破裂，将油聚焦在太阳光谱的紫外线部分。因此，我们在完全黑暗的一段时间后，使底栖硅藻的半自然群落暴露于光之下。我们研究了不同光谱质量的影响：光合有效辐射（PAR，400-700 nm：P处理），PAR + UV-A（UV-A 320-400 nm; PA处理）和PAR + UV-A + UV- B（UV-B 280-320 nm; PAB处理）分别在两个单独的实验中将硅藻分别在黑暗中放置15天和64天，以了解细胞数（生长），物种组成和最佳量子产率（Fv / Fm）。在这两个实验中，最常观察到的物种（> 50％）是Gyrosigma fasciola和G. obscurum。没有观察到生长，也没有发现静止的孢子。在两个实验中，暗处理之前PSII的初始最佳量子产率是可比的（F-n / F-m = 0.70）。在黑暗中孵育15天后F-v / F-m不受影响，但在黑暗中64天后观察到光合作用效率显着下降（F-v / F-m = 0.39）。在不同的黑暗潜伏期后立即暴露于不同的光照处理（P，PA，PAB）显示，在更长的黑暗时期后，F-v / F-m的降低幅度更大（PAB> PA> P）。估计的P-E曲线参数显示了有效的光收集和光合作用转化能力（alpha = 0.20- rER（max）= 14），在天黑后64天后明显降低（alpha = 0.06; rETR（max）= 8）。在黑暗孵育后，这些光生理指标的降低（α和rETR（max））被较高的饱和辐照度（E-k）所补偿，我们认为这是优化光化学过程的一种机制。但是PSII天线对光敏感，因为相对于光适应（> = 972μmol光子），光合作用已经在光子通量密度（> = 585μmol光子m（-2）s（-1））的一半处被光合作用抑制m（-2）s（-1））硅藻。我们得出的结论是，根据我们的研究，底栖硅藻能够在天黑后64天恢复光合作用，并且与自然栖息地相比，它们能够应对相对较高的紫外线辐射强度。

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