High light stress under phosphorus limitation in summer may accelerate diatom shift from Skeletonema to Chaetoceros in an oligotrophic coastal area of Japan
High light stress under phosphorus limitation in summer may accelerate diatom shift from Skeletonema to Chaetoceros in an oligotrophic coastal area of Japan
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DOI：
10.3389/fmars.2023.1095762
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发表时间：
2023-02
期刊：
影响因子：
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通讯作者：
Ryoko Yano;Shizuka Ohara;K. Koike
中科院分区：
文献类型：
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作者：
Ryoko Yano;Shizuka Ohara;K. Koike
在日本最大的半封闭海--濑户内海中，过去最占优势的硅藻--双丝藻属，已被另一种硅藻角毛藻取代。自20世纪80年代以来，这种变化往往被解释为贫营养化的结果。基于先前观察到的从螺旋线虫属转移。角毛藻属（Chaetoceros spp.）在长期阳光充足的情况下，最近30年太阳辐射的增加也可能加速了角毛藻对短丝藻的取代，特别是在营养水平相对较低和太阳辐射较高的夏季。在我们的实验中，在严格的氮限制条件下，中肋骨条藻和洛伦氏角毛藻的培养菌株在长时间暴露于强光（800 µmol-photons m-2 s-1）下（1 h）时表现出较少的非光化学猝灭（NPQ），而光化学猝灭（qP）的减少在S.肋骨相反，在严格磷限制条件下，即使在短时间暴露于强光（30 s）下，也观察到NPQ的显著增加，尽管NPQ的增加不能缓解qP的降低，这在S中更明显。肋骨NPQ和qP的这些趋势归因于有限的养分，因为养分的补充导致NPQ降低和qP增加。有趣的是，这种恢复在C。lorenzianus比S.肋骨结果表明，缺磷引起了严重的光抑制，尤其是S。中肋骨，不考虑活性NPQ诱导。此外，由于严重的磷限制条件下，在濑户内海的一段时间，我们进行了竞争实验，使用连续共培养的两个物种，以模拟典型的夏季环境中，严重的磷限制和高光发生。结果表明，S. costatum到C.持续的强光照射加速了lorenzianus的生长，这可以解释研究区夏季优势种的最近转变。
In the Seto Inland Sea, the largest semi-enclosed sea in Japan, the most dominant diatom in the past, Skeletonema spp., has been replaced by another diatom Chaetoceros spp. since the 1980s, and this shift is often explained as the result of oligotrophication. Based on previous observations of a shift from Skeletonema spp. to Chaetoceros spp. under prolonged sunny conditions, the recent increase in solar insolation over the last 30 years might have also accelerated the replacement of Skeletonema by Chaetoceros, especially during the summer when nutrient levels are relatively low and solar insolation is high. In our experiments, culture strains of Skeletonema costatum and Chaetoceros lorenzianus under severely nitrogen-limited conditions exhibited less non-photochemical quenching (NPQ) under prolonged exposure (1 h) to high light (800 µmol-photons m-2 s-1) and a decrease in photochemical quenching (qP) which was especially notable in S. costatum. Conversely, marked increases in NPQ were observed under severely phosphorus-limited conditions, even under short time exposure (30 s) to high light, even though the increase in NPQ could not relieve the decrease in qP, which was more apparent in S. costatum. These trends in NPQ and qP were attributed to the limited nutrients because replenishment of the nutrients led to a decrease in NPQ and an increase in qP. Interestingly, this recovery was faster in C. lorenzianus than S. costatum. The results showed that phosphorus depletion caused severe photoinhibition especially in S. costatum, irrespective of active NPQ induction. Further, given the severe phosphorus-limited conditions in the Seto Inland Sea for an extended period, we conducted competition experiments using continuous coculture of both species to simulate the typical summer environment where severe phosphorus limitation and high light occur. The results showed that the shift from S. costatum to C. lorenzianus was accelerated by continuous exposure to high light, which could explain the recent shift in the dominant species in the summer in the study area.