| Li Gang. 2019. Fast acclimation of phytoplankton assemblies to acute salinity stress in the Jiulong River Estuary. Acta Oceanologica Sinica, 38(8):78－85 |
| Fast acclimation of phytoplankton assemblies to acute salinity stress in the Jiulong River Estuary |
| 九龙江口浮游植物群体对盐度胁迫的快速适应 |
| Received:May 18, 2018 |
| DOI：10.1007/s13131-019-1389-3 |
| Key words:PSⅡ quantum yield carbon fixation salinity gradients phytoplankton assemblies Jiulong River Estuary |
| 中文关键词: 光系统Ⅱ量子产额 固碳 盐度梯度 浮游植物群体 九龙江口 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41890853 and 41676156; the National Basic Research Program of China (973 Program) under contract No. 2015CB452903; the Strategic Priority Research Program of Chinese Academy of Sciences under contract Nos XDA13020103 and XDA11020305; the Natural Science Foundation of Guangdong Province under contract Nos 2015A030313826 and 2017A030313216; the Special Fund for Agro-scientific Research in the Public Interest under contract No. 201403008; the Science and Technology Planning Project of Guangdong Province under contract No. 2017B030314052. |
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| Abstract: |
| Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor- and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water (salinity 25, 17, 13 and 7.5), the effective Photosystem Ⅱ quantum yield (ΔF/Fm') decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching (NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water (salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased ΔF/Fm' accompanied with increased NPQ, and followed by the recovery-induced increase in ΔF/Fm' and decrease in NPQ. A similar response pattern as ΔF/Fm' to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon (14C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments. |
| 中文摘要: |
| 在河口海域，咸淡混合使其盐度的梯度性变化较大。为了阐明河口浮游植物如何响应该区域剧烈的盐度变化，本文利用室内和室外实验研究了九龙江口原位浮游植物群体对短期盐度变化的响应过程。结果发现，当适应高盐（盐度30）环境的浮游植物群体被转移至原位低盐（盐度25、17、13、7.5）海水时，其有效光化学效率（ΔF/Fm’）迅速降低，如被转移至盐度7.5原位海水内5分钟后，其值降至初始值的1/5，在随后40分钟内ΔF/Fm’迅速升高，至320分钟后恢复至初始值；期间，非光化学淬灭（NPQ）迅速升高，在5分钟内从0升高至0.85，而在随后70分钟内又降至0。类似地，当适应低盐（盐度7.5）环境的浮游植物被转移至高盐（盐度13、17、25、30）原位海水时，ΔF/Fm’迅速降低的同时NPQ迅速升高，随后ΔF/Fm’升高而NPQ降低。浮游植物光合固碳速率对盐度胁迫的响应随时间的序列变化趋势与ΔF/Fm’ 的变化趋势一致。我们的结果证实了河口浮游植物能快速适应河口海域盐度的剧烈变化，揭示了尽管河口海域盐度变化大、不适合浮游植物生长，但该富营养水体内浮游植物仍可经常性地爆发性生长的内在原因。 |
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