Variability of UVR effects on photosynthesis of summer phytoplankton assemblages from a tropical coastal area of the South China Sea
Variability of UVR effects on photosynthesis of summer phytoplankton assemblages from a tropical coastal area of the South China Sea
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DOI：
10.1111/j.1751-1097.2007.00154.x
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发表时间：
2007-07-01
影响因子：
3.3
通讯作者：
Villafane, Virginia E.
中科院分区：
文献类型：
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作者：
Gao, Kunshan;Li, Gang;Villafane, Virginia E.
2005年6月至9月，我们进行了实验，以确定紫外线辐射（UVR）诱导的光抑制的夏季浮游植物组合从中国南海沿岸。在整个夏天的分类组成的变化，确定与峰值叶绿素a（叶绿素a类似于20微克叶绿素a L-1）占主导地位的硅藻中肋骨条藻，在研究期间的早期检测到，其余的时间样本的特点是由单胞菌和鞭毛虫，与低的叶绿素a值（1-5叶绿素a微克L-1）。将地表水样品置于石英管中，接种放射性碳并暴露于太阳辐射2-3 h，以使用不同的滤光器和使用中性密度屏在7个环境辐照度水平下（P vs E曲线）确定在三种质量辐射处理（即PAB，280-700 nm; PA，320-700 nm和P，400-700 nm）下的光合速率。暴露于最大辐照度（即在表面）的样品的UVR抑制从-12.2%至50%不等，而在表层海水中白天积分的UVR相关的光抑制从-62%至7%不等。光合参数p（max）（B）和E-k受UV-B的影响也不同，但UV-B是影响最大的因素。在晴天，微型浮游生物（> 20 μ m）和微微微型浮游生物（< 20 μ m）的光合作用明显受到紫外线辐射（主要是UV-B）的抑制。然而，在阴天，而piconanoplankton细胞仍然抑制紫外线辐射，微型浮游生物细胞使用紫外线辐射（主要是UV-A）作为光合作用的能量来源，导致较高的碳固定在样品暴露于紫外线辐射比暴露于光合有效辐射（PAR）。我们的研究结果表明，大小结构和云量清楚的条件下的总体影响，紫外线辐射对浮游植物光合作用在这个热带网站的中国南方。此外，该地区的模型预测只考虑PAR的初级生产可能低估了由于紫外线辐射的贡献的碳固定。
From June to September 2005, we carried out experiments to determine the ultraviolet radiation (UVR) -induced photoinhibition of summer phytoplankton assemblages from a coastal site of the South China Sea. Variability in taxonomic composition was determined throughout the summer, with a peak chlorophyll a (chl a similar to 20 mu g chl a L-1) dominated by the diatom Skeletonema costatum that was detected early in the study period; the rest of the time samples were characterized by monads and flagellates, with low chi a values (1-5 chl a mu g L-1). Surface water samples were placed in quartz tubes, inoculated with radiocarbon and exposed to solar radiation for 2-3 h to determine photosynthetic rates under three quality radiation treatments (i.e. PAB, 280-700 nm; PA, 320-700 nm and P, 400-700 nm) using different filters and under seven levels of ambient irradiance using neutral density screens (P vs E curves). UVR inhibition of samples exposed to maximum irradiance (i.e. at the surface) varied from -12.2% to 50%, while the daytime-integrated UVR-related photoinhibition in surface seawater varied from -62% to 7%. The effects of UVR on the photosynthetic parameters p(max)(B) and E-k were also variable, but UV-B accounted for most of the observed variability. During sunny days, photosynthesis of microplankton ( > 20 mu m) and piconanoplankton ( < 20 mu m) were significantly inhibited by UVR (mostly by UV-B). However, during cloudy days, while piconanoplankton cells were still inhibited by UVR, microplankton cells used UVR (mostly UV-A) as the source of energy for photosynthesis, resulting in higher carbon fixation in samples exposed to UVR than the ones exposed only to photosynthetically active radiation (PAR). Our results indicate that size structure and cloudiness clearly condition the overall impact of UVR on phytoplankton photosynthesis in this tropical site of South China. In addition, model predictions for this area considering only PAR for primary production might have underestimated carbon fixation due to UVR contribution.