近日获悉，南海海洋所副研究员李刚与加拿大Mount Allison大学Douglas A Campbell教授、厦门大学高坤山教授合作，发现大气CO2升高与太阳紫外辐射（UVR）对海洋浮游植物生长、光合固碳作用能产生明显的影响作用。
在不饱和光照条件下CO2升高会促进浮游植物的生长，而在超饱和光照条件下CO2升高则抑制其生长。光强会改变细胞内RbcL和PsaC蛋白的量及其比例，高光、高CO2条件下培养的浮游植物对强光耐受性更强，光系统II（PS II）不易发生光失活，反之亦然。该成果揭示了CO2升高对海洋浮游植物有正面或负面影响的不一致性的原因。相关成果刊载在国际期刊PLoS One [2013, 8(1): e55562. doi: 10.1371/journal.pone.0055562]。
浮游植物细胞粒径大小不同，对阳光UV 的响应存在较大差异。光强较低时UV促进粒径较大浮游植物光合固碳作用（正面效应），而光强较高时抑制其固碳效率（负面效应），但对于细胞粒径较小的浮游植物，无论光强高低，UV均抑制浮游植物固碳作用。该研究结果不仅阐析了UV对海洋浮游植物存在负面效应或正面效应的原因，也揭示出UV的正面效应只发生在营养盐浓度较高的近岸海域而不发生在寡营养的远洋海域的内在原因。相关成果刊载在国际期刊Estuaries and Coasts [2013, 36 (4): 728-736]。
论文摘要：
（1）Li G & Campbell DA. Rising CO2 Interacts with Growth Light and Growth Rate to Alter Photosystem II Photoinactivation of the Coastal Diatom Thalassiosira pseudonana. PLoS ONE ,2013, 8(1): e55562. doi:10.1371/journal.pone.0055562
Abstract: We studied the interactive effects of pCO2 and growth light on the coastal marine diatom Thalassiosira pseudonana CCMP 1335 growing under ambient and expected end-of-the-century pCO2 (750 ppmv), and a range of growth light from 30 to 380 µmol photons·m−2·s−1. Elevated pCO2 significantly stimulated the growth of T. pseudonana under sub-saturating growth light, but not under saturating to super-saturating growth light. Under ambient pCO2 susceptibility to photoinactivation of photosystem II (σi) increased with increasing growth rate, but cells growing under elevated pCO2 showed no dependence between growth rate and σi, so under high growth light cells under elevated pCO2 were less susceptible to photoinactivation of photosystem II, and thus incurred a lower running cost to maintain photosystem II function. Growth light altered the contents of RbcL (RUBISCO) and PsaC (PSI) protein subunits, and the ratios among the subunits, but there were only limited effects on these and other protein pools between cells grown under ambient and elevated pCO2.
（2）Gang Li & Kunshan Gao. CellSize-Dependent Effects of Solar UV Radiationon Primary Production in Coastal Waters of the South China Sea. Estuaries and Coasts, 2013, 36:728–736
Abstract: In order to examine the effects of solar ultraviolet radiation (UVR, 280–400 nm) on photosynthesis of differently cell-sized phytoplankton, natural phytoplankton assemblages from the coastal waters of the South China Sea were separated into three groups (>20, 5–20, and <5 μm) and exposed to four different solar UV spectral regimes, i.e., 280–700 nm (PAR+UVR), 400–700 nm(PAR), 280–400 nm (UV-A+B), and 315–400 nm (UV-A). In situ carbon fixation measurements revealed that micro-plankton (>20 μm) efficiently utilized UV-A for photosynthetic carbon fixation, with assimilation number of up to1.01 μgC(μg chl a)−1h−1under 21.4 Wm−2UV-A alone(about half of noontime irradiance at the surface), about 40 % higher than nanoplankton (5–20 μm). UV-B (280–315 nm) of 0.95 Wm−2reduced the carbon fixation byapproximately 20 and 57 % in microplankton and nano-plankton assemblages, respectively. In contrast, smallerpicoplankton (<5 μm) was unable to utilize UV-A for the photosynthetic carbon fixation. In addition, only micro-sized assemblages demonstrated the UV enhancement on their primary productivity in the presence of PAR, by about 8 % under moderate intensities of solar radiation.
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