Ocean Biogeochemistry and Ecosystems Research Group, National Oceanography Centre, Southampton, UK.
School of Life Sciences, University of Warwick, Coventry, UK.
ISME J. 2014 Nov;8(11):2280-9. doi: 10.1038/ismej.2014.56. Epub 2014 Apr 24.
Nearly half of the Earth's surface is covered by the ocean populated by the most abundant photosynthetic organisms on the planet--Prochlorococcus cyanobacteria. However, in the oligotrophic open ocean, the majority of their cells in the top half of the photic layer have levels of photosynthetic pigmentation barely detectable by flow cytometry, suggesting low efficiency of CO2 fixation compared with other phytoplankton living in the same waters. To test the latter assumption, CO2 fixation rates of flow cytometrically sorted (14)C-labelled phytoplankton cells were directly compared in surface waters of the open Atlantic Ocean (30°S to 30°N). CO2 fixation rates of Prochlorococcus are at least 1.5-2.0 times higher than CO2 fixation rates of the smallest plastidic protists and Synechococcus cyanobacteria when normalised to photosynthetic pigmentation assessed using cellular red autofluorescence. Therefore, our data indicate that in oligotrophic oceanic surface waters, pigment minimisation allows Prochlorococcus cells to harvest plentiful sunlight more effectively than other phytoplankton.
地球表面近一半被海洋覆盖，而海洋中则生活着地球上数量最丰富的光合生物——海洋聚球藻蓝细菌。然而，在贫营养的开阔海域中，透光层上半部分的大多数细胞的光合色素水平几乎无法用流式细胞术检测到，这表明与生活在同一水域的其他浮游植物相比，其二氧化碳固定效率较低。为了验证后一种假设，我们直接比较了用流式细胞术分选的（14）C 标记浮游植物细胞在开阔大西洋海域（南纬 30°至北纬 30°）的表面水中的二氧化碳固定速率。当用细胞红色自发荧光评估的光合色素归一化时，海洋聚球藻的二氧化碳固定速率至少比最小的质体原生生物和海洋蓝细菌的二氧化碳固定速率高 1.5-2.0 倍。因此，我们的数据表明，在贫营养的海洋表面水中，色素最小化使海洋聚球藻细胞能够比其他浮游植物更有效地捕获丰富的阳光。
