Nitrate increases zooxanthellae population density and reduces skeletogenesis in corals
Nitrate increases zooxanthellae population density and reduces skeletogenesis in corals
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DOI：
10.1007/bf00942117
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发表时间：
1996-12-01
期刊：
影响因子：
2.4
通讯作者：
Davies, PS
中科院分区：
文献类型：
--
作者：
Marubini, F;Davies, PS
关于硝酸盐对珊瑚的影响的资料很少，尽管这是热带富营养化沿海沃茨中氮的主要形式。在这项研究中，我们孵育小块的Porites porites和外植体的Montastrea annularis在实验室photostats照射卤素灯，浓度为0，1，5和20 μ M的硝酸盐，为40和30天，分别。在这一时期结束时，发现虫黄藻的种群密度随着硝酸盐浓度的增加而显著增加，这表明对照组中虫黄藻的生长速率受到氮的限制。每个藻细胞的叶绿素a和cz的量、藻细胞的体积和每个细胞的蛋白质也有显著增加。总体而言，每单位表面的蛋白质增加，但这仅仅是由于增加藻类蛋白质：有没有显着的变化，在主机蛋白质。最大总光合作用归一化表面积的硝酸盐增加，反映了藻类种群密度的增加。当以每个细胞为基础进行标准化时，没有变化。硝酸盐降低了相对于蛋白质含量的呼吸速率。最显着的变化是在率的骨骼，减少了相似或等于50%，在这两个物种时，暴露于硝酸盐富集。提出了一个模型，这表明，从周围的海水中的扩散限制供应的CO2优先使用的扩大的虫黄藻种群进行光合作用，从而减少了无机碳的钙化。它的结论是，在热带沿海沃茨的硝酸盐水平的提高将有一个迄今为止尚未认识到的热带珊瑚礁的生长速度的影响。
Very little information exists on the effects of nitrate on corals, although this is the major form in which nitrogen is present in tropical eutrophic coastal waters. In this study we incubated nubbins of Porites porites and explants of Montastrea annularis in laboratory photostats illuminated by halide lamps, with concentrations of nitrate of 0, 1, 5 and 20 mu M, for 40 and 30 d, respectively. At the end of this period it was found that the population density of the zooxanthellae had increased significantly with increased nitrate concentration, suggesting nitrogen limitation of the growth rate of Zooxanthellae in the control group. There were also significant increases in the amount of chlorophyll a and cz per algal cell, in the volume of the algal cells, and in the protein per cell. Overall, the protein per unit surface increased, but this was attributable solely to increased algal protein: there was no significant change in host protein. Maximum gross photosynthesis normalized to surface area was enhanced by nitrate addition, reflecting the increase in algal population density. There was no change when normalized on a per cell basis. Respiration rate normalized to protein content was decreased by nitrate. The most dramatic change was in the rate of skeletogenesis, which decreased by similar or equal to 50% in both species when exposed to nitrate enrichment. A model is presented which suggests that the diffusion-limited supply of CO2 from surrounding seawater is used preferentially by the enlarged zooxanthellae population for photosynthesis, thereby reducing the availability of inorganic carbon for calcification. It is concluded that enhanced nitrate levels in tropical coastal waters will have a hitherto unrecognized effect on the growth I-ate of tropical coral reefs.