Mitigation of adverse effects of rising CO2 on a planktonic herbivore by mixed algal diets
Mitigation of adverse effects of rising CO2 on a planktonic herbivore by mixed algal diets
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DOI：
10.1111/j.1365-2486.2008.01720.x
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发表时间：
2009-02
影响因子：
11.6
通讯作者：
J. Urabe;Naoko Waki
中科院分区：
文献类型：
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作者：
J. Urabe;Naoko Waki
由于包括植物和藻类物种在内的初级生产者中氮和磷（P）等关键营养物质的含量相对于碳的含量下降，预计未来大气中二氧化碳的增加预计将对草食动物的生长产生不利影响。然而，由于许多食草动物是多食性的，并且初级生产者对二氧化碳浓度升高的反应具有高度的物种特异性，因此二氧化碳浓度升高对食草动物生长的影响可能会因单一生产者饮食和多生产者饮食的饲养条件而有所不同。为了检验这种可能性，我们在 P 限制条件下对浮游草食动物水蚤和三种藻类（绿藻）、小环藻进行了 CO2 操纵实验。 （硅藻）和聚球藻属 sp。 （蓝细菌）。单一藻类（单一培养物）和多种藻类（混合培养物）的半批量培养物在环境（360 ppm）和湖泊自然范围内的高二氧化碳水平（2000 ppm）下生长。在单一培养物和混合培养物中，当藻类在高 CO2 条件下生长时，藻类稳态丰度增加，但藻类 P:C 和 N:C 比率下降。正如预期的那样，尽管藻类丰度增加，但以高二氧化碳培养的单一藻类为食的水蚤的生长速度却下降了。然而，当饲喂在高二氧化碳条件下培养的混合藻类时，特别是由硅藻和蓝细菌或三种藻类组成的藻类，尽管藻类饮食中的磷和氮含量相对于碳含量较低，但水蚤仍保持较高的生长率。这些结果表明，由多种藻类组成的饮食可以减轻二氧化碳浓度升高对草食动物性能的不利影响，尽管这种缓解的程度取决于饮食中涉及的藻类物种的组成。
Putative future increase in atmospheric CO2 is expected to adversely affect herbivore growth due to decrease in contents of key nutrients such as nitrogen and phosphorus (P) relative to carbon in primary producers including plant and algal species. However, as many herbivores are polyphagous and as the response of primary producers to elevated CO2 is highly species‐specific, effects of elevated CO2 on herbivore growth may differ between feeding conditions with monospecific and multiproducer diets. To examine this possibility, we performed CO2 manipulation experiments under a P‐limited condition with a planktonic herbivore, Daphnia, and three algal species, Scenedesmus obliquus (green algae), Cyclotella sp. (diatoms) and Synechococcus sp. (cyanobacteria). Semibatch cultures with single algal species (monocultures) and multiple algal species (mixed cultures) were grown at ambient (360 ppm) and high CO2 levels (2000 ppm) that were within the natural range in lakes. Both in the mono‐ and mixed cultures, algal steady state abundance increased but algal P : C and N : C ratios decreased when they were grown at high CO2. As expected, Daphnia fed monospecific algae cultured at high CO2 had decreased growth rates despite increased algal abundance. However, when fed mixed algae cultured at high CO2, especially consisting of diatoms and cyanobacteria or the three algal species, Daphnia maintained high growth rates despite lowered P and N contents relative to C in the algal diets. These results imply that algal diets composed of multiple species can mitigate the adverse effects of elevated CO2 on herbivore performance, although the magnitude of this mitigation depends on the composition of algal species involved in the diets.