Global Warming: Testing for Direct and Indirect Effects of Temperature at the Interface of Primary Producers and Herbivores Is Required
Global Warming: Testing for Direct and Indirect Effects of Temperature at the Interface of Primary Producers and Herbivores Is Required
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DOI：
10.3389/fevo.2018.00087
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发表时间：
2018-06
影响因子：
3
通讯作者：
E. von Elert;P. Fink
中科院分区：
文献类型：
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作者：
E. von Elert;P. Fink
在水生食物网中，全球变暖可能会通过增加地表水温和改变浮游植物的生化成分来影响更高的营养水平。相关性表明，水蚤（淡水中浮游植物的主要消费者）的生长受到天然浮游植物中多不饱和脂肪酸二十碳五烯酸（EPA）含量低的限制，从而受到食品质量的限制。在这里，我们使用不含 EPA 的绿藻 Chlamydomonas klinabasis 和 Daphnia magna 来测试此类食品质量影响。藻类在 15°C、20°C 和 25°C 的连续培养物中生长，与其他研究不同的是，稀释率解释了温度对藻类生长的影响。这导致在 20°C 下生长时，总脂肪酸、总 PUFA、n-3 PUFA 和 α-亚麻酸含量达到最大，而在 15°C 下，观察到 n-6 PUFA 含量最低，n-3/n-6 比率比 20°C 和 25°C 高出三倍。出乎意料的是，PUFA 含量在 15°C 时并未显示最大值。 D. magna 的生长实验在 15°C、20°C 和 25°C 下进行。当 C. klinobasis 在 20°C 下生长时，水蚤体细胞生长速率随温度升高而增加。当藻类在与水蚤相同的温度下饲养时，水蚤的体细胞生长速率随温度增加而增加，并且补充表明EPA仅在15°C下受到限制。在 15°C 和 25°C 下，在相应温度下生长的 C. klinobasis 上的水蚤生长明显高于在 20°C 下生长的相同藻类。因此，估计温度对水蚤生长的影响需要在相同的温度下种植食物。在 15°C 时，新建水蚤生物质的总 PUFA 和 α-亚麻酸含量最高，而 EPA 含量在 20°C 时最高。 n-6 PUFAs的含量随着温度的升高而增加，导致n-3/n-6 PUFAs的比例在15°C时最高。这反映了水蚤在较低温度下 PUFA 同化增加，但 EPA 合成减少。结果表明，只有当藻类食品和消费者在相同温度下生长时，才能更准确地预测全球变暖对食品质量的影响。
In aquatic food webs, global warming may affect higher trophic levels by increased surface water temperatures and by changing the biochemical composition of phytoplankton. Correlations have suggested that growth of Daphnia, a major consumer of phytoplankton in freshwaters, is limited by a low content of the polyunsaturated fatty acid eicosapentaenoic acid (EPA) in natural phytoplankton and thus by food quality. Here we used the EPA-free green alga Chlamydomonas klinobasis and Daphnia magna to test for such food quality effects. The alga was grown in continuous cultures at 15°C, 20°C and 25°C and, different from other studies, dilution rates accounted for the effects of temperature on algal growth. This resulted in a maximum content of total fatty acids, of total PUFAs, of n-3 PUFAs and of α-linolenic acid when grown at 20°C, whereas at 15°C the lowest content of n-6 PUFAs and a threefold higher n-3/n-6 ratio than at 20°C and 25°C were observed. Unexpectedly the PUFA content did not show a maximum at 15°C. Growth experiments with D. magna were performed at 15°C, 20°C, and 25°C. With C. klinobasis grown at 20°C, Daphnia somatic growth rates increased with temperature. When the alga was raised at the same temperature as Daphnia, somatic growth rates of Daphnia increased with temperature, and supplementation indicated EPA-limitation at 15°C only. At 15°C and at 25°C, Daphnia growth was significantly higher on C. klinobasis raised at the respective temperature than on the same alga grown at 20°C. Hence, estimation of temperature effects on Daphnia growth requires to grow the food at the same temperature. At 15°C Daphnia newly built biomass had the highest content in total PUFAs and in α-linolenic acid, whereas the EPA-content was highest at 20°C. The content of n-6 PUFAs increased with temperature, which lead to the highest ratio of n-3/n-6 PUFAs at 15°C. This reflects increased PUFA-assimilation but decreased EPA-synthesis in Daphnia at lower temperatures. The results indicate that only if both algal food and consumer are grown at the same temperature, food quality effects of global warming can be more precisely predicted.