Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
Ecol Lett. 2013 Feb;16(2):225-33. doi: 10.1111/ele.12033. Epub 2012 Nov 23.
The metabolic theory of ecology predicts that temperature affects heterotrophic processes more strongly than autotrophic processes. We hypothesized that this differential temperature response may shift mixotrophic organisms towards more heterotrophic nutrition with rising temperature. The hypothesis was tested in experiments with the mixotrophic chrysophyte Ochromonas sp., grown under autotrophic, mixotrophic and heterotrophic conditions. Our results show that (1) grazing rates on bacterial prey increased more strongly with temperature than photosynthetic electron transport rates, (2) heterotrophic growth rates increased exponentially with temperature over the entire range from 13 to 33 °C, while autotrophic growth rates reached a maximum at intermediate temperatures and (3) chlorophyll contents during mixotrophic growth decreased at high temperature. Hence, the contribution of photosynthesis to mixotrophic growth strongly decreased with temperature. These findings support the hypothesis that mixotrophs become more heterotrophic with rising temperature, which alters their functional role in food webs and the carbon cycle.
生态代谢理论预测，温度对异养过程的影响比对自养过程的影响更强。我们假设，随着温度的升高，这种差异的温度响应可能会使混合营养体更倾向于以异养方式获取营养。该假说通过对混合营养型金藻 Ochromonas sp.的实验进行了检验，该藻类在自养、混合营养和异养条件下生长。我们的研究结果表明：（1）与光合作用电子传递速率相比，细菌猎物的摄食率随温度升高而增加的幅度更大；（2）异养生长速率随温度呈指数增长，在 13 到 33°C 的整个范围内，而自养生长速率在中等温度下达到最大值；（3）混合营养生长过程中的叶绿素含量在高温下降低。因此，光合作用对混合营养生长的贡献随温度的升高而强烈降低。这些发现支持了这样的假设，即随着温度的升高，混合营养体变得更加异养，从而改变了它们在食物网和碳循环中的功能作用。
