Viergutz Carsten, Kathol Marcel, Norf Helge, Arndt Hartmut, Weitere Markus
Department of General Ecology and Limnology, Zoological Institute, University of Cologne, Cologne 50931, Germany.
Oecologia. 2007 Feb;151(1):115-24. doi: 10.1007/s00442-006-0544-7. Epub 2006 Sep 9.
Climate models predict an increasing frequency of extremely hot summer events in the northern hemisphere for the near future. We hypothesised that microbial grazing by the metazoan macrofauna is an interaction that becomes unbalanced at high temperatures due to the different development of the grazing rates of the metazoans and the growth rates of the microbial community with increasing temperature. In order to test this hypothesis, we performed grazing experiments in which we measured the impact of increasing temperatures on the development of the grazing rates of riverine mussels in relation to the growth rates of a unicellular prey community (a natural heterotrophic flagellate community from a large river). In a first experimental series using Corbicula fluminea as a grazer and under the addition of a carbon source (yeast extract), the increase of the prey's growth rates was considerably stronger than that of the predator's grazing rates when temperatures were increased from 19 to over 25 degrees C. This was also the outcome when the mussels had been acclimatized to warm temperatures. Hereafter, specific experiments with natural river water at temperatures of 25 and 30 degrees C were performed. Again, a strong decrease of the mussels' grazing rates in relation to the flagellate growth rates with increasing temperature occurred for two mussel species (C. fluminea and Dreissena polymorpha). When performing the same experiment using a benthic microbial predator community (biofilms dominated by ciliates) instead of the benthic mussels, an increase of the grazing rates relative to the growth rates with temperature could be observed. Our data suggest that predator-prey interactions (between metazoans and microbes) that are balanced at moderate temperatures could become unbalanced at high temperatures. This could have significant effects on the structure and function of microbial communities in light of the predicted increasing frequency of summer heat waves.
气候模型预测，在不久的将来，北半球极端炎热的夏季事件将越来越频繁。我们假设后生动物大型动物的微生物捕食是一种在高温下会失衡的相互作用，因为后生动物的捕食率和微生物群落的生长率会随着温度升高而呈现不同的发展态势。为了验证这一假设，我们进行了捕食实验，测量温度升高对河蚌捕食率发展的影响，并将其与单细胞猎物群落（一条大河中的天然异养鞭毛虫群落）的生长率进行对比。在第一个实验系列中，以河蚬作为捕食者，并添加碳源（酵母提取物），当温度从19℃升高到25℃以上时，猎物生长率的增加明显强于捕食者的捕食率。当贻贝适应温暖温度时，结果也是如此。此后，在25℃和30℃的温度下，用天然河水进行了特定实验。同样，对于两种贻贝物种（河蚬和多形饰贝），随着温度升高，贻贝的捕食率相对于鞭毛虫生长率大幅下降。当使用底栖微生物捕食者群落（以纤毛虫为主的生物膜）代替底栖贻贝进行相同实验时，可以观察到捕食率相对于生长率随温度升高而增加。我们的数据表明，在中等温度下平衡的捕食者 - 猎物相互作用（后生动物与微生物之间）在高温下可能会失衡。鉴于预计夏季热浪频率增加，这可能会对微生物群落的结构和功能产生重大影响。
