Stoichiometric effects of warming on herbivore growth: experimental test with plankters
Stoichiometric effects of warming on herbivore growth: experimental test with plankters
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DOI：
10.1890/es11-00178.1
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发表时间：
2011-07
期刊：
影响因子：
2.7
通讯作者：
W. Makino;Qingwan Gong;J. Urabe
中科院分区：
文献类型：
--
作者：
W. Makino;Qingwan Gong;J. Urabe
最近的研究表明，假定的变暖提高了许多湖泊的水温。温度升高会直接影响湖泊生物的生长速度；然而，湖泊食草动物对温度升高的生长反应可能是复杂的。例如，在营养供应有限的情况下，温度升高可能会加速浮游植物的生长，但最终会减少它们的营养含量，这反过来又可能减少食草动物的生长。因此，根据栖息地的营养状况，温度驱动的食物营养含量下降可能抵消变暖对食草动物生长的积极影响。我们通过实验室实验，在不同的磷条件下，同时控制绿藻（Scenedesmus）和浮游食草动物（Daphnia）之间的温度和化学计量相互作用，来检验这一假设。在相同的温度下（12、16、20和24℃），用Scenedesmus和Daphnia进行实验。在第一个实验中，在固定的稀释率（即藻损失率）下，以四种不同的供磷率进行半批培养。在第二个实验中，在固定的磷供应水平下，以四种不同的稀释率生长藻类。然后，每天收获稳态藻类，直接喂给水蚤幼鱼，以测量它们在两个实验中的特定生长速率。在两个实验中，温度的升高都加速了水蚤的生长。然而，温度的影响随着磷供应率和稀释率的降低而减弱，尽管藻类足够丰富。这是因为藻类的磷碳比随着温度的升高而降低，特别是当藻类的磷可利用性由于磷供应或稀释率低而很小时。结果首次清楚地表明，变暖对草食动物生长的直接刺激可以被不良的食物化学计量所抵消。我们认为，在由于营养投入低而藻类生长速度低的湖泊或由于缺乏藻类食草动物而藻类损失率低的湖泊中，尽管藻类生物量增加，但变暖可能间接减缓草食动物的生长。
Recent studies have shown that putative warming increases water temperatures in many lakes. A higher temperature would directly affect the growth rates of lake organisms; however, the growth responses of lake herbivores to increased temperatures may be complex. Under limited nutrient supplies, for example, increased temperature may accelerate the growth of phytoplankton but consequently decrease their nutrient content, which may in turn reduce herbivore growth. Thus, temperature-driven declines in food nutrient content may offset the positive effects of warming on herbivore growth depending on the trophic condition of habitats. We examined this hypothesis by laboratory experiments that simultaneously manipulated temperature and stoichiometric interactions between green algae (Scenedesmus) and a planktonic herbivore (Daphnia) under various phosphorous conditions. The following experiments were performed with Scenedesmus and Daphnia at the same temperatures (12, 16, 20 and 24°C). In the first experiment, Scenedesmus were grown in semi-batch cultures at four different phosphorus supply rates with a fixed dilution rate (i.e., algal loss rate). In the second experiment, algae were grown at four different dilution rates with a fixed phosphorus supply level. Then, the steady-state algae were harvested daily and fed directly to juvenile Daphnia to measure their specific growth rates in both experiments. Increased temperature accelerated Daphnia growth in both experiments. However, the effect of temperature decreased with decreasing phosphorus supply rate and dilution rates, although algae were sufficiently abundant. This was because the algal phosphorus:carbon ratio decreased with increasing temperature, especially when phosphorus availability for algae was small due to low phosphorus supply or dilution rates. The results clearly showed for the first time that direct stimulation of herbivore growth by warming can be offset by poor food stoichiometry. We suggest that in lakes with low algal growth rates due to low nutrient inputs or in lakes with low algal loss rates due to a shortage of algal grazers, warming may indirectly slow herbivore growth despite increased algal biomass.