Zhou Libin, Lemmen Kimberley D, Zhang Wei, Declerck Steven A J
Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands.
Jiangxi Provincial Key Laboratory of Water Resources and Environment of Poyang Lake, Jiangxi Institute of Water Sciences, Nanchang, China.
Front Microbiol. 2018 Feb 9;9:172. doi: 10.3389/fmicb.2018.00172. eCollection 2018.
One of the central tenets of ecological stoichiometry is that consumer growth rate is strongly determined by food phosphorus (P) content. In planktonic organisms population growth rates of zooplankton have repeatedly been shown to be reduced when fed with P-limited algal food sources. However, P-limitation may also affect other quality-related aspects of algae, such as biochemical composition or palatability. We studied the population growth, detailed life history and body elemental composition of the herbivorous rotifer, , in response to three different food quality treatments: algae cultured in high phosphorus conditions (average algal molar C:P ≈ 112, 'HP'), algae cultured in low P conditions (molar C:P ≈ 631, 'LP') and low-P cultured algae spiked with P just before feeding (molar C:P ≈ 113, 'LP+P'). LP+P algae thus combined high P content with a history of growth under P-limited conditions. Total P content and the C:P ratio of rotifers in the LP+P treatment equaled those of rotifers in the HP treatment. Rotifer population growth rates were higher in HP than in LP and intermediate in the LP+P treatment. Similarly, many life history traits observed for animals in the LP+P treatment, such as somatic growth rate, age at maturity, and egg production rate were also intermediate to those observed in the LP and HP treatments. However, there were important deviations from this pattern: size at first reproduction and egg mortality in the LP+P treatment equaled the HP treatment, whereas size and development time of the first eggs equaled those of the LP treatment. Our results indicate that elemental limitation cannot fully explain reduced performance of consumers fed with P-limited algae and strongly suggest that indirect, non-stoichiometric effects of P-limitation, e.g., via changes in biochemical composition or morphology of the algae also play a major role. Furthermore, our study highlights that such indirect effects have a differential impact on major fitness components and may as such also determine the population dynamics and demographic structure of consumer populations.
生态化学计量学的核心原则之一是，消费者的生长速率在很大程度上取决于食物中的磷（P）含量。在浮游生物中，当以磷受限的藻类食物为食时，浮游动物的种群增长率多次被证明会降低。然而，磷限制也可能影响藻类的其他与质量相关的方面，如生化组成或适口性。我们研究了草食性轮虫的种群增长、详细的生活史和身体元素组成，以响应三种不同的食物质量处理：在高磷条件下培养的藻类（平均藻类摩尔碳：磷≈112，“HP”）、在低磷条件下培养的藻类（摩尔碳：磷≈631，“LP”）以及在喂食前添加磷的低磷培养藻类（摩尔碳：磷≈113，“LP+P”）。因此，LP+P藻类将高磷含量与磷限制条件下的生长历史结合在一起。LP+P处理中轮虫的总磷含量和碳：磷比与HP处理中轮虫的相等。HP处理中轮虫的种群增长率高于LP处理，LP+P处理中的增长率处于中间水平。同样，在LP+P处理中观察到的许多动物生活史特征，如体细胞生长速率、成熟年龄和产卵率，也处于LP和HP处理中观察到的特征之间。然而，与这种模式存在重要偏差：LP+P处理中的首次繁殖时的大小和卵死亡率与HP处理相等，而第一批卵的大小和发育时间与LP处理相等。我们的结果表明，元素限制不能完全解释以磷受限藻类为食的消费者性能下降的原因，并强烈表明磷限制的间接、非化学计量学效应，例如通过藻类生化组成或形态的变化，也起着重要作用。此外，我们的研究强调，这种间接效应对主要适合度成分有不同的影响，因此也可能决定消费者种群的种群动态和种群结构。
