Altered food-web dynamics under increased nitrogen load in phosphorus deficient lakes
Altered food-web dynamics under increased nitrogen load in phosphorus deficient lakes
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DOI：
10.1007/s00027-017-0551-2
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发表时间：
2017
期刊：
影响因子：
2.4
通讯作者：
G. Trommer;Monika Poxleitner;P. Lorenz;Eleftherios Bitzilekis;Aleksandre Gogaladze;S. Schultes;H. Stibor
中科院分区：
文献类型：
--
作者：
G. Trommer;Monika Poxleitner;P. Lorenz;Eleftherios Bitzilekis;Aleksandre Gogaladze;S. Schultes;H. Stibor
大气氮沉降主要通过将生态系统的可用营养收支向过量氮状态转移来影响生态系统。在温带湖泊中，氮通常自然过剩，磷缺乏，与最佳的Redfield比例为16:1相比。为了研究未来氮含量增加对湖泊浮游生物群落的影响，我们在三个不同的富氮湖泊进行了中生态实验，这些湖泊都具有高氮磷比的特征。为了确定对氮负荷增加的功能响应，我们进行了6个氮肥处理。氮肥的施用是基于自然湿沉积中现有的硝酸盐和铵的浓度以及这些浓度的多次负荷。尽管初始条件是过量氮，但在所有湖泊中都观察到浮游生物群落对额外氮的去除。在一个湖泊中，在物种化学计量中可以看到磷限制的增加。在所有湖泊和每个湖泊的实验氮梯度中，我们发现了氮富集导致中浮游动物减少的证据。中浮游动物对N富集的负响应主要局限于枝海和鹦鹉螺。结果表明，在预测的未来大气氮沉积量范围内的氮富集可能导致缺磷湖泊中浮游动物的长期减少。氮富集的转移效应在较低的食物网动态可能对更高的营养水平，如鱼类的后果。
Atmospheric nitrogen deposition predominantly influences ecosystems by shifting their available nutrient budgets towards excess nitrogen conditions. In temperate lakes nitrogen is often naturally in excess and phosphorus is deficient, when compared with the optimal Redfield ratio of 16:1. To investigate effects of future increasing nitrogen conditions on lake plankton communities, we performed mesocosm experiments in three different nitrogen rich lakes, all characterised by high nitrogen to phosphorus ratios. In order to determine functional responses to increased nitrogen loading, we conducted six nitrogen fertilization treatments. Nitrogen fertilization was based upon existing nitrate and ammonium concentrations in natural wet deposition and multiple loadings of these concentrations. Despite the initial conditions of excess nitrogen, removal of additional nitrogen by the plankton community was observed in all of the lakes. In one lake, an increasing phosphorus limitation became visible in seston stoichiometry. Over all of the lakes and within each lake’s experimental nitrogen gradient, we found evidence for decreased mesozooplankton due to nitrogen enrichment. The negative responses of mesozooplankton to N enrichment were mainly restricted to cladocerans and nauplii. The results indicate that nitrogen enrichment within the magnitudes of projected future atmospheric nitrogen depositions may lead to a long-term reduction of mesozooplankton in phosphorus deficient lakes. The transfer of nitrogen enrichment effects on lower food-web dynamics could have consequences for higher trophic levels, such as fish.