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Episodic nutrient enrichments stabilise protist coexistence in planktonic oligotrophic conditions
Journal of Ecology ( IF 5.3 ) Pub Date : 2021-01-11 , DOI: 10.1111/1365-2745.13591 Aitziber Zufiaurre 1 , Marisol Felip 1, 2 , Pau Giménez‐Grau 3 , Sergi Pla‐Rabès 1 , Lluís Camarero 4 , Jordi Catalan 1, 5
中文翻译：
阵发性营养富集稳定浮游性贫营养条件下原生生物的共存
更新日期：2021-01-11
Journal of Ecology ( IF 5.3 ) Pub Date : 2021-01-11 , DOI: 10.1111/1365-2745.13591 Aitziber Zufiaurre 1 , Marisol Felip 1, 2 , Pau Giménez‐Grau 3 , Sergi Pla‐Rabès 1 , Lluís Camarero 4 , Jordi Catalan 1, 5
Affiliation
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- Seasonal compositional changes in plankton communities are usually considered as species replacements. Given the enormous number of individuals integrating the communities and our limited capacity to count and determine most of them, we likely observe only alternative population peaks of some of the coexisting species. The contemporary coexistence theory addresses coexistence in communities of competing species, considering relative fitness inequalities and stabilising niche differences as components of average long‐term growth rates. Here, we experimentally show that the response patterns predicted by the theory occur when varying nutrient pulses fertilise the planktonic community.
- We used gently self‐filling 100‐L enclosures to minimise the disturbance of the initial community and different pulse P and N additions to manipulate the apparently species‐poor epilimnetic community of an ultraoligotrophic P‐limited lake. We measured and compared the protist species growth response to gradients of P enrichment and N stoichiometric imbalance. The P and N levels used in most treatments were within the oligotrophic seasonal and inter‐annual variations of the lake and were higher in a few extreme treatments that provided mesotrophic conditions of the remote regions affected by N atmospheric contamination. We alternatively replicated all treatments using ammonium or nitrate as the N source.
- Most protist species, recorded in this lake across seasons in previous studies, were recovered, indicating a persistent assemblage of species that is seasonally hidden from observation. Recovery included some rare species observed only in the slush layers of the seasonal snow and ice cover. The coexistence‐stabilising mechanisms were indicated by treatment response features, such as frequency‐dependent growth, inverse relationship between fitness inequality and niche differentiation proxies, high‐rank taxonomic levels clustering across the limiting‐nutrient gradient but segregation at the species level according to the type of N supply and resting stage development depending on nutrient conditions. The response similarities between autotrophic and heterotrophic organisms indicate a network of interactions that may reinforce coexistence.
- Synthesis. The results indicate that many planktonic protist species in oligotrophic waters can show stable long‐term non‐equilibrium coexistence by alternately recovering from very low densities when episodic nutrient enrichments, of varying P and N amounts and composition, occur.
中文翻译：
阵发性营养富集稳定浮游性贫营养条件下原生生物的共存
- 浮游生物群落的季节性组成变化通常被认为是物种的替代。鉴于整合社区的个人数量众多，而我们计数和确定其中大多数的能力有限，因此我们很可能只观察到某些共存物种的另类种群高峰。当代的共存理论将竞争适应性不平等和稳定的生态位差异作为平均长期增长率的组成部分，解决了竞争物种群落中的共存问题。在这里，我们实验表明，当营养素脉冲变化使浮游生物受精时，就会发生该理论所预测的响应模式。
- 我们使用了100 L的自填充容器，以最小化初始群落的扰动，并添加了不同的P和N脉冲，以控制超营养型P限制湖泊中物种贫乏的表生群落。我们测量并比较了原生生物对P富集和N化学计量失衡梯度的生长响应。大多数处理中使用的磷和氮水平都在湖泊的贫营养季节和年际变化范围内，而在一些极端处理中则更高，这些极端处理提供了受N大气污染影响的偏远地区的中营养条件。或者，我们使用氨或硝酸盐作为氮源重复了所有处理。
- 在以前的研究中，该湖中各个季节记录的大多数原生生物都得到了恢复，这表明该物种的持续聚集在季节上是不可观测的。恢复包括仅在季节性冰雪覆盖层的冰层中观察到的一些稀有物种。治疗反应特征表明了共存稳定机制，例如频率依赖性生长，适应性不平等与生态位分化代理之间的逆向关系，高等分类学水平在有限营养梯度上聚集，但根据物种在物种水平上分离。氮素供应的类型和休息阶段的发展取决于养分状况。自养生物和异养生物之间的反应相似性表明可能加强相互作用的相互作用网络。
- 综合。结果表明，当营养盐富集，磷和氮的含量和组成发生变化时，从极低的密度中交替恢复，贫营养水域中的许多浮游生物都可以显示稳定的长期非平衡共存。
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