Nitrate, ammonium, and phosphorus drive seasonal nutrient limitation of chlorophytes, cyanobacteria, and diatoms in a hyper-eutrophic reservoir
Nitrate, ammonium, and phosphorus drive seasonal nutrient limitation of chlorophytes, cyanobacteria, and diatoms in a hyper-eutrophic reservoir
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DOI：
10.1002/lno.11363
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发表时间：
2019-10-25
影响因子：
4.5
通讯作者：
Vanni, Michael J.
中科院分区：
文献类型：
--
作者：
Andersen, Isabelle M.;Williamson, Tanner J.;Vanni, Michael J.
氮(N)和磷(P)输入影响藻类群落结构和功能。氮和磷供应的速率和比例，以及不同的氮形式（如NO3和NH4），从外部负荷和内部循环可以是高度季节性的。然而，营养供应的季节性与藻类营养限制之间的相互作用仍然知之甚少。我们研究了一个超富营养化水库中养分限制的季节性变化和对N形态的响应，该水库经历了季节性的养分投入和比例升高。外部氮磷负荷在春季高，夏季低，此时内部负荷因为更重要，降低了负荷的氮磷比。流域硝态氮供给量在春季占主导地位，而内部氨态氮供给量在夏季变得重要。我们量化了浮游植物群（硅藻、绿藻和蓝藻）如何受到N或P的限制，以及它们的N形态偏好（NH4 vs. NO3），每周进行一次实验（5 - 10月）。浮游植物春季受磷限制，夏季过渡到氮素限制或共生（初级氮素），秋季翻转后恢复到磷限制。在氮素限制（或共仿）条件下，NH4对绿藻和蓝藻的刺激作用更强，而NO3对硅藻的刺激作用通常相同，甚至更强。蓝藻异母细胞的发育伴随着限氮条件的开始，有几周的滞后时间，但异母细胞的产生并没有完全缓解限氮条件。研究表明，浮游植物种群在限制养分和氮形态偏好方面存在季节性差异，表明需要采用氮、磷和氮形态的双重营养管理策略来控制富营养化。
Nitrogen (N) and phosphorus (P) inputs influence algal community structure and function. The rates and ratios of N and P supply, and different N forms (e.g., NO3 and NH4), from external loading and internal cycling can be highly seasonal. However, the interaction between seasonality in nutrient supply and algal nutrient limitation remains poorly understood. We examined seasonal variation in nutrient limitation and response to N form in a hyper-eutrophic reservoir that experiences elevated, but seasonal, nutrient inputs and ratios. External N and P loading is high in spring and declines in summer, when internal loading because more important, reducing loading N:P ratios. Watershed NO3 dominates spring N supply, but internal NH4 supply becomes important during summer. We quantified how phytoplankton groups (diatoms, chlorophytes, and cyanobacteria) are limited by N or P, and their N form preference (NH4 vs. NO3), with weekly experiments (May-October). Phytoplankton were P-limited in spring, transitioned to N limitation or colimitation (primary N) in summer, and returned to P limitation following fall turnover. Under N limitation (or colimitation), chlorophytes and cyanobacteria were more strongly stimulated by NH4 whereas diatoms were often equally, or more strongly, stimulated by NO3 addition. Cyanobacteria heterocyte development followed the onset of N-limiting conditions, with a several week lag time, but heterocyte production did not fully alleviate N-limitation. We show that phytoplankton groups vary seasonally in limiting nutrient and N form preference, suggesting that dual nutrient management strategies incorporating both N and P, and N form are needed to manage eutrophication.