Response of phytoplankton in an alpine lake to inputs of dissolved organic matter through nutrient enrichment and trophic forcing
Response of phytoplankton in an alpine lake to inputs of dissolved organic matter through nutrient enrichment and trophic forcing
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DOI：
10.4319/lo.2013.58.3.0867
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发表时间：
2013-05-01
影响因子：
4.5
通讯作者：
Saros, Jasmine E.
中科院分区：
文献类型：
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作者：
Kissman, Carrie E. H.;Williamson, Craig E.;Saros, Jasmine E.
由于气候变化、林线推进和昆虫流行等多重驱动因素，高山湖泊陆源溶解有机物(DOM)的输入正在增加。21天的微宇宙实验研究了增加陆地DOM补贴投入可能影响浮游植物密度、生长和物种组合的三种潜在机制：(1)直接通过提供营养物质促进选定浮游植物的生长(营养刺激假说)；(2)间接通过浮游动物的营养强迫统一增加所有选择性捕食浮游植物的浮游动物的总生物量(营养强度假说)；(3)通过支持选择性捕食浮游植物的浮游动物物种的营养强迫间接影响浮游动物(营养转移假说)。我们在完整的3x3析因设计中处理了DOM(陆地DOM添加与未处理对照)、浮游动物(存在与不存在)和孵化深度(表层与下层)。在DOM存在的情况下，浮游植物密度和生长显著增加，物种组合向近乎优势的方向转变。浮游动物的生物量和生长量随着DOM的添加而增加，但物种组合在不同处理中保持稳定，并有助于对浮游植物的选择性放牧效应。我们的数据支持营养刺激和营养强度假说。虽然DOM效应被经典地归因于添加固定碳的刺激，但我们的实验表明，营养刺激也很重要。此外，在没有DOM对浮游动物的选择性作用的情况下，营养强迫的间接DOM效应可能会发生。
Inputs of terrestrially derived dissolved organic matter (DOM) are increasing in alpine lakes due to multiple drivers such as climate change, tree line advancement, and insect epidemics. A 21 d microcosm experiment investigated three potential mechanisms by which increased inputs of terrestrial DOM subsidies might affect phytoplankton density, growth, and species assemblage: (1) directly, by providing nutrients enhancing growth of select phytoplankton species (nutrient stimulation hypothesis); (2) indirectly, through trophic forcing of zooplankton uniformly increasing the total biomass of all zooplankton that selectively graze on phytoplankton (trophic intensity hypothesis); and (3) indirectly, through trophic forcing of zooplankton by favoring zooplankton species that selectively graze on phytoplankton (trophic shift hypothesis). We manipulated DOM (terrestrial DOM additions vs. unmanipulated control), zooplankton (presence vs. absence), and incubation depth (epilimnion vs. hypolimnion) in a full 3 x 3 factorial design. Phytoplankton density and growth increased substantially and species assemblage shifted to near dominance by Asterionella formosa in the presence of DOM. Zooplankton biomass and growth increased with the addition of DOM, yet the species assemblage remained stable across treatments, and contributed to selective grazing effects on phytoplankton. Our data support the nutrient stimulation and trophic intensity hypotheses. While DOM effects have been classically attributed to stimulation by addition of fixed carbon, our experiments indicate that nutrient stimulation is also important. Additionally, the indirect DOM effect of trophic forcing can occur in the absence of selective effects of DOM on zooplankton.