Nutrients associated with terrestrial dissolved organic matter drive changes in zooplankton: phytoplankton biomass ratios in an alpine lake
Nutrients associated with terrestrial dissolved organic matter drive changes in zooplankton: phytoplankton biomass ratios in an alpine lake
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DOI：
10.1111/fwb.12847
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发表时间：
2017-01-01
影响因子：
2.7
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.
1.由于气候变化和其他环境胁迫，许多湖泊中的溶解有机物(DOM)正在增加。通过对陆地DOM进行为期21天的微宇宙实验，研究了DOM对浮游动物/浮游植物生物量比(z：P)的影响。我们预测，如果添加DOM通过刺激微生物环路从而增加浮游动物可用于较高营养水平的固定碳量，则z：P将增加。然而，如果DOM的添加增加了固定碳以外的其他营养物质，我们预测由于浮游植物的营养刺激从而增强了浮游动物，z：P保持稳定或下降。在高山湖泊表层(浅；1.5m)和浅层(深；8.0m)中培养的微型宇宙(密封袋)中，评估了陆源DOM对浮游动物、浮游植物、z：P和浮游动物净采食的影响。在实验第21天，添加DOM的处理(DOM+)的浮游植物生物量比对照增加了6.0到7.5倍，但浮游动物生物量只增加了1.3到1.5倍。因此，DOM+处理(比率：2.3深和4.4浅)的z：P低于对照处理(比率：13.4深和17.5浅)，这证明DOM的添加除了提供促进浮游植物生物量积累的固定碳外，还提供了营养补贴。实验期间浮游动物生物量的增加幅度与实验开始时密封袋中DOM中溶解有机碳(DOC)的总量相似，这表明浮游动物生物量的刺激是由于浮游植物生物量的增加，而不是通过微生物环的DOM，后者会有更大的营养转移损失。与对照相比，DOM+处理的消费者净放牧效应在浅层降低了2.8倍，在深层降低了2.9倍，表明浮游动物不能对初级生产力施加强大的自上而下的控制。在研究海洋生态系统对陆地DOM输入的响应时，需要考虑营养物质的作用，特别是在DOC浓度较低的湖泊中。
1. Dissolved organic matter (DOM) is increasing in many lakes due to climate change and other environmental forcing. A 21-day microcosm experiment that manipulated terrestrial DOM was used to determine the effect of DOM on zooplankton: phytoplankton biomass ratios (z:p). We predicted that if DOM additions increase the amount of fixed carbon available for higher trophic levels through stimulation of the microbial loop and hence zooplankton, the z: p will increase. However, if DOM additions increase other nutrients besides fixed carbon, we predict stable or decreasing z: p due to nutrient stimulation of phytoplankton that subsequently enhances zooplankton.2. The effects of experimental additions of terrestrially derived DOM on zooplankton, phytoplankton, z: p and zooplankton net grazing were assessed in microcosms (sealed bags) incubated in the epilimnion (shallow; 1.5 m) and hypolimnion (deep; 8.0 m) strata of an alpine lake.3. DOM addition treatments (DOM+) had a 6.0- to 7.5-fold increase in phytoplankton biomass relative to controls, but only a 1.3- to 1.5-fold increase in zooplankton biomass, on day 21 of the experiment. The z: p was, thus, lower in the DOM+ treatments (ratios: 2.3 deep and 4.4 shallow) than in the control treatments (ratios: 13.4 deep and 17.5 shallow), providing evidence that DOM additions provide nutrient subsidies besides fixed carbon that stimulate phytoplankton biomass accumulation.4. The increase in zooplankton biomass during the experiment was similar in magnitude to the total amount of dissolved organic carbon (DOC) in the DOM added in the sealed bags at the beginning of the experiment, which suggests zooplankton biomass stimulation due to increased phytoplankton biomass, and not from DOM through the microbial loop, which would have greater trophic transfer losses. The consumer net grazing effect in the DOM+ treatments was reduced by 2.8-fold in the shallow stratum and by 2.9-fold in the deep stratum relative to the control treatments, indicating that zooplankton were unable to exert strong top-down control on the primary producers.5. The role of nutrients needs to be considered when examining the response of pelagic ecosystems to inputs of terrestrial DOM, especially in lakes with lower DOC concentrations.