Differing Daphnia magna assimilation efficiencies for terrestrial, bacterial, and algal carbon and fatty acids.
Differing Daphnia magna assimilation efficiencies for terrestrial, bacterial, and algal carbon and fatty acids.
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DOI：
10.1890/13-0650.1
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发表时间：
2014-02
期刊：
影响因子：
4.8
通讯作者：
S. Taipale;M. Brett;Martin W Hahn;D. Martin‐Creuzburg;S. Yeung;Minna Hiltunen;U. Strandberg;P. Kankaala
中科院分区：
文献类型：
--
作者：
S. Taipale;M. Brett;Martin W Hahn;D. Martin‐Creuzburg;S. Yeung;Minna Hiltunen;U. Strandberg;P. Kankaala
碳和限制生长的元素和生化营养物质被提供给上层营养水平的途径引起了相当大的兴趣。脂肪酸和甾醇是通过食物网的动植物界面转移的最重要的分子之一。在湖泊生态系统中，除了浮游植物外，细菌和陆地有机质是浮游动物的潜在营养资源，特别是在那些接受高陆地有机质输入的湖泊生态系统中。因此，我们测试了大型甲壳动物在消耗这些资源时对碳、氮和脂肪酸的同化作用。用优质(隐藻)和中质(衣藻)的单一饲料饲养大型水蚤。和栅栏)浮游植物，两个异养细菌菌株，以及来自全球分散的河滨草芦荟的颗粒，代表陆地颗粒有机碳(t-POC)。我们还用不同的混合饲料喂养水蚤，并比较了不同处理下水蚤对脂肪酸、碳和氮的同化。我们的结果表明，细菌是营养不足的饮食，因为它们缺乏甾醇和多不饱和omega-3和omega-6(omega-3和omega-6)脂肪酸(PUFAs)。然而，如果浮游植物满足其对必需脂肪酸和甾醇的基本需求，水蚤能够有效地利用放线菌中的碳和氮。与细菌相比，t-POC含有甾醇、omega-6和omega-3脂肪酸，但分别只占浮游植物水平的22%、1.4%和0.2%，这表明t-poc食品质量尤其受到omega-3多不饱和脂肪酸的限制。根据稳定同位素和脂肪酸分析，我们的结果还表明，t-POC和细菌对碳的同化比对脂肪酸的同化更高。只有当t-POC的比例为>；60%时，t-POC对碳和脂肪酸的同化率才相对较高(>；20%)，但由于多不饱和脂肪酸与碳的比例较低，这种条件下的水蚤生长较差。由于与混合浮游植物的细菌相比，t-poc对碳、氮和脂肪酸的同化较低，我们得出结论，微生物食物网是由浮游植物支持的，而不是直接的t-poc消耗，可能支持浮游动物的生产。我们的结果表明，陆地颗粒有机碳对湖泊上层营养水平的支持作用很差。
There is considerable interest in the pathways by which carbon and growth-limiting elemental and biochemical nutrients are supplied to upper trophic levels. Fatty acids and sterols are among the most important molecules transferred across the plant-animal interface of food webs. In lake ecosystems, in addition to phytoplankton, bacteria and terrestrial organic matter are potential trophic resources for zooplankton, especially in those receiving high terrestrial organic matter inputs. We therefore tested carbon, nitrogen, and fatty acid assimilation by the crustacean Daphnia magna when consuming these resources. We fed Daphnia with monospecific diets of high-quality (Cryptomonas marssonii) and intermediate-quality (Chlamydomonas sp. and Scenedesmus gracilis) phytoplankton species, two heterotrophic bacterial strains, and particles from the globally dispersed riparian grass, Phragmites australis, representing terrestrial particulate organic carbon (t-POC). We also fed Daphnia with various mixed diets, and compared Daphnia fatty acid, carbon, and nitrogen assimilation across treatments. Our results suggest that bacteria were nutritionally inadequate diets because they lacked sterols and polyunsaturated omega-3 and omega-6 (omega-3 and omega-6) fatty acids (PUFAs). However, Daphnia were able to effectively use carbon and nitrogen from Actinobacteria, if their basal needs for essential fatty acids and sterols were met by phytoplankton. In contrast to bacteria, t-POC contained sterols and omega-6 and omega-3 fatty acids, but only at 22%, 1.4%, and 0.2% of phytoplankton levels, respectively, which indicated that t-POC food quality was especially restricted with regard to omega-3 PUFAs. Our results also showed higher assimilation of carbon than fatty acids from t-POC and bacteria into Daphnia, based on stable-isotope and fatty acids analysis, respectively. A relatively high (>20%) assimilation of carbon and fatty acids from t-POC was observed only when the proportion of t-POC was >60%, but due to low PUFA to carbon ratio, these conditions yielded poor Daphnia growth. Because of lower assimilation for carbon, nitrogen, and fatty acids from t-POC relative to diets of bacteria mixed with phytoplankton, we conclude that the microbial food web, supported by phytoplankton, and not direct t-POC consumption, may support zooplankton production. Our results suggest that terrestrial particulate organic carbon poorly supports upper trophic levels of the lakes.