State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
Environ Pollut. 2022 May 1;300:118968. doi: 10.1016/j.envpol.2022.118968. Epub 2022 Feb 5.
The popular paradigm in trophic dynamic theory is that contemporary autochthonous organic matter (e.g., phytoplankton) sustains consumer growth, whereas aged allochthonous organic matter is conceptually considered recalcitrant resources that may only be used to support consumer respiration but suppress consumer growth. This resource-age paradigm has been challenged by a growing body of recent evidence that ancient (radiocarbon depleted) organic carbon (OC) released from glaciers and permafrost can be incorporated by consumers in aquatic systems. However, little information is available regarding the food quality of ancient terrestrial OC and how it impacts the growth of consumers in lakes. Here, ancient dissolved organic carbon (DOC) was extracted from frozen soils in an alpine lake catchment. The contents of polyunsaturated fatty acids (PUFAs) in soil DOC increased significantly after bioconversion by heterotrophic bacteria. The utilization of soil DOC by heterotrophic bacteria also increased the total phosphorus concentration in the systems. Gammaproteobacteria and Betaproteobacteria showed a strong negative correlation with the percentage contents of fluorescent components, including humic-like and tyrosine-like components. Daphnia magna were fed Auxenochlorella vulgaris and ancient DOC plus heterotrophic bacteria. The contents of PUFAs and the growth of zooplankton were influenced by the pre-conversion time of ancient DOC by bacteria. When ancient DOC was pre-converted by bacteria for 27 days, D. magna fed on the mixed diets showed the highest body length (3.40 mm) and intrinsic rate of increase in population (0.49 d). Our findings provide direct evidence that ancient terrestrial OC can be an important subsidy for lake secondary production, which have important implications for food webs in high-altitude and polar lakes.
trophic 动态理论中的流行范式认为，当代自生有机物质（例如浮游植物）维持消费者的生长，而陈旧的异源有机物质被认为是难以降解的资源，只能用于支持消费者的呼吸作用，而抑制其生长。这种资源年龄范式受到越来越多的新证据的挑战，这些新证据表明，从冰川和永久冻土释放的古老（放射性碳耗尽）有机碳可以被水生系统中的消费者吸收。然而，关于古老陆地有机碳的食物质量及其如何影响湖泊消费者的生长的信息很少。在这里，从高山湖泊集水区的冷冻土壤中提取了古老的溶解有机碳（DOC）。异养细菌生物转化后，土壤 DOC 中的多不饱和脂肪酸（PUFA）含量显著增加。异养细菌对土壤 DOC 的利用也增加了系统中的总磷浓度。γ变形菌和β变形菌与荧光成分（包括腐殖质样和酪氨酸样成分）的荧光强度呈强烈的负相关。大型溞被喂食普通小球藻和古老的 DOC 加上异养细菌。浮游动物的 PUFAs 含量和生长受到细菌对古老 DOC 的预转化时间的影响。当古老的 DOC 被细菌预转化 27 天时，以混合饮食为食的大型溞表现出最高的体长（3.40 毫米）和种群的内禀增长率（0.49 d）。我们的研究结果提供了直接证据，证明古老的陆地有机碳可以成为湖泊次生生产力的重要补充，这对高海拔和极地湖泊的食物网具有重要意义。
