Su, Y.; Hu, E.; Liu, Z.; 等.

    Ancient (i.e., radiocarbon depleted) organic carbon (OC) is exported from ice sheet, glacier, and permafrost systems and may be buried, respired, or assimilated in downstream aquatic systems. Few studies have explored the potential use of this ancient OC in lake food webs. We combined natural abundance radiocarbon and stable carbon isotope data (Delta C-14 and delta C-13) to study ancient OC utilization by zooplankton in six lakes covering a large climate gradient on the central and peripheral Tibetan Plateau. A depleted Delta C-14 signature of dissolved and particulate OC was found in the inflowing streams and lakes, ranging from - 49 parts per thousand to - 569 parts per thousand, corresponding to radiocarbon ages between 403 yr and 6757 yr. The Delta C-14 values for zooplankton in the lakes ranged from - 45 parts per thousand to - 264 parts per thousand, reflecting that zooplankton obtain C-14-depleted signatures through assimilation of ancient OC and/or indirectly through consumption of phytoplankton or aquatic plant utilizing C-14-depleted inorganic carbon. Moreover, ancient OC from inflowing streams contributed more to zooplankton diets in the temperate glacier area than in the cold glacier area. Assimilation of ancient OC by zooplankton in lakes is not only affected by drainage basin characteristics, such as the recharge coefficient of the lake, but also by the biogeochemical properties of OC. Use of ancient OC by zooplankton in high-altitude lakes may constitute an important link between the contemporary aquatic food webs and the glaciated watersheds. Our findings have important implications for the contribution of ancient carbon to the modern lake food webs of high-altitude and polar lakes.

来源：LIMNOLOGY AND OCEANOGRAPHY   卷: 63   期: 6   页: 2359-2371   出版年: NOV 2018