Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden.
Ecol Lett. 2010 Jul;13(7):870-80. doi: 10.1111/j.1461-0248.2010.01483.x. Epub 2010 May 12.
Carbon of terrestrial origin often makes up a significant share of consumer biomass in unproductive lake ecosystems. However, the mechanisms for terrestrial support of lake secondary production are largely unclear. By using a modelling approach, we show that terrestrial export of dissolved labile low molecular weight carbon (LMWC) compounds supported 80% (34-95%), 54% (19-90%) and 23% (7-45%) of the secondary production by bacteria, protozoa and metazoa, respectively, in a 7-km(2) boreal lake (conservative to liberal estimates in brackets). Bacterial growth on LMWC was of similar magnitude as that of primary production (PP), and grazing on bacteria effectively channelled the LMWC carbon to higher trophic levels. We suggest that rapid turnover of forest LMWC pools enables continuous export of fresh photosynthates and other labile metabolites to aquatic systems, and that substantial transfer of LMWC from terrestrial sources to lake consumers can occur within a few days. Sequestration of LMWC of terrestrial origin, thus, helps explain high shares of terrestrial carbon in lake organisms and implies that lake food webs can be closely dependent on recent terrestrial PP.
陆地来源的碳通常构成了非生产性湖泊生态系统中消费者生物量的重要组成部分。然而，陆地支持湖泊次级生产的机制在很大程度上还不清楚。通过使用建模方法，我们表明，溶解的活性低分子量碳（LMWC）化合物的陆地输出分别支持了细菌、原生动物和后生动物的次级生产量的 80%（34-95%）、54%（19-90%）和 23%（7-45%）（括号内为保守至宽松的估计值）。LMWC 上的细菌生长与初级生产（PP）的规模相当，而对细菌的摄食有效地将 LMWC 碳输送到更高的营养级。我们认为，森林 LMWC 库的快速周转使得新鲜光合作用产物和其他活性代谢物能够持续向水生系统输出，而陆地来源的 LMWC 可以在几天内大量转移到湖泊消费者中。因此，陆地来源的 LMWC 的固定有助于解释湖泊生物中高比例的陆地碳，并意味着湖泊食物网可能高度依赖于最近的陆地 PP。
