Particulate carbon pathways in subalpine Findley Lake, Washington, were examined to assess the dependence of invertebrate consumer production upon allochthonous and autochthonous carbon. Results suggest that allochthonous carbon provides a food base for insect production (6.5 kg C∙ha−1) and autochthonous production of carbon appears to maintain zooplankton production (5.0 kg C∙ha−1). Annual inputs of allochthonous carbon from snow, fluvial, and litterfall sources amounted to 75 kg C∙ha−1. Autochthonous production totaled 51 kg C∙ha−1. Most of the allochthonous inputs were lost through sedimentation (63 kg C∙ha−1) and fluvial output (15 kg C∙ha−1). In contrast, most of the autochthonous carbon losses through grazing and respiration were retained in the water column. Total allochthonous and autochthonous inputs were 126 kg C∙ha−1∙yr−1 and outputs were 114 kg C∙ha−1∙yr−1. A pelagic carbon budget did not balance by 12 kg C∙ha−1∙yr−1, a number well within the propagated variation of 26 and 21% for input and outputs, respectively. Key words: allochthonous, carbon, subalpine, lake
Phytoplankton, not allochthonous carbon, sustains herbivorous zooplankton production
