The Importance of Allochthonous Particulate Carbon Pathways in a Subalpine Lake

Abstract

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