Nitrogen, Phosphorus, and Organic Carbon Cycling in an Arctic Lake

Abstract

Budjets for N, P, and organic C in Toolik Lake, Alaska [USA], were assembled from data collected during 1977-1981. The annual total organic C (TOC), total N (TN), and total P (TP) loads to the lake were 8557, 290, and 4.64 mmol .cntdot. m-2. Inlet streams were the major source of nutrients to the lake, as direct precipitation provided only 1, 2 and 5%, respectively, of the annual TOC, TN, and TP loads to the lake. Up to 30% of the annual N and P inputs to the lake from riverine sources occurred during the first 10 days of stream flow following breakup when cold water temperatures and snow-covered ice limited primary production. Due to the short water renewal time (0.5 yr), efficiency of nutrient retention was poor and 90, 82, and 70% of the annual TOC, TN, and TP inputs to the lake were discharged at the outlet stream. Regeneration within the water column supplied 40-66% and 68-78% of the N and P necessary for measured primary production. Yearly accumulation rates for C, N, and P in the sediment were about 220, 21.0, and 1.75 mmol .cntdot. m-2. P remineralized within the sediment was completely retained due to adsorption onto Fe oxide minerals in the oxidizing surface layer. Annual rates of release of C and N to the overlying water column were 110 and 11.5-22.2 mmol .cntdot. m-2. Mass balance considerations showed no serious errors in estimates of any terms of the annual sediment and water column N, P and organic C budgets.