Airborne carbon deposition on a remote forested lake

Abstract

Airborne inputs of terrestrial particulate organic carbon (TPOC) were measured during summ- er stratification for an oligotrophic north temperate lake located in a forested watershed. These inputs were episodic and associated with wind and rain events. The rate of deposition decreased exponentially with distance from shore. Yet, about 55 % of the total airborne TPOC input occurred more than 12 m from shore on this 25.8 ha lake. Of total deposition, 39 % was less than 153 mm in diameter - a size fraction not commonly measured in prior studies. Average air- borne deposition was 5 mg C m -2 d -1 , which is consistent with measurements from other lakes and equivalent to about 1.1 % of daily net primary production in our study lake. C:N ratios of TPOC were between 6:1 and 22:1 (molar), much lower than the values for terrestrial leaves which were between 39:1 and 48:1 (molar). These low C:N ratios suggest that TPOC may be a useful substrate for aquatic consumers and may supplement in-lake primary production as a food source, especially after wind and rain events when airborne TPOC inputs are high.