Airborne carbon deposition on a remote forested lake

Airborne inputs of terrestrial particulate organic carbon (TPOC) we remeasured during summer 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 airborne 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.