Effects of Petroleum Hydrocarbons on Plant Litter Microbiota in an Arctic Lake

Abstract

The effects of petroleum hydrocarbons on the microbial community associated with decomposing Carex leaf litter colonized in Toolik Lake, Alaska, were examined. Microbial metabolic activity, measured as the rate of acetate incorporation into lipid, did not vary significantly from controls over a 12-h period after exposure of colonized Carex litter to 3.0 ml of Prudhoe Bay crude oil, diesel fuel, or toluene per liter. ATP levels of the microbiota became elevated within 2 h after the exposure of the litter to diesel fuel or toluene, but returned to control levels within 4 to 8 h. ATP levels of samples exposed to Prudhoe Bay crude oil did not vary from control levels. Mineralization of specifically labeled 14 C-[lignin]-lignocellulose and 14 C-[cellulose]-lignocellulose by Toolik Lake sediments, after the addition of 2% (vol/vol) Prudhoe Bay crude oil, motor oil, diesel fuel, gasoline, n -hexane, or toluene, was examined after 21 days of incubation at 10°C. Diesel fuel, motor oil, gasoline, and toluene inhibited 14 C-[lignin]-lignocellulose mineralization by 58, 67, 67, and 86%, respectively. Hexane-treated samples displayed an increase in the rate of 14 C-[lignin]-lignocellulose mineralization of 33%. 14 C-[cellulose]-lignocellulose mineralization was inhibited by the addition of motor oil or toluene by 27 and 64%, respectively, whereas diesel fuel-treated samples showed a 17% increase in mineralization rate. Mineralization of the labeled lignin component of lignocellulose appeared to be more sensitive to hydrocarbon perturbations than was the labeled cellulose component.