Effects of chronic exposure to coal-derived oil on freshwater ecosystems: I. Microcosms

Abstract

Abstract Sixteen 67-liter freshwater microcosms were treated for 8 weeks with an unrefined coal-oil in amounts ranging from 0.03 to 7 ml per week. Phenols make up 95% of the water-soluble compounds in this oil, and dissolved phenol concentrations averaged <0.01 mg L−1 in the lowest dose and 10 mg L−1 in the highest. The microcosms were severely damaged at the highest treatment level; macrophytes, zooplankton and insects were eliminated, and the ecosystems became anaerobic. Microcosms did not recover to pretreatment conditions within 5 months. At lower dosages there were temporary effects on ecosystem metabolism, water chemistry and community structure. The most sensitive indices—community respiration, production/respiration ratio, pH and cladoceran zooplankton numbers—were affected at phenol concentrations below the lowest observable effect concentration of a chronic Daphnia magna bioassay.