The use of microcosms to assess the potential impact of underground bunker crude oil on freshwater aquatic organisms

Abstract

Historically, crude oil was stored in old underground coal mines collectively known as the Ogies Terminal. A study was conducted to assess the potential environmental impacts of underground bunker crude oil on freshwater ecosystems. The study assessed the impact of sediment contaminated with crude oil (from the bunker area) on freshwater resources, particularly wetlands and pans. Controlled laboratory conditions, indoor microcosms were being used for this purpose. Artificial sediments of the experimental microcosms were weighed (450 g per chamber) and washed three times with Milli-Q® deionized water before the sediment was spiked with four concentrations of crude oil. Sediments were spiked with 50 mg/kg, 25 mg/kg, 12.5 mg/kg, and 6.25 mg/kg crude oil per dry weight sediment and mixed well before overlaying it carefully with filtered, dechlorinated tap water. Each exposure, including the control microcosm, was conducted in triplicate. The key findings of the study revealed that the impacts on aquatic ecosystems in a crude oil spill will be devastating. From different trophic levels, organisms (Daphnia magna, Physa spp., Lemna giba and Neocaridina spp) had different responses, but overall, were severely affected by the crude oil contamination. Crude oil spill was lethal to D. magna and Neocaridina spp. in all experimental concentrations, 100% mortality was observed within 24 hours of the experiment. While L. giba and Physa spp. were slightly less sensitive to the oil concentrations of 6,25mg/kg and 12,5mg/kg. Therefore, when an oil spill should occur, it will have repercussions for the structure and functioning of an aquatic ecosystem and, subsequently, the goods and services that people rely on for their well-being.