The relative impacts of spills of two alternative fuels on the microalgae of a sandy site: a microcosm study

Electric power generation in the United States uses substantial amounts of fuel oil #6. Orimulsion, an emulsion of bitumen, water, and a surfactant, is an alternative. A portion of the information that managers need to compare the two fuels is their relative environmental impacts. Both fuels are shipped by sea, so the impact of spills on the marine benthos is a concern. We used microcosms to assess the relative impacts of simulated spills of these fuels on the microalgae of shallow subtidal sandy bottoms. Response variables included microalgal abundance, primary productivity, ratio of chlorophyll a to phaeophytin, and ratio of primary production to chlorophyll a. During our 88-day experiment, we found no significant differences between the fuels for any variable. We suggest that weathering before the spill reaches the shore removes the most toxic components, rendering the fuels essentially equal in their impact on benthic microalgae.