Water soluble fuel compounds impair metabolism in benthic foraminifera: Ecotoxicological observations at cellular level

Every year, countless millions of litres of oil and other hydrocarbon products spill uncontrollably into the ocean through ship accidents or other human activities. Although the oil floats on the sea surface, many components dissolve in the seawater and, thus, can infiltrate benthic habitats and organisms living at the seafloor. In this study, we investigated the effect of water-soluble compounds from diesel and gasoline on benthic foraminifera (common unicellular eukaryotes). Our results reveal that aqueous diesel extracts have a strong impact on the metabolism of foraminifera through reduced carbon and nitrogen uptake within three days. Aqueous extracts from gasoline, on the other hand, had no effect on carbon uptake, but reduced nitrogen utilization. Cellular ultrastructure characterization by transmission electron microscopy (TEM) and cutting-edge nanoscale secondary ion mass spectrometry (NanoSIMS) showed that the foraminifera incubated with diesel extract were strongly degraded whereas the cytoplasm in gasoline-extract incubated foraminifera was less affected. Collectively, these observations show that dissolved compounds from oil that enter the sea in an uncontrolled manner do not only float on the ocean surface but exert a negative effect on benthic foraminifera.