Effects of an oil spill in outdoor model tidal flat ecosystems

For several reasons the fate and effects of oil pollution are not easily studied in natural ecosystems. Furthermore, the results of laboratory tests cannot easily be extrapolated to natural systems. A logical objective of ecotoxicological research is, therefore, to simulate natural systems in model ecosystem experiments. A one-year feasibility study was carried out with MOdel TIdal Flat ecosystems (MOTIFs), designed to represent tidal flat systems typical of the Wadden Sea and other temperate estuarine areas. During the first 6 months the 4 MOTIFs studied developed very similarly. After this period an oil spill was simulated by exposing two of the four MOTIFs to a floating oil mousse for one week. During this week part of the oil was buried in the sediment by bioturbation. This sediment-bound fraction caused a prolonged exposure of the MOTIFs to oil compounds. Short- and long-term effects resulted in large differences between oil-treated and control MOTIFs. These differences persisted to the end of the experiment, 7 months after the removal of most of the oil.