To study the impacts of dispersed oil on estuarine organisms and ecosystems, NCCOS scientists used tidal estuarine simulation units (called mesocosms) to mimic the conditions in an estuary affectedby weathered crude oil. In the mesocosms, artificially weathered crude oil, with and without dispersants, was applied during three consecutive high tide events.

Weathered crude oil being added to a mesocosm unit at high tide. Credit: Katy W. Chung

The exposure phase lasted for 45 days from initiation of the simulated spill. Investigators are now examining the data collected during the exposure to evaluate the effects of the oil and dispersed oil on marsh vegetation (cordgrass), sediment organisms (amphipods, polychaetes, and clams), fish, shrimp, and bacterial communities. Additionally, water and sediment samples collected during the study are being analyzed to determine how the oil concentration and composition changed over time. The results of this study will help inform management decisions relative to judging potential risks of using oil dispersants in the coastal zone.

Oil spills that occur in near-coastal, offshore areas have the potential to drift into nearby estuarine and coastal areas.Often this oil is weathered during transit from the spill location offshore to the estuary. Depending on the situation and location, dispersants may be applied to the oil before it reaches the coast.

For more information, contact Paul Pennington or Mike Fulton.