Wednesday, March 18, 2009

Dispersing an Oil Spill Harms Fish

According to a recent study, using chemicals such as detergents to disperse an oil spill helps surface animals but increases the harm to fish:

"The detergents may be the best way to treat spills in the long term because the dispersed oil is diluted and degraded," says Biology professor Peter Hodson. "But in the short term, they increase the bioavailability and toxicity of the fuel to rainbow trout by 100-fold."

The detergents are oil dispersants that decrease the surface tension between oil and water, allowing floating oil to mix with water as tiny droplets. Dr. Hodson and his team found that dispersion reduces the potential impacts of oil on surface-dwelling animals, While this should enhance biodegradation, it also creates a larger reservoir of oil in the water column.

This increases the transfer of hydrocarbons from oil to water, Dr. Hodson explains. The hydrocarbons pass easily from water into tissues and are deadly to fish in the early stages of life. "This could seriously impair the health of fish populations, resulting in long-term reductions in economic returns to fisheries," he says.
This should probably not dissuade recovery teams from doing what they can to remove surface oil. However, the deadly effects on young fish may explain why it takes so long for ecosystems to recover from oil spills. This really emphasizes the need to prevent oil spills from happening in the first place.