"The deepwater plumes of oil from the blowout are spread by deepwater currents; dispersants are largely cosmetic; the particles are spread far, not kept close to the well blowout".

Two techniques were used to apply dispersants, one immediately on the surface and one directly injected at the source of the spill....after the surface application was found to be less effective by weathered oil (rae oil is buoyant and travels to the surface)travelling long distances upward and changing characteristics...that impacted surface applied effectiveness. The injection at source seemed to work...as EPA let BP do it after three experimental applications.      


"The effects of dispersants on marine life, singly or in combination with hyreocarbons, has not been studied in any detail; the added chemicals may prolong the toxicity of the oil"

This is sinmply not the case....and even a GOOGLE search will find such research. EPA, NOAA Universities, Chemical companies and researchers from many countries do conduct many tests on dispersants before they are certified for use. However, some, though not all, of the tests are in labratories or wave tanks. Each dispersant has its area of effectiveness. I suspect few were tested on sites at great water depths, and under cold water and extreme pressure. Many folks are confused at what dispersants do and why they are used. They are never approved for use in cases where they are not needed, as like the oil, do have effects....though not as significant in many cases.

Oil enters waters every day, from natural seeps and a multitude of human causes. Bacteria and natural forces deal with it. But, when huge amounts are released, you have a different scenario.