This article shows the documents from the UK's test of Corexit oil dispersants. Limpets (a type of snail), which were used as the "guinea pigs," were sprayed with either oil or Corexit and the number of snails that lost their adhesion abilities were counted as dead - due to their inability to stick to surfaces and protect themselves. In reality they could have been killed by the oil, dispersants, loss of adhesion abilities or a combination of the three. The test documents' mortality rates show that Corexit alone is twice as lethal as oil.
An update of this article points out that the limpet test does not necessarily extend to other rocky shore animals or animals living in the open sea - which is a good point. Still, the potential damage Corexit may cause cannot be questioned.
Full article here (Clean the Gulf Now!)