Whatever mixture that didn’t get broken down by bacteria would just get mixed in with the deep sea sediments deep in the coastal where the breakdown decreases.
Although dispersants help expose the oil to bacteria and waves that help break it down, it can also expose it to wildlife. A study conducted in 2012 revealed that the oil and dispersant combination to be 3-52 times more toxic to microscopic animals than the oil all by itself! This is because the dispersant makes the oil easily accessible for these microscopic animals to ingest it. There were even some evident effect on animals of the Gulf of Mexico. There were pelicans covered with oil, fish found in brown sludge, and oil smothered turtles washed up on beaches. Seabirds were not able to fly and retrieve food because of surface oil and dolphins were also having difficulty swimming through oil slicks and found stranded and ill. Sea turtles as well. This ordeal continues to increase since the spill, however, we still are unsure how much of their populations in the Gulf or even the endangered Atlantic blue-fin tuna larvae have been affected until many more