Why did spanish colonists begin to rely more heavily on the atlantic slave trade by the mid-1500s?

This was due to the large scale operation the Spaniards were conducting in their colonies.  They needed labor that can do this type of work.  This later led to the Spaniards getting involved in the slave trade as well since it was a convenient way to get workers for them.

nope.

explanation:

“the iliad” (gr: “iliás”) is an epic poem by the ancient greek poet homer, which recounts some of the significant events of the final weeks of the trojan war and the greek siege of the city of troy (which was also known as ilion, ilios or ilium in ancient times).