What particular feature of coastal Louisiana worsened the ecological impacts of the Deepwater Horizon oil spill?

The correct answer highlights that marsh subsidence from historical channelization of the Mississippi River significantly contributed to the ecological impacts of the Deepwater Horizon oil spill. Coastal Louisiana's wetlands, particularly marshes, are vital ecosystems that serve as natural barriers to storm surges and provide critical habitats for many species. However, the management and alteration of the Mississippi River through channelization have led to significant land loss and subsidence in these areas.

This subsidence makes the coastal regions more vulnerable to oil spills and other ecological disruptions because the marshlands are less capable of providing the protective benefits they once did. When these habitats are compromised, they may not be able to effectively filter pollutants, including oil, leading to more severe environmental consequences following incidents like the Deepwater Horizon spill. The combination of increased exposure due to land loss and decreased resilience in these ecosystems contributed to the detrimental effects observed during the disaster.