Does a photo show Mississippi River water meeting but never mixing with salt water of the Gulf of Mexico?

The photo posted on social media shows river water that has reached the Gulf of Mexico and has flowed out over the top of the denser Gulf salt water.

The abundance of nutrients in the river water, much of them from agriculture, can host an algae bloom that can deplete the available oxygen in the saltwater Gulf as the algae decomposes, a condition called hypoxia. This results in problems for the marine life that must either swim away if it can, or die.

For this reason, the area of oxygen-depleted water is known as a "dead zone."

This identical photo was used in an August 22, 2019, Facebook post by the Environmental Protection Agency announcing $1.2 million for hypoxia study.

Scientists at the National Oceanic and Atmospheric Administration have been mapping the oxygen levels and varying size of the dead zone since 1985.