MARTA railcars dumped into the Atlantic Ocean show signs of reef habitat

Zoom in: DNR divers recently made their first visit to the railcars and saw signs of corals, sponges, and other "encrusting organisms" taking hold, MARTA said in a statement.

The intrigue: "You'll notice one of the railcar roofs has collapsed, which is typical," Cameron Brinton, a DNR marine biologist.

• "[We'll] see more changes to the railcars over time as they become part of the essential marine habitat for sea creatures, including popular sport fish and endangered sea turtles."

Zoom out: Other items added to the ocean floor over the past 50 years include "M-60 battle tanks, barges, tugboats, New York City subway cars, and other manmade structures."