
Black algae can weaken a train bridge. Black algae is a type of bacteria that can grow on wet surfaces, such as the underside of a train bridge. As the algae grows, it can form a thick, slimy layer that can trap water and debris. This can increase the weight on the bridge and weaken the structure. In severe cases, the algae can even cause the bridge to collapse.

In 2009, a train bridge in Minnesota collapsed due to black algae. The bridge was carrying a trainload of grain when it gave way, sending the train into the river below. There were no injuries, but the collapse caused millions of dollars in damage.
To prevent black algae from weakening a train bridge, it is important to regularly inspect the bridge for signs of algae growth. If algae is found, it should be removed immediately. There are a number of methods that can be used to remove black algae, including physical removal, chemical treatment, and biological treatment.
Here are some of the dangers of black algae:
- It can weaken structures, such as train bridges.
- It can harbor harmful bacteria, such as E. coli.
- It can produce toxins that can make people sick.
- It can be unsightly and make water bodies unfit for swimming or fishing.

If you see black algae growing on a train bridge or other structure, it is important to report it to the appropriate authorities.