Shark Week shows dead zone effect on Indian River Lagoon bull sharks

• Bull sharks use the Indian River Lagoon as a nursery.
• Juveniles live in the lagoon for up to 8 years before moving to the ocean.
• A Shark Week crew found one dead and one diseased bull shark.
• Shark biologist blames nutrient pollution that feeds algae blooms.

When “Shark Week” scientists and film crews explored the Indian River Lagoon for seven days in May, it took them three days just to find one living bull shark to which they could attach a sensor to monitor water quality.

Bull sharks are supposed to be common in the 156-mile-long lagoon, so shark biologist Craig O’Connell was surprised to find a dead zone with dead fish and dead and diseased sharks in one of North America’s most biologically diverse estuaries.

“At first, I had hope,” the “Shark Week” presenter said. “I was like, ‘These bull sharks can tolerate anything,’ and then I saw this dead zone. There was no life, and it made me realize that this is an absolutely massive problem.”

Database:Shark bites along the Treasure Coast

Harbor Branch study:Finds algae blooms poisoning bull sharks in Indian River Lagoon

What is a dead zone?

The “Sharks of the Dead Zone” episode, which premieres at 9 p.m. Friday, explores how water pollution and algae blooms can create “eerie dead zones” in the lagoon. They can occur naturally or through human activity, such as nutrient pollution, according to the National Oceanic and Atmospheric Administration.