The Gulf of Mexico's 'dead zone' is above average this year.
Also known as , it's an area in the water with low or no oxygen, and it can kill marine life.
The average dead zone in the last five years is about 4,300 square miles.
This year's zone is just over 6,700 square miles, according to the National Oceanic and Atmospheric Administration. It's a jump from the almost 3,000 square mile zone .
Humans have a large impact on the sizes of the zones. It's mostly because of nutrient runoff from fertilizers in the Mississippi River.
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Nancy Rabalais is a Louisiana State University professor of oceanography and wetland studies. She says these zones can economically impact fisheries in the region.
"Any fish that can swim out of the area does swim out," Rabalais said. "It reduces the accessible area for collection of these types of organisms for fisheries, both recreational and commercial."
She adds that dead zones can also be a breeding ground for harmful algal blooms, which could be a risk to humans.
States across the U.S. are working on their conservation efforts, but there are barriers.
"How do you put together the necessary funding to be able to implement these strategies across the basin?" said Mike Naig, Iowa's secretary of agriculture.
NOAA officials add discharge from the Mississippi and Atchafalaya rivers was 5% higher than the long-term average in May.
Read the report .
