NOAA Predicts 'Dead Zone' in the Gulf of Mexico Will be the Size of Connecticut

First Posted: Jun 19, 2015 08:21 AM EDT

Scientists have officially predicted this year's Gulf of Mexico "dead zone." According to new research, this hypoxic zone will be approximately 5,438 square miles, or about the size of Connecticut, which is the same it's averaged over the last several years.

The dead zone in the Gulf of Mexico affects nationally important commercial and recreational fisheries and threatens the region's economy. Hypoxic zones hold very little oxygen, and are caused by excessive nutrient pollution, primarily from activities such as agriculture and wastewater. The low oxygen levels cannot support most marine life and habitats in near-bottom waters.

This year, researchers combined the results from four different models. The four model predictions ranged from 4,344 to 5,985 square miles, and had a collective predictive interval of 3,205 to 7,645 square miles, which take into account variations in weather and oceanographic conditions.

The Gulf of Mexico hypoxia forecast is based on nutrient runoff and river stream data from the USGS, which operates more than 3,000 real-time stream gauges, 50 real-time nitrate sensors, and collects water quality data at long-term stations throughout the Mississippi River basin to track how nutrient loads are changing over time.

Approximately 104,000 metric tons of nitrate and 19,300 metric tons of phosphorus flowed down rivers and into the Gulf of Mexico in May 2015. That's about 21 percent below the long-term average for nitrogen and 16 percent above the long-term average for phosphorus. Both contribute to the dead zone.

"Real-time nitrate sensors are advancing our understanding of how nitrate is transported in small stream and large rivers, including the main stem of the Mississippi River," said William Werkheiser, USGS associate director for water, in a news release. "Long-term monitoring is critical to tracking how nutrient levels are changing in response to management actions and for improving modeling tools to estimate which sources and areas are contributing the largest amounts of nutrients to the Gulf."