Federal scientists reported Tuesday that size of the Gulf of Mexico dead zone is above average this year. It’s a region of oxygen-depleted water off the Louisiana and Texas coasts and is a great threat to survival of sea life.

This year’s zone sprawls over 6,474 square miles, which is equivalent to the size of Connecticut and Rhode Island combined. Incessant rains in June throughout the Mississippi River watershed is the major cause behind its size bigger than average, said the National Oceanic and Atmospheric Administration.

The bottom of a body of water when there isn't enough oxygen to support life is called a dead zone. Nutrient runoff, mostly from over-application of fertilizer on agricultural fields during the spring, creates it. It is also called as hypoxia.

The growth rate of algae increases because of nutrients like nitrogen. The important point to note here is the fact that death of algae results into faster consumption of oxygen than it comes there from the surface, said NOAA. This leads to suffocation in fish, shrimp and crabs. An annual dead zone also exists in the Chesapeake Bay.

“The heavy rains that came in June with additional nitrogen and even higher river discharges in July are the possible explanations for the larger size”, said Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium.

The size of dead zone mainly relies on wind speed, wind direction, precipitation and temperature. Researchers started measuring the Gulf dead zone annually in 1985.