Fish-Killing Dead Zones Set to Swarm Chesapeake Bay

On the eve of the next dead zone invasion, a new study says that past hypoxic zones destroyed the Bay’s bottom-feeding fish.

A dead zone spreads across the Chesapeake Bay in Maryland
A dead zone spreads across the Chesapeake Bay in Maryland. (Photo: The Chesapeake Bay Foundation)
A six-time grantee of the National Geographic Expeditions Council, Jon writes about all things ocean.

In Barry Levinson’s quasi-fictional eco-horror flick The Bay, the abysmal pollution of the Chesapeake Bay results in a Fourth of July weekend gone very, very bad as swimmers and boaters are killed off en masse by toxic waters come to life.

While the Chesapeake remains badly polluted in real life, it’s not so bad that swimmers need to worry about flesh-eating bacteria. Well, not yet at least. Fish, on the other hand, should be worried.

A just-completed, 10-year-long study of the bay’s fishes by researchers from the Virginia Institute of Marine Science proves that low-oxygen dead zones—created by nitrogen runoff from farms and cities—are having a serious impact on bottom-feeding fish, including perch, bass, flounder and more, which are all key members of the local ecosystem. The decline in fish populations is an indication that waters are troubled, but also affects both commercial and recreational fishing economies.

Such dead zones, more formally known as hypoxia, are created by excess amounts of nitrogen in the water, which is contributed primarily by fertilizer and sewage run-off.

The most infamous U.S. dead zone sits at the mouth of the Mississippi River in the Gulf of Mexico and is nurtured each year by pollutants being dumped into the river system by 31 different states and eventually the Gulf south of New Orleans.

With this summer’s already-heavy rains, it’s expected the Gulf’s dead zone will reach record size, possibly the largest since annual measurements began being taken in 1985. It could get as large as 8,561 square miles—about the size of New Jersey, according to scientists from Louisiana State University and the Louisiana Universities Marine Consortium. The official measuring will take place during the week of July 21 to July 28.

The Chesapeake Bay study shows how the physiological stress directly linked to a lack of oxygen in the water impacts the fish primarily by reducing the area from which they can feed. It also shows signs of increased respiration and elevated metabolism in the fish that live in deeper parts of the bay.

The Chesapeake’s dead zone is expected to be at its largest during the next couple weeks, thanks to the mid-summer’s heat; for reasons not yet fully understood, this year’s affected area seems to be smaller than a year ago. Its official 2013 measurements won’t be made public until October.

Despite Levinson’s only slightly-tongue-in-cheek take on the Chesapeake’s future—The Bay shows mutating isopods eating swimmers and water drinkers from the inside out!—the official goal of cleaning up the bay by 2025 is having mixed results, according to a recent report by the Choose Clean Water Coalition. The bay is said to be “40 percent dead.” Clearly, the time for resuscitation is now, but it’s not so simple.

A multibillion-dollar restoration plan overseen by the EPA was devised to ensure a commitment to cleaning up the bay. A recent interim report says progress is being made but is not on track to meet this year’s “pollution diet.” 

The plan is to sharply reduce sediment, nitrogen and phosphorous entering the bay from farm runoff and urban and suburban sprawl by planting buffer zones of trees, keeping livestock away from waters flowing into the bay, and upgrading wastewater treatment plants. That goal is currently being met by about 50 percent, according to CCWC.

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