National Geographic News
An algal bloom in the Gulf of Mexico.

A dead zone-causing algal bloom stained the Gulf of Mexico green in 2007.

Image from NASA/Alamy

Christine Dell'Amore

National Geographic

Published June 24, 2013

A possibly record-breaking, New Jersey-size dead zone may put a chokehold on the Gulf of Mexico (map) this summer, according to a forecast released this week.

Unusually robust spring floods in the U.S. Midwest are flushing agricultural runoff—namely, nitrogen and phosphorus—into the Gulf and spurring giant algal blooms, which lead to dead zones, or areas devoid of oxygen that occur in the summer.

The forecast, developed by the University of Michigan and Louisiana State University with support from the U.S. National Oceanic and Atmospheric Administration, estimates a Gulf dead zone of between 7,286 and 8,561 square miles (18,870 and 22,172 square kilometers). The largest ever reported in the Gulf, 8,481 square miles (21,965 square kilometers), occurred in 2002.

On the flip side, the Chesapeake Bay—the country's biggest estuary—will likely experience a smaller-than-average dead zone this summer.

The forecasts are made using computer models, which are based on U.S. Geological Survey data of nutrient runoff in U.S. rivers and streams.

National Geographic talked to forecast contributor Donald Scavia, an aquatic ecologist at the University of Michigan, about dead zones—and why we should care about them.

What's a dead zone?

A dead zone, which occurs in the oceans and Great Lakes, is an area usually in the bottom waters where there's not enough oxygen to sustain life. It's generally caused by algae stimulated by lots of agricultural nutrients in surface waters. When nutrients enter the water, [they] create an algal bloom. [When] the algae sink, bacteria start decomposing them, which uses up the [available] oxygen. (Also see "World's Largest Dead Zone Suffocating Sea [2010].")

During summer, what you have is a stratified water column that inhibits oxygen from the atmosphere getting down to the deep water. As the bacteria use up oxygen, it's not being replenished, so oxygen concentrations decrease until you get to two milligrams of oxygen per liter of water, which is bad for fish. Below that, fish that can will leave that area. Other organisms that can't [leave] die.

What are examples of organisms that would die?

Animals that live on the bottom. Worms, clams, the kind of things that fish like to eat. Some fish may have trouble.

Why do we track and study dead zones?

It's important because most often those areas that become uninhabitable by fish, are preferred habitat for fish. To draw on an analogy that's ironic, it would be like taking thousands of square miles of land in the Midwest out of production. People wouldn't like it.

So dead zones are an invisible issue.

Yes. They're deep in the bottom waters, and you can't see oxygen.

What was your reaction to your finding that the Gulf of Mexico may have a record-breaking dead zone?

To be honest, I was expecting that, mostly because of reports of massive flooding in the Midwest. The nitrogen and phosphorus in the floodwaters drive the problem.

What's causing the spring floods?

In recent history, the number of larger and more intense storms has been increasing—most climate models suggest storm intensity is going to continue. (See "Global Warming to Create 'Permanent' Ocean Dead Zones?")

Is the news that the Chesapeake Bay's dead zone is small promising?

It's not really, because people in the area are not doing enough nutrient management—it was a dry spring. The amount of nutrients going into systems is really dependent on rainfall. The more water you get, the more nutrients you get going in there. The real management issue—regardless of whether it's a wet or a dry year—is you've got to keep the nitrogen and phosphorus on the land and not in the rivers.

Is that mostly done by state regulations?

It's actually mostly controlled by the Farm Bill, the main funding mechanism for conservation in agriculture. The problem with the Farm Bill is there's far more money for supporting commodities and subsidies and not enough into conservation. I'm not blaming farmers—farmers do what the Farm Bill pays them to do—but we need a Farm Bill that's smarter and supports more conservation programs. (The most recent Farm Bill, which is updated every five years, was rejected by the House of Representatives on Thursday.)

Do dead zones have lasting effects on the environment?

There's a sense in the Chesapeake, Lake Erie, and the Gulf of Mexico that repeated dead zones are somehow making systems more sensitive to nutrients. For instance, the same amount of nutrient load now is producing larger dead zones than a decade ago. (See "Female Fish Develop 'Testes' in Gulf Dead Zone.")

We think it has something to do with residual organic matter that's carried over from one year to the next, or from the changing types of organisms living in the ecosystem. (Also see video: "Did Gulf Spill Boost 'Dead Zone'?")

What should the public know about dead zones?

The key thing is they really have the potential to devastate the fishing industry—for instance, shrimp in the Gulf, walleye in the Great Lakes, and striped bass in the Chesapeake Bay. The solution is really to be more aggressive in dealing with pollution coming from agriculture.

This Q&A has been edited for length and content.

Follow Christine Dell'Amore on Twitter and Google+.

29 comments
Deon Howard
Deon Howard

I just feel this is the result of conflicting interests by many fields of the world. With larger demands in food production, more intensive practices are needed. While that might be good for us Americans who take such a lifestyle for granted, its causing harm to the environment. We all jus need to evaluate the most important aspects of life and work to sustain that.

Deon Howard
Deon Howard

I just feel this is the result of conflicting interests by many fields of the world. With larger demands in food production, more intensive practices are needed. While that might be good for us Americans who take such a lifestyle for granted, its causing harm to the environment. We all jus need to evaluate the most important aspects of life and work to sustain that.on top of 

Herbert Harper
Herbert Harper

HOW ABOUT AN EASY SOLUTION?

Why not make thousands of floating solar powered aerators and anchor them in problem areas?

Fritzi Presley
Fritzi Presley

i live on the coastal gulf of mexico. last night and this morning, we experienced the largest fish kill i have ever seen.  i am a generational native, and i have never HEARD of a kill of this magnitude.  according to our local newspaper, it runs from the west coast of florida to the coastal mexican border, that is the entire northern gulf.  at 7 am, i went to our beach and witnessed absolute carnage.  hundreds of thousands of sea creatures were either dead or dying down the shore as far as the eye could see.  people were parking and running for the water's edge with bait buckets, pillow cases, nets, anything that would hold fish and they were gathering them like manna and rushing back to their cars and speeding away.  i watched in amazement, as people held up their large "catches" (like 3 pound flounders and 20 inch red fish...you don't think this will hurt them, do you?  

Laurence Anderson
Laurence Anderson

government putting massive taxes on N and P fertilizers might help; as well as subsidizing organic and permaculture farmers. Encouraging planting of riversides with belts of woodland and undergrowth. encouraging farmers to create spilldams for the first most n-rich runoff from their lands. grow wetlands for diversion of highwaters and runoff beyond the usual - these will contain mass reeds and other vegetation to soak up the N and P.

Dave N.
Dave N.

Monsanto's wonderful RoundUp which is being sprayed all over the place is high in phosphorous content.  Hmmm.... 

Naturally, most of our regulatory agencies are now being run by ex-Monsanto people (around 20 people at my last count) all with the blessings of the Obama administration. No conflict of interest here.  

Nathan Nelson
Nathan Nelson

how is a dead zon e created? the alge sucked up all the oxygen? flurish alge!!! doesnt seem like a big deal unless somone makes it one. feeling bad for the worms at the bottom and the fish you know weverthing it hurts, but its good for the alge.

drai buizon
drai buizon

its alarming,,,cooperation of all mankind is needed to protect marine diversity

Les Lang
Les Lang

This has absolutely NOTHING to do with the oil and gas industry, nice try. Read the article, “agricultural runoff”, did you miss it? This has EVERYTHING to do with ethanol. When farmers are compelled to grow corn, year after year, for use in ethanol, as opposed to rotating crops for food, and blight the land, they must add tons of chemical fertilizer to continue the process. When the snow melts, or there is a runoff from rain, all that chemical enters the Gulf from all the collective watershed of the Midwest. It figures, a collection of crackpot kooks, would seize on the easy target and blame the oil industry. READ the article, before you make an a** of yourself. 

Penny Melko
Penny Melko

Look closer at the true damage. These are the waters where our fish used to come from and yet,the petroleum, gas and waste industries continues to pollute those waters belonging to the people. Google the keywords sinkhole, assumption and louisiana for a real eye opener..

My advise, is for the people to demand that US Fish and Wildlife Services is disbanded. The old men that run this agency, and in every state office of FWS are hunters who are pure evil and despicable in their torture methods of other species. They're the garbage that should be put into the landfills. Replace every single one of them with environmental personnel who aren't in the pockets of the hunting, ranching and farming industries. This will be a major step in reversing the damage.

Corey McDonald
Corey McDonald

Actually, this is a good thing. Algae blooms offset carbon tremendously. That's why they are trying to stimulate them artificially in a research study by seeding the ocean with iron. While it sucks for the fish in that region (and the fishermen that depend on them), it's good for the green house effect.

Corey McDonald
Corey McDonald

Actually, this is a good thing. Algae blooms offset carbon tremendously. That's why they are trying to stimulate them artificially in a research study by seeding the ocean with iron. While it sucks for the fish in that region (and the fishermen that depend on them), it's good for the green house effect.

Cody Nielsen
Cody Nielsen

Farming needs to change and there are many options available. Cover crop is a good alternative to what is now. Social pressure and information is one step to changing that dead zone. Look up the benefits to cover crop.

A J
A J

Agriculture is the biggest environmental catastrophe that humanity has ever laid at the feet of Mother Nature.

Vanessa Ong
Vanessa Ong

@Nathan Nelson It's actually a pretty big issue.  I don't believe you should be concluding that it isn't a "big deal" if you don't know what a dead zone is in the first place...but maybe that's just me.

Brian Vogler
Brian Vogler

@Nathan Nelson It's really not. Typically one species goes bonkers due to a temporary abundance of nutrients that are then depleted. It destroys the algal diversity and damages the capacity for adaptation. 

Algae are good. This is actually bad for them, in the long run.

Morgan Prewitt
Morgan Prewitt

@Penny Melko As a former environmental employee with Fish and Wildlife, what you're saying is absolutely not true. Management of wildlife and resources is vital to sustaining the balance of nature. We offered controlled hunts on a draw system in our managed areas and after each kill, we removed the jaw bones from the deer harvested for use in various aging and biological studies.

Also, sinkholes are found in predominately karst areas...also not a result of FWS.

Please broaden your outlook on your very narrow-minded view of governemental agencies that are in place to protect wildlife and the environment that they exist in.

Jay Sharpe
Jay Sharpe

@Penny Melko  I have to agree, there is no reason for so called sport hunting. this so called proving ones 'manhood' is stupid, what do you prove when you shot something with a gun...nothing want to hunt with a weapon, hunt something with the same weapon. better yet go hunt a large bear with a knife, then we'll be well rid of you.

secondly we do need to get the 'hunters', and the rest with a vested interest out of the state, and federal office, including the corporations ( ie; Monsanto, and there ink).

Jacues Boullard
Jacues Boullard

@Penny Melko so... yer upset about our fishing grounds being damaged... but hunters are pure evil?  and putting more garbage in landfills is a good idea?  ...and there are plenty of environmental personnel who work for Monsanto and seek to butt-rape the farming industry... so putting them in charge of the environments sounds like a great idea?...  Google the keywords alarmist, liberal propaganda, environmental elitism, climate epochs throughout geologic history, and don't be an ill-informed rhetoric-ranting leftist baby unless you're a San Francisco millionaire hippy who can afford a Prius that has no resale value after 8 years of ownership since current battery technologies provide a built-in obsolescence to hyper-liberal clouds of smug... 

A J
A J

@Corey McDonald How can nearly sterilizing a huge part of ocean be a "good thing?"

Seeding the oceans with anything is a fairly terrible idea. What's the point of fixing the "green house effect" with a method that destroys the oceans?

Eric Paul
Eric Paul

@A J You're absolutely correct.  It's a necessary evil because 'geniuses' like Jacues above (sporting his tinfoil hat and praising Jesus for Armaggedon) refuse to admit to/comprehend the real problem - overpopulation!

Jacues Boullard
Jacues Boullard

@A J ya, without agriculture imagine how advanced humanity would be... and without fire and cutting tools we would probably be supernatural beings of pure energy who could transcend the laws of quantum physics by now...

Eric Paul
Eric Paul

@Jacues Boullard @Penny Melko Gotta love the meaningless rant of erroneous propaganda attempting to label another's comment a meaningless rant.  Anyone who wants to deny that Federally Funded organizations like the EPA aren't paid off by the exact Industries responsible for these environmental disasters need to get their heads out of their azzes!

David Swanick
David Swanick

@A J @Corey McDonald 

How is a temporary, oxygen-depleted zone "sterilized"?  It still has massive amounts of organic material and anaerobic organisms.  The oxygen-depleted state will naturally subside, and then oxygen-breathing organisms will find an abundant supply of food.

Eric Paul
Eric Paul

@David Swanick @A J @Corey McDonald Officially the dumbest posts on NatGeo today...congrats!  Learn the basics about Environmental Science and you'll realize that not everything is a cycle.  Yah, and we should be expecting life to suddenly appear on Mars soon.

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