Dead Zones – why they happen & 11 ways to help!

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Dead zones are areas in bodies of water that have so little oxygen that few things can live there.  They can be huge and kill a lot of different species in oceans and lakes.  Read on to learn how that happens and how you can help!

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What is a Dead Zone?

dead fish due to dead zone/hypoxia
Fish kill due to a dead zone in Greenwich Bay, Rhode Island (U of Maryland CES –

Dead zones are a huge problem in our oceans today – in fact the dead zone in the Gulf of Mexico in 2017 was the largest recorded at 8,776 square MILES (NOAA). And that’s just one of the dead zones!   Dead zones are areas in our oceans or lakes that are called “dead zones” because of low levels of oxygen.  This low oxygen (hypoxia) that mean that many organisms can’t live in that area anymore.  While some animals (like dolphins and whales) get their oxygen from the air above the ocean, other animals (like fish) get their oxygen from the water itself.  If there is very little or no oxygen in the water, those animals can’t live there so they either move away or die. Some species can survive for a while without oxygen, but eventually will die if oxygen levels in the water don’t increase.  Other animals that eat those animals also move away since there is no food for them. The result is an area of the ocean with many fewer species.


Why does it matter?

First off, it’s clearly a problem for many species when large areas of the ocean can’t support most life. In 2017 the dead zone in the Gulf of Mexico was about the size of New Jersey (NOAA).  That’s a massive area of ocean with very little life!

At 8,776 square miles, this year's dead zone in the Gulf of Mexico is the largest ever measured.
The deadzone in the Gulf of Mexico in July 2017 – 8,776 square miles off the coast of Louisiana and Texas with very little oxygen in the water (NOAA)

But it’s not as noticeable to most people since it’s in the water. I’m pretty sure if the state of New Jersey or even a National Park of the same size no longer had enough oxygen to support life people would be really upset about it.  But since it’s in the ocean lots of people don’t even realize it is a problem.

It’s also a huge economic problem. No oxygen in the water means that fish move away from the area.  Dead zones are usually found near the coasts because they are usually caused by nutrients in the water from land (more on that in a sec).  Fish moving further from the coast means that fishers have to go much further to catch fish.  This makes their jobs harder and less profitable. It also makes fish more expensive for consumers. Just to top it off, more gas is used to get to the fish.  That means more cost and more carbon pollution and thus more global climate change, which causes it’s own economic problems – more on that in a future post. It can even reduce tourism – both for recreational fishing and for swimming.

Dead zones are caused by an algal bloom – these algae can be toxic  to humans and other species.  It can also cost areas huge amounts of money. For example, in southern Florida in 2016 there was an algal bloom that led to beach closures across the region…on the 4th of July weekend.  This led the governor to declare a state of emergency in several counties – and even made the news in the UK (The Telegraph).  The toxic algae was hazardous to residents and aquatic life.  The bloom caused huge economic losses on a normally busy holiday weekend.

So how does happen?

Dead zones are caused by an overabundance of nutrients that lead to explosive growth in small algae.  This is called an algae bloom – the bloom makes the water appear green and can even coat the top of the water as seen in the video.  The scientific term for this process is eutrophication. Algae occur naturally and are an important part of the marine ecosystem.  Algae also perform photosynthesis which puts more oxygen into the water.  So why would an algal bloom lead to low oxygen levels?

How dead zones form
How do dead zones form? (New Orleans Times Picayune)

The algae that bloom are small algae (not large algae like kelp) – when these algae die (which doesn’t take that long) they decompose like everything does when it dies.  The chemical process of decomposition removes oxygen from the water.  The algal bloom also blocks sunlight from getting to other plants or algae that would be putting oxygen into the water, so those species die too.  Put together, the reduction of other photosynthesis from longer lived organisms and the decomposition of tons of tiny algae pulls the oxygen out of the water, leading to large regions with low oxygen levels.

The root cause of dead zones is the excess nutrients that fuel algal growth.  Algae need the same type of nutrients that garden or house plants need – nitrogen and phosphorus being the key nutrients in this case.  Normally algal growth is limited by the fact that the algae don’t have enough nitrogen or phosphorus to grow out of control. When extra nitrogen and/or phosphorus is added to the water the small algae can reproduce quickly and become a problematic algal bloom. This bloom then causes the dead zone.

Where are the nutrients coming from?

Unfortunately the answer is generally from human activities.  The Environmental Protection Agency (EPA) says that “nutrient pollution is one of America’s most widespread, costly, and challenging environmental problems.”  Nutrient pollution comes from a lot of different things, which is part of the reason it is so challenging.  Some of the major sources of nutrient pollution are food production, lawn and garden fertilizers, and detergents containing phosphates (though many of these have been phased out).

Source of nutrients that enter the Gulf
Most of the nutrients entering the Gulf are from human activities – these excess nutrients lead to dead zones. (USGS)

A study done by the United states Geological Survey (USGS) found that, for the Gulf of Mexico dead zone, agriculture accounted for 70% of nitrogen and phosphorus and urban areas contributed 9-12%.  This leaves only 8% of the phosphorus entering the gulf from natural sources!  For nitrogen it’s a bit harder to calculate since atmospheric nitrogen is partially natural and partially caused by an increase in nitrogen in the air from air pollution. At most natural nitrogen sources only account for 20% of the nitrogen in the gulf…and it’s probably more like 10-12%.  The rest of the nitrogen comes from human activities.

A huge amount of the nutrients that enter the Gulf or other bodies of water are from agricultural facilities.  A lot of it comes from growing corn and soybeans in a conventional way.  Another major source is from meat and egg production in so-called “factory farms.”

Growing crops conventionally requires adding a lot of synthetic (man-made) fertilizers.  These fertilizers are often sold in forms that are water soluble (they dissolve easily in water).  This makes it easier to apply them since you can just add them to the water source for the plants or spray them on the fields.  This saves time and effort, so it saves farmers money in the short term.  BUT, since they are water soluble where do you think the fertilizer ends up when it rains?  Yep, in bodies of water like lakes and the ocean.  This is also a waste of money in the long run since a lot of the nutrients just runoff instead of feeding the crops. The Gulf of Mexico dead zone is caused by excess nutrients from all the farms ending up in the Mississippi river and eventually flowing into the Gulf.

Poultry on a factory farm
Chickens in a “factory farm” (

Another source of excess nutrients is from farming animals for meat and egg production in intensive ways.  Animals raised in very high densities generate a lot of manure and urine wastes in a very small area.  In a small farm system this manure and urine is a valuable source of nutrients. We use the manure from our animals to fertilize our garden, trees, and pasture (some we compost, others we don’t depending on the source).  But in a huge cattle feedlot or meat chicken “factory” the animals are producing far more waste per acre.  That waste ends up washing into our rivers and makes it to the ocean as well.

A smaller amount of excess nutrients come from “urban and population related” sources. These sources are mostly either fertilizer runoff from people fertilizing their lawns or gardens with synthetic fertilizers (again, many synthetic fertilizers are water soluble, so end up leaving the soil and being carried away in the water to waterways) or from septic systems or waste water treatment plants.  In certain areas that have intense rain (including where we live in Florida) waste water treatment plants regularly release untreated water into bodies of water when too much rainwater enters the treatment plant.  That means untreated human sewage ends up in lakes or the ocean – lovely, right? Both fertilizer and human waste have nitrogen and phosphorus in them, so they increase the nutrients in the water.  Increased nutrients in waterways lead to more dead zones.

So what can you do?

There are actually a lot of things you can do that would help shrink dead zones – here are some of them:

  1. Grow your own veggies!
    mustard greens in garden
    Mustard greens in our FL garden in January

    This way you can control how much fertilizer you use.  Growing your own veggies also means you can choose fertilizers that don’t contribute as much to the dead zones.  Besides, having fresh veggies in your yard helps you eat healthier and saves money too!  There are tons of reasons to grow your own food – we’ll have lots of future posts on how to get started.  But for now, keep reading to see which fertilizer to use to shrink dead zones.

  2.  Make your own compost from veggie scraps and yard waste. Compost will give your garden a great boost without damaging our oceans.  Turn your “waste” into great, natural fertilizer for your veggies. The nutrients in natural fertilizers like this are much less likely to be carried away by rain and end up causing dead zones.The  soil ends up getting more of the actual nutrients than with synthetic fertilizers, so compost is better for your plants too.  We keep a container for scraps on our kitchen counter and add it to our compost pile outside.  You can also get a compost bin in various styles (like this, this or this) if you don’t want an open pile.
    DIY pallet compost pile
    Finished compost in our DIY pallet compost pile (it shrinks a lot)

    Stick with veggie scraps and egg shells (great for additional calcium) from your kitchen and add yard waste to your bin/pile too (we’ll do a post on composting soon!).

  3. Not ready for a compost pile? No worries, you can buy compost too!  You can get it online from places like Amazon, but it’s usually cheaper to buy it locally at your garden or hardware store.  Make sure you are getting one that is just compost with no added synthetic fertilizers that contribute to dead zones.  Check that it is labelled compost, not soil with fertilizer…and check what they say it is made of!  The compost should look like rich soil.  You can just add it on top (top dress) of your soil for larger plants.  If you are planting seeds lightly dig it into the top of your soil before you plant.
  4. Don’t use synthetic fertilizers on your lawn or garden.  In many cases people are WAY over fertilizing their lawn.  More fertilizer is not better, too much fertilizer is actually bad for both your lawn and the planet (and a waste of money).  One easy and cheap way to help the dead zones is just to use less fertilizer!  If you aren’t ready to make or buy compost and still need fertilizer, buy organic fertilizers.  Most organic fertilizers will be incorporated in to your soil more thoroughly than synthetic fertilizer. This keeps the nutrients from being carried off when you get rain or water your garden.  Less nutrients in the water means smaller dead zones.  Some organic fertilizers are quite fragrant, so I suggest using them at the end of your gardening day when you are going inside!
  5. If you absolutely must use synthetic fertilizers use a slow release fertilizer designed to minimize runoff.  It will keep the nutrients where you want them – in the soil!  This will save you money and time reapplying fertilizer and help reduce the dead zones as well!
  6. Keep chickens for eggs or meat (eggs is
    different colored eggs
    Eggs from our flock -we have several different breeds and they lay different colored eggs

    easiest)!  Keeping your own chickens means you can manage the nutrients from their waste responsibly. You can even use it as fertilizer for your garden (see Tip 7).  Most chickens are raised in factory farms where their waste ends up contributing to the dead zones.  Chickens for eggs don’t take a lot of work, space, time or money. We even had them in the city – but check your local laws first! A side benefit is that they lay beautiful eggs you just can’t get in the store!  Ours lay light brown, light green and even speckled eggs. See our post on getting started with chickens if you are ready to jump in – I highly recommend them!

  7. Add the manure from your chickens or any other livestock to your compost pile.  Manure is great to add to compost!  For many manures you want to compost them before adding them as fertilizer.  If you don’t they can be too intense for your plants (too “hot”).  Composting manure will also help kill pathogens if you get your compost warm enough.  Don’t add cat or dog manure to your compost pile, just manure from livestock like horses, goats, chickens, etc.  Composted manure is great for your garden and puts the nutrients where they are needed – in your garden rather than in dead zones.
  8. Buy less (or no) meat and eggs!  This includes what you buy at the store and at a restaurant.  Most of the meat we eat in the US is grain-fed and grown in a factory farm.  This increases the amount of nutrients entering the water from growing crops (to make the grain to feed the animals). This also means a lot of animal manure and urine, which increases the nutrients in the water and ultimately in dead zones.  The less meat/eggs you buy, the less demand for these products. If there is lower demand, companies won’t build as many factory farms.
  9. Not ready to give up eggs or get your own chickens?Buy eggs from farmers using better practices to produce eggs.  We free-range our chickens which leads to happier, healthier chickens and they fertilize the ground naturally when they poop and scratch it into the ground.
    goat and two chickens
    A couple of our hens scratching for food and mixing goat droppings into the soil while Beta (the goat) supervises.

    Free-ranged chickens spread their manure over a large area so it doesn’t lead to much nutrients in the water.  You can buy free-range eggs, but they are often misleadingly labelled, so the best way to be sure you are helping is to buy them from local farmers you can talk with about how they raise their birds.  Try a local farmers market and ask the farmer how they use the chicken manure too.  I used to work at a farmer’s market and one of our farmer’s used to say “With enough chicken s**t, I could feed the world!”

  10. Not ready to give up meat or get livestock?  Just like with eggs, buy meat from sources using better practices.  You can find meat at many farmer’s markets and even grocery stores, Amazon, and big restaurant chains now carry grass-fed beef and free-range chicken.  Animals raised on pasture spread their waste around as they move through the pasture. You can’t pack as many animals onto pasture as you can onto a feed lot where you bring them grain.  Fewer animals in one space means less manure and urine runs off into waterways.  Grass-fed also means less grain, so less fertilizers used to grow grain.  All of this adds up to fewer nutrients in the water and smaller dead zones.
  11. Collect rainwater so it doesn’t run off.
    rain barrel connected to IBC tote
    Just one of our many rain barrels – this one is hooked up to a 330 gallon IBC tote for extra storage.

    The less water running off into fertilized lawns or gardens when it rains the less nutrients end up in rivers and oceans.  The rainwater from your roof doesn’t just stay on your property. Even if you are minimizing your fertilizer use or using organic fertilizers, your neighbor may not be.  Rainwater collection also means less rainwater going to local water treatment plants. That keeps the treatment plant from getting overwhelmed when your area gets lots of rain.  The plant is then less likely to release untreated sewage into local water bodies (Ew!). Capturing rainwater also helps you save water.  You can use the water to water your lawn or garden or to provide water to your livestock.  This reduces your water use and saves you money while reducing dead zones – a win-win-win!

We have over 1200 gallons of rain water storage currently.  See our post on collecting rain water in DIY rain barrels or you can buy all sorts of different rain barrels (try these or these).  You can also check out our post on how to add quick water storage with gutters on an outbuilding and a barrel or bucket underneath. Do note that in some places it isn’t legal to collect rainwater or store it for long. We don’t recommend doing anything illegal of course, so check local laws if you aren’t sure.


Got any other tips on how to shrink dead zones?  Questions on the science behind dead zones?  Let us know!