Modern Biology
Muscle Disease Gene Identified in Fish
Bird Flu Mutation Risk
Platelets Help Tackle Bacteria
Untangling The Model Muddle
Cloning - The Good, The Bad and The Ugly
Unpacking the Human Genome Project
Does a Hot Mint Still Taste Cold?
Do Bald Men get all the Girls?
Why Plants Make Caffeine
Turning your Brain into Blood - How Stem Cells Work
The Microchimera Mixture
Forgetful Flies - A tale of two halves (of the brain)
The Smelly World of Mice and Men!
How animals develop from an embryo
Ricin : The Secret Assassin
Why drink Wine ?
Genetically Modified (GM) Plants
Big Fish, Little Sea
Something in the Air
What's On The Menu ?
What is the purpose of sexual reproduction?
Therapeutic Cloning, and Stem Cell Research
What is Living in my Mouth?
Genes for Bigger Brains
  No Smoke Detectors in the Sea
In the middle of the night we sleep soundly knowing that if something in our house goes awry we'll be warned. If smoke fills the downstairs and threatens the air we breathe, an alarm will sound. There are alarms for odourless toxic gases, for windows broken by would-be thieves and even alarms to tell us when the washing's done. But imagine if there werenít. What if, when we lay our heads upon our pillows, we had no way of knowing what we might breathe? Does this sound dramatic? You bet it does. But if you lived in the ocean, and the sea floor were your home, this would be your reality.

In my previous two essays (see below for links) we have learned that excess nitrogen can lead to increased phytoplankton growth. And when these small microscopic plants die and decay, oxygen in the water column is consumed causing hypoxia (low oxygen) and even anoxia (no oxygen). In some cases this is a natural occurrence, but in many cases it is not and the blame rests with us. Indeed, persistent low-oxygen conditions are developing in various places throughout our oceans and particularly near coasts where humans add nitrogen (mostly in the form of fertilisers washed off the land) to the sea.

If these low oxygen conditions persist they can trigger a phenomenon called habitat compression. This is where the area of hypoxia grows, restricting the remaining habitable space available for organisms to live in. If you are a mobile organism, like a fish, you may be able to escape and there are vivid accounts of animals moving into the shallows and even crawling to the tops of dock pilings to avoid underlying hypoxic conditions. But if you are a sessile animal and unable to move, like a mussel that must remain attached to something, then you are stuck and left to endure the low oxygen event. In severe cases these events cause massive die-offs of marine organisms, known appropriately as "fish kills", and they ultimately decrease ecosystem biodiversity. Dramatic events like these aren't the only way that the ecosystem may be impacted. Less severe, persistent or frequent low oxygen events can also greatly alter the environment. In this case, the organisms exposed to hypoxia grow and reproduce less and are more easily preyed upon.

As a general rule, organisms that inhabit the sediment or benthos have it worst of all. When you dwell on the bottom you live at the greatest distance from the atmosphere, which is a major source of aquatic oxygen replenishment. In addition, marine sediments are generally lower in oxygen compared with the water column above them. And because sediments are typically anoxic below the top few centimeters (or often millimeters), benthic organisms already live on the edge. So any hypoxic event can easily push them past the point of survival.

Of course, low oxygen concentrations donít just impact multi-celled, visible organisms Ė the microbial community can be hard hit too. Microbes are amazing organisms that can tolerate extreme conditions that range from hot springs and hydrothermal vents to glacial ice and polar bear fur. They can consume wood, plastics, oil and even radioactive materials, and one of their critical roles in the ocean is the removal of nitrogen from the water. This process converts a form of nitrogen called nitrate (NO3-), which is the form usually found in fertilisers and is readily consumed by phytoplankton, into di-nitrogen gas (N2), a form which is unuseable by most organisms. This natural nitrogen filter, known as denitrification, can remove a significant portion of the nitrogen we discharge into the coastal ocean. It also occurs under anaerobic (in other words no-oxygen) conditions.

So now you are thinking, "this is perfect Ė we have a way to clean up the nitrogen pollution we add to the environment and which needs no oxygen to work; less nitrogen in the water will decrease excess phytoplankton growth and, subsequently, with less organic matter to decompose, more oxygen will remain in the water column, and dead zones should be a thing of the past."

If this was your thought process, you were partly correct. But there is one critical step missing. Denitrification needs nitrate (NO3-); once the nitrate is gone, the process shuts down. And unfortunately, in many systems, nitrate comes from an aerobic (or oxygen requiring) process called nitrification. In nitrification, ammonium ions (NH4+) are converted to nitrate (NO3-) ions, making nitrate available for denitrification. And if the nitrifying microbes stop making nitrate then denitrification halts. This leaves ammonium lurking in the system to fuel future phytoplankton blooms, exacerbating the problem.

That would be bad enough, but it gets more complicated! Both nitrification and denitrification can produce nitrous oxide (N2O). Nitrous oxide is more commonly known as laughing gas, but I assure you in this case it's no laughing matter. This colourless gas has a heat-trapping (greenhouse gas) potential over 300 times more powerful than carbon dioxide, so it can contribute to global warming. In addition, it reacts in the atmosphere to deplete the ozone layer. Human activities, such as fossil fuel burning and fertiliser application, lead directly to N2O emissions, but low oxygen conditions in the marine environment also lead to the production of the gas. Research has shown that frequent flip flops between oxygen replete and oxygen depleted conditions can cause increased N2O emissions from both nitrification and denitrification. And work is currently underway to see if consistent oxygen-devoid environments, like dead zones, do the same thing.

So, is all lost? Tonight, when we lay our heads upon our pillows, should we feel sad and hopeless? The answer is a resounding, "NO!" First, it is interesting to remember that a dead zone isnít really dead. It turns out that there are numerous microbes that survive and in some cases thrive under hypoxic and anoxic conditions. They might not be the ones that come readily to mind, but that life survives under various conditions is a comforting thought. Second, and most important, there are simple everyday actions we can do to decrease our nitrogen footprint. By decreasing the amount of nitrogen in the environment we lessen our impact on the ocean. Want to know what to do? Stay tuned for the next article, where I'll explain...
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Bigfoot: The Nitrogen Problem
A Traveller's Guide to Bed Bugs
A spider web's strength lies in more than its silk
Thai police bust Bangkok rare wildlife 'butchers'
Castaway lizards provide insight into elusive evolutionary process
Bouquet bargains trade off for life
18 endangered dolphins spotted off Borneo: WWF
Tiny primate 'talks' in ultrasound
Steroids control gas exchange in plants
Fossil cricket reveals Jurassic love song
Rhino dies after anti-poaching treatment in S.Africa
Lions adapt to winter at Canada safari park
Invasive alien predator causes rapid declines of European ladybirds
Not the black sheep of domestic animals
Coaxing a Shy Microbe to Stand Out in a Crowd
How the zebra got its stripes
Fruit flies drawn to the sweet smell of youth
FLORA AND FAUNA Genetic Rosetta Stone unveiled in Nature
Ultraviolet protection molecule in plants yields its secrets
Indian village relocated to protect tigers
Explosive evolution need not follow mass extinctions
Plants use circadian rhythms to prepare for battle with insects
Armenia culls wolves after cold snap attacks
The Developing Genome?
Tempur-Pedic Mattress Comparison
Chromosome analyses of prickly pear cacti reveal southern glacial refugia
Poachers slaughter hundreds of elephants in Cameroon
'Founder effect' observed for first time
A Blue Future For Global Warming
Hitchhikers guide to Science
The Art of The Barbecue
Lost your bottle?
A Crossword a Day keeps the Doctor at Bay
Bio-plastics: Turning Wheat And Potatoes into Plastics
Why Don't Woodpeckers Get Brain Damage?
Protein Origami: Pop-up Books & Nature's Polymers
The Science of Parasites
Synthetic Biology: Making Life from Scratch
Flies are creatures of habit
What is Love?
How do plants develop?
What IQ Tests Can't Tell You
What is the Weirdest Experiment Ever?
Humble Honey Bee Helping National Security
Southern Right Whales
The Ocean's Cleaners
Barnacles "mussel" in
Food Date Coding Decoded
Photorhabdus luminescens: The Angel's Glow
Evolution Through the Looking Glass
I'm a Civet: Get me out of here!
No Smoke Detectors in the Sea