Can you remember this childhood song - Wheels on the bus? It will stick in your head now - Oceancirculating there for at least 2 or 3 days. I think of it often - not because I've particularly fond memories of operating the bus to school, although they are not negative memories either - but because this song is probably the best ways to think around the nitrogen cycle. Yes, nitrogen.
While life as we know it cannot survive without having nitrogen, too much nitrogen may result in deadly consequences in the underwater environment. In the next several essays we're going to explore how nitrogen has converted our coastal oceans. But first we must learn about nitrogen and how it cycles that is known.
Simultaneously, in 1772, the Scottish physician Daniel Rutherford plus a Swedish chemist Carl Wilhelm Scheele, noted that air contained two primary but different "fluids". The first was oxygen and also the second was di-nitrogen, or N2 gasoline. The scientists learned that organisms (in this case a mouse) together with fire were extinguished in the presence of N2 thereby, in time, it earned the name "azote", from the Greek for “without life”.
Of course, this is a bit ironic just as truth Peas in pods. nitrogen is often a fundamental element necessary for all life. It is a critical component of proteins and of DNA in addition to RNA - the blueprints that help define the shapes individuals bodies, the colours of our eyes and regardless of whether our ears attach to our heads. In fact, your body is approximately 3% nitrogen by excess weight (the rest is predominantly consists of carbon, oxygen, and hydrogen).
Nitrogen are available in a variety of forms including the lifeless gas in addition to in dissolved and particulate phases. Scientists separate nitrogen into a pair of categories: 1. un-reactive nitrogen or even N2 gas; and 2. reactive nitrogen (sometimes known as Nr), which includes ammonia (NH3), ammonium (NH4+), nitrate (NO3-), urea along with proteins. All of these forms enable nitrogen to cycle continuously through every perhaps the biosphere, just like the wheels about the bus. And once nitrogen becomes reactive it passes ceaselessly collected from one of form to another, over and over again, round and round.
The largest pool of nitrogen on earth, and the one that Rutherford and Scheele first discovered, is present in the atmosphere. Nitrogen fertilizer applied to cropsIn fact, N2 gas is the reason for approximately 78% of the air flow we breathe. But this vast pool regarding N2 swirling and whirling around us is unusable to most organisms on Earth, apart by nitrogen fixers. Nitrogen fixers are bacteria with the unique ability to take inert N2 gas out from the atmosphere, break apart the two triple bonded nitrogen atoms, and turn them into a new form of nitrogen : ammonia (NH3). You are already familiar with these bacteria when you have munched on a peanut or sneaked a mouthful of peas from the summer-ripened vine. All of these plants are often known as legumes and they have nitrogen-fixing bacteria living on their roots in bumps or nodules. These bacteria be an aid to naturally replenish soil nitrogen adopted by plants when they increase. In fact, since ancient times farmers have planted legumes as an easy way of "reinvigorating" the soil immediately after growing a crop of vegetation without this nitrogen-fixing ability : say wheat or maize (corn). Legumes may also be protein rich and thus they are important components of our diet.
So why does it matter that most nitrogen on Wheels on the bus go round and round is the inert gas? It matters because nitrogen is often a key ingredient in building and maintaining all types of life. This is particularly important on the subject of growing plants - both on land and in the sea. Nitrogen is the "limiting" nutritious in these ecosystems. That is, it is often found in least supply in comparison to the amount required to form life, so whether we are dealing with the grass in your backyard or phytoplankton from the ocean (the microscopic grass with the sea), plant The Nitrogen Cyclegrowth is ultimately restricted because of the supply of nitrogen. Until just spanning a hundred years ago nitrogen-fixing bacteria were the sole organisms that could tap in the vast, un-reactive pool of N2 gas inside atmosphere. Thus plants and ultimately adult population were capped by the amount of reactive nitrogen naturally available in the world. In the past if we desired to grow more crops to feed more people there was to harvest fertilizer from different locations. For example, we have applied cow and pig manure to our farm fields, we have harvested seaweed for our vegetable gardens, and we have traveled throughout the world to mine guano (or hen waste) deposits. We've even used your own sewage.
But none of these actions were actually adding reactive nitrogen to the earth. Instead, we were merely, and perhaps wisely, recycling by now available nitrogen. For many years scientists tried to mimic the capabilities of nitrogen-fixing bacteria so we could add nitrogen to the soil and increase our capacity to grow food. While many attempts were made and various items of the puzzle discovered, it wasn't prior to the early 1900s that we learned to solve nitrogen in what we today call the Haber-Bosch process. The Haber-Bosch process uses high temperature and pressure to make ammonia and is regarded as being the most "important technical invention of the twentieth century" (Smil 2001). The truth is, over 48% of the 7 billion people alive today are living because of a chemical engineering feat of this Haber-Bosch process (Erisman et al. 2008).
Because My aim is to help you can be transformed through various chemical and microbial processes in one form to another it constantly flows with the environment. You can think of nitrogen as a shape-shifter as it can be taken up by biology, secreted like a waste, and taken up all over again. It can be transformed from the gas to a particulate type bound up in cell and then it might be dissolved in water and make its way to the sea. Between cultivating nitrogen-fixing herbs, burning fossil fuels, and fixing nitrogen in this Haber-Bosch process humans have doubled the amount of nitrogen cycling through the biosphere! While this additional nitrogen have been beneficial to many it has also caused unanticipated and negative consequences to terrestrial and aquatic ecosystems and even human health.
In marine systems nitrogen energizes plant growth - both microscopic phytoplankton as well as larger macro algae. At 1st, increased growth of Phytoplanktonphytoplankton might be beneficial as they are the base of food chains and in the long run support the growth of species of fish. But as nitrogen additions increase way too many phytoplankton and macro algae expand. First, as they grow in the surface waters, this increased phytoplankton or macro algae growth may block light from reaching the lower thus killing submerged aquatic plants (or SAVs). SAVs are crucial nursery habitats for important b and shellfish. In addition, increased nitrogen loading can alter the species composition of phytoplankton and harmful algal blooms, like reddish colored tide, which are associated along with excess nitrogen loading. When the phytoplankton die they sink to the bottom and the natural decomposition by bacteria use up the oxygen in the stream column thus creating hypoxic (little oxygen) and anoxic (no oxygen) conditions. Pertaining to organisms that cannot move out - like shellfish - these kinds of low oxygen conditions can wipe out them. Thus too much nitrogen brings about excess phytoplankton growth, low breathable oxygen conditions, habitat destruction, and a lowering in biodiversity.
In Part II of this series we'll target low oxygen conditions in marine environments - generally known as Dead Zones.
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