Does one remember this childhood song - Wheels on the bus song for baby? It will stick in your head now - Oceancirculating there for at least a few days. I think of it often - not because I've particularly fond memories of riding the bus to school, although they are not awful memories either - but because this song is amongst the best ways to think around the nitrogen cycle. Yes, nitrogen.
While life as we know it cannot survive devoid of nitrogen, too much nitrogen can result in deadly consequences in the underwater environment. In the next several essays we're going to explore how nitrogen has altered our coastal oceans. But first we must learn about nitrogen and how it cycles on the planet.
Simultaneously, in 1772, the Scottish physician Daniel Rutherford as well as a Swedish chemist Carl Wilhelm Scheele, noted that air contained two primary but different "fluids". The first was oxygen along with the second was di-nitrogen, or N2 petrol. The scientists learned that organisms (in this case a mouse) along with fire were extinguished in the presence of N2 and therefore, in time, it earned the name "azote", from the Ancient greek language 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 along with RNA - the blueprints that help define the shapes of our own bodies, the colours of our eyes and regardless of whether our ears attach to your heads. In fact, your body is approximately 3% nitrogen by excess weight (the rest is predominantly consists of carbon, oxygen, and hydrogen).
Nitrogen can be found in a variety of forms including the lifeless gas in addition to in dissolved and particulate periods. Scientists separate nitrogen into two categories: 1. un-reactive nitrogen or N2 gas; and 2. reactive nitrogen (sometimes termed Nr), which includes ammonia (NH3), ammonium (NH4+), nitrate (NO3-), urea and proteins. All of these forms permit nitrogen to cycle continuously through every the main biosphere, just like the wheels around the bus. And once nitrogen becomes reactive it passes ceaselessly collected from one of form to another, over and once again, round and round.
The largest pool of nitrogen on the planet, and the one that Rutherford in addition to Scheele first discovered, is present in the atmosphere. Nitrogen fertilizer applied to cropsIn fact, N2 gas makes up approximately 78% of the fresh air we breathe. But this vast pool of N2 swirling and whirling around us is unusable to most organisms on Earth, apart via nitrogen fixers. Nitrogen fixers are bacteria using the unique ability to take inert N2 gas from the atmosphere, break apart the a couple of triple bonded nitrogen atoms, and turn them in to a new form of nitrogen - ammonia (NH3). You are already familiar with these bacteria should you have munched on a peanut or maybe sneaked a mouthful of peas over summer-ripened vine. All of these plants are also called legumes and they have nitrogen-fixing bacteria living on their roots in bumps or nodules. These bacteria help naturally replenish soil nitrogen adopted by plants when they mature. In fact, since ancient times farmers have planted legumes as an easy way of "reinvigorating" the soil soon after growing a crop of vegetation without this nitrogen-fixing ability - say wheat or maize (corn). Legumes are protein rich and thus they are important components of our diet.
So why does it matter that many nitrogen on Wheels on the bus song for baby is a inert gas? It matters because nitrogen is really a key ingredient in building and maintaining all varieties of life. This is particularly important with regards to growing plants - both on land and within the sea. Nitrogen is the "limiting" nutritional in these ecosystems. That will be, it is often found in least supply compared to the amount required to form lifestyle, so whether we are speaking about the grass in your backyard or phytoplankton within the ocean (the microscopic grass from the sea), plant The Nitrogen Cyclegrowth is ultimately restricted because of the supply of nitrogen. Until just on the hundred years ago nitrogen-fixing bacteria were the only organisms that could tap to the vast, un-reactive pool of N2 gas within the atmosphere. Thus plants and ultimately human population were capped by the volume of reactive nitrogen naturally available in the world. In the past if we needed to grow more crops to feed more people we had to harvest fertilizer from some other 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 across the world to mine guano (or fowl waste) deposits. We've even used our personal sewage.
But none of these actions were actually adding reactive nitrogen for the earth. Instead, we were purely, and perhaps wisely, recycling already available nitrogen. For many years scientists experimented with to mimic the capabilities associated with nitrogen-fixing bacteria so we would be able to add nitrogen to the soil and increase our capability to grow food. While many attempts were made and various bits of the puzzle discovered, it wasn't before early 1900s that we learned to fix nitrogen in what we currently 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 with the twentieth century" (Smil 2001). In fact, over 48% of the 7 billion people alive today are living because of a chemical engineering feat of the particular Haber-Bosch process (Erisman et al. 2008).
Because My aim is to assist can be transformed through various chemical and microbial processes derived from one of form to another it constantly flows from the environment. You can think of nitrogen as a shape-shifter as it can be taken up by biology, secreted as being a waste, and taken up yet again. It can be transformed from your gas to a particulate style bound up in cell and then it could be dissolved in water and make its strategy to the sea. Between cultivating nitrogen-fixing crops, burning fossil fuels, and fixing nitrogen in the particular Haber-Bosch process humans have doubled the amount of nitrogen cycling through the biosphere! While this additional nitrogen has become beneficial to many it has also caused unanticipated and negative penalties to terrestrial and aquatic ecosystems and in many cases human health.
In marine systems nitrogen stimulates plant growth - both microscopic phytoplankton as well as larger macro algae. At very first, increased growth of Phytoplanktonphytoplankton can 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 develop. First, as they grow from the surface waters, this increased phytoplankton or macro algae increase may block light from reaching the lower thus killing submerged aquatic crops (or SAVs). SAVs are critical nursery habitats for important udemrket and shellfish. In addition, increased nitrogen loading can alter the species composition of phytoplankton along with harmful algal blooms, like reddish tide, which are associated using excess nitrogen loading. When the phytoplankton die they sink on the bottom and the natural decomposition by bacteria use up the oxygen in water column thus creating hypoxic (little oxygen) and anoxic (no oxygen) conditions. Intended for organisms that cannot move out - like shellfish - these types of low oxygen conditions can destroy them. Thus too much nitrogen causes excess phytoplankton growth, low air conditions, habitat destruction, and a decrease in biodiversity.
In Part II of this series we'll target low oxygen conditions in marine environments - also referred to as Dead Zones.
