Does one remember this childhood song - Wheels on the bus go round and round? It will stick in your thoughts now - Oceancirculating there for at least a couple of days. I think of it often - not because I've particularly fond memories of cycling the bus to school, although they are not bad 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 with no nitrogen, too much nitrogen can cause deadly consequences in the boat environment. In the next several essays we are going to explore how nitrogen has developed 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 as well as a Swedish chemist Carl Wilhelm Scheele, noted that air contained two primary but completely different "fluids". The first was oxygen plus the second was di-nitrogen, or N2 gas. The scientists learned that organisms (in this case a mouse) and also fire were extinguished in the presence of N2 and thus, in time, it earned the particular name "azote", from the Language of ancient greece for “without life”.
Of training course, this is a bit ironic as with truth Peas in pods. nitrogen is often a fundamental element necessary for most life. It is a critical component of proteins and of DNA in addition to RNA - the blueprints that help define the shapes your bodies, the colours of our eyes and no matter whether our ears attach to the heads. In fact, your body is approximately 3% nitrogen by bodyweight (the rest is predominantly constructed from carbon, oxygen, and hydrogen).
Nitrogen come in a variety of forms including the lifeless gas along with in dissolved and particulate phases. Scientists separate nitrogen into two categories: 1. un-reactive nitrogen as well as 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 permit nitrogen to cycle continuously through every perhaps the biosphere, just like the wheels for the bus. And once nitrogen becomes reactive it passes ceaselessly from form to another, over and over again, round and round.
The largest pool of nitrogen we know, and the one that Rutherford in addition to Scheele first discovered, is seen in the atmosphere. Nitrogen fertilizer used on cropsIn fact, N2 gas makes up about approximately 78% of the oxygen we breathe. But this vast pool involving N2 swirling and whirling around us is unusable to most organisms on Earth, apart by nitrogen fixers. Nitrogen fixers are bacteria while using the unique ability to take inert N2 gas out of the atmosphere, break apart the a couple of triple bonded nitrogen atoms, and turn them right into a new form of nitrogen - ammonia (NH3). You are already familiar with these bacteria in case you have munched on a peanut as well as sneaked a mouthful of peas over 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 help naturally replenish soil nitrogen taken on by plants when they expand. In fact, since ancient times farmers have planted legumes in order of "reinvigorating" the soil right after growing a crop of plants without this nitrogen-fixing ability - say wheat or maize (corn). Legumes will also be protein rich and thus there're important components of our diet regime.
So why does it matter that a majority of nitrogen on Wheels on the bus is a good inert gas? It matters because nitrogen is really a key ingredient in building and maintaining all forms of life. This is particularly important on the subject of growing plants - both on land and in the sea. Nitrogen is the "limiting" vitamin in these ecosystems. That is, it is often found in least supply in comparison to the amount required to form existence, so whether we are dealing with the grass in your backyard or phytoplankton inside the ocean (the microscopic grass in the sea), plant The Nitrogen Cyclegrowth is ultimately restricted with the supply of nitrogen. Until just on the hundred years ago nitrogen-fixing bacteria were the only real organisms that could tap into the vast, un-reactive pool of N2 gas inside the atmosphere. Thus plants and ultimately adult population were capped by the number of reactive nitrogen naturally available on the planet. In the past if we wished to grow more crops to feed more people there were to harvest fertilizer from 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 worldwide to mine guano (or bird waste) deposits. We've even used our own sewage.
But none of these activities were actually adding reactive nitrogen towards the earth. Instead, we were basically, and perhaps wisely, recycling by now available nitrogen. For many years scientists tried to mimic the capabilities connected with nitrogen-fixing bacteria so we would be able to add nitrogen to the soil and increase our chance to grow food. While many attempts were made and various components of the puzzle discovered, it wasn't until the early 1900s that we learned to mend nitrogen in what we right now call the Haber-Bosch process. The Haber-Bosch process uses high temperature and pressure to make ammonia and is regarded as 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 the Haber-Bosch process (Erisman et al. 2008).
Because My aim is that can help can be transformed through various chemical and microbial processes from 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 like a waste, and taken up once again. It can be transformed at a gas to a particulate type bound up in cell and then it is usually dissolved in water and make its way to the sea. Between cultivating nitrogen-fixing plants, burning fossil fuels, and fixing nitrogen in the particular Haber-Bosch process humans have doubled how much nitrogen cycling through the biosphere! While this additional nitrogen has become beneficial to many it has also caused unanticipated and negative implications to terrestrial and aquatic ecosystems and in some cases human health.
In marine systems nitrogen stimulates plant growth - both microscopic phytoplankton together with larger macro algae. At first, increased growth of Phytoplanktonphytoplankton can be beneficial as they are the base of food chains and ultimately support the growth of species of fish. But as nitrogen additions increase a lot of phytoplankton and macro algae increase. First, as they grow inside the surface waters, this increased phytoplankton or macro algae progress may block light from reaching the end thus killing submerged aquatic plants (or SAVs). SAVs are important nursery habitats for important b and shellfish. In addition, increased nitrogen loading can change the species composition of phytoplankton and harmful algal blooms, like reddish colored tide, which are associated together with excess nitrogen loading. When the phytoplankton die they sink to the bottom and the natural decomposition by bacteria will use up the oxygen in the river column thus creating hypoxic (little oxygen) along with anoxic (no oxygen) conditions. With regard to organisms that cannot move absent - like shellfish - most of these low oxygen conditions can kill them. Thus too much nitrogen contributes to excess phytoplankton growth, low fresh air conditions, habitat destruction, and a lowering in biodiversity.
In Part II of this series we'll concentrate on low oxygen conditions in marine environments - also called Dead Zones.
