Dead zones
Dead zones could be referred to as regions of lakes and oceans which are depleted of oxygen because of nutrient influx. One of the worst dead zones in the world is in the Gulf of Mexico and off the coast of the US. The oxygen content in these waters is less than 2ppm. Fertilizer runoff from the Mississippi River Basin has also created a dead zone which stretches 8,463 sq. miles. Over the years the number of dead zones has increased and as of 2008, the total number is more than 400.
Why is the phosphorus cycle important?
Phosphorus is an important element and is a major component of many cellular components, Not only in nucleic acid but for other organic molecules like phospholipids, P is an integral part of their structure. Phosphorus also plays a role in the transport of energy within cells and provides structure to cell membranes, teeth and bone. Plants need phosphorus for growth and development. As the element is not found abundantly in nature, the phosphorus cycle ensures the phosphorus taken up by plants and animals is always replenished.
FAQs on Phosphorus Cycle
1. Why is phosphorus not available in free form in nature?
Elemental phosphorus is highly reactive and when exposed to air it goes through a chemical reaction with oxygen. That is why in nature phosphorus is found a phosphate (PO4-3). Phosphates contain one phosphorus atom that is bound to four oxygen atoms, and all oxygen atoms are bound to each other. The general form of phosphate that we see in nature is HPO4-2.
The phosphate anion bonds with carbon, nitrogen, and hydrogen to form ATP, for example. Also with calcium (and occasionally hydrogen), it forms calcium phosphate which is a component of bones.
2. What is Eutrophication?
Eutrophication can be defined as a process of enrichment of water by nutrient salts that causes structural changes to the aquatic ecosystem. Examples of these changes are increased growth of algae and aquatic plants, general deterioration of the quality of water, depletion of fish species etc.
Eutrophication is harmful to the aquatic ecosystem as some algae produce toxic compounds and when they die, they are decomposed by microbes. During decomposition, a large amount of oxygen is used to break down algal bodies. The spike in oxygen usage lowers the levels of oxygen in water bodies which can lead to the death of many aquatic organisms by hypoxia (lack of oxygen). It can be controlled by reducing the usage of artificial fertilisers.
3. Why is most phosphorous not available to plants?
Most of the available P in soil is not available to plants. There are many reasons.
Bacteria convert the available phosphate into organic which cannot be taken up by plants.
Inorganic phosphorus available in the soil can be chemically bound to soil particles, which makes it unavailable for plants.
Also, inorganic phosphorus compounds need to be soluble so they can be taken up by plants. If the soil’s pH is less than 4 or more than 8, the available phosphorus becomes tied up with other compounds which cannot be utilised by plants.
