Today’s topic was the first of three types of water pollution: Cultural Eutrophication. Eutrophication is the process of Natural Nutrient Enrichment of Phosphates and Nitrates to a body of water. Cultural Eutrophication is when humans speed up this process, and this is when problems occur.
The process of Cultural Eutrophication takes place in a few steps.
1. Excess Nitrates and Phosphates run off into bodies of water. The sources of the excess of Nitrates and Phospahtes are mainly inorganic fertilizers and feedlot waste lagoons.
2. The excess nutrients in the water enable algae to grow at a ridiculously fast (exponential) rate. When this occurs in Coastal Ocean aras, it can cause a Harmful Algal Bloom (HAB). Common examples of Harmful Algal Blooms are Red Tides which are caused by microscopic algae that give off a red colored toxin.
3. The algae undergoes a dieback in which all the algae dies.
4. All of the dead organic algae matter causes the population of Decomposing oragnisms to rise rapidly. The increased amount of organisms performing cellular respiration causes the dissolved oxygen to lower even further. The water is now said to be hypoxic meaning that it is very low in dissolved oxygen.
5. Within the Oxygen Depleted Zone the animals that rely on large amounts of oxygen begin to die. Basically, the fish die.
Here is a link to a website that offers a great animation of the process:
It is also important to note that Cultural Eutrophication is worse in rivers, Lakes, streams and coastal areas of the ocean. Obviously the problem is not as bad in the open ocean which is far from any excess run off of nutrients. The problems is also worse in areas without any current where the nutrients collect and don’t move on elsewhere. Areas where this problem has been horrible recently include the Gulf of Mexico and Chesapeke Bay. (Both which are coastal areas with little water movement.)
Here is a current event article about the problem in the Gulf of Mexico. Note the image that shows the problematic areas across the world.