An unusually snowy winter, and weeks of heavy rainfall in south east USA has resulted in the Mississippi River flooding to record levels. As a response, US engineers have released the rising waters onto the floodplains surrounding the river, in order to save the heavily populated regions further downstream. The economic costs of such an action are huge – some reports put the cost at $295 million a day. Ecologically, there is more bad news. River water naturally contains large amounts of sediments that have eroded as the river travels downstream. This sediment is incredibly rich in nutrients, and as it flows into the Gulf of Mexico it allows a huge algal bloom to form. As the algae multiply and multiply, the supply of nutrients runs out. Eventually, there is nothing left and the algae die. Their remains are decomposed by bacteria, which causes the majority of the dissolved oxygen in the water to be depleted. No oxygen means fish have nothing to respire, resulting in huge swathes of dead fish floating on the surface. This process is well documented by scientists – it is known by the term – eutrophication.
Normally seen as a harmful event, new research published in BioScience may show it in a more positive light. Algal blooms, once the scurge of oxygen-loving fish, may help fight water pollution – in controlled situations.
Field sized tanks of algae may one day be erected that take in water contaminated with nitrogen and phosphorous from industry and agriculture. The algae grow on specially designed screens which trap the algae. The purified water that is left can then be released back into the environment. As an added bonus, the nitrogen rich algae can be collected and used either as fertilizer or converted to biofuels. The tanks can either operate on land, or in the open sea. So, whereas the algae would be left uncontrolled to eventually decompose and suffocate any sea life in the area, we can now harness the benefits for ourselves and remove the costs to the environment.