What are the consequences from human activity that cause algal blooms?
Uploaded by Adelle on May 04, 2002
Streams, rivers, lakes, and wetlands contain a large part of our precious fresh water. Unfortunately they also act like drains, and everything we leave lying around ends up in them – acids, mercury, cadmium, and lead from industry and other resources; soil from logging operations; phosphorus and nitrogen from detergents; sewage, petrol, oil, plastic bags, aluminum cans and paper from roads and parks – the list is never ending. More often than not, the results are catastrophic. Being thoroughly discussed will be information about the death of rivers due to algal blooms e.g. Murray River, consequences the irrigation and agriculture organizations are causing, what is being done to prevent these problems and what the communities can do to help.
“In 1991, a 1000-km-long stretch of the Darling River in New South Wales was entirely covered in poisonous blue-green algae…”(The State Of The Planet, John Nicholson, Pg.22), it was the largest toxic ‘algal bloom’ the world has ever seen. It happened because of two human activities. Algal blooms thrive on phosphorus and nitrogen – two important ingredients of farm fertilizers, animal and human waste, and detergents. Every year 440 tones of phosphorus and 1890 tones of nitrogen end up in the Darling River, mainly from farms and sewage treatment plants. Most rivers around the world have so much nitrogen in them they are unsafe for humans to drink. The algal blooms then use up all the oxygen in the water, so the fish suffocate and some water plants die. The poisonous algae also kill animals that drink at the river.
This process only happens if the water is not moving. People pumping water out for irrigation, or holding it back in hydroelectric dams or town water storages and farm dams have reduced the flow of water in most rivers. The Goulburn River has 870 different engineering works along it, each of them helping to reduce the flow. The Upper Murray has 44. Many of the world’s major rivers have so much water taken out of them that they no long reach the sea, at least during the drier months. Another three examples of these situations are The Colorado (USA), Huang He (China), and the Murray (Australia). This is very bad news for many ocean fish, as they need to travel up the rivers every year to spawn in fresh water. And the problem doesn't stop there. Large areas of costal waters,...