What Are The Consequences From Human Activity

That Cause Algal Blooms? Essay, Research Paper

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, near where major rivers emerge contain no living things. Much of the Gulf of Mexico has been killed off by the Mississippi River. The Baltic and Black Seas have also suffered a similar disaster.

Many may argue that algae are one of the most important organisms in a river or pond. Many animals in a river depend on one another. Green algae produce their own food by converting sunlight, carbon dioxide and water into energy through a chemical process called ?photosynthesis?. The algae are then eaten by the insect larvae, which are in turn, eaten by the platypus, ducks, water rats and the trout. At the top of the food chain are the human and the eels, both of which eat the trout. As the waste of the ducks and platypus falls to the bottom of the river (or when they die and their bodies fall), this organic material is broken down by bacteria on the river floor. The algae and insect larvae then absorb the decaying material, and the cycle begins again. If the algae were to be poisoned or reduced in numbers, many of the other creatures in the river ecosystem would die.

A further consequence of irrigation and current agricultural practices is the alarming appearance, since the early 1990?s of toxic blue-green algal blooms in our waterways. Blue-green algae are unicellular (one-celled) organisms that thrive in water that has a high nutrient content. Reduced river flow as a result of diverting water for irrigation and building dams and reservoirs means that sewage effluent and run-off from farmland make up a greater part of the flow. Nitrogen and phosphate concentrations rise, creating ideal conditions for blue-green algae to flourish, especially when there is plenty of sunlight.

Normal levels of blue-green algae in water are quite harmless. However, a dramatic increase in the numbers of these organisms is a serious environmental problem, as blue-green algae release waste products, which, at high levels, are toxic to animals and humans. They also block out sunlight, so preventing other underwater plants from photosynthesizing, and use up large amounts of oxygen, which leads to the death of fish and other aquatics animals.

When combined with drought conditions, a blue-green algal bloom has the potential to pollute an entire river system. As mentioned above, this happened to the Murray River in the early 1990?s. One of the first solutions proposed was to release extra water from dams to flush out the algae from the river. Soon after it was discovered that algal blooms were appearing all over the Murray-Darling system. In 1993, blue-green algae were reported in Lake Tuggeranong in the ACT, Centennial Park in the center of Sydney, and the Darebin parklands in suburban Melbourne. Some country towns had their water supplies threatened, and warning signs were put up along affected waters.

Many other chemical methods for controlling the algae were suggested, but now we understand that the only way to reduce the likelihood of blue-green algal blooms is to reduce our own water use, and to control the entry of phosphates and nitrates into our waterways from their sources. This means that farming must find more efficient ways of irrigating and fertilizing land, and treated sewage effluent must be used for other purposes than draining into our waterways.

Some irrigation schemes, up to 80 per cent of the water transported in channels is evaporated or lost though seepage before it even reaches the crop. Simply covering or lining the irrigation channels with plastic, or switching to piping the water, would reduce this wasteful evaporation.

The high use of pesticides in crops such as cotton and the constant use of fertilizers in farming are all polluting our waterways. Maintaining streamside vegetation can reduce fertilizer run-off. Animal waste effluent from feedlots and dairy sheds can be diverted away from streams and into artificial wetlands, where nutrients can be trapped.

Household detergents can also contribute to the phosphate content of sewage effluent (up to 50 per cent). The use of phosphate free detergents would greatly reduce the levels of this nutrient reaching waterways.

Only few things are being done to prevent these problems. Some governments are now allowing more water, called environmental flows, to run down rivers, but still nowhere near their original flow. Most detergents now contain only small amounts of phosphorus. In some countries, sewage is more carefully purified before it is released into rivers.

Communities should try and get involved in organizations that help minimize these problems. Such simple things as the reduction in the use of water used on the garden can have incredible effects. Make sure hoses aren?t left on for hours, mulch garden beds and water them at night rather in the hot sun, grow plants that don?t need lots of water. Also try to wash things such as the car and dog on the lawn, using a bucket instead of the hose. To save water in the house, fix leaking taps, don?t leave them running when you clean your teeth, and don?t stand under the shower for hours. Also, if living on a farm, don?t build a farm dam unless it is highly necessary. Not buying many cotton garments also helps contribute to helping, all fabrics have an environmental impact, because it needs such enormous quantities of water to grow, cotton probably has the greatest. Some of these are very difficult choices, but what is more important, healthy flowing rivers or a wardrobe full of clothes?

There are many different arguments one could discuss on the topic of algae. Some believe that algae plays a vital part in the ecosystem of a river, others may say that it destroys anything it can. In the last five years we have begun to see serious effects of current farming practices on our waterways, with toxic blue-green algal blooms along the Murray-Darling River system. Yet large amounts of water are still being used and household water use has doubled since 1980 and is continuing to rise. There are many consequences of these catastrophes, such as the prevention of using the water in the rivers for human use. Governments are helping, well trying to help the reduction of algal blooms in our waterways, and local communities are underway in organizing comities to help as well.



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