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This week I read an article about water quality indicators. The term communities is a good term to use when thinking about aquatic ecosystems because the organisms in the ecosystems depend on each other and the state of the water they live in to survive and thrive. One thing I learned more about was the effect of phosphates and nitrates on water, and how that directly affects the growth of water plants. I was slightly surprised to learn that many types of aquatic life prefer cooler water to warmer water.
Temperature is one big indicator of water quality because it directly affects the amount of dissolved oxygen, or DO, in the water. Cooler water higher levels of DO, and warmer water has lower levels of DO. If temperature in the water increases, many of the aquatic organisms inhabiting it leave or die, because the water is too warm for them to thrive. Often, warm-water organisms will replace them. One big reason for temperature change like that is humans, and the many things we dump into lakes, rivers, and streams. Temperature changes caused by humans are called thermal pollution. Scientists and aquatic environmentalists can check for thermal pollution by testing the temperature of a river, lake, or stream at its source. Then, they move to a different point in the river, lake, or stream, and test the temperature again. If there is a big difference, then the water is probably thermally polluted. Generally, excellent quality water is 0-4 °F, and poor quality water is 18°F or greater.
Another indicator of water quality is turbidity. Turbidity is basically the measure of how clear the water is. Turbid water has things like clay, silt, and bottom sediment suspended in it, which makes the water brownish or murky. Turbidity affects the quality of water because it affects the temperature of the water - suspended particles block and absorb sunlight. Then, of course, all of the effects of temperature start to occur. Turbidity levels are mainly affected by soil erosion, bottom sediment disturbance, and urban runoff.
The last indicator of water quality I'm going to write about is plant growth. Algae and other water plants need a small amount of phosphates to grow. Too many phosphates or nitrates, however, increase the plant growth drastically. When there is too much algae, from increased amounts of phosphates and nitrates, it's called an algal bloom. The algal blooms are not good for the waterway, because they block sunlight from the roots of water plants, and when they decompose, the DO levels decrease. The main human sources of phosphates and nitrates in the water are fertilizer, laundry detergent, and sewage. The way to stop water quality decreasing from human-affected plant growth, is to be more effective about stopping phosphates and nitrates from entering the water. This can be done at farms, by building a barrier to stop large quantities of fertilized earth entering the water, and by watching were we dump our sewage.
In class I have been studying water quality, and how fertilizer concentration affects the growth of duckweed. The article I read relates to my learning because knowing the indicators of water quality will help me understand other things about water quality. I would like to learn more about turbidity, and what natural levels of it are good for common aquatic life.
