5.4.1 Outline the processes of eutrophication.
Eutrophication is the addition of excess nutrients to a water system, which leads to the growth and subsequent death of algae, which reduces the dissolved oxygen available for other aquatic organisms. The main stages or steps of eutrophication are (in order):
Nutrients wash into a river or stream.
Algae grow quickly in response to the added nutrients.
The algae block sunlight to aquatic plants, so photosynthesis slows, and less oxygen is released into the water - low DO levels. Decomposer populations increase because they have more food (the algae), and they use up all the oxygen for respiration - high BOD levels. Fish and other consumers die due to the lack of oxygen and the lack of producers at the base of the food web. Nitrates and phosphates are the most common nutrients responsible for eutrophication. They tend to come from a few major sources: detergents (laundry soap and dish soap washed down the drain) agricultural fertilizers
livestock waste from farms
5.4.2 Evaluate the impacts of eutrophication.
What effects would each of the following have on an aquatic ecosystem? depleted oxygen levels
collapse of food chains → decreased biodiversity
water contaminated with nitrites
cloudy water (turbidity caused by buildup of sediment)
5.4.3 Describe and evaluate pollution management strategies with respect to eutrophication. Minimize the amount of nutrients being released into the system by: limiting production/use of detergents containing phosphates
create buffer zones between agricultural land and water sources prevent animal waste from leaching into groundwater and rivers/streams Treat the polluted area by:
pumping air into the water source
divert or treat sewage properly
dredge (dig up) contaminated sediments
physically remove algae blooms
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