Put the events of cultural eutrophication in the correct order. a. Dead zones (hypoxic zones)

b. Algal blooms

c. Increase in nutrient levels

d. Algae dies, microbes decompose using oxygen

c. Increase in nutrient levels

b. Algal blooms

d. Algae dies, microbes decompose using oxygen

a. Dead zones (hypoxic zones)

Explanation:

The term eutrophication refers to the enrichment of surface water with nutrients. This process is related to human pollution activities.

Eutrophication is the biological process that generates in water by an oversupply of nutrients or organic matter. This matter, mainly compounded with nitrogen or phosphorous, favors the phytoplankton multiplication (microscopic plants growing on the water surface) and other aquatic plants. This overgrowth leads to an enhance in primary productivity.

Little by little begin sedimentation is caused by the death of some vegetable organisms that sink in the bottom. These sediments rich in organic matter suffer decomposition in the presence of oxygen.

When oxygen disappears, anaerobic bacteria act and produce fermentation.

On the surface, plants and phytoplankton keep growing, creating a mantle that impedes the light reach deeper areas. The phytoplankton overgrowth on the water surface and the fermentation processes in the bottom originate toxic compounds that damage the animals. Animals die, creating more sediments in the bottom where there are anaerobic conditions.

Decomposition and fermentation processes increase, producing a bad smell.

The result of eutrophication is the stratification of the water mass:

·        First superficial layer, the overgrowth of blue-green algae, produces toxins and interrupts the pass of light to deeper areas. The surface then becomes warmer.

·        The second layer might have oxygen available for the animals.

·       In the third layer, there is no oxygen, so life is impossible for animals or plants.

·        In the fourth layer, there are animals and plant remains in the process of sedimentation.

·        At the bottom, there are organic matter and anaerobic bacteria in charge of decomposition and fermentation, through which they produce toxic gases and smell.

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