Final answer:
Decomposition of dead fish or elodea in water leads to microorganisms consuming oxygen and releasing compounds like CO2, which can acidify the water (lower pH). This resembles eutrophication, where excess nutrients cause algae overgrowth, then decay, creating dead zones with low oxygen and altered pH affecting aquatic life.
Step-by-step explanation:
When a fish or elodea (an aquatic plant) dies in water, the process of decay starts, involving microorganisms that break down the dead material. During this decomposition process, the microorganisms consume dissolved oxygen in the water and release various compounds, including phosphorus, nitrogen, and carbon dioxide (CO2). The excess CO2 can combine with water to form carbonic acid, which then lowers the pH of the water. A decrease in the pH indicates that the water is becoming more acidic. This effect is similar to eutrophication, a phenomenon where excess nutrients from sources such as fertilizer runoff lead to the overgrowth of algae and other plants, followed by their decay, and further consumption of oxygen, thus creating dead zones that lack sufficient oxygen to support aquatic life. When these excessive nutrients are followed by the decay of organisms, it fuels a cycle that depletes more oxygen and can lower the pH of the water further, affecting the survivability of the aquatic ecosystem.