A healthy environment depends on biogeochemical cycles maintaining a balance of input and output. High levels of nitrogenous compounds in the waterways can cause an algal bloom. How does an algal bloom affect a marine ecosystem?

This should be the omitted answer choices to the question:

a. It decreases the carbon dioxide in the water, creating a toxic environment.

b. It decreases oxygen in the water, creating a toxic environment.

c. It increases the carbon dioxide in the water, stimulating plant growth.

d. It increases the oxygen in the water, stimulating plankton growth.

Answer:

b. It decreases oxygen in the water, creating a toxic environment.

Explanation:

A rapid increase in algae populations in a marine ecosystem as a result of high levels of nitrogenous compound would result in increased level of dead organic matters from algae. This would mean more food for bacteria that are present in the marine ecosystem, which would further lead to the rapid increase in the population of bacteria in the marine ecosystem. The presence of more dead organic matters would favor the surge in the population of bacteria. Bacteria require oxygen to survive. As the population of bacteria increases rapidly, the level of dissolved oxygen in the water would drop as bacteria would make use of most of the dissolved oxygen available, thereby disrupting the ecosystem of the marine habitat.

The survival of most aquatic organisms is dependent on the level of dissolved oxygen available as most aquatic fish and insects would die as the level drops. Some species of algae produce toxins which also harmful to aquatic life.

Alga bloom would affect a marine ecosystem by reducing the level of dissolved oxygen needed by other aquatic organisms to survive, and also leads to high level of production toxins detrimental to other aquatic organisms.