Florida Wastewater Practice Test

In what way does excess algae growth affect aquatic ecosystems?

1. Increases light penetration

2. Reduces oxygen availability

3. Improves water quality

4. Promotes fish breeding

The correct answer is: Reduces oxygen availability

Excess algae growth in aquatic ecosystems primarily reduces oxygen availability, making this the most accurate choice. When algae flourish, especially in a phenomenon known as algal blooms, they may initially increase oxygen levels during the day through photosynthesis. However, as these algae die off, a significant decay process begins. This decomposition, carried out by bacteria, consumes large amounts of dissolved oxygen in the water. The depletion of oxygen can create a hypoxic environment, which is detrimental to aquatic life. Many fish and other marine organisms depend on sufficient oxygen levels to survive, and reduced oxygen availability can lead to fish kills and a decline in biodiversity. The other choices do not accurately represent the overall impact of excess algae growth. Increased light penetration is often hindered rather than enhanced due to the density of algae, which blocks light from reaching lower depths. Water quality typically deteriorates, rather than improves, as high nutrient levels that lead to algal blooms can also promote harmful substances and toxins. Lastly, while some fish may breed in nutrient-rich environments, the overall health of the aquatic ecosystem declines due to the negative consequences associated with oxygen depletion and the presence of toxins from certain algal species.