What is a primary consequence of an algal bloom in aquatic ecosystems?

An algal bloom primarily leads to decreased light penetration in aquatic ecosystems. Algal blooms consist of rapid increases in the population of algae, often due to excess nutrients like nitrogen and phosphorus. When these algae proliferate, they form a dense layer on the surface of the water, which limits the amount of sunlight that can reach deeper layers.

This reduction in light penetration has significant consequences for the entire ecosystem. Photosynthetic organisms, such as aquatic plants and phytoplankton, rely on sunlight to produce energy through photosynthesis. With diminished light availability, their growth is hindered, which can disrupt the food chain and affect the overall health of the ecosystem.

In contrast to the consequences of decreased light, increased oxygen levels may occur in some cases but is often not sustainable, as the decay of dead algal blooms can consume oxygen and lead to hypoxic conditions. Enhanced growth of aquatic plants is unlikely because the algal bloom blocks sunlight. Additionally, nutrient competition is actually intensified since the algae absorb available nutrients, leaving less for other aquatic plants and organisms.