AICE Environmental Case Studies Practice Exam 2026 - Free AICE Environmental Practice Questions and Study Guide

Nutrient runoff fuels rapid growth of algae and aquatic plants in water bodies (eutrophication). When these algal blooms die, bacteria break down the dead matter, and this decomposition consumes a lot of dissolved oxygen. That drop in oxygen can create low-oxygen, or hypoxic, zones, especially at night when photosynthesis isn’t adding oxygen and in parts of the water where mixing is limited. So, nutrient runoff can lead to algal blooms and, after those blooms die, oxygen depletion, harming aquatic life.