How do temperature changes impact an aquatic ecosystem in spring?

In spring, temperature changes in aquatic ecosystems typically result in an increase in dissolved oxygen levels. As water warms up due to rising temperatures, the solubility of oxygen in water decreases; however, this period is characterized by biological activity. The growth of phytoplankton (algae) and increased photosynthesis as sunlight becomes more available lead to higher oxygen production in the water.

Moreover, during spring, the mixing of water layers, or turnover, occurs as the surface water warms and becomes less dense, leading to better oxygen distribution throughout the water column. This increased biological activity combined with physical mixing enhances overall dissolved oxygen levels, which is critical for the survival of aquatic organisms.

In contrast, the other choices do not accurately reflect the conditions in a spring aquatic ecosystem. Algal growth often increases in the spring due to the availability of sunlight and nutrients after the cold winter months, and water stratification can be disrupted rather than stabilized as temperatures change. Lastly, complete freezing of water bodies is more characteristic of winter than spring, as rising temperatures during this season lead to thawing.