What is the impact of nutrient runoff into aquatic ecosystems?

Nutrient runoff into aquatic ecosystems often introduces large quantities of fertilizers and organic materials, such as nitrogen and phosphorus. These nutrients can stimulate rapid growth of algae, leading to what are known as harmful algal blooms (HABs). These blooms can deplete oxygen in the water when they decompose, making it difficult for fish and other aquatic life to survive. Additionally, some algal blooms produce toxins that can harm or kill aquatic organisms, disrupt food webs, and even affect human health and recreational water activities.

In contrast, while nutrient inputs can indeed support plant growth, excessive levels result in ecological imbalance, which is why the phenomenon of harmful algal blooms is a significant concern. The idea that nutrient runoff has no effect on aquatic life overlooks the critical environmental changes it can instigate, such as reduced oxygen levels and changes in water quality. As for restricting water movement, while nutrient pollution can affect water quality, it does not inherently restrict the movement of water itself.