What can excessive nutrient loading in surface waters lead to?

Excessive nutrient loading in surface waters can lead to eutrophication and hypoxia. Eutrophication occurs when high concentrations of nutrients, particularly nitrogen and phosphorus, stimulate the rapid growth of algae, known as algal blooms. While these blooms may initially increase biomass, they can have detrimental effects on water quality.

As the algae die and decompose, the process consumes a significant amount of oxygen in the water, leading to hypoxia, or low oxygen conditions. These hypoxic conditions can be harmful or even lethal to aquatic life, such as fish and invertebrates. Ultimately, this process degrades the overall health of aquatic ecosystems, causing shifts in species composition and loss of biodiversity.

In contrast, the other options do not accurately reflect the outcomes associated with excessive nutrient loading. Improved water clarity is often a result of lower nutrient levels, while increased biodiversity and lower water temperatures are not direct consequences of nutrient enrichment and can instead be associated with healthier, balanced ecosystems.