What is a significant consequence of high nitrogen loading in ecosystems?

High nitrogen loading in ecosystems primarily leads to imbalances in the food chain, which is correctly highlighted in the chosen answer. When excessive nitrogen enters an ecosystem—often from agricultural run-off, wastewater discharge, or fossil fuel combustion—it can cause rapid growth of algae and aquatic plants, a phenomenon known as eutrophication. This uncontrolled growth can deplete oxygen levels in the water as the algae die and decompose, leading to hypoxic conditions where aquatic life, such as fish and invertebrates, cannot survive. Consequently, imbalances arise as populations of certain species may thrive due to increased food availability, while others may decline or even face extinction due to the altered habitat and oxygen depletion.

This contrasts with increased biodiversity and improved water quality, which would not typically result from high nitrogen loading. Elevated nutrient levels usually reduce water quality and can lead to a more uniform, less diverse ecosystem as dominant species outcompete others. Similarly, the growth of endangered species is unlikely in conditions where water quality has deteriorated, as these species often have specific habitat requirements that are compromised by nitrogen pollution. Thus, the correct answer emphasizes a realistic and significant consequence of high nitrogen loading in ecosystems.