The primary factor influencing water quality in aquatic habitats is nutrient loading, often from agricultural runoff and wastewater discharge. Excessive nutrients, particularly nitrogen and phosphorus, lead to eutrophication, characterized by algal blooms that deplete oxygen levels in the water. This impacts aquatic life, leading to die-offs of fish and other organisms. Overall, maintaining water quality is essential for safeguarding ecosystem health and ensuring clean water resources for human use.