Which two nutrients are primarily linked to HAB development?

• A. Potassium and Calcium
• B. Sodium and Chloride
• C. Phosphorus and Nitrogen
• D. Magnesium and Sulfate

Answer: (C)

The main idea is that excess nutrients in water fuel algal growth, leading to harmful algal blooms. The two nutrients most closely linked to these blooms are phosphorus and nitrogen. Phosphorus provides the energy and growth-building blocks algae need, while nitrogen supplies essential proteins and amino acids. When runoff from fertilizer, manure, or wastewater introduces both nutrients into lakes and rivers, algae can multiply rapidly, sometimes producing toxins that threaten water quality, aquatic life, and human health.

Other common minerals like potassium and calcium, or salts like sodium and chloride, aren’t the primary drivers of HABs. They’re important for general cell function or water chemistry, but they don’t typically trigger the kind of widespread, toxin-producing blooms that phosphorus and nitrogen do. Magnesium and sulfate play roles in metabolism too, but they’re not the main culprits behind HAB development.