Which of the following lists includes factors associated with HAB development?

• A. Excess nutrients, sunlight, low-water conditions, calm water, warmer temperatures
• B. High salinity, cold temperatures
• C. Low nutrients and turbulent water
• D. High turbidity and acidic water

Answer: (A)

Harmful algal blooms develop when the water has plenty of nutrients and the conditions allow algae to grow rapidly. Excess nutrients like nitrogen and phosphorus act as a fertilizer, giving algae the food they need to multiply. Sunlight provides the energy for photosynthesis, so bright, sunny days help algae grow more quickly. Calm or still water reduces mixing and dilution, letting nutrients and algae stay concentrated near the surface where light is abundant. Warmer temperatures also speed up growth and reproduction, making blooms more likely. In many Ohio aquatic systems, this combination—high nutrients, abundant sunlight, still water, and warmth—creates the ideal setup for HABs to form.

Other options don’t fit as well because they emphasize conditions that don’t typically promote HABs: high salinity and cold temperatures generally slow or inhibit growth in freshwater blooms; low nutrients and turbulent water spread nutrients and disrupt accumulation; high turbidity or acidic water reduce light or create conditions that are not conducive to the rapid growth that drives HABs.