What does chlorophyll-a indicate when used as a proxy in watershed nutrient assessments?

What does chlorophyll-a indicate when used as a proxy in watershed nutrient assessments?

• A. It measures sediment load
• B. It reflects algal biomass and nutrient enrichment
• C. It measures dissolved oxygen
• D. It indicates groundwater depth

Answer: (B)

Chlorophyll-a serves as a measure of algal biomass in aquatic systems, which rises when nutrients are plentiful. In watershed nutrient assessments, higher chlorophyll-a indicates more algae, signaling nutrient enrichment and potential eutrophication. This makes chlorophyll-a a useful proxy for the biological response to nutrient loads, capturing how much algae is growing in response to available nitrogen and phosphorus. It does not directly measure sediment load, dissolved oxygen, or groundwater depth—those relate to solids, oxygen dynamics, or hydrology rather than algal biomass driven by nutrients.

Chlorophyll-a serves as a measure of algal biomass in aquatic systems, which rises when nutrients are plentiful. In watershed nutrient assessments, higher chlorophyll-a indicates more algae, signaling nutrient enrichment and potential eutrophication. This makes chlorophyll-a a useful proxy for the biological response to nutrient loads, capturing how much algae is growing in response to available nitrogen and phosphorus. It does not directly measure sediment load, dissolved oxygen, or groundwater depth—those relate to solids, oxygen dynamics, or hydrology rather than algal biomass driven by nutrients.