High-nutrient, low-chlorophyll regions

High-nutrient, low-chlorophyll (HNLC) regions refer to ocean areas that have an abundance of essential nutrients, such as nitrogen, phosphorus, and iron, but exhibit low concentrations of chlorophyll-a, a pigment associated with phytoplankton growth. Chlorophyll-a is commonly used as an indicator of phytoplankton biomass in marine ecosystems.