Primary productivity provides the foundational energy for virtually all aquatic ecosystems. Formally defined as the increase in organic material per unit of area or volume with time, this process represents the conversion of inorganic matter into organic biomass by primary producers, including algae, bacteria, and higher plants. This addition of organic material forms the base of the food web, supporting every subsequent trophic level. The accurate measurement of this rate is therefore a cornerstone of aquatic science, enabling researchers to assess the health, capacity, and dynamics of these vital environments.

This review is designed for environmental scientists and resource managers seeking a clear understanding of the principal methodologies used to measure aquatic primary productivity. It will systematically evaluate and compare the key techniques, from foundational, indirect methods to more precise, direct measurements of metabolic rates. The document will cover historical methods based on system proxies, modern techniques that quantify metabolic processes, and will conclude with a practical guide for method selection, highlighting the critical link between the research objective and the choice of methodology.