Biomass was measured by wet weight and dry weight of zooplankton samples collected in the Bay of Tumaco. Sampling was conducted during june 2009 – june 2010 and for four climatic periods. The highest average wet biomass and dry biomass were recorded in June 2009 and the lowest values in September 2009. Significant differences in the values of wet and dry biomass between sampling months. Taking into account the climatic periods the highest values were average during both wet to dry wet biomass to dry biomass, the lowest values were recorded during the wet to dry wet biomass and the wet period dry biomass. The four climatic periods showed no significant variations in the values of zooplankton biomass by wet weight but did show significant differences in the values of zooplankton biomass by dry weight.