<p>The relationship between functional diversity and secondary production is known to influence ecosystem stability and can be used to measure the functioning of an ecosystem. The objective here is to determine the relationship between secondary production and functional diversity and species diversity in estuary benthos to test the hypothesis that there is a positive relationship between functional diversity and secondary benthic productivity. Long-term data is used to compare four mid-coastal Texas estuaries (Nueces, Laguna Madre, Guadalupe, and Lavaca-Colorado Estuaries) to test the hypothesis. Freshwater inflow differences among these estuaries affect nutrient supply, habitat, biodiversity, and productivity. Functional diversity was calculated based on seven classifiers: feeding strategy, habitat, mobility, lifespan, reproduction, sediment depth, and body size. There was a positive correlation between benthic secondary production and diversity for species richness, species diversity, and species evenness. Most functional diversity indices did not correlate with production, except for functional dispersion, which explains &gt; 77% of variation for secondary production. Apart from functional originality, there were no relationships between indicators of freshwater inflow influence (i.e., increase in nutrients and decrease in salinity) and the diversity metrics. Overall, classical taxonomic measures of macrofauna species diversity have a strong relationship with secondary production, while functional diversity does not appear to have any relationship. Thus, for Texas, USA, estuaries, it appears that functional diversity metrics do not explain or drive benthic ecosystem processes.</p>