Temporal shifts in functional traits of the fish community in Terminos Lagoon (Mexico) in three periods (1980, 1998 and 2011)

The trophic structure of the fish community ecosystem in the Terminos Lagoon (southern Gulf of Mexico) has shown a range of functional changes. The description of the heterogeneity of functional traits in a biological community allows the identification of the relevant functions in an ecosystem. An analysis was conducted of the functional traits (trophic level, reproductive and trophic guild, habitat, estuary use, essential habitat, salinity tolerance, body shape, mouth type, caudal fin type, and maximum length) of the fish community of the lagoon for three different years (1980, 1998 and 2011). We developed a new index to analyze the variation of functional diversity called the functional traits diversity index (FADI). This index takes into account the abundance of traits and emphasizes less common traits (i.e., those that are less redundant). The functional redundancy was different in the three periods studied. The FADI value for 1998 was the highest and was outside of the expected probability distribution, indicating a greater abundance of species with unique functional traits. A principal components analysis was performed to assess the relative contribution of functional traits to the overall variance of functional diversity over the three periods. We found that the trophic level, body shape, and mouth type were the most influential traits in the functional diversity changes. The environmental changes were correlated with the variability of the functional structure. Depth was the most influential environmental variable in the principal component analysis. The results indicate a reorganization of the functional structure of the fish community in the Terminos Lagoon. The FADI was helpful in explaining these changes observed throughout the three periods studied.