No abstract

In this study we analyze the faunal changes along 2 transects (5 stations each) across Términos Lagoon. We also examined the role of the environmental gradients in controlling the number and composition of the polychaete species, and evaluated the spatial changes of beta-diversity. In total, 299 individuals from 51 species and 24 families were identified. Salinity was the most important factor to define the environmental gradients (r 2 > 0.83), but the variations in the number of species did not follow this spatial trend. The highest species richness was found in the eastern transect (mean: 12 spp./station, 78.0 ind./0.1 m 2), while the western transect harbored a less diverse (mean: 6 spp./station) and less abundant fauna (mean: 21.67 ind./0.1 m 2). A high similarity value (0.70) was found between the transects, but the distribution of each species was very irregular, which in turn caused a decrease in the similarity among stations at each transect (< 0.54). Except among the middle stations of the western transect, where the nestedness component represented all the beta-diversity value (βnes: 0.80 to 0.88), the species turnover (βsim: 0.38-1.0) was the dominant factor of the total dissimilarity among the polychaetes inhabiting Términos Lagoon.