Spatial heterogeneity and seasonal structure of physical factors and benthic species in a tropical coastal lagoon, Celestun, Yucatan Peninsula

Spatial heterogeneity is an attribute of ecosystems that plays a central role in ecological theory, as it can be an explanatory factor for numerous processes that result in recognizable spatial structure. The aims of this study were to determine the potential presence of recognizable spatial structure in the distribution and abundance of dominant benthic species and to examine whether this spatial variability is explained by habitat-specific factors. The study was performed at Celestun, a coastal lagoon with a marked horizontal salinity gradient, based upon historical data obtained seasonally during the 1998-1999 annual cycle. Sampling was carried out in the inner zone of the lagoon, which is considered the steadiest and most homogeneous zone. Physicochemical factors were recorded in order to characterize the habitat, and benthic macroinfauna were collected to assess species composition and abundance. The benthic assemblage we sampled included 23 species, dominated in terms of abundance by mollusks, two gastropods, and one bivalve. One-way ANOVA and geostatistical analysis determined that the species and measured factors were not distributed homogeneously in this zone but were instead spatially structured in the form of patches and gradients that varied over time. A generalized linear model identified the factors (water salinity, organic matter, and sand) that explained between 17% and 30% of the variance in abundance of dominant species depending on the season. These results provide important information about the ecological quality of the lagoon inner zone and the tolerance of species to environmental factors.