José Ángel García-Trasvina ^a, Daniel Pech ^a,*, Mariana E. Callejas Jiménez ^b, Alberto De Jesus Navarrete ^c

ABSTRACT We evaluated the diel variability of abundance and species diversity of the epibenthic community associated with seagrasses in Los Petenes Biosphere Reserve (LPBR) in the southwestern Gulf of Mexico. For this purpose, four collection campaigns were conducted (rainy season: October 2011 and June 2016, dry season: March 2012 and 2016) in a diel cycle with a periodicity of 3 h. Our results showed significant differences in diversity, richness, and abundance as a function of the diel cycle (p < 0.05), and in the community structure as a function of the diel cycle and the climatic sampling periods. Two different benthic assemblages, one for the day and the other for the night period were identified. Each assemblage varies on its species composition according to the climatic periods but maintains the general day-night pattern at all the sampled years. The abundance of diurnal species was significantly (p < 0.01) associated with the temperature, salinity, oxygen, and depth values. Our results suggest that the epibenthic community associated with seagrass habitats shows significant diurnal and nocturnal changes in community composition and abundance due to changes in light intensity that favors the appearance of characteristic species in each period. Understanding such community changes will allow us to establish the baseline parameters for assessing the environmental health of the benthic habitats of the LPBR with greater accuracy.