Marine tardigrade ecology across the transverse zonation of a coral reef in Xcalak Quintana Roo, Mexico

Mexican marine tardigrade fauna is poorly understood, and available information is limited to their taxonomy. We sampled a coral reef area along the Xcalak coast in August, November 2021, and June 2022. The sampling was conducted according to the transverse zonation of the reef. Temperature and dissolved oxygen levels were measured, and sediment grain size, permeability, and porosity were determined. We collected 45 samples and found 1291 tardigrades in four zones (reef lagoon, back reef, reef crest, and reef front). In the mangroves, tardigrades were absent. Tardigrades belonged to 29 species. Chao1 index estimated a mean of 30 species (+/- 7 species). The Hill-Shannon diversity index and Hill-Simpson diversity index showed that back reef and reef crest had the highest diversity, with 6 effective species. The grain size, permeability, porosity, and sediment sorting correlated with the diversity of tardigrades, while dissolved oxygen correlated with abundance. Non-metric multi-dimensional scaling determined differences in species composition between the ecological zones. The sediment compositions and dissolved oxygen are associated with the richness and abundance, parameters that showed their higher values in the reef crest.