First evidence of microplastics in the stygobiotic isopod Creaseriella anops from a karst cenote of the Yucatán peninsula.

The cenotes of the Yucatán Peninsula are unique subterranean ecosystems that host stigobiontic fauna, yet contamination of groundwater organisms remains poorly understood. Microplastics (MPs) are emerging pollutants widely documented in aquatic environments, but data on their occurrence in groundwater fauna are scarce. This study provides baseline information on the presence and characteristics of MPs in the stigobiontic isopod Creaseriella anops (Isopoda: Cirolanidae), collected via scuba diving at a depth of 30 m in the Xelactún cenote (Kinchil, Yucatán, México). Organisms were chemically digested, and the residues were vacuum-filtered and analyzed under a stereomicroscope. Suspected MPs were quantified and categorized by shape and color, and polymer composition was determined using μFTIR spectroscopy. Only fibers were detected, with a mean abundance of 12.29 ± 3.65 MPs g-1 w.w., predominantly transparent (75.64%). Identified polymers included polyester (20%), polyethylene (7%), rayon (7%), and polypropylene (2%). Given the ecological fragility, high endemism, and importance of cenotes as a regional water source, the relatively high MP concentrations observed highlight the need for further research using C. anops as a model species to assess groundwater contamination.