This study evaluated the impact of a desalination plant\'s waste discharge on the adjacent biocenosis in the Pelo de Oro inlet, Santa Maria Key, Cuba. The research area was divided into eight layers, and sampling was conducted in four stages to measure salinity, species richness of selected megazoobents, and variations in Thalassia testudinum coverage. The salinity showed no anthropogenic variations, and three species of megazoobents were identified: Holothuria floridana, Echinaster sp., and Lytechinus variegatus. The abundance of L. variegatus decreased in the RSDESCARGA layer due to the plant\'s cleaning procedures, while the CONTROL layer showed higher abundance and stability. No significant differences were observed in Echinaster sp. abundance across layers. H. floridana was most abundant in the RSDESCARGA layer during the pre-start stage. The study found no evidence of brine discharge impact but provides a baseline for future comparisons once the plant begins operation.