LAUSR

Upside-down jellyfish are a group of benthic scyphozoans belonging to the genus Cassiopea, whose members are in symbiosis with dinoflagellates and inhabit tropical and subtropical waters. Although there are some studies of the genus in the Caribbean, these are limited. In Cuba, the group’s studies are restricted to reports on taxonomic lists and, as far as we know, no one has performed any analyzes of the densities of these jellyfish in seagrass or mangrove ecosystems in Cuba. In this work, the populations of Cassiopea spp. in Jardines de la Reina National Park (JRNP) were characterized, for the first time for this Marine Protected Area and Cuba. One hundred 1m2 square frames were placed at 14 JRNP sites. For each site, the species, density, size of the individuals and abiotic factors were determined. Density and diameter comparisons were made between sites, zones and regions within the JRNP. The percentage of the benthic cover was determined and a correlation was made between density and diameter. A total of 10,803 individuals were recorded, of which 7,618 belong to Cassiopea xamachana and 3,185 belong to Cassiopea frondosa. Both species share a niche and no evident segregation was detected according to abiotic variables. Significant differences were detected in comparisons of density and size across sites and zones. Density and size in the JRNP were negatively correlated, and higher aggregations of the species were observed at lower sizes. Density mean values ranged from 2.18 to 14.52 ind. /m2 with maximum values of 79 ind. /m2. Cayo Alcatraz was the site found to have the highest density while Cachiboca was the site with the lowest density. The average bell diameter size of the individuals ranged from 9.34 to 15.31 cm for the sampled sites, with minimum and maximum values of 2.5 cm and 32.6 cm. The smallest size was recorded at Cayo Alcatraz while the largest size was reported for Boca de las Anclitas. The environmental factors evaluated showed no significant relationship with the density or diameter of Cassiopea, while the Thalassia testudinum cover was negatively correlated with Cassiopea density at all fourteen sites in the JRNP. The percentage of Cassiopea coverage was higher than those reported in the literature, with four sites exceeding 20% coverage. In general, the populations of Cassiopea spp. in the JRNP did not differ greatly, although a higher density was observed towards the eastern region of the park. It was shown for the first time for the species that density and size have a negative correlation. Future studies are required to quantify the impact of Cassiopea on coastal marine ecosystem processes, and to further determine how anthropogenic changes may be altering the function of these tropical ecosystems.