Characterization of Marine Fauna Assemblages in the Presence of Upside-Down Jellyfish (Genus Cassiopea) at Jobos Bay National Estuarine Research Reserve (JBNERR), Puerto Rico

Estuaries are highly productive systems that sustain diverse assemblages of fauna. In tropical estuaries such as the Jobos Bay National Estuarine Research Reserve (JBNERR), faunal composition plays a critical role in maintaining ecosystem services. Organisms such as fishes and macroinvertebrates provide essential ecosystem services, including trophic balance, nutrient recycling, bioturbation, and support for local economies. Despite their importance, faunal inventories and their ecological interactions within Jobos Bay NERR remain limited. In this study, we characterized the faunal community present in the estuary, focusing on fishes and macroinvertebrates. Sampling was conducted between October 2022 and April 2024 using bimonthly video transects (five 10 m transects per site) across three sites. Results showed that Cassiopea spp. were the most abundant macroinvertebrate and present at all sites. The faunal composition and Cassiopea abundance exhibited spatial variability, with bony fishes dominating assemblages. PERMANOVA results indicated that while community composition differed significantly among sites, Cassiopea abundance was not a significant driver of these assemblages (p = 0.635). Additionally, burrows were observed at all sites, showing an inverse relationship with Cassiopea abundance. Our findings suggest a potential relationship between the presence of Cassiopea and other fauna in Jobos Bay and highlight the need for a better understanding of the potential effects that high Cassiopea densities may have on the structure of faunal communities.