Sponges (Porifera) are a major component of coral reef ecosystems. They outnumber coral species on the Florida Reef Tract, and in places, account for more living cover. Because coral reefs are a vital part of Florida’s economy, it is important to understand how local sponge assemblages vary spatially and temporally, especially as corals continue to decline. However, long-term observations of sponge assemblages (species richness, diversity and abundance) are lacking. To address this, annual photoquadrats were analyzed from a series of 25 sites off Broward County between 2000 and 2015. Variations in sponge assemblages were then compared to several natural and anthropogenic stressors. Statistical analysis via PERMANOVA, PERMDISP and linear mixed-effect (lme) models revealed significant changes in total sponge composition, with spatial and temporal trends evident among different habitat types and sites. A total of 85 species were identified to the lowest taxonomic level. Common species included Spirastrella coccinea, Niphates erecta, Aplysina cauliformis, and Amphimedon compressa. Species richness increased with depth and habitat type. The Linear Middle Reef had the highest species abundance and richness, while the Shallow Ridge had the lowest of both. Contrary to trends seen in coral species, sponge composition did not decrease with an increase in latitude. Natural fluctuations in sponge abundance and richness via the sponge loop were intensified by natural events. Five common species (Amphimedon compressa, Aiolochroia crassa, Desmapsamma anchorata, Ircinia strobilina, and Xestospongia muta) were selected to monitor growth and mortality over time. All species except for Am. compressa had significant change in area from 2000 to 2015, and D. anchorata exhibited faster growth rates than all other species. This 15-year study provides a baseline of sponge assemblages on the Southeast Florida Reef Tract and insights into individual sponge communities. Sponges are essential organisms on coral reefs. As hard coral continues to decline, and natural and anthropogenic events intensify, this baseline data will serve to inform future studies.