Marine sponges are foundational components of coastal hardbottom ecosystems, providing habitat structure, water filtration, and nutrient cycling that support fisheries and coastal resilience. In Florida, widespread losses associated with harmful algal blooms have motivated sponge enhancement efforts, yet there remains limited empirical guidance on best-practice propagation and scaling methods to enhance ecosystem function. Here, we present results from field-based experimentation conducted off Hernando Beach, Florida, designed to identify biological and ecological drivers of growth and survival. We first established an offshore nursery using fragments from five native sponge species to evaluate survivorship following fragmentation and attachment to artificial substrates. After ~12 months, four species exhibited consistently high survival and were selected for two subsequent field experiments: (1) an elevation experiment comparing sponges placed directly on substrate versus raised placements, and (2) a partner-interaction experiment testing intra- and interspecific pairings. Survival and growth responses were quantified over 14 months using changes in sponge volume, surface area, and height while accounting for initial fragment size and site effects.
Across both experiments, treatment effects were weak over the study period. Elevation did not significantly influence survival or growth, and partner identity did not alter survival or growth outcomes, despite high overall survival (generally ≥93%). In contrast, species identity and initial fragment size consistently explained variation in performance. Larger starting size strongly increased survival, and species differed significantly in growth trajectories across all metrics. Together, these findings emphasize that sponge enhancement benefits from integrating ecological theory with applied experimentation. Species choice, deployment size, and time are critical considerations for designing sponge-based strategies aimed at enhancing ecosystem function through living marine infrastructure.