Impacts of multiple environmental factors on the native Caribbean seagrasses and the invasive sea vine <i>Halophila stipulacea</i>

Abstract The abundance of Caribbean seagrass meadows has declined due to multiple human-induced stressors and the recent introduction of the invasive seagrass species Halophila stipulacea , a native to the Red Sea and Indo-Pacific regions. To investigate how environmental factors influence the interaction between the native Caribbean seagrasses and the invasive Halophila , a 13-month study was conducted in four seagrass meadows along the coast of Culebra, Puerto Rico. These meadows had varying environmental conditions and different levels of Halophila invasion. At each site, we monitored water movement, temperature, solar radiation, sedimentation rate, and five allometric measurements of seagrass; seagrass coverage, canopy height, shoot density, and above/below-ground biomass at 3-month intervals. The environmental factors varied over time and by site. Thalassia was the most common native seagrass species found at three sites. Halophila was present in all study sites but showed no direct impact on the native seagrasses. Water motion emerged as the most significant factor influencing allometric measures, affecting these characteristics positively or negatively, depending on the specific metric rather than the seagrass species.