Plant characteristics of the non-native seagrass Halophila stipulacea in recently colonized beds of Puerto Rico

The seagrass Halophila stipulacea is native to the Red Sea and Indian Ocean, and since entering the Caribbean in 2002 has spread rapidly throughout eastern islands including Puerto Rico, and as far as Venezuela and Florida, USA. We documented the presence of H. stipulacea and characterized plant traits from the southern Puerto Rico coast, showing extensive spread since it was first documented off the coast of Puerto Rico in 2017. In 2022 we surveyed shallow seagrass communities at 10 sites across 3 estuaries, with H. stipulacea present at 5 of the sites. We measured leaf morphology on individual shoots, and collected samples for biomass, density, and leaf C:N:P. Like other Caribbean studies, we observed longer, and larger leaves compared to plants in its native range. Density estimates ranged from 3,000 to over 11,000 shoots m-2 and biomass varied from 65 and 266 gdw m-2. At a mangrove dominated site H. stipulacea leaf C:P was 772 suggesting phosphorous limitation, while at other sites plants were nutrient replete. The range expansion and exceptionally dense H. stipulacea beds observed in this study provide supporting evidence that the Caribbean seagrass landscape is changing. Establishing a population status baseline in recently colonized areas can help understand which areas are susceptible to colonization as well as the trajectory of establishment.

Impact/Purpose

            Seagrasses are flowering plants that live in the marine environment and provide important services such as food and habitat for a wide variety of organisms including commercial and recreational fisheries.  Of the 70 seagrass species in the world, only 2 are known to have been transported across ocean basins and successfully established new colonies.  Halophila stipulacea, is native to the Red Sea, Persian Gulf and Indian Ocean.  But it has also colonized both the Mediterranean and the Western Tropical Atlantic from Venezuela to Florida.  Given its broad physiological tolerances, it is expected to continue to spread in the Caribbean and Gulf.  This work documents the morphology, biomass and density characteristics of recently colonized beds (since about 2010) in Puerto Rico and provides baseline information about extent and morphological characteristics.  We found that H. stipulacea occurred in 50% of the sites that we examined, was not present along the northern coast of Puerto Rico (San Juan) and had higher density, biomass and leaf area than previously reported for this species in the Caribbean.  Establishing a population status baseline in recently colonized areas can help understand local ecological impacts through time.

Citation

Ebersole, A., Jim Kaldy, C. Sullivan, A. Dieppa, I. Cappielo Cosme, AND M. Orizondo Lugo. Plant characteristics of the non-native seagrass Halophila stipulacea in recently colonized beds of Puerto Rico. Elsevier Science Ltd, New York, NY, 201:103926, (2025). [DOI: 10.1016/j.aquabot.2025.103926]

DOI: Plant characteristics of the non-native seagrass Halophila stipulacea in recently colonized beds of Puerto Rico