Background/Question/Methods

Macrophytes such as seagrass and macroalgae are essential in coastal environments as they support marine life, stabilize soil, and improve water quality. However, they are constantly threatened by anthropogenic activities such as nutrient enrichment, pollution, overfishing, and climate change. The combination of these disturbances negatively impacts the biological cycles and biodiversity of coastal ecosystems. Nutrient enrichment in benthic macrophyte meadows can promote increased abundance of the benthic upside-down jellyfish Cassiopea. Blooms of these jellies are known to compete with seagrass for light. However, less is known about the species composition of other macrophytes associated with seagrass beds and how they might be affected by jellyfish. This project aims to identify the benthic macrophytes in areas of Cassiopea blooms and to determine if the blooms are affecting the abundance and diversity of the macrophytes. Our study área is in Jobos Bay National Estuarine Research Reserve in Puerto Rico (JBNERR), an area that has been exposed to extensive anthropogenic activity including illegal waste discharges and industrial activity. Ten sampling areas were designated by their level of human activity (high, medium, and low), and photogrammetric surveys were carried out at each site every two months. Benthic coverage of macrophytes was estimated using 10 random quadrat tosses of 1 m2 around the 10 x 25m plot.  Macrophyte samples were collected to assess for nutrient content, and water samples were collected do characterize water quality. Nutrient concentrations in macrophytes will be used as a proxy for long term nutrient availability in oligotrophic systems.

Results/Conclusions

Preliminary results indicate that Halophila stipulacea, an invasive seagrass in JBNERR, is the most abundant macrophyte at sampling sites associated with Cassiopea proliferations. Other macrophytes include green algae, Caulerpa sertulatioides, Penicillus capitatus, and Udotea spp., which are common in areas of seagrass beds in Puerto Rico. Other algal species found were Acantophora spicifera and Sargassum fluitans in areas of mostly bare sediment. Future research will focus on analyzing the relationship between jellyfish abundance and nutrient concentrations obtained from associated macrophyte samples. This study will contribute to understanding the health of aquatic ecosystems in Jobos Bay, so that appropriate conservation measures can be taken to ensure the survival of aquatic species, including jellyfish.