VARIATIONS IN STREAM SEDIMENT MICROBIAL COMMUNITIES ACROSS A NATURAL CLIMATE GRADIENT IN SOUTHEASTERN PUERTO RICO

The area from El Yunque southwest to Patillas, Puerto Rico is underlain by two large granodiorite plutons with very similar geochemistry. As typical throughout Puerto Rico, the area is drained by a series of small watersheds that flow out of the central highlands to the coast. Across this same area, however, annual precipitation varies from approximately 430 to 140 cm per year. This creates a natural laboratory to investigate climate-based variations.

In this study, samples from 6 watersheds were collected in March 2018, six months after Hurricane Maria made landfall in this same area of the southeast coast. Samples were collected near to where the streams exit the highlands and onto the coastal plain. Variations in the sediment microbial community were investigated to evaluate the spatial-based climate variations and to establish a baseline for ongoing studies of system rebound. Although species diversity and total colony forming units does not appear to vary spatially, there are two distinct outliers. Variations were seen across the climate gradient for some species. Moving from the most humid region in the El Yunque rainforest to the drier area around Patillas found an increase in several pseudomonas species, especially pseudomonas aeruginosa, while two bacillus species were found to increase. Other organisms, such as Acinetobacter, may be found in only one location. Detailed species identification is underway.