Mangrove forests are important stores of organic carbon, sequester contaminants, and provide protection to coastal areas. Mangroves are threatened by a combination of stressors, including sea level rise and impacts from agricultural production and urbanization. In Puerto Rico, these forests are dominated by 3 species: white (Laguncularia racemosa), black (Avicennia germinans), and red mangroves (Rhizophora mangle). This research focuses on the urbanized mangroves of Piñones, located just east of San Juan, Puerto Rico. The objective was to determine how nutrients, trace metals, organic matter, and soil properties vary down core and between two mangrove sites located at varying distances to tidal influence and dominated by different species of mangroves. In June 2017, we collected two 10 cm diameter cores to a depth of 50 cm using a PVC tube. Cores were sliced into 35 1–2 cm intervals and analyzed for loss on ignition(LOI), dry bulk density(DBD), and total carbon, nitrogen, and phosphorus(CNP). Sediments were dated using 210Pb and analyzed for trace metals. The mean LOI for the red mangrove-dominated site (28.5% ± 2.2) was greater than the black-white mangrove-dominated site (10.7% ± 1.6), while the converse was observed for DBD. The average value for total N and P of the red mangrove site 0.53%, and 0.02% was higher in comparison with the black-white mangrove site 0.26%, and 0.01%, respectively. Preliminary results suggest that despite their geographic proximity, one site is much more highly influenced by tidal exchange, while the other site is receiving larger amounts of allochthonous sediments.

Variation in sediment nutrient concentrations in an urban-mangrove ecosystem, Piñones, Puerto Rico

2019 Spring National Meeting

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