Ecophysiological responses of plant functional types to environmental conditions in a coastal urban wetland, Ciénaga Las Cucharillas in Northeastern Puerto Rico

Abstract

Coastal wetlands are influenced by their terrestrial-marine connectivity. Anthropogenic changes in these ecosystems have added additional stressors to plants, like the presence of heavy metals in soils. We evaluated ecophysiological responses of predominant plant functional types in an urban coastal wetland to local and temporal conditions such as local rainfall, spatio-temporal dynamics of water quality (salinity, pH) regulated by the input of fresh inland water or seawater, and variations in soil concentrations and availability of metals derived from anthropogenic disturbances. In addition, we assessed temporal changes in land and vegetation cover in the wetland after the passage of Hurricane Maria and how it affected plant responses. Depending on the local rainfall regimen, wetlands are either a source or sink of available elements and heavy metals. It works as a sink during wet periods with waterlogged conditions, changing to a nutrient source during the dry period with aerobic soils. We found that Laguncularia can accumulate Pb in leaf biomass and Acrostichum can accumulate Pb in roots, making them both good candidates for phytoremediation practices. Plant functional types differed in their photosynthetic capacity which showed temporal and species variability. According to precipitation, water level, and salinity, they displayed leaf morphology plasticity. We found that plant functional types proved to be resilient to the initial hurricane effect and subsequent changes. These studies have shown that vegetation communities in coastal urban wetlands seem to be adapted to large-scale anthropogenic changes to the ecosystem. Future studies should focus on how exponential increases in human activities paired with sea-level rise and extremes of precipitations will impact the overall long-term responses of these ecosystems.