Disciplines
Biochemistry | Biodiversity | Biogeochemistry | Climate | Environmental Chemistry | Integrative Biology | Marine Biology | Organic Chemistry | Plant Biology | Sedimentology | Soil Science | Terrestrial and Aquatic Ecology
Abstract (300 words maximum)
Jobos Bay Estuary is an intertidal, tropical estuary located in southern Puerto Rico. The estuary covers about 12 km2 and has a variety of habitats, such as seagrass beds, mangroves, mud flats, and coral reefs, which play important roles in sediment trapping and water quality maintenance. Seagrasses also serve as nursery and feeding grounds and provide shelter for macrofauna. Currently, the role of seagrasses and water quality on nitrogen (N) cycling in trophic estuaries is not well constrained. Understanding variations in sediment-based effects on N cycling rates and transformations, and how they are associated with water quality, is an emerging area of research. Intact sediment cores will be collected to measure N cycling rates using continuous-flow incubations from invasive (Halophila stipulacea) and native (Thalassia testudinum) seagrass meadows, as well as unvegetated sediments. By measuring dissolved gas (O2 and N2) and net nutrient (N and phosphorus (P)) fluxes at four sites in Jobos Bay, during rainy and dry seasons, we will characterize the potential of sediments to act as a net bioavailable N sink (e.g., anammox/denitrification) or source (e.g., remineralization and N fixation). In March (dry), July (wet), and October (transition) 2023, intact sediment cores will be incubated with and without 15N added as ammonium or nitrate. We expect variations in N sources and removal as a seasonal response to freshwater inputs and N loading, with Jobos Bay sediments acting as a net N sink on an annual basis. Vegetated sites will have higher sediment N cycling rates versus unvegetated sites for total N2 export via microbial N removal, a valuable ecosystem service. We anticipate results that show active ammonium cycling within the water column. Bare sediment sites expected to exhibit net N fixation or DNRA, and sites with seagrasses will maintain coupled nitrification/denitrification. This research will aid our understanding of the impacts of climate change on microbial N removal to help inform effective management of these ecosystems.
Academic department under which the project should be listed
CSM - Ecology, Evolution, and Organismal Biology
Primary Investigator (PI) Name
Troy Mutchler
Additional Faculty
Angel Dieppa-Ayala, JBNERR, adieppa@drna.pr.gov
Milton Munoz Hincapie, JBNERR, adieppa@drna.pr.gov
Included in
Biochemistry Commons, Biodiversity Commons, Biogeochemistry Commons, Climate Commons, Environmental Chemistry Commons, Integrative Biology Commons, Marine Biology Commons, Organic Chemistry Commons, Plant Biology Commons, Sedimentology Commons, Soil Science Commons, Terrestrial and Aquatic Ecology Commons
Quantifying the Role of Water Quality on Nitrogen Cycling in a Trophic Estuary
Jobos Bay Estuary is an intertidal, tropical estuary located in southern Puerto Rico. The estuary covers about 12 km2 and has a variety of habitats, such as seagrass beds, mangroves, mud flats, and coral reefs, which play important roles in sediment trapping and water quality maintenance. Seagrasses also serve as nursery and feeding grounds and provide shelter for macrofauna. Currently, the role of seagrasses and water quality on nitrogen (N) cycling in trophic estuaries is not well constrained. Understanding variations in sediment-based effects on N cycling rates and transformations, and how they are associated with water quality, is an emerging area of research. Intact sediment cores will be collected to measure N cycling rates using continuous-flow incubations from invasive (Halophila stipulacea) and native (Thalassia testudinum) seagrass meadows, as well as unvegetated sediments. By measuring dissolved gas (O2 and N2) and net nutrient (N and phosphorus (P)) fluxes at four sites in Jobos Bay, during rainy and dry seasons, we will characterize the potential of sediments to act as a net bioavailable N sink (e.g., anammox/denitrification) or source (e.g., remineralization and N fixation). In March (dry), July (wet), and October (transition) 2023, intact sediment cores will be incubated with and without 15N added as ammonium or nitrate. We expect variations in N sources and removal as a seasonal response to freshwater inputs and N loading, with Jobos Bay sediments acting as a net N sink on an annual basis. Vegetated sites will have higher sediment N cycling rates versus unvegetated sites for total N2 export via microbial N removal, a valuable ecosystem service. We anticipate results that show active ammonium cycling within the water column. Bare sediment sites expected to exhibit net N fixation or DNRA, and sites with seagrasses will maintain coupled nitrification/denitrification. This research will aid our understanding of the impacts of climate change on microbial N removal to help inform effective management of these ecosystems.