Investigating Seasonal Changes in Sediment Porewater Nutrient Pools in Seagrass Beds of Jobos Bay, Puerto Rico
Disciplines
Biogeochemistry | Marine Biology | Sedimentology | Terrestrial and Aquatic Ecology
Abstract (300 words maximum)
Seagrass meadows are critical to marine ecosystems, providing habitats and stabilizing sediments. However, human activities contribute to excess nutrient loading, which can alter nutrient budgets and cause eutrophication. While nitrogen cycling in seagrass beds has been studied, limited research examines how seasonal variations in freshwater input influence sediment porewater nutrients, particularly in the tropical estuaries. This study explores the relationship between seasonal precipitation and nitrogen availability in seagrass meadows in Jobos Bay, Puerto Rico. The hypothesis predicts that increased rainfall during the wet season (April–November) leads to higher terrestrial runoff, elevating nitrogen concentrations in sediment porewater, particularly in inner bay sites. Sediment cores (~7cm deep) were collected from four sites, stored on dry ice, and transported to the lab for analysis. Samples were centrifuged to extract porewater and analyzed with standard spectrophotometric techniques to quantify ammonium concentrations. Initial findings revealed high but variable, porewater ammonium concentrations at Station 10 (225±134 µM) and Cayo Barca (213±203 µM) in March 2023. Concentrations were 85±28 µM in vegetated sediments and 125±45 µM in unvegetated sediments at the Mar Negro site. Comparisons will be made to measurements made during the wet season (August and October) to determine if seasonal precipitation influences the cycling of nutrients and may have an effect on the production and health of seagrass. Conservation initiatives and management plans to reduce manmade nutrient inputs in coastal ecosystems can benefit from understanding these trends.
Academic department under which the project should be listed
CSM - Ecology, Evolution, and Organismal Biology
Primary Investigator (PI) Name
Troy Mutchler
Additional Faculty
Mark McCarthy, Biology, mmccar49@kennesaw.edu
Investigating Seasonal Changes in Sediment Porewater Nutrient Pools in Seagrass Beds of Jobos Bay, Puerto Rico
Seagrass meadows are critical to marine ecosystems, providing habitats and stabilizing sediments. However, human activities contribute to excess nutrient loading, which can alter nutrient budgets and cause eutrophication. While nitrogen cycling in seagrass beds has been studied, limited research examines how seasonal variations in freshwater input influence sediment porewater nutrients, particularly in the tropical estuaries. This study explores the relationship between seasonal precipitation and nitrogen availability in seagrass meadows in Jobos Bay, Puerto Rico. The hypothesis predicts that increased rainfall during the wet season (April–November) leads to higher terrestrial runoff, elevating nitrogen concentrations in sediment porewater, particularly in inner bay sites. Sediment cores (~7cm deep) were collected from four sites, stored on dry ice, and transported to the lab for analysis. Samples were centrifuged to extract porewater and analyzed with standard spectrophotometric techniques to quantify ammonium concentrations. Initial findings revealed high but variable, porewater ammonium concentrations at Station 10 (225±134 µM) and Cayo Barca (213±203 µM) in March 2023. Concentrations were 85±28 µM in vegetated sediments and 125±45 µM in unvegetated sediments at the Mar Negro site. Comparisons will be made to measurements made during the wet season (August and October) to determine if seasonal precipitation influences the cycling of nutrients and may have an effect on the production and health of seagrass. Conservation initiatives and management plans to reduce manmade nutrient inputs in coastal ecosystems can benefit from understanding these trends.