Analysis of Atlantic and Northern Gulf Coast Wetland Bacterial Extracellular Enzyme Activity

Sea-level rise is projected to cause saltwater marshes to migrate landward replacing brackish and freshwater marshes. Coastal wetlands are important sinks of carbon, phosphorous, and nitrogen, so it is important to understand the function of their microbial communities. This study aims to categorize the difference in function between different spatially distinct wetland marsh types in advance of the expected alteration of the wetland ecosystems. Extracellular microbial enzymatic activity was measured to understand organic matter decomposition and nutrient mineralization in different marsh types. We measured the activities of the extracellular enzymes β-glucosidase, NAGase, peroxidase, phenol oxidase, and phosphatase across sites along the Northern Gulf of Mexico and Atlantic coast. Both tidal salt and tidal fresh marsh sediment were sampled at each location. Higher salinity depressed the activity of NAGase. Salinity did not have a significant effect on phosphatase activity. High salinity slightly repressed carbon-degrading enzyme β-glucosidase activity but increased peroxidase and phenol oxidase activities. Sediments with high organic matter content had lower enzyme activities. Warmer water temperature sites tended to exhibit higher overall enzyme activity. This study finds that increasingly saline wetlands will cause a change in nutrient cycling functionality. Saltwater intrusion into fresh marsh will reduce the capacity for nitrate removal leading to potential coastal eutrophication, and saltwater intrusion will increase carbon metabolism leading to less accretion than in freshwater marshes further amplifying the effect of sea-level rise