CHANGING AQUATIC CARBON AND NUTRIENTS WITH HYDROLOGIC PRESSES AND PULSES IN COASTAL WETLANDS

Climate change is increasing storms and sea levels throughout coastal regions. Humans can both increase and decrease freshwater presses (long-term patterns) and pulses (episodic fluctuations). How freshwater and marine hydrologic presses and pulses are impacting aquatic carbon and nutrients in ecosystems is uncertain. We measured long-term (2000-2022) changes in precipitation and surface water chemistry [salinity, dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) concentrations] in subtropical wetlands in the Everglades (Florida, USA). Precipitation pulses (i.e., rainfall at a site exceeding 2.5 cm h-1) were variable over space and time (< 2 to 24 cm d-1). Pulses both increased and decreased TN (from -100 to +170 μMol L-1) and TP (from -1 to 5 μMol L-1) above mean monthly concentrations. Pulsed increases in TN and TP were higher at brackish than freshwater sites, and changes in TN and TP were greatest from 5-10 cm d-1 rainfall. Hurricane storm surge and freshwater flooding increased DOC concentrations in mangrove estuaries and reduced DOC aromaticity (SUVA254). Long-term freshwater restoration is reducing salinities in brackish estuaries, and freshwater DOC concentrations declined at brackish salinities above 10 ppt. Sea-level rise is increasing saltwater intrusion and carbon losses in brackish wetlands, but freshwater restoration is reducing peak dry-season salinities. Hydrologic changes from storms and sea-level rise are mobilizing fluxes of aquatic carbon and nutrients, requiring long-term research to understand net ecosystem effects.

Primary Presenter: John Kominoski, Florida International University (jkominos@fiu.edu)

Authors:

Evelyn Gaiser, Florida International University  (gaisere@fiu.edu)

Rafael Travieso, Florida International University  (travieso@fiu.edu)

Tiffany Troxler, Florida International University  (troxlert@fiu.edu)

Emily Standen, Florida International University  (estanden@fiu.edu)