278 Understanding Temporal Dynamics in Hydrogeochemistry and Sedimentary Processes in Estuarine Environments

This session explores temporal changes in estuarine environments with respect to water chemistry and sediment inputs. Effects of evolving physiochemical properties and isotopic composition of water, as well as the geochemical attributes of sediments on the environment will be presented.

Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 213AB

INVESTIGATING THE TEMPORAL BEHAVIOR OF SOLUTES AND DISSOLVED INORGANIC CARBON AND THEIR HYDROLOGIC CONTROLS IN TIDAL CREEKS OF TROPICAL MANGROVE ESTUARIES

Paper number: 278-1
Program: Technical Sessions
Time: 1:35 PM – 1:55 PM

Authors

Abstract

We used salinity-tide relationships to design an experiment to measure the sources of water, and the processes that control solutes and dissolved inorganic carbon (DIC) cycling in a tidal creek at the land-estuary boundary in a tropical mangrove estuary. The experiment was conducted through semidiurnal mixed tides and over a diel cycle. We measured salinity, geogenic solutes (silica, Ca, Mg), DIC components (partial pressure of CO2 (pCO2), alkalinity, and total DIC), and stable isotopes of water (δ18O and δD) and DIC (δ13CDIC). The relationship between salinity and δ18O indicates two sources of water input into the creek. The relationships between salinity-DO, salinity-solute, and salinity-DIC implicate submarine groundwater discharge (SGD) as the water source providing the DIC processed and transported to the open estuary. Normalized water level vs. salinity reveals that SGD-sourced DIC dominates the water column during tidal ebbing and halfway through tidal flooding. In contrast, freshwater from the open estuary mainly dilutes the solutes and DIC from halfway during tidal flooding to peak high tide. The photocycle, heterotrophic, and autotrophic processes cannot be used to explain the more than 5 times greater than atmospheric pCO2 recorded during the daytime and at low tide. Our findings demonstrate that SGD is a significant DIC source in tidal creeks at the land-estuary transition zones, which indicates the important role of SGD in the cycling of carbon in the freshwater tidal zones of mangrove estuaries. These results are realized because of the use of the tide salinity behavior for this tidal creek and have implications for investigating solutes and carbon cycling in tidal creeks in tropical mangrove estuaries

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413913

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