131 D12. Marine/Coastal Science

Wednesday, 28 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

SEDIMENTARY METHANE EMISSION IN SUBTROPICAL ESTUARIES AT SOUTHERN TEXAS, USA

Paper number: 131-5
Program: Technical Sessions
Time: 2:10 PM – 2:20 PM

Authors

  • Hao Yu Presenting Author
    3106 Charter Ln, Corpus Christi, TX
  • Richard B. Coffin
    Texas A&M University - Corpus Christi, Corpus Christi, TX

Abstract

Methane (CH4) is a greenhouse gas with an atmospheric warming potential 84-86 times over CO2 through 20 years (IPCC, 2004). Coastal sediment is one of the crucial sources of atmospheric CH4. To evaluate CH4 contribution from sediment of subtropical estuaries to the atmosphere, we studied CH4 concentration profiles in sediment porewater and CH4 fluxes at the sediment-water interfaces in May and August 2019 at lagoonal estuaries of southern Texas, USA.

Results showed that CH4 concentrations in sediment porewater were highest in mangrove sediment (1121.8~15418.7 nmol/L), then channel sediment (17.1~760.7 nmol/L) and least in seagrass sediment in May 2019 (11.3~259.8 nmol/L). However, porewater CH4 concentrations decreased to similar levels from May to August (mangrove, channel, and seagrass: 20.1~85.9, 7.7~97.0, 30.6~56.2 nmol/L, respectively). Such variation corresponded to the increase of dissolved CH4 concentration in the overlying water column from spring to summer. However, both calculations using the Fick’s First Law of diffusion and sediment core incubation experiments manifested CH4 fluxes at the sediment-water interface were quite low, which indicated minor transport of diffusive CH4 from sediment to water directly. Moreover, the increase of CH4 concentration in overlying water during sediment incubation was higher in the seagrass site than in the mangrove site, indicating more CH4 was released from seagrass sediment than from mangrove sediment. It implied the role of vegetation in transporting CH4 from sediment to water column, e.g., tubing structure of seagrass. Another thing that we have noticed is that after incubation, porewater CH4 concentrations in seagrass increased dramatically in comparison with those in channel and mangrove sediment. It further proved that seagrass vegetation could mediate sediment environments and explained the higher CH4 concentration in nearby channel sediment.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-357892

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