Publication Date:
2017-08-15
Description:
Globally, estuaries are considered important CO 2 sources to the atmosphere. However, estuarine water carbonate chemistry and CO 2 flux studies have focused on temperate and high latitude regions, leaving a significant data gap in subtropical estuaries. In this study, we examined water column carbonate system and air–water CO 2 flux in the Mission-Aransas Estuary, a subtropical semiarid estuary in the northwestern Gulf of Mexico, by collecting samples at five System Wide Monitoring Program stations from 05/2014 to 04/2015. The carbonate system parameters (total alkalinity [TA], dissolved inorganic carbon [DIC], pH, CO 2 partial pressure [ p CO 2 ], and carbonate saturation state with respect to aragonite [Ω Ar ]) and air–water CO 2 flux all displayed substantial seasonal and spatial variations. Based on freshwater inflow conditions, a drought period occurred between 05/2014 and 02/2015, while a flooding period occurred from 03/2015 to 04/2015. Average DIC was 2194.7 ± 156.8 μmol kg −1 and 2132.5 ± 256.8 μmol kg −1 , TA was 2497.6 ± 172.1 μmol·kg −1 and 2333.4 ± 283.1 μmol kg −1 , p CO 2 was 477 ± 94 μatm and 529 ± 251 μatm, and CO 2 flux was 28.3 ± 18.0 mmol C·m −2 ·d −1 and 51.6 ± 83.9 mmol·C·m −2 ·d −1 in the drought and flooding period, respectively. Integrated annual air–water CO 2 flux during our studied period was estimated to be 12.4 ± 3.3 mol·C·m −2 ·yr −1 , indicating that this estuary was a net CO 2 source. High wind speed, warm climate, riverine input, and estuarine biogeochemical processes all contributed to the high CO 2 efflux despite the modest p CO 2 levels year round.
Print ISSN:
0024-3590
Electronic ISSN:
1939-5590
Topics:
Biology
,
Geosciences
,
Physics
Permalink