Dataset: Houston Galveston Bay Carbonate

Preliminary and in progressVersion 1 (2024-11-19)Dataset Type:Cruise Results

Principal Investigator: Hui Liu (Texas A&M, Galveston)

Co-Principal Investigator: Xinping Hu (Texas A&M, Corpus Christi)

Scientist, Contact: Larissa Marie Dias (Texas A&M, Corpus Christi)

BCO-DMO Data Manager: Sawyer Newman (Woods Hole Oceanographic Institution)


Project: RAPID: Capturing the Signature of Hurricane Harvey on Texas Coastal Lagoons (Hurricane Harvey Texas Lagoons)


Abstract

Quantifying the direction and magnitude of CO2 flux in estuaries is necessary to constrain the global carbon cycle, yet carbonate systems and CO2 flux in subtropical and urbanized estuaries are not yet fully determined. To estimate the CO2 flux for Galveston Bay, a subtropical estuary located in the northwestern Gulf of Mexico proximal to the Houston-Galveston metroplex, monthly cruises were conducted along a transect extending from the Houston ship channel to the mouth of Galveston Bay and Gulf...

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Field Sampling

Galveston Bay is a semi-enclosed microtidal estuary located in the NWGOM (Montagna et al., 2013). With an average water depth of 3 m and a surface area covering 1,554 km², Galveston Bay is the seventh-largest estuary in the U.S. and the second-largest estuary on the Texas coast (Bass et al., 2018; Morse et al., 1993; Solis & Powell, 1999). Galveston Bay receives freshwater from the Trinity River, San Jacinto River, Clear Creek, and smaller bayous and creeks, with the Trinity River providing 70% of the freshwater entering the Bay (Bass et al., 2018; Dellapenna et al., 2020; Morse et al., 1993; Solis & Powell, 1999). The Bolivar Peninsula and Galveston Island separate Galveston Bay from the GOM, with the exchange of water between the Bay and the GOM occurring through Bolivar Roads, i.e., the mouth of the Bay (Glass et al., 2008; Morse et al., 1993).

Monthly cruises were conducted between October 2017 and September 2018 onboard the R/V Trident. Timing of the study allowed for the examination of the factors regulating CO₂ flux over the course of a year following Hurricane Harvey in late August 2017. Although the study began more than 45 days (the residence time of the Bay) after Harvey, salinity recovery of the Bay was likely still ongoing in the inner and middle sections of the Bay (Du & Park, 2019; Du et al., 2019).

During each monthly survey, a transect was run between five water sampling stations, extending northwest from the Bay mouth (Station 1) opening to the Five Mile Marker on the Houston Ship Channel (Station 5). One offshore cruise in the NWGOM outside Galveston Bay was conducted in October 2018. At each station, surface (~0.5 m below water surface) and bottom water (~0.5 m above the sediment) samples for carbonate analyses were collected. A van Dorn sampler was used to collect unfiltered surface and bottom water into 250 mL borosilicate glass bottles for total alkalinity (TA), dissolved inorganic carbon (DIC), and pH analyses. A total of 100 μL saturated HgCl₂ was added to each water sample to cease biological activity, and bottle stoppers were replaced following the application of Apiezon® grease and secured with rubber bands and hose clamps. The samples were stored at 4 °C in the dark until analyses, usually within 2–3 weeks of sample collection. Surface and bottom unpreserved water samples were collected in 125 mL polypropylene bottles for Ca²⁺ analysis.

Discrete Sample Analyses

Water samples collected at the surface and bottom at each station were analyzed for DIC, TA, pH, and salinity (Dickson et al., 2003; Bass et al., 2018). DIC was analyzed by acidifying 0.5 mL water samples with 0.5 mL 10% H₃PO₄ using a 2.5 mL syringe pump on an AS-C3 DIC analyzer (Apollo SciTech Inc.) with a precision of ±0.1%. TA was analyzed at 22.0 ± 0.1 °C using Gran titration of a 25 mL water sample with 0.1 M HCl solution (in 0.5 M NaCl) on an AS-Alk2 alkalinity titrator (Apollo SciTech Inc.), with a precision of ±0.1%. Precisions were estimated based on randomly collected duplicate samples. Reference Material (RM) produced in the lab of Andrew Dickson at Scripps was used in both TA and DIC analysis to ensure data quality (Dickson et al., 2003).

A spectrophotometric method with a precision of ±0.0004 and purified m-cresol purple (mCP) obtained from Dr. Robert Byrne’s lab (University of South Florida) (Liu et al., 2011) was used for pH (on the total scale) analysis (Carter et al., 2013). Prior to each sample analysis, a calibrated Orion™ Ross™ glass electrode was used to adjust the indicator to pH 7.92 ± 0.01. A 10 cm water-jacketed absorbance cell for pH measurements (Carter et al., 2013) was kept at 25 ± 0.01 °C. Consecutive runs were done for each sample whereby two volumes (30 μL and 60 μL) of mCP were added to correct the dye effect (Clayton & Byrne, 1993). Equations from Liu et al. (2011) were used when salinity was greater than 20 for the entirety of a sampling trip, and equations from Douglas and Byrne (2017), which allow for a wider salinity range (0–40 vs. 20–40) (Douglas & Byrne, 2017), were used when salinity was less than 20 for an entire sampling trip for pH calculations. Calculated pH values (on the total scale) were converted to in situ temperature using the program CO2SYS with DIC as the other input parameter.

Salinity was measured with a benchtop salinometer (Orion Star™ A12, Thermo Scientific), which was calibrated using Milli-Q water and known salinity CRM seawater before each sample analysis. Calcium ([Ca²⁺]) concentration was measured using automatic potentiometric titration with ethylene glycol tetraacetic acid (EGTA), with a precision of ±0.2% (Kanamori & Ikegami, 1980). A Metrohm® Titrando calcium-selective electrode on a titration system (Metrohm Titrando 888) was used to detect the endpoint.

Meteorological Data

United States Geological Survey (USGS, 2021) streamgages for the Trinity River (gage #08066500) and San Jacinto River, east fork (SJE; gage #08070200) and west fork (SJW; gage #08068000), were used to obtain freshwater discharge. These stations were identified as the closest gages to the mouths of the rivers having complete discharge data for the study period. Discharges of less than or equal to 45 days (residence time of the Bay) prior to flux estimates were utilized (Morse et al., 1993; Solis & Powell, 1999). The Texas Commission on Environmental Quality (TCEQ, 2022) performs routine water quality monitoring, and TCEQ water sampling stations were used for river endmember values from the San Jacinto (average of west fork station #11243 and east fork station #11238) and Trinity (station #10896) rivers. River endmember DIC was calculated from TA and pH measurements using K₁ and K₂ constants from Millero (2010) and pH values on the NBS scale. Seasonally weighted averages were calculated by summing the TA or DIC concentration multiplied by daily discharge values for all river measurements of that season and dividing by the sum of all discharge values for all river measurements of that season (using meteorological seasons).


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Methods

Bass, B., Torres, J. M., Irza, J. N., Proft, J., Sebastian, A., Dawson, C., & Bedient, P. (2018). Surge dynamics across a complex bay coastline, Galveston Bay, TX. Coastal Engineering, 138, 165–183. https://doi.org/10.1016/j.coastaleng.2018.04.019
Methods

Carter, B. R., Radich, J. A., Doyle, H. L., & Dickson, A. G. (2013). An automated system for spectrophotometric seawater pH measurements. Limnology and Oceanography: Methods, 11(1), 16–27. doi:10.4319/lom.2013.11.16
Methods

Chen, N., Bianchi, T. S., & McKee, B. A. (2005). Early diagenesis of chloropigment biomarkers in the lower Mississippi River and Louisiana shelf: implications for carbon cycling in a river-dominated margin. Marine Chemistry, 93(2–4), 159–177. https://doi.org/10.1016/j.marchem.2004.08.005
Methods

Clayton, T. D., & Byrne, R. H. (1993). Spectrophotometric seawater pH measurements: total hydrogen ion concentration scale calibration of m-cresol purple and at-sea results. Deep Sea Research Part I: Oceanographic Research Papers, 40(10), 2115–2129. doi:10.1016/0967-0637(93)90048-8
Methods

Dellapenna, T. M., Hoelscher, C., Hill, L., Al Mukaimi, M. E., & Knap, A. (2020). How tropical cyclone flooding caused erosion and dispersal of mercury-contaminated sediment in an urban estuary: The impact of Hurricane Harvey on Buffalo Bayou and the San Jacinto Estuary, Galveston Bay, USA. Science of The Total Environment, 748, 141226. https://doi.org/10.1016/j.scitotenv.2020.141226