Seasonal variability of carbonate chemistry and decadal changes in waters of a marine sanctuary in the Northwestern Gulf of Mexico

Hu, Xinping; Nuttall, Marissa F.; Wang, Hongjie; Yao, Hongming; Staryk, Cory J.; McCutcheon, Melissa R.; Eckert, Ryan J.; Embesi, John A.; Johnston, Michelle; Hickerson, Emma L.; Schmahl, George P.; Manzello, Derek P.; Enochs, Ian C.; DiMarco, Steven F.; Barbero, Leticia

doi:10.1016/j.marchem.2018.07.006

Cited by 16 publications

(13 citation statements)

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“…Hypoxia and associated bottom water acidification are predicted to intensify due to increased nutrient loadings and organic matter production 16 , 17 . Decadal declines in subsurface (100–250 m) Ω and pH have been reported on the outer continental shelf region, and are attributed to uptake of anthropogenic CO 2 and elevated respiration 18 . Therefore, hypoxia and ocean acidification are highly relevant stressors for GoM ecosystem management.…”

Section: Introductionmentioning

confidence: 89%

Surface Water CO2 variability in the Gulf of Mexico (1996–2017)

Kealoha

Shamberger

DiMarco

et al. 2020

Sci Rep

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Approximately 380,000 underway measurements of sea surface salinity, temperature, and carbon dioxide (co 2) in the Gulf of Mexico (GoM) were compiled from the Surface Ocean CO 2 Atlas (SOCAT) to provide a comprehensive observational analysis of spatiotemporal CO 2 dynamics from 1996 to 2017. An empirical orthogonal function (EOF) was used to derive the main drivers of spatial and temporal variability in the dataset. In open and coastal waters, drivers were identified as a biological component linked to riverine water, and temperature seasonality. Air-sea flux estimates indicate the GoM open (− 0.06 ± 0.45 mol C m −2 year −1) and coastal (− 0.03 ± 1.83 mol C m −2 year −1) ocean are approximately neutral in terms of an annual source or sink for atmospheric CO 2. Surface water pCO 2 in the northwest and southeast GoM open ocean is increasing (1.63 ± 0.63 µatm year −1 and 1.70 ± 0.14 µatm year −1 , respectively) at rates comparable to those measured at long-term ocean time-series stations. The average annual increase in coastal CO 2 was 3.20 ± 1.47 µatm year-1 for the northwestern GoM and 2.35 ± 0.82 µatm year −1 for the west Florida Shelf. However, surface CO 2 in the central (coastal and open) GoM, which is influenced by Mississippi and Atchafalaya River outflow, remained fairly stable over this time period. Since the onset of the Industrial Revolution, atmospheric carbon dioxide (CO 2) has increased by approximately 40% 1. The ocean is responsible for absorbing ~ 25% of anthropogenic CO 2 emissions, which modulates climate by reducing global warming 1. However, oceanic absorption of atmospheric CO 2 also leads to an increase in seawater partial pressure of CO 2 (pCO 2), and a decrease in seawater pH and calcium carbonate (CaCO 3) saturation state (Ω) 2,3. This process, termed ocean acidification, has numerous negative consequences for marine organisms, especially those that form CaCO 3 skeletons and shells (e.g. corals and shellfish), including a reduction in biogenic calcification and an increase in CaCO 3 dissolution 4-8. Gulf of Mexico (GoM) ecosystems support fisheries that are essential to the Gulf Coast and U.S. economies 9. The 2015 GoM seafood landings revenue was $858 million, which is almost 20% of the total U.S. landings revenue 9. Despite serving as a critical component for regional economic stability, the GoM is subject to numerous anthropogenic pressures that contribute to the decline of ecosystem health, including eutrophication, hypoxia, oil spills, warming, and acidification 10-12. Hypoxia in the northern GoM is driven by the spring flux of nutrients from the Mississippi and Atchafalaya River systems, combined with water column stratification that prevents mixing of bottom waters with oxygenated surface water 13-15. The production of CO 2 through respiratory processes also lowers bottom water pH (i.e., increases acidity) 11. Hypoxia and associated bottom water acidification are predicted to intensify due to increased nutrient loadings and organic matter production 16,17. Decadal declines in subsur...

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Section: Introductionmentioning

confidence: 89%

Surface Water CO2 variability in the Gulf of Mexico (1996–2017)

Kealoha

Shamberger

DiMarco

et al. 2020

Sci Rep

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“…More substantial temperature swings between seasons would result in more temperature control over a seasonal timescale. ASC seems to have less thermal control of the carbonate system than offshore GOM waters, as temperature had substantially higher explanatory value for pH and pCO 2 based on simple linear regressions in offshore GOM waters (R 2 = 0.81 and 0.78, respectively, Hu et al, 2018) than at ASC (R 2 = 0.30 and 0.52, respectively, for sensor data and R 2 = 0.38 and 0.25, respectively, for discrete data).…”

Section: Thermal and Biological Controls On Carbonate Chemistrymentioning

confidence: 95%

“…The GOM estuaries currently have less exposure to concerning levels of acidification than other estuaries because of their high temperatures (causing water to hold less CO 2 and support high productivity year-round) and often suitable river chemistries (i.e., relatively high buffer capacity) (McCutcheon et al, 2019;Yao et al, 2020). However, respiration-induced acidification is present in both the open GOM (e. g., subsurface water influenced by the Mississippi River Plume and outer shelf region near the Flower Garden Banks National Marine Sanctuary) and GOM estuaries, and most estuaries in the northwestern GOM have also experienced long-term acidification (Cai et al, 2011;Hu et al, 2015Hu et al, , 2018Kealoha et al, 2020;Mc-Cutcheon et al, 2019;Robbins and Lisle, 2018). This evidence of acidification as well as the relatively high CO 2 efflux from the estuaries of the northwest GOM illustrates the necessity to study the baseline variability and driving factors of carbonate chemistry in the region.…”

Section: Introductionmentioning

confidence: 99%

Temporal variability and driving factors of the carbonate system in the Aransas Ship Channel, TX, USA: a time series study

et al. 2021

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Abstract. The coastal ocean is affected by an array of co-occurring biogeochemical and anthropogenic processes, resulting in substantial heterogeneity in water chemistry, including carbonate chemistry parameters such as pH and partial pressure of CO2 (pCO2). To better understand coastal and estuarine acidification and air-sea CO2 fluxes, it is important to study baseline variability and driving factors of carbonate chemistry. Using both discrete bottle sample collection (2014–2020) and hourly sensor measurements (2016–2017), we explored temporal variability, from diel to interannual scales, in the carbonate system (specifically pH and pCO2) at the Aransas Ship Channel located in the northwestern Gulf of Mexico. Using other co-located environmental sensors, we also explored the driving factors of that variability. Both sampling methods demonstrated significant seasonal variability at the location, with highest pH (lowest pCO2) in the winter and lowest pH (highest pCO2) in the summer. Significant diel variability was also evident from sensor data, but the time of day with elevated pCO2 and depressed pH was not consistent across the entire monitoring period, sometimes reversing from what would be expected from a biological signal. Though seasonal and diel fluctuations were smaller than many other areas previously studied, carbonate chemistry parameters were among the most important environmental parameters for distinguishing between time of day and between seasons. It is evident that temperature, biological activity, freshwater inflow, and tide level (despite the small tidal range) are all important controls on the system, with different controls dominating at different timescales. The results suggest that the controlling factors of the carbonate system may not be exerted equally on both pH and pCO2 on diel timescales, causing separation of their diel or tidal relationships during certain seasons. Despite known temporal variability on shorter timescales, discrete sampling was generally representative of the average carbonate system and average air-sea CO2 flux on a seasonal and annual basis when compared with sensor data.

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“…Most observational studies on carbon dynamics in the GoM have been conducted on the Louisiana-Texas shelf (e.g., Cai, 2003;Lohrenz et al, 2010Lohrenz et al, , 2018Guo et al, 2012;Cai et al, 2013;Huang et al, 2012;Hu et al, 2018). In this region, the Mississippi-Atchafalaya river system (MARS) has a strong influence, delivering a significant amount of freshwater, carbon, and nutrients, the latter fueling high biological production (Green et al, 2008;Lehrter et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…In this region, the Mississippi-Atchafalaya river system (MARS) has a strong influence, delivering a significant amount of freshwater, carbon, and nutrients, the latter fueling high biological production (Green et al, 2008;Lehrter et al, 2013). Enhanced primary production during spring and summer periods increases carbon uptake near the MARS delta, which results in decreased surface partial pressure of CO 2 (pCO 2 ) and increased ocean uptake of CO 2 (Lohrenz et al, 2010(Lohrenz et al, , 2018Guo et al, 2012;Huang et al, 2015;Hu et al, 2018). Subsequent sinking and remineralization of large amounts of organic carbon over the Louisiana-Texas shelf, concurrent with strong water column stratification, results in bottom acidification during the summer (Cai et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Seasonal patterns of surface inorganic carbon system variables in the Gulf of Mexico inferred from a regional high-resolution ocean biogeochemical model

et al. 2020

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Abstract. Uncertainties in carbon chemistry variability still remain large in the Gulf of Mexico (GoM), as data gaps limit our ability to infer basin-wide patterns. Here we configure and validate a regional high-resolution ocean biogeochemical model for the GoM to describe seasonal patterns in surface pressure of CO2 (pCO2), aragonite saturation state (ΩAr), and sea–air CO2 flux. Model results indicate that seasonal changes in surface pCO2 are strongly controlled by temperature across most of the GoM basin, except in the vicinity of the Mississippi–Atchafalaya river system delta, where runoff largely controls dissolved inorganic carbon (DIC) and total alkalinity (TA) changes. Our model results also show that seasonal patterns of surface ΩAr are driven by seasonal changes in DIC and TA, and reinforced by the seasonal changes in temperature. Simulated sea–air CO2 fluxes are consistent with previous observation-based estimates that show CO2 uptake during winter–spring, and CO2 outgassing during summer–fall. Annually, our model indicates a basin-wide mean CO2 uptake of 0.35 molm-2yr-1, and a northern GoM shelf (< 200 m) uptake of 0.93 molm-2yr-1. The observation and model-derived patterns of surface pCO2 and CO2 fluxes show good correspondence; thus this study contributes to improved constraints of the carbon budget in the region.

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Seasonal variability of carbonate chemistry and decadal changes in waters of a marine sanctuary in the Northwestern Gulf of Mexico

Cited by 16 publications

References 54 publications

Surface Water CO2 variability in the Gulf of Mexico (1996–2017)

Surface Water CO2 variability in the Gulf of Mexico (1996–2017)

Temporal variability and driving factors of the carbonate system in the Aransas Ship Channel, TX, USA: a time series study

Seasonal patterns of surface inorganic carbon system variables in the Gulf of Mexico inferred from a regional high-resolution ocean biogeochemical model

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