Alkalinity in Tidal Tributaries of the Chesapeake Bay

Najjar, Raymond G.; Herrmann, Maria; Valle, Sebastian Cintron Del; Friedman, J.; Friedrichs, Marjorie A. M.; Harris, Lora A.; Shadwick, Elizabeth H.; Stets, Edward G.; Woodland, Ryan J.

doi:10.46427/gold2020.1885

Cited by 9 publications

(14 citation statements)

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“…The seasonal pattern of Ca 2+ removal (or CaCO 3 formation) in the upper Bay generally coincides with the seasonal cycle of aboveground biomass of SAV in Chesapeake Bay (Moore et al 2000; Gurbisz et al 2017), which begins to increase in late spring, reaches a growth peak in the late summer, and declines in the fall, making SAV‐driven CaCO 3 formation a strong candidate process for CaCO 3 sources in Chesapeake Bay. However, Najjar et al (2019) suggested that bivalve calcification was more explanatory than SAV coverage to interpret a significant TA sink in the low salinity zone of Potomac River Estuary, one of the main tributaries in Chesapeake Bay. It is clear that both abiotic precipitation and the activity of marine calcifiers (e.g., SAV leaves, epiphytes, bivalves) can contribute to sinks of Ca 2+ and TA in low‐salinity waters, but how the CaCO 3 solids can be transported downstream and support further carbonate dissolution in the mid‐bay subsurface water needs additional explanation.…”

Section: Resultsmentioning

confidence: 99%

“…Compared with the relatively consistent ocean endmember values, large variations exist in the riverine endmember due to the temporal variations of freshwater discharge (Joesoef et al 2017; Najjar et al 2019). Previous study has revealed that the riverine carbonate endmembers negatively correlate with river discharge (Su et al 2020 a ), thus we derived the riverine endmember of DIC, TA, and Ca 2+ from the specific discharge rate during each cruise period and 10 d prior (Joesoef et al 2017).…”

Section: Methodsmentioning

confidence: 99%

“…To resolve the apparent TA removal in the upper bay and dissolution signal in the mid‐bay bottom water, Su et al (2020 a ) proposed that CaCO 3 solids formed by precipitation and biocalcification within submerged aquatic vegetation (SAV) beds contribute to dissolution in the mid‐bay and thus buffer acidification. Najjar et al (2019) also found a significant TA sink in the low salinity region of the Potomac estuary, but suggested that the TA sink was likely caused by calcification by invasive bivalve Corbicula fluminea . Thus, it appears that CaCO 3 dynamics exert great influence on the carbonate system of Chesapeake Bay.…”

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confidence: 99%

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Supply‐controlled calcium carbonate dissolution decouples the seasonal dissolved oxygen andpHminima in Chesapeake Bay

Cai

Testa

et al. 2021

Limnology & Oceanography

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Acidification can present a stress on organisms and habitats in estuaries in addition to hypoxia. Although oxygen and pH decreases are generally coupled due to aerobic respiration, pH dynamics may be more complex given the multiple modes of buffering in the carbonate system. We studied the seasonal cycle of dissolved oxygen (DO), pH, dissolved inorganic carbon, total alkalinity, and calcium ion (Ca 2+ ) along the main channel of Chesapeake Bay from May to October in 2016. Contrary to the expected co-occurrence of seasonal DO and pH declines in subsurface water, we found that the pH decline ended in June while the DO decline continued until August in mid-Chesapeake Bay. We discovered that aerobic respiration was strong from May to August, but carbonate dissolution was minor in May and June and became substantial in August, which buffered further pH declines and caused the seasonal DO and pH minima mismatch. The rate of calcium carbonate (CaCO 3 ) dissolution was not primarily controlled by the saturation state in bottom water, but was instead likely controlled by the supply of CaCO 3 particles. The seasonal variability of Ca 2+ addition in the mid-bay was connected to Ca 2+ removal in the upper bay, and the timing of high carbonate dissolution coincided with peak seasonal biomass of upper Bay submerged aquatic vegetation. This study suggests a mechanism for a novel decoupling of DO and pH in estuarine waters associated with CaCO 3 , but future studies are needed to fully investigate the seasonality of physical transport and cycling of CaCO 3 .

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Supply‐controlled calcium carbonate dissolution decouples the seasonal dissolved oxygen andpHminima in Chesapeake Bay

Cai

Testa

et al. 2021

Limnology & Oceanography

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“…Secondly, due to the lack of observations required for developing model parameterizations suitable for the time and space scales analyzed here, the biogeochemical module does not include calcium carbonate cycling. Finally, Herrmann et al (2020) estimated that organic alkalinity concentration in the Chesapeake Bay has a mean of 20 meq m −3 and standard deviation of 30 meq m −3 , which are both much smaller than typical TA concentrations throughout the main stem Bay (600–2,200 meq m −3 ; Najjar et al., 2020). Therefore, organic alkalinity is assumed to be insignificant in this study.…”

Section: Methodsmentioning

confidence: 99%

“…Najjar et al. (2020) identified TA increases over many decades in tidal tributaries of the Chesapeake Bay, including the upper main stem Bay, which reflected a combination of increasing riverine TA and, in the Potomac River Estuary, a declining TA sink.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms Driving Decadal Changes in the Carbonate System of a Coastal Plain Estuary

Friedrichs

St‐Laurent

et al. 2021

JGR Oceans

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Global atmospheric CO 2 concentrations have increased from 320 ppm in the 1960s to a present-day value of 410 ppm due to anthropogenic activities (Keeling & Keeling, 2017). This increase has resulted in significant warming in the atmosphere and the global ocean (Hartmann et al., 2013;Johnson & Lyman, 2020), and significant reductions in open ocean pH and aragonite saturation state (Ω AR ) at mean rates of −0.02 pH units decade −1 and 0.08 decade −1 , respectively, over the past three decades (Doney et al., 2009;Takahashi et al., 2014). These changes, along with other human-driven environmental alterations, will likely impact marine ecosystem services, such as fisheries and aquaculture (Doney, et al., 2020).

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Controls on buffering and coastal acidification in a temperate estuary

Hunt

Salisbury

Vandemark

2022

Limnology & Oceanography

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Estuaries may be uniquely susceptible to the combined acidification pressures of atmospherically driven ocean acidification (OA), biologically driven CO2 inputs from the estuary itself, and terrestrially derived freshwater inputs. This study utilized continuous measurements of total alkalinity (TA) and the partial pressure of carbon dioxide (pCO2) from the mouth of Great Bay, a temperate northeastern U.S. estuary, to examine the potential influences of endmember mixing and biogeochemical transformation upon estuary buffering capacity (β–H). Observations were collected hourly over 28 months representing all seasons between May 2016 and December 2019. Results indicated that endmember mixing explained most of the observed variability in TA and dissolved inorganic carbon (DIC), concentrations of which varied strongly with season. For much of the year, mixing dictated the relative proportions of salinity‐normalized TA and DIC as well, but a fall season shift in these proportions indicated that aerobic respiration was observed, which would decrease β–H by decreasing TA and increasing DIC. However, fall was also the season of weakest statistical correspondence between salinity and both TA and DIC, as well as the overall highest salinity, TA and β–H. Potential biogeochemically driven β–H decreases were overshadowed by increased buffering capacity supplied by coastal ocean water. A simple modeling exercise showed that mixing processes controlled most monthly changes in TA and DIC, obscuring impacts from air–sea exchange or metabolic processes. Advective mixing contributions may be as important as biogeochemically driven changes to observe when evaluating local estuarine and coastal OA.

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Alkalinity in Tidal Tributaries of the Chesapeake Bay

Cited by 9 publications

References 0 publications

Supply‐controlled calcium carbonate dissolution decouples the seasonal dissolved oxygen andpHminima in Chesapeake Bay

Supply‐controlled calcium carbonate dissolution decouples the seasonal dissolved oxygen andpHminima in Chesapeake Bay

Mechanisms Driving Decadal Changes in the Carbonate System of a Coastal Plain Estuary

Controls on buffering and coastal acidification in a temperate estuary

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