Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay

Cai, Wei‐Jun; Huang, Wei‐Jen; Luther, George W.; Pierrot, Denis; Li, Ming; Testa, Jeremy M.; Xue, Ming; Joesoef, Andrew; Mann, Roger; Brodeur, Jean; Xu, Yuan‐Yuan; Chen, Baoshan; Hussain, N.; Waldbusser, George G.; Cornwell, Jeffrey C.; Kemp, W. Michael

doi:10.1038/s41467-017-00417-7

Cited by 139 publications

(201 citation statements)

References 85 publications

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“…CO 2 concentrations were ∼70–80 μM in the waters from which the CP strains were isolated (Cai et al, 2017). These concentrations are within the K m,CO 2 ranges for both Form I and Form II RuBisCO (Badger and Bek, 2008), so either should be functional in this environment.…”

Section: Resultsmentioning

confidence: 99%

Novel Pelagic Iron-Oxidizing Zetaproteobacteria from the Chesapeake Bay Oxic–Anoxic Transition Zone

et al. 2017

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Chemolithotrophic iron-oxidizing bacteria (FeOB) could theoretically inhabit any environment where Fe(II) and O2 (or nitrate) coexist. Until recently, marine Fe-oxidizing Zetaproteobacteria had primarily been observed in benthic and subsurface settings, but not redox-stratified water columns. This may be due to the challenges that a pelagic lifestyle would pose for Zetaproteobacteria, given low Fe(II) concentrations in modern marine waters and the possibility that Fe oxyhydroxide biominerals could cause cells to sink. However, we recently cultivated Zetaproteobacteria from the Chesapeake Bay oxic–anoxic transition zone, suggesting that they can survive and contribute to biogeochemical cycling in a stratified estuary. Here we describe the isolation, characterization, and genomes of two new species, Mariprofundus aestuarium CP-5 and Mariprofundus ferrinatatus CP-8, which are the first Zetaproteobacteria isolates from a pelagic environment. We looked for adaptations enabling strains CP-5 and CP-8 to overcome the challenges of living in a low Fe redoxcline with frequent O2 fluctuations due to tidal mixing. We found that the CP strains produce distinctive dreadlock-like Fe oxyhydroxide structures that are easily shed, which would help cells maintain suspension in the water column. These oxides are by-products of Fe(II) oxidation, likely catalyzed by the putative Fe(II) oxidase encoded by the cyc2 gene, present in both CP-5 and CP-8 genomes; the consistent presence of cyc2 in all microaerophilic FeOB and other FeOB genomes supports its putative role in Fe(II) oxidation. The CP strains also have two gene clusters associated with biofilm formation (Wsp system and the Widespread Colonization Island) that are absent or rare in other Zetaproteobacteria. We propose that biofilm formation enables the CP strains to attach to FeS particles and form flocs, an advantageous strategy for scavenging Fe(II) and developing low [O2] microenvironments within more oxygenated waters. However, the CP strains appear to be adapted to somewhat higher concentrations of O2, as indicated by the presence of genes encoding aa3-type cytochrome c oxidases, but not the cbb3-type found in all other Zetaproteobacteria isolate genomes. Overall, our results reveal adaptations for life in a physically dynamic, low Fe(II) water column, suggesting that niche-specific strategies can enable Zetaproteobacteria to live in any environment with Fe(II).

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Section: Resultsmentioning

confidence: 99%

Novel Pelagic Iron-Oxidizing Zetaproteobacteria from the Chesapeake Bay Oxic–Anoxic Transition Zone

et al. 2017

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“…Estuarine systems are complex, cover large salinity ranges that challenge current measurement techniques and are generally under-sampled Cai et al, 2017). The carbonate chemistry in the rivers that feed these estuaries may also be exceptionally variable (Cai et al, 1998), ranging from rivers with low DIC to total alkalinity (DIC : TA) ratios and high pH (> 8) like the Mississippi River (Hu and Cai, 2013) to blackwater rivers that have low pH (< 5) (Cai et al, 1998;de Fátima et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Those organisms using the calciumcarbonate mineral form aragonite in their external hard parts (e.g., some molluscs) are especially vulnerable since oceanic CO 2 uptake lowers the aragonite saturation state ( A ) of seawater (Waldbusser et al, 2015). While carbonate system dynamics and/or acid-base chemistry have been studied extensively in marine (e.g., Jiang et al, 2015) and freshwater (e.g., Schindler, 1988) environments, less is known in the diverse estuaries where these two zones meet (Salisbury et al, 2008;Hagens and Middelburg, 2016;Cai et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…In the Congo River for example, TA is flow-dependent but DIC is persistently high year-round (Wang et al, 2013). On top of natural variability, many estuaries also experience heavy anthropogenic pressure (Frankignoulle et al, 1996;Zhai et al, 2007;Cai et al, 2017), making them particularly vulnerable to ocean acidification (Cai et al, 2011 and in some cases the subject of intensive management and policy initiatives (Fennel et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

2018

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Abstract. Ocean acidification threatens to reduce pH and aragonite saturation state ( A ) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and A in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and A to river TA and DIC using a coupled biogeochemical model of the Strait of Georgia on the Canadian Pacific coast and place the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA observations from this river plume and pH from the river mouth, we find that the Fraser is moderately alkaline (TA 500-1000 µmol kg −1 ) but relatively DICrich. Model results show that estuarine pH and A are sensitive to freshwater DIC and TA, but do not vary in synchrony except at high DIC : TA. The asynchrony occurs because increased freshwater TA is associated with increased DIC, which contributes to an increased estuarine DIC : TA and reduces pH, while the resulting higher carbonate ion concentration causes an increase in estuarine A . When freshwater DIC : TA increases (beyond ∼ 1.1), the shifting chemistry causes a paucity of the carbonate ion that overwhelms the simple dilution/enhancement effect. At this high DIC : TA ratio, estuarine sensitivity to river chemistry increases overall. Furthermore, this increased sensitivity extends to reduced flow regimes that are expected in future. Modulating these negative impacts is the seasonal productivity in the estuary which draws down DIC and reduces the sensitivity of estuarine pH to increasing DIC during the summer season.

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“…CC BY 4.0 License. exceed concentrations projected for the end of the century (>2,000 µatm), as well as result in the undersaturation of aragonite (Ωaragonite < 1; Cai et al, 2017;Wallace et al, 2014).…”

Section: Introduction 25mentioning

confidence: 99%

The ability of macroalgae to mitigate the negative effects of ocean acidification on four species of North Atlantic bivalve

Young¹,

Gobler²

2018

Preprint

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Abstract. Coastal ecosystems can experience acidification via upwelling, eutrophication, riverine discharge, and climate change. While the resulting increases in pCO2 can have deleterious effects on calcifying animals, this change in carbonate 10 chemistry may benefit some marine autotrophs. Here, we report on experiments performed with North Atlantic populations of hard clams (Mercenaria mercenaria), eastern oysters (Crassostrea virginica), bay scallops (Argopecten irradians), and blue mussels (Mytilus edulis) grown with and without North Atlantic populations of the green macroalgae, Ulva. In 6 of 7 experiments, exposure to elevated pCO2 levels (~1,700 µatm) resulted in depressed shell-and/or tissue-based growth rates of bivalves compared to control conditions (p<0.05) whereas rates were significantly higher in the presence of Ulva in all 15 experiments (p<0.05). In many cases, the co-exposure elevated pCO2 levels and Ulva had an antagonistic effect on bivalve growth rates whereby the presence of Ulva under elevated pCO2 levels significantly improved their performance compared to the acidification only treatment (p<0.05). Saturation states for calcium carbonate (Ω) were significantly higher in the presence of Ulva under both ambient and elevated CO2 delivery rates (p<0.05). Collectively, the results suggest that photosynthesis and/or nitrate assimilation by Ulva increased alkalinity, fostering a carbonate chemistry regime more suitable 20 for optimal growth of calcifying bivalves. This suggests that large natural and/or aquacultured collections of macroalgae in acidified environments could serve as a refuge for calcifying animals that may otherwise be negatively impacted by elevated pCO2 levels and depressed Ω.

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Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay

Cited by 139 publications

References 85 publications

Novel Pelagic Iron-Oxidizing Zetaproteobacteria from the Chesapeake Bay Oxic–Anoxic Transition Zone

Novel Pelagic Iron-Oxidizing Zetaproteobacteria from the Chesapeake Bay Oxic–Anoxic Transition Zone

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

The ability of macroalgae to mitigate the negative effects of ocean acidification on four species of North Atlantic bivalve

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