Uptake of anthropogenic carbon dioxide (CO2) from the atmosphere has acidified the ocean and threatened the health of marine organisms and their ecosystems. In coastal waters, acidification is often enhanced by CO2 and acids produced under high rates of biological respiration. However, less is known about buffering processes that counter coastal acidification in eutrophic and seasonally hypoxic water bodies, such as the Chesapeake Bay. Here, we use carbonate chemistry, mineralogical analyses and geochemical modelling to demonstrate the occurrence of a bay-wide pH-buffering mechanism resulting from spatially decoupled calcium carbonate mineral cycling. In summer, high rates of photosynthesis by dense submerged aquatic vegetation at the head of the bay and in shallow, nearshore areas generate high pH, an elevated carbonate mineral saturation state and net alkalinity uptake. Calcium carbonate particles produced under these conditions are subsequently transported downstream into corrosive subsurface waters, where their dissolution buffers pH decreases caused by aerobic respiration and anthropogenic CO2. Because this pH-buffering mechanism would be strengthened by further nutrient load reductions and associated submerged aquatic vegetation recovery, our findings suggest that the reduction of nutrient inputs into coastal waters will not only reduce eutrophication and hypoxia, but also alleviate the severity of coastal ocean acidification.
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Gattuso, J.-P. et al. Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios. Science 349, aac4722 (2015).
Feely, R. A. et al. The combined effects of acidification and hypoxia on pH and aragonite saturation in the coastal waters of the California current ecosystem and the northern Gulf of Mexico. Cont. Shelf Res. 152, 50–60 (2018).
Fabry, V. J., Seibel, B. A., Feely, R. A. & Orr, J. C. Impacts of ocean acidification on marine fauna and ecosystem processes. ICES J. Mar. Sci. 65, 414–432 (2008).
Cai, W.-J. et al. Acidification of subsurface coastal waters enhanced by eutrophication. Nat. Geosci. 4, 766–770 (2011).
Wallace, R. B., Baumann, H., Grear, J. S., Aller, R. C. & Gobler, C. J. Coastal ocean acidification: the other eutrophication problem. Estuar. Coast. Shelf Sci. 148, 1–13 (2014).
Andersson, A. J., Mackenzie, F. T. & Lerman, A. Coastal ocean and carbonate systems in the high CO2 world of the Anthropocene. Am. J. Sci. 305, 875–918 (2005).
Macreadie, P. I., Serrano, O., Maher, D. T., Duarte, C. M. & Beardall, J. Addressing calcium carbonate cycling in blue carbon accounting. Limnol. Oceanogr. Lett. 2, 195–201 (2017).
Cai, W.-J. et al. Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay. Nat. Commun. 8, 369 (2017).
Green, M. A., Waldbusser, G. G., Reilly, S. L., Emerson, K. & O’Donnell, S. Death by dissolution: sediment saturation state as a mortality factor for juvenile bivalves. Limnol. Oceanogr. 54, 1037–1047 (2009).
Abril, G., Etcheber, H., Delille, B., Frankignoulle, M. & Borges, A. V. Carbonate dissolution in the turbid and eutrophic Loire estuary. Mar. Ecol. Prog. Ser. 259, 129–138 (2003).
Waldbusser, G. G., Powell, E. N. & Mann, R. Ecosystem effects of shell aggregations and cycling in coastal waters: an example of Chesapeake Bay oyster reefs. Ecology 94, 895–903 (2013).
Ware, J. R., Smith, S. V. & Reaka-Kudla, M. L. Coral reefs: sources or sinks of atmospheric CO2? Coral Reefs 11, 127–130 (1992).
Borowitzka, M. A. & Larkum, A. W. D. Calcification in algae: mechanisms and the role of metabolism. Crit. Rev. Plant Sci. 6, 1–45 (1987).
Chauvaud, L., Thompson, J. K., Cloern, J. E. & Thouzeau, G. Clams as CO2 generators: the Potamocorbula amurensis example in San Francisco Bay. Limnol. Oceanogr. 48, 2086–2092 (2003).
Warren, L. A., Maurice, P. A., Parmar, N. & Ferris, F. G. Microbially mediated calcium carbonate precipitation: implications for interpreting calcite precipitation and for solid-phase capture of inorganic contaminants. Geomicrobiol. J. 18, 93–115 (2001).
Perry, C. T. et al. Fish as major carbonate mud producers and missing components of the tropical carbonate factory. Proc. Natl Acad. Sci. USA 108, 3865–3869 (2011).
Borowitzka, M. A. Calcification in aquatic plants. Plant Cell Environ. 7, 457–466 (1984).
Mazarrasa, I. et al. Seagrass meadows as a globally significant carbonate reservoir. Biogeosciences 12, 4993–5003 (2015).
Enríquez, S. & Schubert, N. Direct contribution of the seagrass Thalassia testudinum to lime mud production. Nat. Commun. 5, 3835 (2014).
Corlett, H. & Jones, B. Epiphyte communities on Thalassia testudinum from Grand Cayman, British West Indies: their composition, structure, and contribution to lagoonal sediments. Sediment. Geol. 194, 245–262 (2007).
Koch, E. W. Sediment resuspension in a shallow Thalassia testudinum banks ex König bed. Aquat. Bot. 65, 269–280 (1999).
Orth, R. J. & Moore, K. A. Chesapeake Bay: an unprecedented decline in submerged aquatic vegetation. Science 222, 51–53 (1983).
Orth, R. J. et al. Long-term trends in submersed aquatic vegetation (SAV) in Chesapeake Bay, USA, related to water quality. Estuaries Coasts 33, 1144–1163 (2010).
Orth, R. J., Batiuk, R. A., Bergstrom, P. W. & Moore, K. A. A perspective on two decades of policies and regulations influencing the protection and restoration of submerged aquatic vegetation in Chesapeake Bay, USA. Bull. Mar. Sci. 71, 1391–1403 (2002).
Lefcheck, J. S. et al. Long-term nutrient reductions lead to the unprecedented recovery of a temperate coastal region. Proc. Natl Acad. Sci. USA 115, 3658–3662 (2018).
Kemp, W. et al. Eutrophication of Chesapeake Bay: historical trends and ecological interactions. Mar. Ecol. Prog. Ser. 303, 1–29 (2005).
Murphy, R. R., Kemp, W. M. & Ball, W. P. Long-term trends in Chesapeake Bay seasonal hypoxia, stratification, and nutrient loading. Estuaries Coasts 34, 1293–1309 (2011).
Su, J. et al. Source partitioning of oxygen-consuming organic matter in the hypoxic zone of the Chesapeake Bay. Limnol. Oceanogr. https://doi.org/10.1002/lno.11419 (2020).
Gurbisz, C. & Kemp, W. M. Unexpected resurgence of a large submersed plant bed in Chesapeake Bay: analysis of time series data. Limnol. Oceanogr. 59, 482–494 (2014).
Waldbusser, G. G., Steenson, R. A. & Green, M. A. Oyster shell dissolution rates in estuarine waters: effects of pH and shell legacy. J. Shellfish Res. 30, 659–669 (2011).
Waldbusser, G. G., Voigt, E. P., Bergschneider, H., Green, M. A. & Newell, R. I. E. Biocalcification in the eastern oyster (Crassostrea virginica) in relation to long-term trends in Chesapeake Bay pH. Estuaries Coasts 34, 221–231 (2011).
Schulte, D. M. History of the Virginia oyster fishery, Chesapeake Bay, USA. Front. Mar. Sci. 4, 127 (2017).
Officer, C. B. in Estuarine and Wetland Processes: With Emphasis on Modeling (eds Hamilton, P. & Macdonald, K. B.) 65–114 (Springer, 1980).
Beer, D. D. & Larkum, A. W. D. Photosynthesis and calcification in the calcifying algae Halimeda discoidea studied with microsensors. Plant Cell Environ. 24, 1209–1217 (2001).
Semesi, I. S., Beer, S. & Björk, M. Seagrass photosynthesis controls rates of calcification and photosynthesis of calcareous macroalgae in a tropical seagrass meadow. Mar. Ecol. Prog. Ser. 382, 41–47 (2009).
Koch, E. W. Hydrodynamics, diffusion-boundary layers and photosynthesis of the seagrasses Thalassia testudinum and Cymodocea nodosa. Mar. Biol. 118, 767–776 (1994).
Du, J. & Shen, J. Water residence time in Chesapeake Bay for 1980–2012. J. Mar. Syst. 164, 101–111 (2016).
Officer, C. B. Discussion of the behaviour of nonconservative dissolved constituents in estuaries. Estuar. Coast. Mar. Sci. 9, 91–94 (1979).
Cai, W.-J., Wiebe, W. J., Wang, Y. & Sheldon, J. E. Intertidal marsh as a source of dissolved inorganic carbon and a sink of nitrate in the Satilla River–estuarine complex in the southeastern U.S. Limnol. Oceanogr. 45, 1743–1752 (2000).
Heck, K. L. & Orth, R. J. Structural components of eelgrass (Zostera marina) meadows in the lower Chesapeake Bay—decapod crustacea. Estuaries 3, 289–295 (1980).
Karlsen, A. W. et al. Historical trends in Chesapeake Bay dissolved oxygen based on benthic foraminifera from sediment cores. Estuaries 23, 488–508 (2000).
Kemp, W. M., Smith, E. M., Marvin-DiPasquale, M. & Boynton, W. R. Organic carbon balance and net ecosystem metabolism in Chesapeake Bay. Mar. Ecol. Prog. Ser. 150, 229–248 (1997).
Malone, T. C. et al. Lateral variation in the production and fate of phytoplankton in a partially stratified estuary. Mar. Ecol. Prog. Ser. 32, 149–160 (1986).
Valle-Levinson, A. & Lwiza, K. M. M. The effects of channels and shoals on exchange between the Chesapeake Bay and the adjacent ocean. J. Geophys. Res. Oceans 100, 18551–18563 (1995).
Fugate, D. C., Friedrichs, C. T. & Sanford, L. P. Lateral dynamics and associated transport of sediment in the upper reaches of a partially mixed estuary, Chesapeake Bay, USA. Cont. Shelf Res. 27, 679–698 (2007).
Saderne, V. et al. Role of carbonate burial in Blue Carbon budgets. Nat. Commun. 10, 1106 (2019).
Gruber, R. K. & Kemp, W. M. Feedback effects in a coastal canopy-forming submersed plant bed. Limnol. Oceanogr. 55, 2285–2298 (2010).
Cafrey, J. M. & Kemp, W. M. Influence of the submersed plant, Potamogeton perfoliatus, on nitrogen cycling in estuarine sediments. Limnol. Oceanogr. 37, 1483–1495 (1992).
Gurbisz, C. et al. Interactive effects of physical and biogeochemical feedback processes in a large submersed plant bed. Estuaries Coasts 40, 1626–1641 (2017).
Orth, R. J. et al. Submersed aquatic vegetation in Chesapeake Bay: sentinel species in a changing world. BioScience 67, 698–712 (2017).
Bockmon, E. E. & Dickson, A. G. A seawater filtration method suitable for total dissolved inorganic carbon and pH analyses. Limnol. Oceanogr. Methods 12, 191–195 (2014).
Huang, W. J., Wang, Y. & Cai, W. J. Assessment of sample storage techniques for total alkalinity and dissolved inorganic carbon in seawater. Limnol. Oceanogr. Methods 10, 711–717 (2012).
Goyet, C., Bradshaw, A. L. & Brewer, P. G. The carbonate system in the Black Sea. Deep Sea Res. A 38, S1049–S1068 (1991).
Hiscock, W. T. & Millero, F. J. Alkalinity of the anoxic waters in the Western Black Sea. Deep Sea Res. II 53, 1787–1801 (2006).
Verdugo, P. et al. The oceanic gel phase: a bridge in the DOM–POM continuum. Mar. Chem. 92, 67–85 (2004).
Cai, W.-J., Wang, Y. & Hodson, R. E. Acid–base properties of dissolved organic matter in the estuarine waters of Georgia, USA. Geochim. Cosmochim. Acta 62, 473–483 (1998).
Millero, F. J. Carbonate constants for estuarine waters. Mar. Freshwater Res. 61, 139–142 (2010).
Hunt, C. W., Salisbury, J. E. & Vandemark, D. Contribution of non-carbonate anions to total alkalinity and overestimation of pCO2 in New England and New Brunswick rivers. Biogeosciences 8, 3069–3076 (2011).
Yang, B., Byrne, R. H. & Lindemuth, M. Contributions of organic alkalinity to total alkalinity in coastal waters: a spectrophotometric approach. Mar. Chem. 176, 199–207 (2015).
Cai, W.-J. et al. Alkalinity distribution in the western North Atlantic Ocean margins. J. Geophys. Res. Oceans 115, C08014 (2010).
Xu, Y.-Y., Pierrot, D. & Cai, W.-J. Ocean carbonate system computation for anoxic waters using an updated CO2SYS program. Mar. Chem. 195, 90–93 (2017).
Pai, S. C., Gong, G. C. & Liu, K. K. Determination of dissolved oxygen in seawater by direct spectrophotometry of total iodine. Mar. Chem. 41, 343–351 (1993).
Fonselius, S., Dyrssen, D. & Yhlen, B. in Methods of Seawater Analysis (eds Grasshoff, K. et al.) 91–100 (Wiley, 2007).
Kanamori, S. & Ikegami, H. Computer-processed potentiometric titration for the determination of calcium and magnesium in sea water. J. Oceanogr. Soc. Japan 36, 177–184 (1980).
Mucci, A. The solubility of calcite and aragonite in seawater at various salinities, temperatures, and one atmosphere total pressure. Am. J. Sci. 283, 780–799 (1983).
Stainton, M. P. A syringe gas-stripping procedure for gas-chromatographic determination of dissolved inorganic and organic carbon in fresh water and carbonates in sediments. J. Fish. Res. Board Can. 30, 1441–1445 (1973).
Joesoef, A., Kirchman, D. L., Sommerfield, C. K. & Cai, W.-J. Seasonal variability of the inorganic carbon system in a large coastal plain estuary. Biogeosciences 14, 4949–4963 (2017).
Taylor, J. R. An Introduction to Error Analysis Ch. 3 (University Science Books, 1997).
Hong, Q., Cai, P., Shi, X., Li, Q. & Wang, G. Solute transport into the Jiulong River estuary via pore water exchange and submarine groundwater discharge: new insights from 224Ra/228Th disequilibrium. Geochim. Cosmochim. Acta 198, 338–359 (2017).
Hussain, N., Church, T. M. & Kim, G. Use of 222Rn and 226Ra to trace groundwater discharge into the Chesapeake Bay. Mar. Chem. 65, 127–134 (1999).
Luek, J. L. & Beck, A. J. Radium budget of the York River estuary (VA, USA) dominated by submarine groundwater discharge with a seasonally variable groundwater end-member. Mar. Chem. 165, 55–65 (2014).
Brewer, P. G. & Goldman, J. C. Alkalinity changes generated by phytoplankton growth. Limnol. Oceanogr. 21, 108–117 (1976).
Wolf-Gladrow, D. A., Zeebe, R. E., Klaas, C., Körtzinger, A. & Dickson, A. G. Total alkalinity: the explicit conservative expression and its application to biogeochemical processes. Mar. Chem. 106, 287–300 (2007).
Fonseca, M. S. in Estuarine Shores: Evolution, Environments and Human Alterations (eds Nordstrom, K. & Roman, C. T.) 261–286 (Wiley, 1996).
Ward, L. G., Michael Kemp, W. & Boynton, W. R. The influence of waves and seagrass communities on suspended particulates in an estuarine embayment. Mar. Geol. 59, 85–103 (1984).
Russ, E. R. & Palinkas, C. M. Seasonal-scale and decadal-scale sediment-vegetation interactions on the subaqueous Susquehanna River Delta, Upper Chesapeake Bay. Estuaries Coasts 41, 2092–2104 (2018).
Gurbisz, C., Kemp, W. M., Sanford, L. P. & Orth, R. J. Mechanisms of storm-related loss and resilience in a large submersed plant bed. Estuaries Coasts 39, 951–966 (2016).
Marani, M. et al. On the drainage density of tidal networks. Water Resour. Res. 39, 1040 (2003).
Temmerman, S., Bouma, T. J., Govers, G. & Lauwaet, D. Flow paths of water and sediment in a tidal marsh: relations with marsh developmental stage and tidal inundation height. Estuaries 28, 338–352 (2005).
D’Alpaos, A., Lanzoni, S., Marani, M. & Rinaldo, A. Landscape evolution in tidal embayments: modeling the interplay of erosion, sedimentation, and vegetation dynamics. J. Geophys. Res. Earth Surf. 112, F01008 (2007).
Xie, X., Li, M. & Ni, W. Roles of wind-driven currents and surface waves in sediment resuspension and transport during a tropical storm. J. Geophys. Res. Oceans 123, 8638–8654 (2018).
This work was supported by grants from the US National Oceanic and Atmospheric Administration (NA15NOS4780184, NA15NOS4780190 and NA18NOS4780179). We acknowledge the USGS, Maryland Department of Natural Resources and Virginia Institute of Marine Science (VIMS) for the monitoring data. We thank C. Hodgkins for assistance with the field work. This is University of Maryland Center for Environmental Science publication number 5821 and reference number UMCES CBL 2020-101.
The authors declare no competing interests.
Peer review information Primary Handling Editors: James Super; Xujia Jiang.
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Green areas show the coverage of Submersed Aquatic Vegetation (SAV) beds in the Chesapeake Bay in 2016 (http://www.vims.edu/bio/sav/maps.html). The upper, mid and lower bay (separated by the black lines) accounted for 16.4%, 64.0% and 19.6% of the total SAV coverage in 2016 (39,524 hectares). The arrow shows the outlet of the Susquehanna River. Red circles show the related locations of the four endmembers. Note that stations 82, 83, 85 and 87 are located further offshore in the Mid-Atlantic Bight and were visited during July 2015.
Extended Data Fig. 2 Carbonate system variations and bottom depths in the vicinity of the Susquehanna Flats in 2018.
The dashed line separates the western deep channel and eastern shallow flats, where SAV beds were present. The arrows show the cruise path. Sampling sites are labelled in the inserted maps. The SAV biomass was low in early June (a, c), but was high in early September (b, d) 2018. The Δ values in each station are relative to CB1.1, which was our uppermost station near the Susquehanna River mouth.
Extended Data Fig. 3 SEM images of CaCO3 precipitates on the leaf surface of Vallisneria americana collected from Susquehanna Flats in 2018.
a, semi-spherical crystallites; b, ellipsoidal crystallites; c, polycrystalline maze-like aggregates; d, aggregates with other materials; e, arborisation-like aggregates; f, rice-like aggregates. The atomic composition in Spectrum 32: 41.8% C, 18.4% Ca, 17.2% O, 10.5% K, 6.5% C, 1.9% Na, 1.6% S, 1.3% Mg, 0.8% P; Spectrum 27: 40.8% C, 25.2% O, 14.4% Ca, 9.2% N, 5.3% K, 2.4% Mg, 1.6% P, 1.0% Na; Spectrum 1: 42.9% O, 27.7% Ca, 25.4% C, 1.4% K, 1.2% Si, 0.9% Al, 0.2% Na, 0.2% Mg; sum spectrum in (e): 31.1% C, 29.9% O, 22.3% Ca, 4.6% Fe, 4.4% Si, 3.8% Al, 2.0% K, 1.9% Mg; Spectrum 13: 41.6% O, 38.1% Ca, 12.5% C, 3.7% K, 1.5% Cl, 1.1% Mg, 0.9% Si, 0.5% Na, 0.2% Al.
Extended Data Fig. 4 Effective concentration (C*) and removal (percentage) of TA and Ca2+ in the Chesapeake Bay in August 2016.
The fitting equation for TA (a) at salinity < =22 is C = 0.00002708×S6-0.00336738×S5+0.17376067×S4-4.6574875×S3+64.65219917×S2-344.24526458×S+1342.095396, whereas at salinity >22 the equation is C = 31.791176×S +1172.4787872. The fitting equation for Ca2+ (b) at salinity < =22 is C = -0.00001835×S6+0.00171504×S5-0.05591518×S4+0.67310609×S3-0.73633157×S2+265.9022229×S+368.4115086, while at salinity >22 the equation is C = 270.483366×S +740.833973. C* can be acquired by extending the derivative at any salinity to zero salinity in a concentration-salinity plot. The removal percentage at any salinity relative to freshwater input can be calculated via removal (%) = (C0-C*)/C0×100, where C0 means the concentration at freshwater end.
Extended Data Fig. 5 Numerical model simulation of the transport of fine particles from the Susquehanna Flats in the Chesapeake Bay.
The model simulates suspended sediment concentration (SSC) at surface, mid-depth and bottom water in the bay after the initial release of sediment particles (diameter = 2 μm) from all water depths on the Susquehanna Flats. SSC is shown on a logarithmic scale. The initial concentration is set as 0.5 kg m-3 over the Susquehanna Flats and the release time is on 00:00:00 May 31th, 2016. The output snapshots are the concentrations 1 hour, 1 day, 10 days, 30 days, 60 days and 90 days after the initial release of particles.
Water property data for section plot.
Cruise data, endmember values and deviation values.
Sensor data, SEM images and CaCO3 content data.
ΔpH for different biogeochemical processes.
Latitude and longitude of sampling sites.
Carbonate chemistry on the Susquehanna Flats.
SEM images and atomic composition of CaCO3 precipitates on the leaf surface.
TA and Ca2+ data in August 2016.
The full path of data repository for model simulation.
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Su, J., Cai, WJ., Brodeur, J. et al. Chesapeake Bay acidification buffered by spatially decoupled carbonate mineral cycling. Nat. Geosci. 13, 441–447 (2020). https://doi.org/10.1038/s41561-020-0584-3
Outwelling of total alkalinity and dissolved inorganic carbon from the Hooghly River to the adjacent coastal Bay of Bengal
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