Porewater Carbonate Chemistry Dynamics in a Temperate and a Subtropical Seagrass System

Abstract Seagrass systems are integral components of both local and global carbon cycles and can substantially modify seawater biogeochemistry, which has ecological ramifications. However, the influence of seagrass on porewater biogeochemistry has not been fully described, and the exact role of this marine macrophyte and associated microbial communities in the modification of porewater chemistry remains equivocal. In the present study, carbonate chemistry in the water column and porewater was investigated over diel timescales in contrasting, tidally influenced seagrass systems in Southern California and Bermuda, including vegetated (Zostera marina) and unvegetated biomes (0–16 cm) in Mission Bay, San Diego, USA and a vegetated system (Thallasia testudinium) in Mangrove Bay, Ferry Reach, Bermuda. In Mission Bay, dissolved inorganic carbon (DIC) and total alkalinity (TA) exhibited strong increasing gradients with sediment depth. Vertical porewater profiles differed between the sites, with almost twice as high concentrations of DIC and TA observed in the vegetated compared to the unvegetated sediments. In Mangrove Bay, both the range and vertical profiles of porewater carbonate parameters such as DIC and TA were much lower and, in contrast to Mission Bay where no distinct temporal signal was observed, biogeochemical parameters followed the semi-diurnal tidal signal in the water column. The observed differences between the study sites most likely reflect a differential influence of biological (biomass, detritus and infauna) and physical processes (e.g., sediment permeability, residence time and mixing) on porewater carbonate chemistry in the different settings.

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Early Diagenesis in Sediments of the Venice Lagoon (Italy) and Its Relationship to Hypoxia

Frontiers in Marine Science ◽

10.3389/fmars.2020.575547 ◽

2021 ◽

Vol 7 ◽

Author(s):

Daniele Brigolin ◽

Christophe Rabouille ◽

Clément Demasy ◽

Bruno Bombled ◽

Gaël Monvoisin ◽

...

Keyword(s):

Water Column ◽

Heat Waves ◽

Dissolved Inorganic Carbon ◽

Multiple Stressors ◽

Regional Climate ◽

Oxygen Demand ◽

Sediment Oxygen Demand ◽

Total Alkalinity ◽

Organic Carbon Content ◽

Climate Conditions

This work focuses on sediments of a shallow water lagoon, located in a densely populated area undergoing multiple stressors, with the goal of increasing the understanding of the links between diagenetic processes occurring in sediments, the dynamics of dissolved oxygen (DO) in the water column, and potential consequences of hypoxia. Sediment data were collected over three consecutive years, from 2015 to 2017, during spring–summer, at five stations. Measured variables included: sediment porosity, grain size and organic carbon content, porewater microprofiles of O2, pH and H2S, porewater profiles of dissolved inorganic carbon (DIC), total alkalinity (TA), NH4+, NO3–, dissolved Fe, and SO42–. In addition, long-term time series of oxygen saturations in the water column (years 2005–2017) were utilized in order to identify the occurrence and duration of hypoxic periods. The results show that the median DO saturation value in summer months was below 50% (around 110 μmol L–1), and that saturation values below 25% (below the hypoxic threshold) can persist for more than 1 week. Sediment stations can be divided in two groups based on their diagenetic intensity: intense and moderate. At these two groups of stations, the average DIC net production rates, estimated trough a steady-state model (Profile) were, respectively, of 2.8 and 1.0 mmol m–2 d–1, SO42– consumption rates were respectively 1.6 and 0.4 mmol m–2 d–1, while diffusive oxygen uptake fluxes, calculated from the sediment microprofile data, were of 28.5 and 17.5 mmol m–2 d–1. At the stations characterized by intense diagenesis, total dissolved sulfide accumulated in porewaters close to the sediment-water interface, reaching values of 0.7 mM at 10 cm. Considering the typical physico-chemical summer conditions, the theoretical time required to consume oxygen down to the hypoxic level by sediment oxygen demand ranges between 5 and 18 days, in absence of mixing and re-oxygenation. This estimation highlights that sediment diagenesis may play a crucial role in triggering and maintaining hypoxia of lagoon waters during the summer season in specific high intensity diagenesis zones. This role of the sediment could be enhanced by changes in regional climate conditions, such as the increase in frequency of summer heat waves.

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Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Biogeosciences Discussions ◽

10.5194/bgd-11-2793-2014 ◽

2014 ◽

Vol 11 (2) ◽

pp. 2793-2822 ◽

Cited By ~ 3

Author(s):

M. Ribas-Ribas ◽

V. M. C. Rérolle ◽

D. C. E. Bakker ◽

V. Kitidis ◽

G. A. Lee ◽

...

Keyword(s):

Degrees Of Freedom ◽

Dissolved Inorganic Carbon ◽

Maximum Amplitude ◽

Total Alkalinity ◽

Carbonate Chemistry ◽

Carbonate System ◽

European Shelf ◽

Shelf Seas ◽

The Difference ◽

System Variables

Abstract. Four carbonate system variables were measured in surface waters during a cruise traversing northwestern European shelf seas in the summer of 2011. High resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pHT, in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom) which allowed us to evaluate the level of agreement between the variables. Calculations of carbonate system variables from other measurements generally compared well (Pearson's correlation coefficient always &geq; 0.94; mean residuals similar to the respective uncertainties of the calculations) with direct observations of the same variables. We therefore conclude that the four independent datasets of carbonate chemistry variables were all of high quality, and as a result that this dataset is suitable to be used for the evaluation of ocean acidification impacts and for carbon cycle studies. A diurnal cycle with maximum amplitude of 41 μatm was observed in the difference between the pCO2; values obtained by the two independent analytical pCO2; systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on research cruises.

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CO<sub>2</sub> perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations

Biogeosciences ◽

10.5194/bg-6-2145-2009 ◽

2009 ◽

Vol 6 (10) ◽

pp. 2145-2153 ◽

Cited By ~ 80

Author(s):

K. G. Schulz ◽

J. Barcelos e Ramos ◽

R. E. Zeebe ◽

U. Riebesell

Keyword(s):

Ocean Acidification ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Total Alkalinity ◽

Calcium Carbonate Precipitation ◽

Carbonate Chemistry ◽

Carbonate System ◽

Experimental Conditions ◽

Saturation State ◽

Basic Approaches

Abstract. Increasing atmospheric carbon dioxide (CO2) through human activities and invasion of anthropogenic CO2 into the surface ocean alters the seawater carbonate chemistry, increasing CO2 and bicarbonate (HCO3−) at the expense of carbonate ion (CO32−) concentrations. This redistribution in the dissolved inorganic carbon (DIC) pool decreases pH and carbonate saturation state (Ω). Several components of the carbonate system are considered potential key variables influencing for instance calcium carbonate precipitation in marine calcifiers such as coccolithophores, foraminifera, corals, mollusks and echinoderms. Unravelling the sensitivities of marine organisms and ecosystems to CO2 induced ocean acidification (OA) requires well-controlled experimental setups and accurate carbonate system manipulations. Here we describe and analyse the chemical changes involved in the two basic approaches for carbonate chemistry manipulation, i.e. changing DIC at constant total alkalinity (TA) and changing TA at constant DIC. Furthermore, we briefly introduce several methods to experimentally manipulate DIC and TA. Finally, we examine responses obtained with both approaches using published results for the coccolithophore Emiliania huxleyi. We conclude that under most experimental conditions in the context of ocean acidification DIC and TA manipulations yield similar changes in all parameters of the carbonate system, which implies direct comparability of data obtained with the two basic approaches for CO2 perturbation.

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Winter measurements of biogeochemical parameters in the Rockall Trough (2009–2012)

Earth System Science Data Discussions ◽

10.5194/essdd-6-389-2013 ◽

2013 ◽

Vol 6 (2) ◽

pp. 389-409

Author(s):

T. McGrath ◽

C. Kivimäe ◽

E. McGovern ◽

R. R. Cave ◽

E. Joyce

Keyword(s):

Dissolved Oxygen ◽

Water Column ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Total Alkalinity ◽

Dissolved Inorganic Nutrients ◽

Chemical Signatures ◽

Rockall Trough ◽

Biogeochemical Parameters ◽

Oxidised Nitrogen

Abstract. This paper describes the sampling and analysis of biogeochemical parameters collected in the Rockall Trough in January/February of 2009, 2010, 2011 and 2012. Sampling was carried out across two transects, one southern and one northern transect each year. Samples for dissolved inorganic carbon (DIC) and total alkalinity (TA) were taken alongside salinity, dissolved oxygen and dissolved inorganic nutrients (total-oxidised nitrogen, nitrite, phosphate and silicate) to describe the chemical signatures of the various water masses in the region. These were taken at regular intervals through the water column. The 2009 and 2010 data are available on the CDIAC database.

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Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

The Cryosphere ◽

10.5194/tc-10-2173-2016 ◽

2016 ◽

Vol 10 (5) ◽

pp. 2173-2189 ◽

Cited By ~ 10

Author(s):

Nicolas-Xavier Geilfus ◽

Ryan J. Galley ◽

Brent G. T. Else ◽

Karley Campbell ◽

Tim Papakyriakou ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Carbon Dynamics ◽

Total Alkalinity ◽

Main Process ◽

Saturation State ◽

Ice Growth ◽

Ice Melt

Abstract. The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice–seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmolkg−1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64–66 µmolkg−1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 µmolkg−1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and in winter in ice-covered areas, at the time when Ωaragonite is smallest.

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Coral calcifying fluid pH is modulated by seawater carbonate chemistry not solely seawater pH

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.1669 ◽

2017 ◽

Vol 284 (1847) ◽

pp. 20161669 ◽

Cited By ~ 35

Author(s):

S. Comeau ◽

E. Tambutté ◽

R. C. Carpenter ◽

P. J. Edmunds ◽

N. R. Evensen ◽

...

Keyword(s):

Dissolved Inorganic Carbon ◽

Reef Coral ◽

Total Alkalinity ◽

Published Data ◽

Carbonate Chemistry ◽

Stylophora Pistillata ◽

Coral Calcification ◽

Seawater Ph ◽

Constant Ph ◽

Seawater Carbonate Chemistry

Reef coral calcification depends on regulation of pH in the internal calcifying fluid (CF) in which the coral skeleton forms. However, little is known about calcifying fluid pH (pH CF ) regulation, despite its importance in determining the response of corals to ocean acidification. Here, we investigate pH CF in the coral Stylophora pistillata in seawater maintained at constant pH with manipulated carbonate chemistry to alter dissolved inorganic carbon (DIC) concentration, and therefore total alkalinity (A T ). We also investigate the intracellular pH of calcifying cells, photosynthesis, respiration and calcification rates under the same conditions. Our results show that despite constant pH in the surrounding seawater, pH CF is sensitive to shifts in carbonate chemistry associated with changes in [DIC] and [A T ], revealing that seawater pH is not the sole driver of pH CF . Notably, when we synthesize our results with published data, we identify linear relationships of pH CF with the seawater [DIC]/[H + ] ratio, [A T ]/ [H + ] ratio and [ ]. Our findings contribute new insights into the mechanisms determining the sensitivity of coral calcification to changes in seawater carbonate chemistry, which are needed for predicting effects of environmental change on coral reefs and for robust interpretations of isotopic palaeoenvironmental records in coral skeletons.

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Calcification in Three Common Calcified Algae from Phuket, Thailand: Potential Relevance on Seawater Carbonate Chemistry and Link to Photosynthetic Process

Plants ◽

10.3390/plants10112537 ◽

2021 ◽

Vol 10 (11) ◽

pp. 2537

Author(s):

Pimchanok Buapet ◽

Sutinee Sinutok

Keyword(s):

Environmental Changes ◽

Dissolved Inorganic Carbon ◽

Critical Role ◽

Photosynthetic Electron Transport ◽

Marine Ecosystems ◽

Total Alkalinity ◽

Natural Setting ◽

Carbonate Chemistry ◽

Seawater Ph ◽

Seawater Carbonate Chemistry

Calcifying macroalgae contribute significantly to the structure and function of tropical marine ecosystems. Their calcification and photosynthetic processes are not well understood despite their critical role in marine carbon cycles and high vulnerability to environmental changes. This study aims to provide a better understanding of the macroalgal calcification process, focusing on its relevance concerning seawater carbonate chemistry and its relationship to photosynthesis in three dominant calcified macroalgae in Thailand, Padina boryana, Halimeda macroloba and Halimeda opuntia. Morphological and microstructural attributes of the three macroalgae were analyzed and subsequently linked to their calcification rates and responses to inhibition of photosynthesis. In the first experiment, seawater pH, total alkalinity and total dissolved inorganic carbon were measured after incubation of the macroalgae in the light and after equilibration of the seawater with air. Estimations of carbon uptake into photosynthesis and calcification and carbon release into air were obtained thereafter. Our results provide evidence that calcification of the three calcified macroalgae is a potential source of CO2, where calcification by H. opuntia and H. macroloba leads to a greater release of CO2 per biomass weight than P. boryana. Nevertheless, this capacity is expected to vary on a diurnal basis, as the second experiment indicates that calcification is highly coupled to photosynthetic activity. Lower pH as a result of inhibited photosynthesis under darkness imposes more negative effects on H. opuntia and H. macroloba than on P. boryana, implying that they are more sensitive to acidification. These effects were worsened when photosynthesis was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, highlighting the significance of photosynthetic electron transport-dependent processes. Our findings suggest that estimations of the amount of carbon stored in the vegetated marine ecosystems should account for macroalgal calcification as a potential carbon source while considering diurnal variations in photosynthesis and seawater pH in a natural setting.

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CO<sub>2</sub> perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations

Biogeosciences Discussions ◽

10.5194/bgd-6-4441-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 4441-4462 ◽

Cited By ~ 6

Author(s):

K. G. Schulz ◽

J. Barcelos e Ramos ◽

R. E. Zeebe ◽

U. Riebesell

Keyword(s):

Carbon Dioxide ◽

Atmospheric Carbon Dioxide ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Total Alkalinity ◽

Carbonate Chemistry ◽

Surface Ocean ◽

Seawater Carbonate Chemistry ◽

Similarities And Differences ◽

Carbon Dioxide Co2

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Intercomparison of carbonate chemistry measurements on a cruise in northwestern European shelf seas

Biogeosciences ◽

10.5194/bg-11-4339-2014 ◽

2014 ◽

Vol 11 (16) ◽

pp. 4339-4355 ◽

Cited By ~ 20

Author(s):

M. Ribas-Ribas ◽

V. M. C. Rérolle ◽

D. C. E. Bakker ◽

V. Kitidis ◽

G. A. Lee ◽

...

Keyword(s):

Degrees Of Freedom ◽

Dissolved Inorganic Carbon ◽

Maximum Amplitude ◽

Total Alkalinity ◽

Future Research ◽

Carbonate Chemistry ◽

Carbonate System ◽

European Shelf ◽

Shelf Seas ◽

System Variables

Abstract. Four carbonate system variables were measured in surface waters during a cruise aimed at investigating ocean acidification impacts traversing northwestern European shelf seas in the summer of 2011. High-resolution surface water data were collected for partial pressure of carbon dioxide (pCO2; using two independent instruments) and pH using the total pH scale (pHT), in addition to discrete measurements of total alkalinity and dissolved inorganic carbon. We thus overdetermined the carbonate system (four measured variables, two degrees of freedom), which allowed us to evaluate the level of agreement between the variables on a cruise whose main aim was not intercomparison, and thus where conditions were more representative of normal working conditions. Calculations of carbonate system variables from other measurements generally compared well with direct observations of the same variables (Pearson's correlation coefficient always greater than or equal to 0.94; mean residuals were similar to the respective accuracies of the measurements). We therefore conclude that four of the independent data sets of carbonate chemistry variables were of high quality. A diurnal cycle with a maximum amplitude of 41 μatm was observed in the difference between the pCO2 values obtained by the two independent analytical pCO2 systems, and this was partly attributed to irregular seawater flows to the equilibrator and partly to biological activity inside the seawater supply and one of the equilibrators. We discuss how these issues can be addressed to improve carbonate chemistry data quality on future research cruises.

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Concomitant ocean acidification and increasing total alkalinity at a coastal site in the NW Mediterranean Sea (2007-2015)

10.5194/os-2016-71 ◽

2016 ◽

Cited By ~ 1

Author(s):

Lydia Kapsenberg ◽

Samir Alliouane ◽

Frédéric Gazeau ◽

Laure Mousseau ◽

Jean-Pierre Gattuso

Keyword(s):

Ocean Acidification ◽

Mediterranean Sea ◽

Dissolved Inorganic Carbon ◽

Coastal Ocean ◽

Total Alkalinity ◽

Global Ocean ◽

Coastal Zones ◽

Carbonate Chemistry ◽

Nw Mediterranean ◽

Nw Mediterranean Sea

Abstract. Monitoring of global ocean change is necessary in coastal zones due to their physical and biological complexity. Here, we document changes in coastal carbonate chemistry at the coastal time-series station, Point B, in the NW Mediterranean Sea from 2007 through 2015 at 1 and 50 m. The rate of surface ocean acidification (−0.0028 ± 0.0003 units pHT yr−1) was faster-than-expected based on atmospheric carbon dioxide forcing alone. Changes in carbonate chemistry were predominantly driven by an increase in total dissolved inorganic carbon (CT, +2.97 ± 0.20 μmol kg−1 yr−1), > 50 % of which was buffered by a synchronous increase in total alkalinity (AT, +2.08 ± 0.19 μmol kg−1 yr−1). The increase in AT was unrelated to salinity and its cause remains to be identified. Interestingly, concurrent increases in AT and CT were most rapid from May to July. Changes at 50 m were slower compared to 1 m. It seems therefore likely that changes in coastal AT cycling via a shallow coastal process gave rise to these observations. This study exemplifies the importance of understanding coastal ocean acidification through localized biogeochemical cycling that extends beyond simple air-sea gas exchange dynamics, in order to make relevant predictions about future coastal ocean change and ecosystem function.

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