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

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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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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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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Carbonate System Parameters of an Algal-dominated Reef along West Maui

10.5194/bg-2018-35 ◽

2018 ◽

Cited By ~ 1

Author(s):

Nancy G. Prouty ◽

Kimberly K. Yates ◽

Nathan Smiley ◽

Chris Gallagher ◽

Olivia Cheriton ◽

...

Keyword(s):

Coral Reef ◽

Reef Flat ◽

Sampling Period ◽

Total Alkalinity ◽

Carbonate Chemistry ◽

Diurnal Variability ◽

Carbon Chemistry ◽

Sources Of Pollution ◽

Seawater Ph ◽

Chemistry Dynamics

Abstract. Constraining coral reef metabolism and carbon chemistry dynamics are fundamental for understanding and predicting reef vulnerability to rising coastal CO2 concentrations and decreasing seawater pH. However, few studies exist along reefs occupying densely inhabited shorelines with known input from land-based sources of pollution. The shallow coral reefs off Kahekili, West Maui, are exposed to nutrient-enriched, low-pH submarine groundwater discharge (SGD) and are particularly vulnerable to the compounding stressors from land-based sources of pollution and lower seawater pH. To constrain the carbonate chemistry system, nutrients and carbonate chemistry were measured along the Kahekili reef flat every 4 h over a 6-d sampling period in March 2016. Abiotic process – primarily SGD fluxes – controlled the carbonate chemistry adjacent to the primary SGD vent site, with nutrient-laden freshwater decreasing pH levels and favoring undersaturated aragonite saturation (Ωarag) conditions. In contrast, diurnal variability in the carbonate chemistry at other sites along the reef flat was driven by reef community metabolism. Superimposed on the diurnal signal was a transition during the second sampling period to a surplus of total alkalinity (TA) and dissolved inorganic carbon (DIC) compared to ocean end-member TA and DIC measurements. A shift from net community production and calcification to net respiration and carbonate dissolution was identified. This transition occurred during a period of increased SGD-driven nutrient loading, lower wave height, and reduced current speeds. This detailed study of carbon chemistry dynamics highlights the need to incorporate local effects of nearshore oceanographic processes into predictions of coral reef vulnerability and resilience.

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Acid–base physiology over tidal periods in the mussel Mytilus edulis : size and temperature are more influential than seawater pH

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.2863 ◽

2019 ◽

Vol 286 (1897) ◽

pp. 20182863 ◽

Cited By ~ 2

Author(s):

Stephanie Mangan ◽

Rod W. Wilson ◽

Helen S. Findlay ◽

Ceri Lewis

Keyword(s):

Mytilus Edulis ◽

Environmental Changes ◽

Interactive Effect ◽

Marine Biota ◽

Acid Base ◽

Tidal Cycles ◽

Seawater Ph ◽

Seawater Carbonate Chemistry ◽

Two Populations

Ocean acidification (OA) studies to date have typically used stable open-ocean pH and CO 2 values to predict the physiological responses of intertidal species to future climate scenarios, with few studies accounting for natural fluctuations of abiotic conditions or the alternating periods of emersion and immersion routinely experienced during tidal cycles. Here, we determine seawater carbonate chemistry and the corresponding in situ haemolymph acid–base responses over real time for two populations of mussel ( Mytilus edulis ) during tidal cycles, demonstrating that intertidal mussels experience daily acidosis during emersion. Using these field data to parameterize experimental work we demonstrate that air temperature and mussel size strongly influence this acidosis, with larger mussels at higher temperatures experiencing greater acidosis. There was a small interactive effect of prior immersion in OA conditions (pH NBS 7.7/pCO 2 930 µatm) such that the haemolymph pH measured at the start of emersion was lower in large mussels exposed to OA. Critically, the acidosis induced in mussels during emersion in situ was greater (ΔpH approximately 0.8 units) than that induced by experimental OA (ΔpH approximately 0.1 units). Understanding how environmental fluctuations influence physiology under current scenarios is critical to our ability to predict the responses of key marine biota to future environmental changes.

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PyCO2SYS v1.7: marine carbonate system calculations in Python

10.5194/gmd-2021-159 ◽

2021 ◽

Author(s):

Matthew P. Humphreys ◽

Ernie R. Lewis ◽

Jonathan D. Sharp ◽

Denis Pierrot

Keyword(s):

Automatic Differentiation ◽

Dissolved Inorganic Carbon ◽

Total Alkalinity ◽

Carbonate System ◽

Chemical Equilibria ◽

Ph Response ◽

Carbonate Ion ◽

Seawater Ph ◽

Marine Carbonate ◽

Carbon Dioxide Co2

Abstract. Oceanic dissolved inorganic carbon (TC) is the largest pool of carbon that interacts considerably with the atmosphere on human timescales. Oceanic TC is increasing through uptake of anthropogenic carbon dioxide (CO2), and seawater pH is decreasing as a consequence. Both the exchange of CO2 between ocean and atmosphere and the pH response are governed by a set of parameters that interact through chemical equilibria, collectively known as the marine carbonate system. To investigate these processes, at least two of the marine carbonate system's parameters are typically measured – most commonly, two from TC, total alkalinity (AT), pH, and seawater CO2 fugacity (fCO2; or its partial pressure, pCO2, or its dry-air mole fraction, xCO2) – from which the remaining parameters can be calculated and the equilibrium state of seawater solved. Several software tools exist to carry out these calculations, but no fully functional and rigorously validated tool was previously available for Python, a popular scientific programming language. Here, we present PyCO2SYS, a Python package intended to fill this capability gap. We describe the elements of PyCO2SYS that have been inherited from the existing CO2SYS family of software and explain subsequent adjustments and improvements. For example, PyCO2SYS uses automatic differentiation to solve the marine carbonate system and calculate chemical buffer factors, ensuring that the effect of every solute and reaction is accurately included in all its results. We validate PyCO2SYS with internal consistency tests and comparisons against other software, showing that PyCO2SYS produces results that are either virtually identical or different for known reasons, with the differences negligible for all practical purposes. We discuss new insights that arose during the development process, for example that the marine carbonate system cannot be unambiguously solved from the total alkalinity and carbonate ion parameter pair. Finally, we consider potential future developments to PyCO2SYS and discuss the outlook for this and other software for solving the marine carbonate system. The code for PyCO2SYS is distributed via GitHub (https://github.com/mvdh7/PyCO2SYS) under the GNU General Public License v3, archived on Zenodo (Humphreys et al., 2021), and documented online (https://PyCO2SYS.readthedocs.io).

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Continuous fluorescence-based monitoring of seawater pH in a temperate estuary

10.5194/bg-2017-222 ◽

2017 ◽

Author(s):

John W. Runcie ◽

Christian Krause ◽

Sergio A. Torres Gabarda ◽

Maria Byrne

Keyword(s):

Surface Waters ◽

Ph Monitoring ◽

Good Resolution ◽

Carbonate Chemistry ◽

Temperature Drift ◽

Seawater Ph ◽

Calcite Saturation ◽

Seawater Carbonate Chemistry ◽

Diel Variability ◽

Diel Fluctuations

Abstract. Abstract. Electrical conductivity (salinity), temperature and fluorescence-based measurements of pH were employed to examine diel fluctuations in seawater carbonate chemistry of surface waters in Sydney Harbour over two multiple-day periods. The fluorescence-based technique provided a useful time-series for pH. Alkalinity with pH and temperature were used to calculate the degree of aragonite and calcite saturation (ΩCa and ΩAr respectively). Alkalinity was determined from an alkalinity-salinity relationship. Variation in pH over minute- to hour-long periods was distinguishable from background variability. Diel variability in pH, Ωara and Ωcal showed a clear pattern that appeared to correlate with both salinity and temperature. Drift due to photodegradation of the fluorophore was minimised by reducing exposure to ambient light. ΩCa and ΩAr fluctuated approximately on a daily cycle. The net result of changes in pH, salinity and temperature combined to influence seawater carbonate chemistry. The fluorescence-based pH monitoring technique is simple, provides good resolution and is unaffected by moving parts or leaching of solutions over time. The use of optics is pressure insensitive, making this approach to ocean acidification monitoring well suited to deepwater applications.

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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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A Unique Diel Pattern in Carbonate Chemistry in the Seagrass Meadows of Dongsha Island: The Enhancement of Metabolic Carbonate Dissolution in a Semienclosed Lagoon

Frontiers in Marine Science ◽

10.3389/fmars.2021.717685 ◽

2021 ◽

Vol 8 ◽

Author(s):

Wen-Chen Chou ◽

Lan-Feng Fan ◽

Chang-Chang Yang ◽

Ying-Hsuan Chen ◽

Chin-Chang Hung ◽

...

Keyword(s):

Total Alkalinity ◽

Carbonate Dissolution ◽

Diel Pattern ◽

Carbonate Chemistry ◽

Seagrass Meadows ◽

Diel Variations ◽

Seawater Carbonate Chemistry ◽

Aerobic And Anaerobic ◽

Organic Matter Loading ◽

Photosynthesis And Respiration

In contrast to other seagrass meadows where seawater carbonate chemistry generally shows strong diel variations with higher pH but lower partial pressure of CO2 (pCO2) during the daytime and lower pH but higher pCO2 during nighttime due to the alternation in photosynthesis and respiration, the seagrass meadows of the inner lagoon (IL) on Dongsha Island had a unique diel pattern with extremely high pH and low pCO2 across a diel cycle. We suggest that this distinct diel pattern in pH and pCO2 could be associated with the enhancement of total alkalinity (TA) production coupled to carbonate sediment dissolution in a semienclosed lagoon. The confinement of the IL may hamper water exchange and seagrass detritus export to the adjacent open ocean, which may result in higher organic matter loading to the sediments, and longer residence time of the water in the IL, accompanied by microbial respiration (both aerobic and anaerobic) that may reduce carbonate saturation level to drive carbonate dissolution and thus TA elevation, thereby forming such a unique diel pattern in carbonate chemistry. This finding further highlights the importance of considering TA production through metabolic carbonate dissolution when evaluating the potential of coastal blue carbon ecosystems to buffer ocean acidification and to absorb atmospheric CO2, in particular in a semienclosed setting.

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

Aquatic Geochemistry ◽

10.1007/s10498-020-09378-8 ◽

2020 ◽

Vol 26 (4) ◽

pp. 375-399

Author(s):

Theodor Kindeberg ◽

Nicholas R. Bates ◽

Travis A. Courtney ◽

Tyler Cyronak ◽

Alyssa Griffin ◽

...

Keyword(s):

Water Column ◽

Dissolved Inorganic Carbon ◽

Total Alkalinity ◽

Carbonate Chemistry ◽

Carbon Cycles ◽

Mission Bay ◽

High Concentrations ◽

Study Sites ◽

Tidal Signal ◽

Sediment Permeability

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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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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