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1. Examining the impacts of elevated, variable pCO2 on larval Pacific razor clams (Siliqua patula) in Alaska

   https://doi.org/10.3389/fmars.2024.1253702  

   Alcantar, Marina W; Hetrick, Jeff; Ramsay, Jacqueline; Kelley, Amanda L (January 2024, Frontiers in Marine Science)

   An increase in anthropogenic carbon dioxide is driving oceanic chemical shifts resulting in a long-term global decrease in ocean pH, colloquially termed ocean acidification (OA). Previous studies have demonstrated that OA can have negative physiological consequences for calcifying organisms, especially during early life-history stages. However, much of the previous research has focused on static exposure to future OA conditions, rather than variable exposure to elevatedpCO₂, which is more ecologically relevant for nearshore species. This study examines the effects of OA on embryonic and larval Pacific razor clams (Siliqua patula), a bivalve that produces a concretion during early shell development. Larvae were spawned and cultured over 28 days under threepCO₂treatments: a static highpCO₂of 867 μatm, a variable, dielpCO₂of 357 to 867 μatm, and an ambientpCO₂of 357 μatm. Our results indicate that the calcium carbonate polymorphism of the concretion phase ofS. patulawas amorphous calcium carbonate which transitioned to vaterite during the advanced D-veliger stage, with a final polymorphic shift to aragonite in adults, suggesting an increased vulnerability to dissolution under OA. However, exposure to elevatedpCO₂appeared to accelerate the transition of larvalS. patulafrom the concretion stage of shell development to complete calcification. There was no significant impact of OA exposure to elevated or variablepCO₂conditions onS. patulagrowth or HSP70 and calmodulin gene expression. This is the first experimental study examining the response of a concretion producing bivalve to future predicted OA conditions and has important implications for experimentation on larval mollusks and bivalve management. 

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2. Pelagic calcium carbonate production and shallow dissolution in the North Pacific Ocean

   https://doi.org/10.1038/s41467-023-36177-w  

   Ziveri, Patrizia; Gray, William Robert; Anglada-Ortiz, Griselda; Manno, Clara; Grelaud, Michael; Incarbona, Alessandro; Rae, James William Buchanan; Subhas, Adam V.; Pallacks, Sven; White, Angelicque; et al (February 2023, Nature Communications)

   Abstract Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmospheric CO₂. Surprisingly, references to the absolute and relative contribution of these organisms to calcium carbonate production are lacking. Here we report quantification of pelagic calcium carbonate production in the North Pacific, providing new insights on the contribution of the three main planktonic calcifying groups. Our results show that coccolithophores dominate the living calcium carbonate (CaCO₃) standing stock, with coccolithophore calcite comprising ~90% of total CaCO₃production, and pteropods and foraminifera playing a secondary role. We show that pelagic CaCO₃production is higher than the sinking flux of CaCO₃at 150 and 200 m at ocean stations ALOHA and PAPA, implying that a large portion of pelagic calcium carbonate is remineralised within the photic zone; this extensive shallow dissolution explains the apparent discrepancy between previous estimates of CaCO₃production derived from satellite observations/biogeochemical modeling versus estimates from shallow sediment traps. We suggest future changes in the CaCO₃cycle and its impact on atmospheric CO₂will largely depend on how the poorly-understood processes that determine whether CaCO₃is remineralised in the photic zone or exported to depth respond to anthropogenic warming and acidification. 

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3. Controls on buffering and coastal acidification in a temperate estuary

   https://doi.org/10.1002/lno.12085  

   Hunt, Christopher W.; Salisbury, Joseph E.; Vandemark, Douglas (June 2022, Limnology and Oceanography)

   Abstract Estuaries may be uniquely susceptible to the combined acidification pressures of atmospherically driven ocean acidification (OA), biologically driven CO 2 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 (pCO 2 ) 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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4. Organic alkalinity distributions, characteristics, and application to carbonate system calculations in estuarine and coastal systems

   https://doi.org/10.1002/lno.12761  

   Hunt, Christopher_W; Salisbury, Joseph_E; Liu, Xuewu; Byrne, Robert_H (December 2024, Limnology and Oceanography)

   Abstract The capacity of aquatic systems to buffer acidification depends on the sum contributions of various chemical species to total alkalinity (TA). Major TA contributors are inorganic, with carbonate and bicarbonate considered the most important. However, growing evidence shows that many rivers, estuaries, and coastal waters contain dissolved organic molecules with charge sites that create organic alkalinity (OrgAlk). This study describes the first comparison of (1) OrgAlk distributions and (2) acid–base properties in contrasting estuary‐plume systems: the Pleasant (Maine, USA) and the St. John (New Brunswick, CA). The substantial concentrations of OrgAlk in each estuary were sometimes not conservative with salinity and typically associated with very low pH. Two approaches to OrgAlk measurement showed consistent differences, indicating acid–base characteristics inconsistent with the TA definition. The OrgAlk fraction of TA ranged from 78% at low salinity to less than 0.4% in the coastal ocean endmember. Modeling of titration data identified three groups of organic charge sites, with mean acid–base dissociation constants (pK_a) of 4.2 (± 0.5), 5.9 (± 0.7) and 8.5 (± 0.2). These represented 21% (± 9%), 8% (± 5%), and 71% (± 11%) of titrated organic charge groups. Including OrgAlk, pK_a, and titrated organic charge groups in carbonate system calculations improved estimates of pH. However, low and medium salinity, organic‐rich samples demonstrated persistent offsets in calculated pH, even using dissolved inorganic carbon and CO₂partial pressure as inputs. These offsets show the ongoing challenge of carbonate system intercomparisons in organic rich systems whereby new techniques and further investigations are needed to fully account for OrgAlk in TA titrations. 

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5. Ocean Acidification and Climate Change as Determinants of Marine Phytoplankton Communities along the U.S. East Coast

   Huntsman, C; Gomes, H; Goes, J (December 2024, Proceedings American Geophysical Union)

   Goes, J (Ed.)

   As climate change and carbon dioxide (CO2) emissions continue to alter oceans, it is critical to understand how marine life will respond. Atmospheric CO2 dissolves into ocean water, beginning a series of chemical reactions that lower pH and deplete free carbonate ions—this phenomenon is called ocean acidification (OA). Marine phytoplankton impact ocean chemistry by performing photosynthesis and cycling carbon. They also form the base of marine food webs and are thus implicated in fishery productivity and human food security. As part of the National Oceanic and Atmospheric Administration's Ocean Acidification Program, this research aimed to document the progression of OA and its effects on marine life. The project combined data analysis, remote sensing, and laboratory experiments to understand phytoplankton community change. Data from scientific cruises in 2018 and 2022 were compared to investigate inter-annual variability in phytoplankton distribution, size, and efficiency. These cruises measured chemical and biological indicators, including pH, temperature, and pigments associated with particular plankton taxa. Water samples collected at various depths were imaged to gather phytoplankton cell counts. The findings demonstrate a clear pH gradient along the East Coast, with northern waters being significantly more acidic than southern waters. This difference is primarily driven by increased precipitation, land characteristics, and ocean current dynamics. Biological community structure and the photosynthetic efficiency of the phytoplankton sampled along the coast varied with latitude and time, demonstrating that continued climate change and intensifying acidification will affect phytoplankton distribution and consumption of CO2, with reverberations throughout the ocean and climate systems at large. 

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