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pH or pCO 2 are usually taken to study the impact of ocean acidification on molluscs. Here we studied the different impact of seawater carbonate parameters on embryonic development and calcification of the Pacific abalone (Haliotis discus hannai). Early embryonic development was susceptible to elevated pCO 2 level. Larvae hatching duration was positively and hatching rate was negatively correlated with the pCO 2 level, respectively. Calcium carbonate (CaCO 3 ) deposition of larval shell was found to be susceptible to calcium carbonate saturation state (Ω) rather than pCO 2 or pH. Most larvae incubated in seawater with Ω arag  = 1.5 succeeded in shell formation, even when seawater pCO 2 level was higher than 3700 μatm and pH T was close to 7.4. Nevertheless, larvae failed to generate CaCO 3 in seawater with Ω arag ≤ 0.52 and control level of pCO 2 , while seawater DIC level was lowered (≤ 852 μmol/kg). Surprisingly, some larvae completed CaCO 3 deposition in seawater with Ω arag  = 0.6 and slightly elevated DIC (2266 μmol/kg), while seawater pCO 2 level was higher than 2700 μatm and pH T was lower than 7.3. This indicates that abalone may be capable of regulating carbonate chemistry to support shell formation, however, the capability was limited as surging pCO 2 level lowered growth rate and jeopardized the integrity of larval shells. Larvae generated thicker shell in seawater with Ω arag  = 5.6, while adult abalone could not deposit CaCO 3 in seawater with Ω arag  = 0.29 and DIC = 321 μmol/kg. This indicates that abalone may lack the ability to directly remove or add inorganic carbon at the calcifying sites. In conclusion, different seawater carbonate parameters play different roles in affecting early embryonic development and shell formation of the Pacific abalone, which may exhibit limited capacity to regulate carbonate chemistry., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Greenland's fjords and coastal waters are highly productive and sustain important fisheries. However, retreating glaciers and increasing meltwater are changing fjord circulation and biogeochemistry, which may threaten future productivity. The freshening of Greenland fjords caused by unprecedented melting of the Greenland Ice Sheet may alter carbonate chemistry in coastal waters, influencing CO 2 uptake and causing biological consequences from acidification. However, few studies to date explore the current acidification state in Greenland coastal waters. Here we present the first-ever large-scale measurements of carbonate system parameters in 16 Greenlandic fjords and seek to identify the drivers of acidification state in these freshening ecosystems. Aragonite saturation state (Ω), a proxy for ocean acidification, was calculated from dissolved inorganic carbon (DIC) and total alkalinity from fjords along the east and west coast of Greenland spanning 68-75°N. Aragonite saturation was primarily >1 in the surface mixed layer. However, undersaturated-or corrosive--conditions (Ω < 1) were observed on both coasts (west: Ω = 0.28-3.11, east: Ω = 0.70-3.07), albeit at different depths. West Greenland fjords were largely corrosive at depth while undersaturation in East Greenland fjords was only observed in surface waters. This reflects a difference in the coastal boundary conditions and mechanisms driving acidification state. We suggest that advection of Sub Polar Mode Water and accumulation of DIC from organic matter decomposition drive corrosive conditions in the West, while freshwater alkalinity dilution drives acidification in the East. The presence of marine terminating glaciers also impacted local acidification states by influencing fjord circulation: upwelling driven by subglacial discharge brought corrosive bottom waters to shallower depths. Meanwhile, discharge from land terminating glaciers strengthened stratification and diluted alkalinity. Regardless of the drivers in each system, increasing freshwater discharge will likely lower carbonate saturation states and impact biotic and abiotic carbon uptake in the future., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Shallow submarine gas vents in Levante Bay, Vulcano Island (Italy), emit around 3.6t CO2 per day providing a natural laboratory for the study of biogeochemical processes related to seabed CO2 leaks and ocean acidification. The main physico-chemical parameters (T, pH and Eh) were measured at more than 70 stations with 40 seawater samples were collected for chemical analyses. The main gas vent area had high concentrations of dissolved hydrothermal gases, low pH and negative redox values all of which returned to normal seawater values at distances of about 400m from the main vents. Much of the bay around the vents is corrosive to calcium carbonate; the north shore has a gradient in seawater carbonate chemistry that is well suited to studies of the effects of long-term increases in CO2 levels. This shoreline lacks toxic compounds (such as H2S) and has a gradient in carbonate saturation states., (Copyright © 2013 Elsevier Ltd. All rights reserved.)