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1. Ocean acidification alters properties of the exoskeleton in adult Tanner crabs, Chionoecetes bairdi

   https://doi.org/10.1242/jeb.232819  

   Dickinson, Gary H. ; Bejerano, Shai ; Salvador, Trina ; Makdisi, Christine ; Patel, Shrey ; Long, W. Christopher ; Swiney, Katherine M. ; Foy, Robert J. ; Steffel, Brittan V. ; Smith, Kathryn E. ; et al ( February 2021 , Journal of Experimental Biology)

   null (Ed.)

   ABSTRACT Ocean acidification can affect the ability of calcifying organisms to build and maintain mineralized tissue. In decapod crustaceans, the exoskeleton is a multilayered structure composed of chitin, protein and mineral, predominately magnesian calcite or amorphous calcium carbonate (ACC). We investigated the effects of acidification on the exoskeleton of mature (post-terminal-molt) female southern Tanner crabs, Chionoecetes bairdi. Crabs were exposed to one of three pH levels – 8.1, 7.8 or 7.5 – for 2 years. Reduced pH led to a suite of body region-specific effects on the exoskeleton. Microhardness of the claw was 38% lower in crabs at pH 7.5 compared with those at pH 8.1, but carapace microhardness was unaffected by pH. In contrast, reduced pH altered elemental content in the carapace (reduced calcium, increased magnesium), but not the claw. Diminished structural integrity and thinning of the exoskeleton were observed at reduced pH in both body regions; internal erosion of the carapace was present in most crabs at pH 7.5, and the claws of these crabs showed substantial external erosion, with tooth-like denticles nearly or completely worn away. Using infrared spectroscopy, we observed a shift in the phase of calcium carbonate present in the carapace of pH 7.5 crabs: a mix of ACC and calcite was found in the carapace of crabs at pH 8.1, whereas the bulk of calcium carbonate had transformed to calcite in pH 7.5 crabs. With limited capacity for repair, the exoskeleton of long-lived crabs that undergo a terminal molt, such as C. bairdi, may be especially susceptible to ocean acidification. 

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2. Temperature but not ocean acidification affects energy metabolism and enzyme activities in the blue mussel, Mytilus edulis

   https://doi.org/10.1002/ece3.7289  

   Matoo, Omera B. ; Lannig, Gisela ; Bock, Christian ; Sokolova, Inna M. ( March 2021 , Ecology and Evolution)

   In mosaic marine habitats, such as intertidal zones, ocean acidification (OA) is exacerbated by high variability of pH, temperature, and biological CO₂production. The nonlinear interactions among these drivers can be context‐specific and their effect on organisms in these habitats remains largely unknown, warranting further investigation.

   We were particularly interested inMytilus edulis(the blue mussel) from intertidal zones of the Gulf of Maine (GOM), USA, for this study. GOM is a hot spot of global climate change (average sea surface temperature (SST) increasing by >0.2°C/year) with >60% decline in mussel population over the past 40 years.

   Here, we utilize bioenergetic underpinnings to identify limits of stress tolerance inM. edulisfrom GOM exposed to warming and OA. We have measured whole‐organism oxygen consumption rates and metabolic biomarkers in mussels exposed to control and elevated temperatures (10 vs. 15°C, respectively) and current and moderately elevatedP_CO2levels (~400 vs. 800 µatm, respectively).

   Our study demonstrates that adultM. edulisfrom GOM are metabolically resilient to the moderate OA scenario but responsive to warming as seen in changes in metabolic rate, energy reserves (total lipids), metabolite profiles (glucose and osmolyte dimethyl amine), and enzyme activities (carbonic anhydrase and calcium ATPase).

   Our results are in agreement with recent literature that OA scenarios for the next 100–300 years do not affect this species, possibly as a consequence of maintaining its in vivo acid‐base balance.

    

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3. Parental exposure of Eastern oysters ( Crassostrea virginica ) to elevated pCO2 mitigates its negative effects on early larval shell growth and morphology

   https://doi.org/10.1002/lno.12162  

   McNally, Elise M. ; Downey‐Wall, Alan M. ; Titmuss, F. Dylan ; Cortina, Camila ; Lotterhos, Kathleen ; Ries, Justin B. ( June 2022 , Limnology and Oceanography)

   Larvae of marine calcifying organisms are particularly vulnerable to the adverse effects of elevatedpCO₂on shell formation because of their rapid calcification rates, reduced capacity to isolate calcifying fluid from seawater, and use of more soluble polymorphs of calcium carbonate. However, parental exposure to elevatedpCO₂could benefit larval shell formation through transgenerational plastic responses. We examined the capacity of intergenerational exposure to mitigate the adverse effects of elevatedpCO₂on Eastern oyster (Crassostrea virginica) early larval shell growth, shell morphology, and survival. Adult oysters were exposed to control (572 ppmpCO₂) or elevatedpCO₂(2827 ppmpCO₂) conditions for 30 d during reproductive conditioning. Offspring from each parental treatment were produced using a partial North Carolina II cross design and grown under control and elevatedpCO₂conditions for 3 d. We found evidence of transgenerational plasticity in early larval shell growth and morphology, but not in survival, in response to the parentalpCO₂exposure. Larvae from parents exposed to elevatedpCO₂exhibited faster shell growth rates than larvae from control parents, with this effect being significantly larger when larvae were grown under elevatedpCO₂compared to control conditions. Parental exposure to elevatedpCO₂, however, was insufficient to completely counteract the adverse effects of the prescribed elevatedpCO₂on early larval shell formation and survival. Nevertheless, these results suggest that oysters have some capacity to acclimate intergenerationally to ocean acidification.

    

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4. Consequences of warming and acidification for the temperate articulated coralline alga, Calliarthron tuberculosum (Florideophyceae, Rhodophyta)

   https://doi.org/10.1111/jpy.13272  

   Donham, Emily M. ; Hamilton, Scott L. ; Aiello, Ivano ; Price, Nichole N. ; Smith, Jennifer E. ; Amsler, ed., C. ( July 2022 , Journal of Phycology)

   Global climate changes, such as warming and ocean acidification (OA), are likely to negatively impact calcifying marine taxa. Abundant and ecologically important coralline algae may be particularly susceptible to OA; however, multi‐stressor studies and those on articulated morphotypes are lacking. Here, we use field observations and laboratory experiments to elucidate the impacts of warming and acidification on growth, calcification, mineralogy, and photophysiology of the temperate articulated coralline alga,Calliarthron tuberculosum.We conducted a 4‐week fully factorial mesocosm experiment exposing individuals from a southern CA kelp forest to current and future temperature and pH/pCO₂conditions (+2°C, −0.5 pH units). Calcification was reduced under warming (70%) and further reduced by highpCO₂or highpCO₂x warming (~150%). Growth (change in linear extension and surface area) was reduced by warming (40% and 50%, respectively), highpCO₂(20% and 40%, respectively), and highpCO₂x warming (50% and 75%, respectively). The maximum photosynthetic rate (P_max) increased by 100% under highpCO₂conditions, but we did not detect an effect ofpCO₂or warming on photosynthetic efficiency (α). We also did not detect the effect of warming orpCO₂on mineralogy. However, variation in Mg incorporation in cell walls of different cell types (i.e., higher mol % Mg in cortical vs. medullary) was documented for the first time in this species. These results support findings from a growing body of literature suggesting that coralline algae are often more negatively impacted by warming than OA, with the potential for antagonistic effects when factors are combined.

    

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5. 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)

   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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