Archive for December, 2020

Evaluation of the temperature dependence of dissociation constants for the marine carbon system using pH and certified reference materials


  • CO2 system calculation recommendations are made for near-surface ocean-open seawater.
  • Nearly all K1 and K2 evaluated were internally consistent within the accuracy of pH measurements.
  • Measurements of pH at lower temperatures (≤ 20 °C) are more internally consistent than higher temperatures.


Due to the uptake of anthropogenic carbon dioxide (CO2) from the atmosphere, and the resulting ocean acidification, long term monitoring of the marine carbon cycle is of utmost importance and requires high precision and accuracy across many laboratories over several decades. Despite this, many uncertainties still remain in carbon system measurements and calculations. Calculations of the carbon system are facilitated by publicly available software, but the large number of options for various constants make data and study inter-comparability challenging. Here, the carbon system is evaluated using internal consistency calculations and spectrophotometric pH measurements on two batches of Certified Reference Material over the full oceanic range of temperatures (−1.7–40 °C). The choice of formulation for the bisulfate dissociation constant is insignificant over at least the salinity range of the CRM (S = 33.4–33.8). The choice of formulation of the hydrogen fluoride dissociation constant adds a small amount of uncertainty, but the best option is unclear. The total boron concentration significantly impacts the calculated pH, with the value of Lee et al. (2010) being more internally consistent and, thus, recommended. Of the 8 carbonic acid dissociation constant sets evaluated, nearly all remain internally consistent at near-surface open-ocean salinities (~31–36) within the accuracy of pH measurements. Nevertheless, the values of Mehrbach et al. (1973), as refit by Dickson and Millero (1987), and Lueker et al. (2000) were the most internally consistent and therefore are preferred for current surface ocean studies (S ≈ 31–36, T = −1.7–40 °C, fCO2 < 500 μatm). The pH was more internally consistent at lower temperatures than higher temperatures.

Continue reading ‘Evaluation of the temperature dependence of dissociation constants for the marine carbon system using pH and certified reference materials’

Potential acclimatization and adaptive responses of adult and trans-generation coral larvae from a naturally acidified habitat

Coral reefs are one of the most susceptible ecosystems to ocean acidification (OA) caused by increasing atmospheric carbon dioxide (CO2). OA is suspected to impact the calcification rate of corals as well as multiple early life stages including larval and settlement stages. Meanwhile, there is now a strong interest in evaluating if organisms have the potential for acclimatization or adaptation to OA. Here, by taking advantage of a naturally acidified site in Nikko Bay, Palau where corals are presumably exposed to high CO2 conditions for their entire life history, we tested if adult and the next-generation larvae of the brooder coral Pocillopora acuta originating from the high-CO2 site are more tolerant to high CO2 conditions compared to the individuals from a control site. Larvae released from adults collected from the high-CO2 site within the bay and a control site outside the bay were reciprocally cultivated under experimental control or high-CO2 seawater conditions to evaluate their physiology. Additionally, reciprocal transplantation of adult P. acuta corals were conducted between the high-CO2 and control sites in the field. The larvae originating from the control site showed lower Chlorophyll-a content and lipid percentages when reared under high-CO2 compared to control seawater conditions, while larvae originating from the high-CO2 site did not. Additionally, all 10 individuals of adult P. acuta from control site died when transplanted within the bay, while all P. acuta corals within the bay survived at both control and high-CO2 site. Furthermore, P. acuta within the bay showed higher calcification and net photosynthesis rates when exposed to the condition they originated from. These results are one of the first results that indicate the possibility that the long-living corals could enable to show local adaptation to different environmental conditions including high seawater pCO(2).

Continue reading ‘Potential acclimatization and adaptive responses of adult and trans-generation coral larvae from a naturally acidified habitat’

Multiple linear regression models for reconstructing and exploring processes controlling the carbonate system of the northeast US from basic hydrographic data

In the coastal ocean, local carbonate system variability is determined by the interaction between ocean acidification and local processes. Sporadic observations indicate that biological metabolism, river input, and water mass mixing are dominant local processes driving carbonate system variability in northeast US shelf waters. These processes are also reflected in the variability of observed temperature (T), salinity (S), oxygen concentration (O2), and nitrate concentration (NO3). Therefore, regionally specific empirical models can be developed, which relate carbonate system parameters to a combination of basic hydrographic parameters. Here, we develop multiple linear regression models that represent the processes that drive carbonate system variability in the Mid‐Atlantic Bight and Gulf of Maine using observations obtained on three hydrographic surveys in summers between 2007 and 2015. The empirical model equations reveal the observation‐based relationships between carbonate parameters and basic hydrographic variables. Unlike other regions where empirical models have been developed, salinity appears in all models. T is the most important parameter for predicting aragonite saturation state (ΩAR), while S and O2 are most important for predicting pH on total scale (pHT). The basic hydrographic variables explain over 98% of the variability in total alkalinity (TA), dissolved inorganic carbon (DIC), and ΩAR and 89% of the variability in pHT in the calibration data. We recommend applying models that depend on T, S, O2, and NO3 as predictors, which reproduce TA and DIC with R2 > 0.97, ΩAR with R2 > 0.93, and pHT with R2 > 0.77, to reconstruct carbonate system parameters in the region.

Continue reading ‘Multiple linear regression models for reconstructing and exploring processes controlling the carbonate system of the northeast US from basic hydrographic data’

Chapter: Volcanic past cycles indicators: paleoclimatology and extinctions using benthic and planktonic forams community dynamics

The Benthic and planktonic foraminiferal communities’ dynamics as volcanic past cycles indicators are very well placed within the Paleoclimatology and extinctions studies. We have showed a bit, of what is available to explain how communities have evolved in the past. The past volcanic activity has released as much carbon dioxide into the atmosphere as anthropogenic as predicted emissions projections for the twenty-first century and they are linked to increases in carbon dioxide emissions and with faunal patterns, with marine extinctions observed sediment cores after volcanic episodes, and this increase in carbon dioxide and other volcanic gaseous influences on global warming and ocean acidification is responsible for the extinction of three quarters of species on Earth on the past. For example, dinosaurs were pretty much extinct because of “The Deccan Traps”, an igneous province, one of the largest volcanic features on Earth, located on the west-central India, and the Siberian Traps have influenced the end-Permian extinction, in which more than 90% of life on Earth disappeared. Many patterns should be first understood to be able to forecast future climate change scenarios. We can however explain that the modern ongoing carbon dioxide emissions are similar to those that led to the end-Triassic mass extinction. The importance of understanding Earth’s deep water past is predicated on predicting how it will respond to future climate change. The mass extinction and high-stress conditions were explained by the intense Deccan volcanism leading to rapid global warming and cooling, with enhanced weathering, continental runoff, and ocean acidification, resulting in a carbonate crisis in the marine environment. The chronic explosive volcanic activity generated unstable benthic habitat colonized by only a few species. The increase in atmospheric CO2 concentrations lead to decreased pH and carbonate availability in the ocean, known as Ocean Acidification, and the ability of marine invertebrates to tolerate acidity are the ‘windows into the future’ to study. Cores with ashes and tephra in Papua New Guinea (PNG) during Expedition 363 sampled by the IODP show that total foraminiferal diversity was low when volcanic activity was in place detected by the presence of tephra and volcanic ashes. Foraminiferal density and diversity in PNG were high and similar to those observed on the Great Barrier Reef or other sites, however diversity decreases, and show inverse correlation by benthic foraminifera to high presence of ashes and tephra in the past. However, ecological studies from shallow reef environments observed increased foraminiferal dominance of opportunists when corals became rare from chronic or acute anthropogenic influences, for example with sewage and oil spills. Agglutinate taxa that do not rely on calcification will replace calcifying species, and we call it a fauna replacement by invasive species. Density and diversity of agglutinated taxa is also in decline, but are less marked than calcifying taxa in an environment where pH is low. Dissolution of foraminifera seen in marine sediment under elevated pCO2 unravels other direct ecological impacts. Impacts such as dissolution and loss of biogenesis of carbonate by other organisms that are under near-future pCO2 conditions, which will reach a problematic real-time scenario. None of the previous extinctions were as severe as the ecological or even taxonomic extinction in shallow carbonate areas which we are predicting. Because of the rate of increasing pCO2, and unfortunately, we expect that the increase in the temperature in the Holocene and the tendency until 2100 will take us to the warmest Pliocene climate with the unfortunate consequences of living in a warmer than optimum world. The variability based on the frequency and intensity of some events are one of the warmest our world has ever seen, reflecting changes in temperature derived from data from deep sea sediment core samples, and of course shells of benthic and planktonic Forams and other organisms like pollen act as proxies in drilled marine sediment cores reflecting historic climate. A unique fauna of foraminiferal species from these highly opposed environments created by differences in temperature in the past are recorded paleo cycles, of which responds to the amount of ice in the world, due to their high sensitivity to the environmental changes in the modern and past sediments. Here we show that tephra and ashes of IODP Hole U1485A (Exp. 363 WPWP) record a periodicity of explosive volcanism within the last 0.8 Myr. Possible triggering mechanisms for these mass flow deposits include earthquakes and associated tsunamis and shelf/slope sediment instabilities during times of rapid deposition such as can occur during river flood events. Over longer timescales, it is also possible that sea level played a role in the storage and release of sediment from the PNG shelf (although the shelf itself is very narrow) and from the paleo-valley of the Sepik River, which is a relatively large area presently few meters above sea level. Changes in diversity shows balance of alternating deep (cold) and shallow (warm) benthic foraminifera fauna along time in the past. The “at least” five decreases in diversity peaks in the past show that the response of the benthic community to adverse climate is a change in their ecological pattern. These changes can take a whole community and an entire ecosystem to extinctions, and we have already seen five extinctions along Earth’s history. And if history teaches us anything, it is how to react to and prepare for crisis rather than repeat mistakes. Research suggests we are fast approaching disastrous effects of this sixth Anthropocene extinction. However, we can successfully surmount the challenges of biodiversity loss and climate change and dramatically alter the trajectory if we can pinpoint and remediate problems within a near future. With our planet “in crisis”, evidence demonstrates widespread ecological collapse and biodiversity loss. We know that as average temperatures rise and the frequency of extremely warm years increases, the impacts of habitat loss and fragmentation become even more increasingly apparent. We are with without a doubt entering a sixth mass extinction event because of the rapid decline in biodiversity. The majority of these species inhabit environmentally delicate tropical and subtropical areas susceptible to human impacts. This refers to a situation where the extinction of one species affects other species that rely on it for survival, thereby also placing them at a ‘domino effect’ risk of extinction as part of a destructive chain reaction. Stop cutting and burn forests, stop global trade of wild species, study and protect, preserve, and conserve our planet’s biodiversity.

Continue reading ‘Chapter: Volcanic past cycles indicators: paleoclimatology and extinctions using benthic and planktonic forams community dynamics’

Effect of elevated pCO2 on thermal performance of Chattonella marina and Chattonella ovata (Raphidophyceae)

Ocean acidification and warming, identified as environmental concerns likely to be affected by climate change, are crucial determinants of algal growth. The ichthyotoxic raphidophytes Chattonella species are responsible for huge economic losses and environmental impact worldwide. In this study, we investigated the impact of CO2 on the thermal performance curves (TPCs) of Chattonella marina and Chattonella ovata grown under temperatures ranging from 13 to 34°C under ambient pCO2 (350 μatm) and elevated pCO2 (950 μatm). TPCs were comparable between the species or even between pCO2 levels. With the exception of the critical thermal minimum (CTmin) for C. ovataCTmin for C. marina and the thermal optimum (Topt) and critical thermal maximum (CTmax) for both species did not change with elevation of pCO2 levels. While CO2 enrichment increased the maximum photosynthetic rates (Pmax) up to 125% at the Topt of 30°C, specific growth rates were not significantly different under elevated pCO2 for the two species. Overall, C. ovata is likely to benefit from climate change, potentially widening its range of thermal tolerance limit in highly acidic waters and contributing to prolonged phenology of future phytoplankton assemblages in coastal waters.

Continue reading ‘Effect of elevated pCO2 on thermal performance of Chattonella marina and Chattonella ovata (Raphidophyceae)’

Responses of branching reef corals Acropora digitifera and Montipora digitata to elevated temperature and pCO2

Anthropogenic emission of CO2 into the atmosphere has been increasing exponentially, causing ocean acidification (OA) and ocean warming (OW). The “business-as-usual” scenario predicts that the atmospheric concentration of CO2 may exceed 1,000 µatm and seawater temperature may increase by up to 3 °C by the end of the 21st century. Increases in OA and OW may negatively affect the growth and survival of reef corals. In the present study, we separately examined the effects of OW and OA on the corals Acropora digitifera and Montipora digitata, which are dominant coral species occurring along the Ryukyu Archipelago, Japan, at three temperatures (28 °C, 30 °C, and 32 °C) and following four pCO2 treatments (400, 600, 800, and 1,000 µatm) in aquarium experiments. In the OW experiment, the calcification rate (p = 0.02), endosymbiont density, and maximum photosynthetic efficiency (Fv/Fm) (both p < 0.0001) decreased significantly at the highest temperature (32 °C) compared to those at the lower temperatures (28 °C and 30 °C) in both species. In the OA experiment, the calcification rate decreased significantly as pCO2 increased (p < 0.0001), whereas endosymbiont density, chlorophyll content, and Fv/Fm were not affected. The calcification rate of A. digitifera showed greater decreases from 30 °C to 32 °C than that of M. digitata. The calcification of the two species responded differently to OW and OA. These results suggest that A. digitifera is more sensitive to OW than M. digitata, whereas M. digitata is more sensitive to OA. Thus, differences in the sensitivity of the two coral species to OW and OA might be attributed to differences in the endosymbiont species and high calcification rates, respectively.

Continue reading ‘Responses of branching reef corals Acropora digitifera and Montipora digitata to elevated temperature and pCO2’

Leaf proteome modulation and cytological features of seagrass Cymodocea nodosa in response to long-term high CO2 exposure in volcanic vents

Seagrass Cymodocea nodosa was sampled off the Vulcano island, in the vicinity of a submarine volcanic vent. Leaf samples were collected from plants growing in a naturally acidified site, influenced by the long-term exposure to high CO2 emissions, and compared with others collected in a nearby meadow living at normal pCO2 conditions. The differential accumulated proteins in leaves growing in the two contrasting pCO2 environments was investigated. Acidified leaf tissues had less total protein content and the semi-quantitative proteomic comparison revealed a strong general depletion of proteins belonging to the carbon metabolism and protein metabolism. A very large accumulation of proteins related to the cell respiration and to light harvesting process was found in acidified leaves in comparison with those growing in the normal pCO2 site. The metabolic pathways linked to cytoskeleton turnover also seemed affected by the acidified condition, since a strong reduction in the concentration of cytoskeleton structural proteins was found in comparison with the normal pCO2 leaves. Results coming from the comparative proteomics were validated by the histological and cytological measurements, suggesting that the long lasting exposure and acclimation of C. nodosa to the vents involved phenotypic adjustments that can offer physiological and structural tools to survive the suboptimal conditions at the vents vicinity.

Continue reading ‘Leaf proteome modulation and cytological features of seagrass Cymodocea nodosa in response to long-term high CO2 exposure in volcanic vents’

Interactive effects of increasing atmospheric CO2 and copper exposure on the growth and photosynthesis in the young sporophytes of Sargassum fusiforme (Phaeophyta)


  • Effects of Cu2+ and elevated atmospheric CO2 on young sporophytes of Sargassum fusiforme were investigated.
  • At elevated CO2, growth inhibition and pigment damage caused by Cu2+ remain at the same level.
  • Elevated CO2 alleviates the Cu-induced suppression on photosystem.
  • Elevated CO2 down-regulates the enzymatic antioxidant system against Cu2+.


Little attention has been given to the combined effects of elevated atmospheric CO2-induced ocean acidification (OA) and heavy metal pollution on marine macroalgae at the young stage. This study investigated the mutual effects of copper (Cu) and elevated CO2 on the young sporophytes of brown macroalgae Sargassum fusiforme. A matrix of four copper concentrations, 0, 0.025, 0.075 and 0.15 mg‧L-1, and two levels of CO2 (ambient CO2: 400 μatm; elevated CO2: 1,000 μatm) were used. High concentration of copper exposure greatly depressed photosynthesis and growth of the young sporophytes of S. fusiforme by reducing the apparent photosynthetic efficiency (ɑ), maximum net photosynthetic oxygen evolution rate (Pmax), maximum photochemical quantum yield (Fv/Fm) and pigments content (Chl a and Car). While elevated CO2 alone had obscure impact on this alga. However, the inhibition of Cu stress on Fv/Fm was weakened by elevated CO2, which also decreased the light compensation point (Ic). Meanwhile, the Cu2+-induced ascent in the dark respiration rate (Rd) and superoxide dismutase (SOD) activity was mitigated under the growth with elevated CO2, suggesting an alleviated oxidative stress. Overall, we propose that, under CO2 enrichment condition, the young sporophytes of S. fusiforme may increase photosynthesis efficiency and synthesize less enzymatic antioxidants in face of increasing Cu stress.

Continue reading ‘Interactive effects of increasing atmospheric CO2 and copper exposure on the growth and photosynthesis in the young sporophytes of Sargassum fusiforme (Phaeophyta)’

Windows of vulnerability: seasonal mismatches in exposure and resource identity determine ocean acidification’s effect on a primary consumer at high latitude

It is well understood that differences in the cues used by consumers and their resources in fluctuating environments can give rise to trophic mismatches governing the emergent effects of global change. Trophic mismatches caused by changes in consumer energetics during periods of low resource availability have received far less attention, although this may be common for consumers during winter when primary producers are limited by light. Even less is understood about these dynamics in marine ecosystems, where consumers must cope with energetically costly changes in CO2‐driven carbonate chemistry that will be most pronounced in cold temperatures. This may be especially important for calcified marine herbivores, such as the pinto abalone (Haliotis kamschatkana). H. kamschatkana are of high management concern in the North Pacific due to the active recreational fishery and their importance among traditional cultures, and research suggests they may require more energy to maintain their calcified shells and acid/base balance with ocean acidification. Here we use field surveys to demonstrate seasonal mismatches in the exposure of marine consumers to low pH and algal resource identity during winter in a subpolar, marine ecosystem. We then use these data to test how the effects of exposure to seasonally relevant pH conditions on H. kamschatkana are mediated by seasonal resource identity. We find that exposure to projected future winter pH conditions decreases metabolism and growth, and this effect on growth is pronounced when their diet is limited to the algal species available during winter. Our results suggest that increases in the energetic demands of pinto abalone caused by ocean acidification during winter will be exacerbated by seasonal shifts in their resources. These findings have profound implications for other marine consumers and highlight the importance of considering fluctuations in exposure and resources when inferring the emergent effects of global change.

Continue reading ‘Windows of vulnerability: seasonal mismatches in exposure and resource identity determine ocean acidification’s effect on a primary consumer at high latitude’

Environmental changes affecting physiological responses and growth of hybrid grouper – the interactive impact of low pH and temperature


  • Effects of warm temperature and/or low water pH were studied.
  • Growth performance were negatively either warm temperature or low pH exposure.
  • Interactive exposure of warm temperature and low water pH induced high living cost of hybrid grouper.
  • Hybrid grouper adjusted energy metabolism needs to cope with the changing environment.


Rising of temperature in conjunction with acidification due to the anthropogenic climates has tremendously affected all aquatic life. Small changes in the surrounding environment could lead to physiological constraint in the individual. Therefore, this study was designed to investigate the effects of warm water temperature (32 oC) and low pH (pH 6) on physiological responses and growth of hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) juveniles for 25 days. Growth performance was significantly affected under warm water temperature and low-pH conditions. Surprisingly, the positive effect on growth was observed under the interactive effects of warm water and low pH exposure. Hybrid grouper exposed to the interactive stressor of warm temperature and low pH exhibited higher living cost, where HSI content was greatly depleted to about 2.3-folds than in normal circumstances. Overall, challenge to warm temperature and low pH induced protein mobilization as an energy source followed by glycogen and lipid to support basal metabolic needs.

Continue reading ‘Environmental changes affecting physiological responses and growth of hybrid grouper – the interactive impact of low pH and temperature’

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Ocean acidification in the IPCC AR5 WG II

OUP book