Potential role of major phytoplankton communities on pCO2 modulation in the Indian sector of Southern Ocean

Spatial variations in the phytoplankton community compositions, carbon dioxide system and ancillary water column properties, were monitored across various frontal systems in the Indian Sector of Southern Ocean (ISSO) during austral summer 2013. Four major frontal systems, namely, the Agulhas Return Front (ARF), Southern Subtropical Front (SSTF), Subantarctic Front (SAF) and Polar Front (PF) were identified along the study area. Major groups of phytoplankton were distinguished adopting single marker pigment approach. Statistical computations showed the distribution of diatoms were influenced by the availability of inorganic nutrients (primarily silicate and nitrate) and mixed layer depths (MLD). Haptophytes were strongly dependent on phosphate availability, whereas, picoplankton flourished in water where regenerated nutrient ammonium was present. The lowest surface pCO2 (267.26–291.5 µatm) along with in situ oxygen production (> 10 µM) was encountered at the two warmer fronts, ARF and SSTF, dominated by haptophytes and picoplankton. The colder Antarctic fronts, SAF and PF were dominated by diatoms where surface pCO2 was relatively higher (> 350µatm). Poor statistical correlation among temperature and total chlorophyll with pCO2 revealed complex interplay of multiple factors. Contribution of major phytoplankton groups towards pCO2 drawdown was computed using a one-dimensional model describing the relative contributions of biological activities. In ISSO, calcifying and photosynthesizing haptophytes were observed to play a crucial role in the “biological pump” of CO2 drawdown at ARF, SSTF and SAF, while the silicifying micro phytoplankton diatoms and picoplankton were more effective at PF.

Continue reading ‘Potential role of major phytoplankton communities on pCO2 modulation in the Indian sector of Southern Ocean’

The enzymology of ocean global change

A small subset of marine microbial enzymes and surface transporters have a disproportionately important influence on the cycling of carbon and nutrients in the global ocean. As a result, they largely determine marine biological productivity and have been the focus of considerable research attention from microbial oceanographers. Like all biological catalysts, the activity of these keystone biomolecules is subject to control by temperature and pH, leaving the crucial ecosystem functions they support potentially vulnerable to anthropogenic environmental change. We summarize and discuss both consensus and conflicting evidence on the effects of sea surface warming and ocean acidification for five of these critical enzymes [carbonic anhydrase, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), nitrogenase, nitrate reductase, and ammonia monooxygenase] and one important transporter (proteorhodopsin). Finally, we forecast how the responses of these few but essential biocatalysts to ongoing global change processes may ultimately help to shape the microbial communities and biogeochemical cycles of the future greenhouse ocean.

Continue reading ‘The enzymology of ocean global change’

Cold-water coral reefs in the Langenuen Fjord, Southwestern Norway—a window into future environmental change

Ocean warming and acidification pose serious threats to cold-water corals (CWCs) and the surrounding habitat. Yet, little is known about the role of natural short-term and seasonal environmental variability, which could be pivotal to determine the resilience of CWCs in a changing environment. Here, we provide continuous observational data of the hydrodynamic regime (recorded using two benthic landers) and point measurements of the carbonate and nutrient systems from five Lophelia pertusa reefs in the Langenuen Fjord, southwestern Norway, from 2016 to 2017. In this fjord setting, we found that over a tidal (<24 h) cycle during winter storms, the variability of measured parameters at CWC depths was comparable to the intra-annual variability, demonstrating that single point measurements are not sufficient for documenting (and monitoring) the biogeochemical condiotions at CWC sites. Due to seasonal and diurnal forcing, parts of the reefs experienced temperatures up to 4 ◦C warmer (i.e., >12 ◦C) than the mean conditions and high CT concentrations of 20 µmol kg−1 over the suggested threshold for healthy CWC reefs (i.e., >2170 µmol kg−1 ). Combined with hindcast measurements, our findings indicate that these shallow fjord reefs may act as an early hotspot for ocean warming and acidification. We predict that corals in Langenuen will face seasonally high temperatures (>18 ◦C) and hypoxic and corrosive conditions within this century. Therefore, these fjord coral communities could forewarn us of the coming consequences of climate change on CWC diversity and function.

Continue reading ‘Cold-water coral reefs in the Langenuen Fjord, Southwestern Norway—a window into future environmental change’

Ocean acidification news stream gets new features

Dear Users,  

The OA-ICC has supported the ocean acidification community by maintaining the ocean acidification news stream and OA-ICC bibliographic database for nearly 10 years. This year in light of the increased importance of the virtual space in the time of COVID-19, we dedicated additional resources to update and grow our site, enhancing the tools available to our community. In addition to updating the Bibliographic Database, which now contains more than 8,800 scientific papers on ocean acidification, we have developed new guides and features on the site which you may be interested in.

These include: 

  • A calendar with descriptions and links to events on OA, which you may sync with your google calendar. This calendar is updated regularly, and we welcome submissions of events.
  • A resource library, which contains a vast selection of topics on OA, for example: educational materials, projects and programs, general articles, reports and newsletters, and organizations. More resources and categories will be added continuously and we welcome resource submissions.
  • An enhanced basic search and new advanced search option, which will help you explore our archives and resource library.
  • A summary of our methods for maintaining this news stream, as well as detailed documentation of our procedures. 
  • A page providing quick links and information about our bibliographic database and data portal.   

We invite you to explore the site and benefit from the additional resources made available to the ocean acidification community. If you are interested in collaborating with the OA-ICC projects, programs and events, please contact us at oa-icc@iaea.org

Kind regards,  

OA-ICC team 

OA-ICC bibliographic database updates and user guide

We are happy to inform you that the latest version of the OA-ICC bibliographic database, now containing more than 8,800 scientific articles, books and more on ocean acidification, is available for public use on Zotero and for download on pCloud. The database is no longer available on Mendeley because the public groups feature has been discontinued, but you may still download the database and add it to your Mendeley library.

We have also created a new user guide and a page on our methodology to improve your experience using the bibliographic resources. You may find our user guide and more information on OA-ICC bibliographic resources, including the biological response data portal, on our new bibliographic database page. This page includes our updated friendly user’s guide, featuring explanations to our custom keywords with links to clear examples. In addition, we will be sharing a tutorial on navigating the bibliographic resources soon.

Continue reading ‘OA-ICC bibliographic database updates and user guide’

Combined effects of ocean warming and acidification on marine fish and shellfish: a molecule to ecosystem perspective


  • Climate change would have profound repercussion on fisheries sector
  • Multiple interactive stressors can incapacitate biological functioning.
  • Trophic pyramids and food web architecture studies need to be approached.
  • Combined in situ monitoring and laboratory studies should be prioritized.


It is expected that by 2050 human population will exceed nine billion leading to increased pressure on marine ecosystems. Therefore, it is conjectured various levels of ecosystem functioning starting from individual to population-level, species distribution, food webs and trophic interaction dynamics will be severely jeopardized in coming decades. Ocean warming and acidification are two prime threats to marine biota, yet studies about their cumulative effect on marine fish and shellfishes are still in its infancy. This review assesses existing information regarding the interactive effects of global environmental factors like warming and acidification in the perspective of marine capture fisheries and aquaculture industry. As climate change continues, distribution pattern of species is likely to be altered which will impact fisheries and fishing patterns. Our work is an attempt to compile the existing literatures in the biological perspective of the above-mentioned stressors and accentuate a clear outline of knowledge in this subject. We reviewed studies deciphering the biological consequences of warming and acidification on fish and shellfishes in the light of a molecule to ecosystem perspective. Here, for the first time impacts of these two global environmental drivers are discussed in a holistic manner taking into account growth, survival, behavioural response, prey predator dynamics, calcification, biomineralization, reproduction, physiology, thermal tolerance, molecular level responses as well as immune system and disease susceptibility. We suggest urgent focus on more robust, long term, comprehensive and ecologically realistic studies that will significantly contribute to the understanding of organism’s response to climate change for sustainable capture fisheries and aquaculture.

Continue reading ‘Combined effects of ocean warming and acidification on marine fish and shellfish: a molecule to ecosystem perspective’

Eutrophication overcoming carbonate precipitation in a tropical hypersaline coastal lagoon acting as a CO2 sink (Araruama Lagoon, SE Brazil)

The carbonate chemistry was investigated in the semiarid eutrophic Araruama Lagoon (Brazil), one of the largest hypersaline coastal lagoons in the world. Spatial surveys during winter and summer periods were performed, in addition to a diurnal sampling in summer. The hypersaline waters have higher concentrations of total alkalinity (TA) and dissolved inorganic carbon (DIC) than the seawater that feed the lagoon, due to evaporation. However, TA and DIC concentrations were lower than those expected from evaporation. Calcium carbonate (CaCO3) precipitation partially explained these deficits. The negative correlation between the partial pressure of CO2 (pCO2) and chlorophyll a (Chl a) indicated that DIC was also consumed by primary producers. The uptake by photosynthesis contributes to 57–63% of DIC deviation from evaporation, the remaining credited to CaCO3 precipitation. Marked pCO2 undersaturation was prevalent at the innermost region with shallow, confined, and phytoplankton-dominated waters, with a strong enrichment of heavier carbon isotope (δ13C-DIC up to 5.55%), and highest pH (locally counter-acting the process of ocean acidification). Oversaturation was restricted to an urbanized region, and during night-time. The lagoon behaved as a marked CO2 sink during winter (− 15.32 to − 10.15 mmolC m−2 day−1), a moderate sink during summer (− 5.50 to − 4.67 mmolC m−2 day−1), with a net community production (NCP) of 93.7 mmolC m−2 day−1 and prevalence of net autotrophic metabolism. A decoupling between CO2 and O2 exchange rate at the air–water interface was attributed to differences in gas solubility, and high buffering capacity. The carbonate chemistry reveals simultaneous and antagonistic actions of CaCO3 precipitation and autotrophic metabolism on CO2 fluxes, and could reflect future conditions in populated and semiarid coastal ecosystems worldwide.

Continue reading ‘Eutrophication overcoming carbonate precipitation in a tropical hypersaline coastal lagoon acting as a CO2 sink (Araruama Lagoon, SE Brazil)’

How do coral reefs respond to climate change? Investigating the role of Symbiodiniaceae community composition on coral performance under long-term exposure to warming and acidification

Coral reefs are one of the most biodiverse and ecologically important ecosystems on the planet, but they are increasingly threatened by ocean acidification and warming. Changes in environmental factors can cause the coral to expel their endosymbiotic community of single-celled dinoflagellates (family: Symbiodiniaceae), leaving them more vulnerable to disease and mortality. One proposed method through which coral can acclimatize to the fluctuations in ocean temperature is by shuffling their Symbiodiniaceae community compositions to increase the relative proportions of temperature-tolerant symbionts. However, the effects of ocean acidification on Symbiodiniaceae community compositions are still unknown. Here, I present data from a two-year mesocosm experiment investigating the effects of long-term exposure to ocean acidification and warming on Symbiodiniaceae community composition in eight common species of Hawaiian coral. Coral were collected from six geographically distinct locations around O’ahu and exposed to predicted end-of-century temperature and pH conditions for two years. Next Generation Sequencing (NGS) of the ribosomal internal transcribed spacer 2 (ITS2) region of the Symbiodiniaceae provided detailed insight into the distinct symbiont types and the changes in community composition resulting from environmental stressors. Our findings indicate that temperature is a more significant driver of changes to the Symbiodiniaceae community compositions than pH in Hawaiian corals. We additionally demonstrate that the changes in symbiont communities in response to experimental temperature and pCO2 conditions arise from the shuffling of current symbionts and the incorporation of novel symbionts from the environment, which has implications for future coral resilience against climate change.

Continue reading ‘How do coral reefs respond to climate change? Investigating the role of Symbiodiniaceae community composition on coral performance under long-term exposure to warming and acidification’

The ocean’s chemistry is changing. Why does it matter? (video)

Excessive CO2 emissions isn’t just an atmospheric problem, it’s changing the chemistry of our oceans through ocean acidification and impacting ocean life.

Continue reading ‘The ocean’s chemistry is changing. Why does it matter? (video)’

Impact of ocean acidification on the intestinal microflora of the Pacific oyster Crassostrea gigas


  • Ocean acidification changed the community structure of the intestinal microflora in Crassostrea gigas.
  • The relative abundance of Firmicutes and the Firmicutes/Bacteroides ratio decreased under ocean acidification.
  • Mycoplasma was significantly enriched under ocean acidification.
  • The pathways related to proliferation were significantly enhanced in the intestinal microflora under ocean acidification.


The intestinal microflora is critical for the health of hosts by affecting their nutrient absorption and immune response. Increasing evidences demonstrate that environmental stress can lead to the dysbiosis of intestinal microflora, which increases the susceptibility of host to pathogens. Ocean acidification (OA) is one of the greatest environmental threats for marine mollusks with the negative effects on growth and calcification, but its impact on intestinal microflora is poorly understood. In the present study, the intestinal microflora of the Pacific oyster Crassostrea gigas reared at seawater with pH values of 8.1 (control group), 7.8 (AC78 group) and 7.4 (AC74 group) were characterized and compared using 16S rRNA gene sequencing. The composition of oyster intestinal microflora changed significantly after acidification, while no significant difference of α-diversity was observed between the control and acidification groups. At the phylum level, the relative abundance of Firmicutes decreased in acidification groups, and the Firmicutes/Bacteroides ratio in AC78 and AC74 groups were 0.53 and 0.31-fold of that in the control group, respectively. At the genus level, the intestinal microflora was dominated by Mycoplasma, which was significantly enriched in the two acidification groups. LEfSe analysis showed that Mycoplasma was one of the most discriminative biomarkers in the AC78 group, while AlteromonadalesAmphriteaSalinirepens and Alteromonas were the biomarker taxa in the AC74 group. The functional prediction results indicated that the pathways related to protein and nucleic acid synthesis were enriched in the two acidification groups, while those related to carbohydrate catabolism were blocked in the AC78 group but enhanced in the AC74 group. These results suggested that the relative abundance of probiotic bacteria decreased upon ocean acidification, which favored the proliferation of pathogenic species in the intestine of oysters. The increased consumption of nutrients caused by microflora proliferation would aggravate the susceptibility of oysters to pathogens. Under greater OA stress, the intestinal microflora would enhance the competition for energy source with their hosts, consequently posing a great challenge to the host health. The information contributed to the better understanding of the oyster-microflora interactions under environmental stress.

Continue reading ‘Impact of ocean acidification on the intestinal microflora of the Pacific oyster Crassostrea gigas’

Elevated acidification rates due to deposition of atmospheric pollutants in the coastal Bay of Bengal

Human inputs of pollutants to the atmosphere and subsequent deposition may decrease pH in the coastal waters. Significant rate of decrease in pH and increase in pCO2 by 3–5 times is noticed in the coastal Bay of Bengal (BoB) than the low-latitude global ocean trends in the last few decades. We provide evidence for the first time for a rapid decrease in surface water pH due to atmospheric deposition of pollutants in the coastal BoB. The decrease in pH in the coastal BoB over the last decade is associated with concomitant increase in aerosol optical depth (AOD), total suspended particles (TSP) in air, sulfate and nitrate concentrations in TSP. This study suggests that contamination of surface coastal BoB by atmospheric pollutants not only acidifies surface ocean but also potentially amplifies CO2 emission with immediate implications to regional weather and climate.

Continue reading ‘Elevated acidification rates due to deposition of atmospheric pollutants in the coastal Bay of Bengal’

Climate change effects on North American fish and fisheries to inform adaptation strategies.

Climate change is a global persistent threat to fish and fish habitats throughout North America. Climate-induced modification of environmental regimes, including changes in streamflow, water temperature, salinity, storm surges, and habitat connectivity can change fish physiology, disrupt spawning cues, cause fish extinctions and invasions, and alter fish community structure. Reducing greenhouse emissions remains the primary mechanism to slow the pace of climate change, but local and regional management agencies and stakeholders have developed an arsenal of adaptation strategies to help partially mitigate the effects of climate change on fish. We summarise common stressors posed by climate change in North America, including (1) increased water temperature, (2) changes in precipitation, (3) sea level rise, and (4) ocean acidification, and present potential adaptation strategies that fishery professionals may apply to help vulnerable fish and fisheries cope with a changing climate. Although our adaptation strategies are primarily from North America, they have broader geographic applicability to fish and aquatic biota in other jurisdictions. These strategies provide opportunities for managers to mitigate the effects of climate change on fish and fish habitat while needed global policies to reduce greenhouse gas emissions emerge, which may offer more lasting solutions.

Continue reading ‘Climate change effects on North American fish and fisheries to inform adaptation strategies.’

How do nuclear techniques contribute to measuring and adapting to Climate Change?

(Image: A. Vargas/IAEA)

Nuclear and isotopic techniques can help us to better understand the world we live in. The data we gather with these techniques can lead to improved, science-based policy making, including in relation to climate change. We can study both land and water systems using various nuclear techniques to evaluate the effects of climate change on the environment.

These techniques and tools are effective in monitoring greenhouse gas emissions such as carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), understanding environmental changes to oceans, mountains and their ecosystems, and developing ways to adapt to food and water shortages exacerbated by changing weather patterns.

“Countries all over the world are increasingly recognising the value of using nuclear techniques to combat various challenges faced by climate change. They are discovering first-hand how beneficial the technologies promoted by the IAEA are,” said Najat Mokhtar, IAEA Deputy Director General and Head of the Department of Nuclear Sciences and Applications.

Data for identifying, monitoring and managing sources of greenhouse gas emissions are collected using isotopic techniques to understand how they are connected to changes occurring on land, in oceans and throughout the atmosphere. We explain how.

Continue reading ‘How do nuclear techniques contribute to measuring and adapting to Climate Change?’

2021 Ocean acidification and hypoxia RFP informational webinar (video)

Sea Grant California, 6 August 2021. Video.

Foras na Mara Marine Institute

The Marine Institute was set up under the Marine Institute Act 1991: to undertake, to coordinate, to promote and to assist in marine research and development and to provide such services related to research and development, that in the opinion of the Institute, will promote economic development and create employment and protect the marine environment.

Foras na Mara Marine Institute. Resource.

Resource type: website

Resource format: webpage


Since 1998, The MarineBio Conservation Society (MarineBio) has been a nonprofit volunteer marine conservation and science education group working online together to educate the world about ocean life, marine biology, marine conservation, and to provide a sea ethic that we should all attempt to follow.

MarineBio. Resource.

Resource type: website

Resource format: webpage

Woods Hole: What is Ocean Acidification?

Since the beginning of the Industrial Revolution, when humans began burning coal in large quantities, the world’s ocean water has gradually become more acidic. Like global warming, this phenomenon, which is known as ocean acidification, is a direct consequence of increasing levels of carbon dioxide (CO2) in Earth’s atmosphere.

Woods Hole Oceanographic Institution. Resource.

Resource type: website

Resource format: webpage

MCCIP – Marine Climate Change Impacts Partneship

The United Kingdom Marine Climate Change Impacts Partnership (MCCIP) brings together scientists, government, its agencies and NGOs to provide coordinated advice on climate change impacts and adaptation around our coast and in our seas.

We collate and synthesise evidence on climate change impacts and adaptation in a timely, impartial and independent manner, and disseminate this information to stakeholders.

Resource type: website

Resource format: webpage

Pacific Islands – Climate Adaptation Science Center

Observed climatic trends across the Pacific Basin, rising sea levels, increasing sea surface temperatures, shifts in ocean chemistry with increased ocean acidification, increasingly variable precipitation and wind patterns, rising air temperatures, increasing storm and cyclone intensity, and more prominent droughts, all promise growing stresses on terrestrial, coastal, and marine ecosystems, as well as on human communities. This wide, complex, intertwined spread of issues offer many challenges.

Pacific Islands – Climate Adaptation Science Center. Resource.

Resource type: website

Resource format: webpage

EMODnet – The European Marine Observation and Data Network

The European Marine Observation and Data Network (EMODnet) is the long-term initiative launched in 2009 by the DG MARE (EU Commission’s Directorate-General for Maritime Affairs and Fisheries). EMODnet is part of the Blue Growth strategy, Marine Knowledge 2020, and its main task is to ensure that European marine data will become easily accessible, interoperable, and free of restrictions on use.
EMODnet Chemistry is focused on eutrophication, ocean acidification, contamination, and marine litter issues which are relevant to the Marine Strategy Framework Directive and to global climate change. The data have been brought together for different group of variables in seawater, sediment and biota.

EMODnet. Resource.

Resource type: website

Resource format: webpage

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