Declines in shellfish species on rocky seashores match climate-driven changes

Two decades of data document a dwindling of mussels, barnacles and snails

The waters of the Gulf of Maine are warming faster than oceans almost anywhere on Earth. As the level of carbon dioxide rises in the atmosphere, it’s absorbed by the sea, causing pH levels to fall. Ocean acidification makes it difficult for shellfish to thicken their shells –their primary defense against predators.

In a U.S. National Science Foundation-funded study published in Communications Biology, researchers Peter Petraitis of the University of Pennsylvania and Steve Dudgeon of California State University, Northridge, show that the changing climate is taking a toll on Maine’s sea life.

Continue reading ‘Declines in shellfish species on rocky seashores match climate-driven changes’

SDG 14.3 data portal launched

The International Oceanographic Data and Information Exchange (IODE; WDS Network Member), international ocean acidification experts (including data managers), and the Global Ocean Acidification Observing Network have supported the development of the indicator methodology tool, SDG 14.3.1 Data Portal, which is now freely available.

This SDG 14.3.1 Data Portal is a tool for the submission, collection, validation, storage, and sharing of ocean acidification data and metadata submitted towards the Sustainable Development Goal 14.3.1 Indicator: Average marine acidity (pH) measured at agreed suite of representative sampling stations.

The SDG Indicator 14.3.1 Methodology provides the necessary guidance on how to conduct ocean acidification observation, what to measure and how, providing best practice, and methods approved by the scientific ocean acidification community. It further offers support on how to and what types of datasets to submit to the Intergovernmental Oceanographic Commission of UNESCO, to ensure the production of quality-controlled global and possibly regional products.

Continue reading ‘SDG 14.3 data portal launched’

Communicating OA science to policy makers (webinar recording)

On October 20 and 21, the OA Alliance and The Ocean Foundation co- hosted a Communications Workshop for OA Scientists.

This virtual workshop provided an overview of best practices in communicating OA science to decision and policy makers and other stakeholders, drawing upon lessons learned and experiences from our national and subnational government members.  It also described how governments are increasingly tackling ocean acidification through legislation, climate action strategies and other international frameworks and specifically—exploring how scientists and in-region stakeholders can most effectively contribute to those processes.

This workshop was meant for scientists working on ocean acidification who are interested in learning how to interact with policymakers.

Continue reading ‘Communicating OA science to policy makers (webinar recording)’

The uncertain future of the oceans

Study analyzes the reaction of plankton communities to increased carbon dioxide

26 October 2020 / Kiel. Marine food webs and biogeochemical cycles react very sensitively to the increase in carbon dioxide (CO2) – but the effects are far more complex than previously thought. This is shown in a study published by a team of researchers from the GEOMAR Helmholtz Centre for Ocean Research Kiel in the journal Nature Climate Change. Data were combined from five large-scale field experiments, which investigated how the carbon cycle within plankton communities reacts to the increase of CO2.

The ocean plays a key role in the current climate change, as it absorbs a considerable part of the atmospheric carbon dioxide emitted by mankind. On the one hand, this slows down the heating of the climate, and on the other hand, the dissolution of CO2 in seawater leads to acidification of the oceans. This has far-reaching consequences for many marine organisms and thus also for the oceanic carbon cycle. One of the most important mechanisms in this cycle, is called the biological carbon pump. Part of the biomass that phytoplankton forms in the surface ocean through photosynthesis sinks to the depths in the form of small carbonaceous particles. As a result, the carbon is stored for a long time in the deep sea. The ocean thus acts as a carbon sink in the climate system. How strongly this biological pump acts varies greatly from region to region and depends on the composition of species in the ecosystem.

Continue reading ‘The uncertain future of the oceans’

Impact of ocean warming and acidification on symbiosis establishment and gene expression profiles in recruits of reef coral Acropora intermedia

The onset of symbiosis and the early development of most broadcast spawning corals play pivotal roles in recruitment success, yet these critical early stages are threatened by multiple stressors. However, molecular mechanisms governing these critical processes under ocean warming and acidification are still poorly understood. The present study investigated the interactive impact of elevated temperature (∼28.0°C and ∼30.5°C) and partial pressure of carbon dioxide (pCO2) (∼600 and ∼1,200 μatm) on early development and the gene expression patterns in juvenile Acropora intermedia over 33 days. The results showed that coral survival was >89% and was unaffected by high temperature, pCO2, or the combined treatment. Notably, high temperature completely arrested successful symbiosis establishment and the budding process, whereas acidification had a negligible effect. Moreover, there was a positive exponential relationship between symbiosis establishment and budding rates (y = 0.0004e6.43xR = 0.72, P < 0.0001), which indicated the importance of symbiosis in fueling asexual budding. Compared with corals at the control temperature (28°C), those under elevated temperature preferentially harbored Durusdinium spp., despite unsuccessful symbiosis establishment. In addition, compared to the control, 351 and 153 differentially expressed genes were detected in the symbiont and coral host in response to experimental conditions, respectively. In coral host, some genes involved in nutrient transportation and tissue fluorescence were affected by high temperature. In the symbionts, a suite of genes related to cell growth, ribosomal proteins, photosynthesis, and energy production was downregulated under high temperatures, which may have severely hampered successful cell proliferation of the endosymbionts and explains the failure of symbiosis establishment. Therefore, our results suggest that the responses of symbionts to future ocean conditions could play a vital role in shaping successful symbiosis in juvenile coral.

Continue reading ‘Impact of ocean warming and acidification on symbiosis establishment and gene expression profiles in recruits of reef coral Acropora intermedia’

Differential sensitivity of a symbiont‐bearing foraminifer to seawater carbonate chemistry in a decoupled DIC‐pH experiment

Larger benthic foraminifera (LBF) are unicellular eukaryotic calcifying organisms and an important component of tropical and subtropical modern and ancient oceanic ecosystems. They are major calcium carbonate producers and important contributors to primary production due to the photosynthetic activity of their symbiotic algae. Studies investigating the response of LBF to seawater carbonate chemistry changes are therefore essential for understanding the impact of climate changes and ocean acidification (OA) on shallow marine ecosystems. In this study, calcification, respiration, and photosynthesis of the widespread diatom‐bearing LBF Operculina ammonoides were measured in laboratory experiments that included manipulation of carbonate chemistry parameters. pH was altered while keeping dissolved inorganic carbon (DIC) constant, and DIC was altered while keeping pH constant. The results show clear vulnerability of O. ammonoides to low pH and CO32− under constant DIC conditions, and no increased photosynthesis or calcification under high DIC concentrations. Our results call into question previous hypotheses, suggesting that mechanisms such as the degree of cellular control on calcification site pH/DIC and/or enhanced symbiont photosynthesis in response to OA may render the hyaline (perforate and calcitic‐radial) LBF to be less responsive to OA than porcelaneous LBF. In addition, manipulating DIC did not affect calcification when pH was close to present seawater levels in a model encompassing the total population size range. In contrast, larger individuals (>1,200 μm, >1 mg) were sensitive to changes in DIC, a phenomenon we attribute to their physiological requirement to concentrate large quantities of DIC for their calcification process.

Continue reading ‘Differential sensitivity of a symbiont‐bearing foraminifer to seawater carbonate chemistry in a decoupled DIC‐pH experiment’

Seasonal controls of the carbon biogeochemistry of a fringing coral reef in the Gulf of California, Mexico

The surface of the ocean has absorbed one-third of the CO2gas that has been released by anthropogenic activities, which has resulted in a reduction in pH and the aragonite saturation state (Ωara) with potential negative impacts in calcifying organisms, such as corals. To evaluate these effects, the natural variability present must first be understood, including that of processes that operate at diurnal, seasonal, and interannual frequencies. The objective of this study was to determine the influence of physical and biogeochemical processes on the seasonal variability of the CO2-system in a fringe coral reef of the Eastern Tropical Pacific (ETP). To achieve this, a SeapHOx sensor was installed to measure temperature, salinity, dissolved oxygen, and pHTot at 30-min intervals from November 2013 (early winter) to July 2014 (early summer). The recorded temperature and salinity data fed a mixing model to identify the water masses present in the reef. We show how physical and biogeochemical oceanic processes influence and control the variability of the carbonate system. The presence of water masses with different carbon chemistries responded to two scenarios: (1) seasonal circulation on the order of months and (2) an intermittence between water masses related to mesoscale structures (eddies) on the order of weeks. A low-pH and Ωara condition was detected during summer, which was related to the presence of warm and respired Tropical Surface Water. The broadest changes in Ωara were the result of physical processes (winter ΔΩara = 0.14 and summer ΔΩara = 0.34 units) and corresponded to the transition between water masses with different carbon-biogeochemistry signals. Our results suggest that the Cabo Pulmo coral community develops in an environment with a wide range of pH and Ωara conditions and that seasonal changes are controlled by open ocean carbon biogeochemistry.

Continue reading ‘Seasonal controls of the carbon biogeochemistry of a fringing coral reef in the Gulf of California, Mexico’

Ocean freshening and acidification differentially influence mortality and behavior of the Antarctic amphipod Gondogeneia antarctica


  • Glacial retreat induced by global warming can decrease salinity and pH of the Antarctic ocean.
  • The Antarctic amphipod Gondogeneia antarctica was exposed to low salinity (27 psu) and low pH (7.6) conditions.
  • Low salinity increased cannibalism and induced adjusted swimming.
  • Low pH increased mortality, impaired food detection and reduced daytime shelter use.
  • Ocean freshening and acidification act as independent stressors influencing behavior and physiology of Antarctic amphipods.


The Western Antarctic Peninsula (WAP) has experienced rapid atmospheric and ocean warming over the past few decades and many marine-terminating glaciers have considerably retreated. Glacial retreat is accompanied by fresh meltwater intrusion, which may result in the freshening and acidification of coastal waters. Marian Cove (MC), on King George Island in the WAP, undergoes one of the highest rates of glacial retreat. Intertidal and shallow subtidal waters are likely more susceptible to these processes, and sensitive biological responses are expected from the organisms inhabiting this area. The gammarid amphipod Gondogeneia antarctica is one of the most abundant species in the shallow, nearshore Antarctic waters, and it occupies an essential ecological niche in the coastal marine WAP ecosystem. In this study, we tested the sensitivity of G. antarctica to lowered salinity and pH by meltwater intrusion following glacial retreat. We exposed G. antarctica to four different treatments combining two salinities (34 and 27 psu) and pH (8.0 and 7.6) levels for 26 days. Mortality, excluding cannibalized individuals, increased under low pH but decreased under low salinity conditions. Meanwhile, low salinity increased cannibalism, whereas low pH reduced food detection. Shelter use during the daytime decreased under each low salinity and pH condition, indicating that the two stressors act as disruptors of amphipod behavior. Under low salinity conditions, swimming increased during the daytime but decreased at night. Although interactions between low salinity and low pH were not observed during the experiment, the results suggest that each stressor, likely induced by glacial melting, causes altered behaviors in amphipods. These environmental factors may threaten population persistence in Marian Cove and possibly other similar glacial embayments.

Continue reading ‘Ocean freshening and acidification differentially influence mortality and behavior of the Antarctic amphipod Gondogeneia antarctica’

A review of mesocosm experiments on heavy metals in marine environment and related issues of emerging concerns

Mesocosms are real-world environmental science tools for bridging the gap between laboratory-scale experiments and actual habitat studies on ecosystem complexities. These experiments are increasingly being applied in understanding the complex impacts of heavy metals, ocean acidification, global warming, and oil spills. The insights of the present review indicate how metals and metal-bound activities impact on various aspects of ecological complexities like prey predator cues, growth, embryonic development, and reproduction. Plankton and benthos are used more often over fish and microbes owing to their smaller size, faster reproduction, amenability, and repeatability during mesocosm experiments. The results of ocean acidification reveal calcification of plankton, corals, alteration of pelagic structures, and plankton blooms. The subtle effect of oil spills is amplified on sediment microorganisms, primary producers, and crustaceans. An overview of the mesocosm designs over the years indicates that gradual changes have evolved in the type, size, design, composition, parameters, methodology employed, and the outputs obtained. Most of the pelagic and benthic mesocosm designs involve consideration of interactions within the water columns, between water and sediments, trophic levels, and nutrient rivalry. Mesocosm structures are built considering physical processes (tidal currents, turbulence, inner cycling of nutrients, thermal stratification, and mixing), biological complexities (population, community, and ecosystem) using appropriate filling containers, and sampling facilities that employ inert materials. The principle of design is easy transportation, mooring, deployment, and free floating structures besides addressing the unique ecosystem-based science problems. The evolution of the mesocosm tools helps in understanding further advancement of techniques and their applications in marine ecosystems.

Continue reading ‘A review of mesocosm experiments on heavy metals in marine environment and related issues of emerging concerns’

Effects of low pH and low salinity induced by meltwater inflow on the behavior and physical condition of the Antarctic limpet, Nacella concinna

Seawater acidification and freshening in the intertidal zone of Marian Cove, Antarctica, which occurs by the freshwater inflow from snow fields and glaciers, could affect the physiology and behavior of intertidal marine organisms. In this study, we exposed Antarctic limpets, Nacella concinna, to two different pH (8.00 and 7.55) and salinity (34.0 and 27.0 psu) levels and measured their righting ability after being flipped over, mortality, condition factor, and shell dissolution. During the 35-day exposure, there was no significant difference in behavior and mortality between different treatments. However, the condition factor was negatively affected by low salinity. Both low pH and low salinity negatively influenced shell formation by decreasing the aragonite saturation state (Ωarg) and enhancing shell dissolution. Our results suggest that, though limpets can tolerate short-term low pH and salinity conditions, intrusions of meltwater accompanied by the glacial retreat may act as a serious threat to the population of N. concinna.

Continue reading ‘Effects of low pH and low salinity induced by meltwater inflow on the behavior and physical condition of the Antarctic limpet, Nacella concinna’

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Ocean acidification in the IPCC AR5 WG II

OUP book