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Proteomic and transcriptomic responses enable clams to correct the pH of calcifying fluids and sustain biomineralization in acidified environments

Seawater pH and carbonate saturation are predicted to decrease dramatically by the end of the century. This process, designated ocean acidification (OA), threatens economically and ecologically important marine calcifiers, including the northern quahog (Mercenaria mercenaria). While many studies have demonstrated the adverse impacts of OA on bivalves, much less is known about mechanisms of resilience and adaptive strategies. Here, we examined clam responses to OA by evaluating cellular (hemocyte activities) and molecular (high-throughput proteomics, RNASeq) changes in hemolymph and extrapallial fluid (EPF—the site of biomineralization located between the mantle and the shell) in M. mercenaria continuously exposed to acidified (pH ~7.3; pCO2 ~2700 ppm) and normal conditions (pH ~8.1; pCO2 ~600 ppm) for one year. The extracellular pH of EPF and hemolymph (~7.5) was significantly higher than that of the external acidified seawater (~7.3). Under OA conditions, granulocytes (a sub-population of hemocytes important for biomineralization) were able to increase intracellular pH (by 54% in EPF and 79% in hemolymph) and calcium content (by 56% in hemolymph). The increased pH of EPF and hemolymph from clams exposed to high pCO2 was associated with the overexpression of genes (at both the mRNA and protein levels) related to biomineralization, acid–base balance, and calcium homeostasis, suggesting that clams can use corrective mechanisms to mitigate the negative impact of OA.

Continue reading ‘Proteomic and transcriptomic responses enable clams to correct the pH of calcifying fluids and sustain biomineralization in acidified environments’

Combined effects of climate change stressors and predators with contrasting feeding-digestion strategies on a mussel species

Graphical abstract


  • Combined effects of climate change stressors and Predator Cues (PC) were evaluated.
  • Ocean Acidification (OA), Warming (OW) and PC affected mussel traits.
  • At the control temperature (15 °C), mussel byssal biogenesis increased with PC.
  • PC affected mussel size, wet mass and calcification rate.
  • The effects of starfish PC on some mussel traits were larger than those of snail PC.


We investigated the combined effects of Ocean Warming (OW), Acidification (OA) and predator cues (Non-Consumptive Effects; NCEs) of two predators with contrasting feeding-digestion strategies on the mussel Perumytilus purpuratus. We considered starfish-NCEs (partially external digestion) and snail-NCEs (internal digestion). Mussels were exposed for 13 weeks to cross-factored OA (~500 and ~1400 μatm, pCO2) and OW (~15 and ~20 °C) conditions, in the presence/absence of NCEs from one or both predators. Mussels exposed to both NCEs exhibited smaller length and buoyant weight growth than those under control or snail-NCEs conditions. Mussels exposed to starfish-NCEs exhibited smaller wet mass than control mussels. OW and starfish-NCEs in isolation or combined with snail-NCEs increased mussel oxygen consumption. Byssal biogenesis was affected by the three-factors interaction. Clearance rates were affected by the OW × OA interaction. We suggest that mainly starfish-NCEs, in isolation or interacting with OA or/and OW, can threat mussel traits and the associated community.

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Assessing annual nearshore carbonate chemistry trends in Alaska’s marginal seas

One of the consequences of anthropogenic carbon emissions is ocean acidification (OA). As atmospheric concentrations of carbon dioxide (CO₂) continue to rise, oceanic absorption of CO₂ changes the balance of dissolved inorganic carbon species (DIC) in seawater and alters marine carbonate chemistry. OA is predicted to be more pronounced in high-latitude environments, highlighting the importance of characterizing nearshore carbonate chemistry in polar and subpolar habitats, such as Alaska’s marginal seas. OA can have significant impacts on calcifying organisms (including pteropods, clams, mussels, and oysters), lowering the saturation of calcium carbonate minerals that are essential for shell formation in seawater. Despite the economic, subsistence, and cultural importance of vulnerable Alaskan marine biota, to date there are limited in situ data tracking the nearshore carbonate chemistry fluctuations of coastal Alaskan waters. To address this knowledge gap, this study’s research goal is to compare, in highfrequency resolution, the seasonal carbonate chemistry fluctuations in two representative nearshore Alaskan ecosystems: Kaktovik Lagoon (Arctic Ocean) and Kachemak Bay (Gulf of Alaska). Moored sensors detected pH, temperature, salinity, and O₂ data to characterize which physicochemical variables have the greatest average contributions to site-specific pH variability across one year (September 2018-August 2019) in these two regions. Analyses of the annual time series from both regions revealed interregional disparities, especially related to seasonality, biotic activity, and physicochemical fluctuations in the seawater. The pH dynamics of the Kachemak Bay mooring sites demonstrated a strong connection to a seasonal biotic signal, specifically through the push-pull effect of photosynthesis and respiration on DIC. Kaktovik’s pH dynamics suggested an interplay among salinity, biotic activity, and seasonal ice coverage. Both regions demonstrated high pH variability, with pH values shifting a maximum of 0.85 and 0.39 pH units over three hours in the two Kachemak Bay mooring sites, and 0.49 pH units over one hour in Kaktovik Lagoon. Forecast data for these regions project large declines in pH values over the coming century, with potentially deleterious impacts on local biota. Forecasted average monthly values based on 2018/2019 sampling reached pH < 7.5 for at least one month at all sites. Given the ocean change expectations for Alaskan marine environments, it is highly important that we establish seasonal carbonate chemistry baselines for Alaskan nearshore ecosystems.

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Best practices and tools for assessing trends in ocean acidification released

Ocean Station Papa is a long term surface mooring that monitors ocean-atmosphere interactions, carbon uptake, and ocean acidification in the Gulf of Alaska. As part of the global network of OceanSITES reference stations, measurements from the mooring are used to improve satellite products and forecast models as well our understanding of air-sea interactions, and their role within the climate system.

For the first time, an international research team compiled a set of best practices to assess and report ocean acidification trends. Standardized procedures for measuring ocean carbon chemistry are already largely  established, but a common set of best practices for trend analysis are missing. These best practices will facilitate ocean acidification comparison of trends across different regions. They also allow the research community to establish enduring accurate records of change that communicate the current status of ocean acidification to the public. 

Ocean acidification occurs when  the ocean absorbs carbon dioxide from the atmosphere, causing  a fundamental chemical change. The global rise in ocean acidity is fueled by human-emitted greenhouse gases. The global ocean has absorbed approximately 620 billion tons of carbon dioxide (~25%) from emissions released into the atmosphere by burning fossil fuels. Impacts from ocean acidification will vary by region. In order to implement adaptation and mitigation strategies, managers need an accurate and comparable understanding of how ocean acidification progresses globally, regionally and locally. This requires standardized procedures at all levels of data collection, dissemination, and analysis.

Newly published work in Frontiers in Marine Science describes these best practices developed from input from the ocean carbon science community and established best practices already adopted for atmospheric greenhouse gases. Just as NOAA’s Earth System Research Laboratories’ (ESRL) researchers played an active role in establishing standards for assessing trends in atmospheric CO2, PMEL researchers are now doing the same for ocean carbonate records. 

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Elevated CO2 reduces copper accumulation and toxicity in the diatom Thalassiosira pseudonana

The projected ocean acidification (OA) associated with increasing atmospheric CO2 alters seawater chemistry and hence the bio-toxicity of metal ions. However, it is still unclear how OA might affect the long-term resilience of globally important marine microalgae to anthropogenic metal stress. To explore the effect of increasing pCO2 on copper metabolism in the diatom Thalassiosira pseudonana (CCMP 1335), we employed an integrated eco-physiological, analytical chemistry, and transcriptomic approach to clarify the effect of increasing pCO2 on copper metabolism of Thalassiosira pseudonana across different temporal (short-term vs. long-term) and spatial (indoor laboratory experiments vs. outdoor mesocosms experiments) scales. We found that increasing pCO2 (1,000 and 2,000 μatm) promoted growth and photosynthesis, but decreased copper accumulation and alleviated its bio-toxicity to T. pseudonana. Transcriptomics results indicated that T. pseudonana altered the copper detoxification strategy under OA by decreasing copper uptake and enhancing copper-thiol complexation and copper efflux. Biochemical analysis further showed that the activities of the antioxidant enzymes glutathione peroxidase (GPX), catalase (CAT), and phytochelatin synthetase (PCS) were enhanced to mitigate oxidative damage of copper stress under elevated CO2. Our results provide a basis for a better understanding of the bioremediation capacity of marine primary producers, which may have profound effect on the security of seafood quality and marine ecosystem sustainability under further climate change.

Continue reading ‘Elevated CO2 reduces copper accumulation and toxicity in the diatom Thalassiosira pseudonana’

Potential ecosystem regime shift resulting from elevated CO2 and inhibition of macroalgal recruitment by turf algae

Rising carbon dioxide (CO2) concentrations are predicted to cause an undesirable transition from macroalgae-dominant to turf algae-dominant ecosystems due to its effect on community structuring processes. As turf algae are more likely to proliferate due to the CO2 fertilization effect than macroalgae and often inhibit macroalgal recruitment, increased CO2 beyond certain levels may produce novel positive feedback loops that promote turf algae growth and thus can stabilize turf algae-dominant ecosystems. In this study, we built a simple competition model between macroalgae and turf algae in a homogeneous space to investigate the steady-state response of the ecosystem to changes in the partial pressure of CO2 (pCO2). We found that discontinuous regime shifts in response to pCO2 change can occur once turf algae coverage reaches a critical level capable of inhibiting macroalgal recruitment. The effect of localized turf algae density on the success rate of macroalgae recruitment was also investigated using a patch model that simulated a two-dimensional heterogeneous space. This suggested that in addition to the inhibitory effect by turf algae, a self-enhancing effect by macroalgae could also be important in predicting the potential discontinuous regime shifts in response to future pCO2 changes.

Continue reading ‘Potential ecosystem regime shift resulting from elevated CO2 and inhibition of macroalgal recruitment by turf algae’

Assessment of CO2 and O2 spatial variability in an indigenous aquaculture system for restoration impacts

Spatial variability in carbon dioxide (CO2) and oxygen (O2) was assessed within an Indigenous Hawaiian fishpond undergoing active ecosystem restoration. The brackish, tidal fishpond is located within Kāne‘ohe Bay, Hawai‘i. Following a year of monthly discrete sampling, a significant shift in DIC and percent O2 saturation was observed along the North-South axis within the pond. The south end of the pond was higher in DIC (+35 μmol·kg⁻¹) and lower in percent O2 saturation (-19%) than the north end, which exhibited values similar to those observed in water entering the fishpond from the bay. Water quality parameters and inequal proximity to water flux sites suggested that a difference in residence time may exist along the north-south axis. In addition, ΔTA/ΔDIC relationships revealed a respiration signal in south end of the pond, which was enhanced at depth. While physical processes strongly affect CO2 and O2 across various temporal scales, spatial patterns in biological processes may also affect variability within the fishpond. These findings demonstrate that changes in water chemistry within the fishpond are the result of ecosystem restoration efforts. In turn, future management decisions at the fishpond will play an important role in preserving its viability as a healthy habitat for the intended marine species.

Continue reading ‘Assessment of CO2 and O2 spatial variability in an indigenous aquaculture system for restoration impacts’

GOA-ON webinar: mediterranean calcifying organisms under ocean acidification and warming (audio & video)

Dr. Chloe Carbonne (Laboratory of Oceanography of Villefranche, Sorbonne University, Villefranche-sur-Mer, France) and Maximiliano Szkope (University of Malaga, Malaga, Spain) will be presenting their work on calcifying organisms in the Mediterranean Sea under the effects of ocean acidification and warming.

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Ocean acidification: a crisis in the making


Ocean health and climate change are inextricably linked: as CO2 becomes more concentrated in the atmosphere, it also builds up in the seas. The result, ocean acidification, will have disastrous effects to livelihoods if left unchecked. Already, coastal industries such as fishing and aquaculture are being hurt. Natural assets such as biodiversity and coral reefs are threatened. The consequences will be both ecological and economic. Yet solutions exist.

Join us as we explore what ocean acidification is, what we can do to avoid its worst impacts, and how governments, business leaders and scientists can co-operate to better respond to this existential threat within Japan and around the globe

Event schedule

2 – 2:15 pm JST
Opening remarks | Welcome address
2:15 – 2:30 pm JST
Film screening (15 minutes) | The threat bubbling up
2:35 – 3:30 pm JST
Panel: pH 7: de-acidifying our oceans
3:30 – 3:50 pm JST
Intermission (20 minutes)
3:50 – 4:50 pm JST
Panel: Mitigating ocean acidification along the coastlines of Japan
4:50 – 5:10 pm JST
5:10 – 5:20 pm JST
Closing remarks and event end

Virtual Registration Link: Ocean acidification: a crisis in the making (

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Clay-shielded estuarine gastropods are better protected against environmental acidification than unshielded individuals

Graphical abstract.


  • Acidified estuaries compromise building and threaten dissolution of gastropods shells.
  • Periostracum of Neripteron snails directs formation of an outer shell clay shield.
  • Shield constructed of the mineral illite is tightly chemically-bonded to the periostracum.
  • The more reflective unshielded shells showed a greater rate of dissolution.
  • Ecological and evolutionary constraints on carbonate shell building predict outer protection.


The effects of progressive global acidification on the shells of marine organisms is a topic of much current interest. Most studies on molluscan shell resistance to dissolution consider the carbonate mineral component, with less known about the protective role of the outer organic periostracum. Outer-shell resistance would seem especially important to gastropods living in carbonate-undersaturated and calcium-deficient estuarine waters that threaten shell dissolution and constrain CaCO3 production. We tested this prediction using gastropods from an acidified estuarine population (Neripteron violaceum) that form a clay shield outside the periostracum. Specifically, we aimed to show that the carbonate shell component lacks integrity, that the formation of the clay shield is directed by the organism, and that the clay shield functions to protect against shell dissolution. We found no evidence for any specific carbonate dissolution resistance strategy in the thin, predominantly aragonitic shells of these gastropods. Shield formation was directed by an ornamented periostracum which strongly bonded illite elements (e.g., Fe, Al and S), that become available through suspension in the water column. In unshielded individuals, CaCO3 erosion was initiated randomly across the shell (not age-related) and progressed rapidly when the periostracum was breached. A light reflectance technique showed qualitatively that shield consolidation is negatively-related to shell erosion. These findings support a conceptual framework for gastropod outer-shell responses to acidification that considers both environmental and evolutionary constraints on shell construction. We describe a novel strategy for shell protection against dissolution, highlighting the diversity of mechanisms available to gastropods facing extreme coastal acidification.

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Resistant calcification responses of Arctica islandica clams under ocean acidification conditions


  • We cultured both juvenile and adult A. islandica collected from northern Norway under a range of pH
  • Arctica islandica from Norway can maintain its shell growth even in aragonite undersaturated (Ω < 1) conditions.
  • Our results show that shell growthresilience in acidified seawater is likely a multi-population adaptation in A. islandica.


Ocean acidification (OA) directly impacts marine calcifying organisms including ecologically and commercially important shellfish species such as Arctica islandica (A. islandica). To test whether documented growth resilience of A. islandica to OA is a general response across ages and populations or a function of adaptation to local habitat, we cultured juvenile and adult clams collected from an environment with little pH variation under four pH levels (7.5, 7.7, 7.9, and 8.1) for three months and integrated our understanding with relevant literature. The average shell growth over the experiment among all (69) individuals was 57 ± 55 μm, and there were no statistically significant differences in growth among pH treatments, including the control treatment, despite the general growth rate differences between juveniles and adults. Our results show that A. islandica can maintain its shell growth even in aragonite undersaturated (Ω < 1) conditions (0.65 and 0.83 for pH 7.5 and 7.7 treatments, respectively), supporting the hypothesis that resistance to OA conditions is likely a generalized response across populations. Although the present results show A. islandica can maintain their shell growth under short-term OA, long-term impacts of OA on A. islandica shell growth and other physical parameters including shell density and microstructure are still needed to better assess the sustainability of A. islandica in a more acidified future and to provide guidance on managing this important shellfish stock.

Continue reading ‘Resistant calcification responses of Arctica islandica clams under ocean acidification conditions’

Response mechanism of harmful algae Phaeocystis globosa to ocean warming and acidification

Graphical abstract

Simultaneous ocean warming and acidification will alter marine ecosystem structure and directly affect marine organisms. The alga Phaeocystis globosa commonly causes harmful algal blooms in coastal areas of eastern China. P. globosa often outcompetes other species due to its heterotypic life cycle, primarily including colonies and various types of solitary cells. However, little is known about the adaptive response of P. globosa to ocean warming and acidification. This study aimed to reveal the global molecular regulatory networks implicated in the response of P. globosa to simultaneous warming and acidification. After exposure to warming and acidification, the phosphatidylinositol (PI) and mitogen-activated protein kinase (MAPK) signaling pathways of P. globosa were activated to regulate other molecular pathways in the cell, while the light harvesting complex (LHC) genes were downregulated to decrease photosynthesis. Exposure to warming and acidification also altered the intracellular energy flow, with more energy allocated to the TCA cycle rather than to the biosynthesis of fatty acids and hemolytic substances. The upregulation of genes associated with glycosaminoglycan (GAG) degradation prevented the accumulation of polysaccharides, which led to a reduction in colony formation. Finally, the upregulation of the Mre11 and Rad50 genes in response to warming and acidification implied an increase in meiosis, which may be used by P. globosa to increase the number of solitary cells. The increase in genetic diversity through sexual reproduction may be a strategy of P. globosa that supports rapid response to complex environments. Thus, the life cycle of P. globosa underwent a transition from colonies to solitary cells in response to warming and acidification, suggesting that this species may be able to rapidly adapt to future climate changes through life cycle transitions.

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No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies

In a future ocean, dissolved organic carbon (DOC) release by seaweed has been considered a pathway for organic carbon that is not incorporated into growth under carbon dioxide (CO2) enrichment/ocean acidification (OA). To understand the influence of OA on seaweed DOC release, a 21-day experiment compared the physiological responses of three seaweed species, two which operate CO2 concentrating mechanisms (CCMs), Ecklonia radiata (C. Agardh) J. Agardh and Lenormandia marginata (Hooker F. and Harvey) and one that only uses CO2 (non-CCM), Plocamium cirrhosum (Turner) M.J. Wynne. These two groups (CCM and non-CCM) are predicted to respond differently to OA dependent on their affinities for Ci (defined as CO2 + bicarbonate, HCO3). Future ocean CO2 treatment did not drive changes to seaweed physiology—growth, Ci uptake, DOC production, photosynthesis, respiration, pigments, % tissue carbon, nitrogen, and C:N ratios—for any species, regardless of Ci uptake method. Our results further showed that Ci uptake method did not influence DOC release rates under OA. Our results show no benefit of elevated CO2 concentrations on the physiologies of the three species under OA and suggest that in a future ocean, photosynthetic CO2 fixation rates of these seaweeds will not increase with Ci concentration.

Continue reading ‘No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies’

Spatial pH variability of coral reef flats of Kiritimati Island, Kiribati

Ocean acidification poses a threat to carbonate-dominated marine systems, such as tropical coral reefs, as it impacts the ability of organisms to calcify. For assessing the susceptibility of coral reef flats to open ocean acidification it is crucial to better understand the dynamics between the carbonate chemistry of open ocean waters flowing onto coral reef flats and the ecological and hydrodynamic processes that locally modify seawater conditions.

In this study, variations in seawater pH and temperature were measured along cross-reef flat transects in high resolution (∼0.3 m) and complemented by surveys of the benthic community composition and reef flat bathymetry.

Results represent a snapshot in time and suggest that reef flat hydrodynamic processes determine spatial pH modifications, with little influence of variations in benthic community composition. As mean reef flat pH largely equals ocean conditions, ocean acidification has had and will have an unhampered impact on narrow fringing reef flats.

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Testing hypotheses on the calcification in scleractinian corals using a spatio-temporal model that shows a high degree of robustness


  • Several hypotheses on coral calcification are tested using a computational model.
  • The model is able to reproduce the experimental data of three separate studies.
  • The model finds that paracellular ion transport into the ECM plays a minor role.
  • Implementing OA in the model increased the calcification rate and ATP consumption.
  • In the model, LEC is the result of increased metabolism and Ca2+-ATPase activity.


Calcification in photosynthetic scleractinian corals is a complicated process that involves many different biological, chemical, and physical sub-processes that happen within and around the coral tissue. Identifying and quantifying the role of separate processes in vivo or in vitro is difficult or not possible. A computational model can facilitate this research by simulating the sub-processes independently. This study presents a spatio-temporal model of the calcification physiology, which is based on processes that are considered essential for calcification: respiration, photosynthesis, Ca2+-ATPase, carbonic anhydrase. The model is used to test different hypotheses considering ion transport across the calicoblastic cells and Light Enhanced Calcification (LEC). It is also used to quantify the effect of ocean acidification (OA) on the Extracellular Calcifying Medium (ECM) and ATP-consumption of Ca2+-ATPase. It was able to reproduce the experimental data of three separate studies and finds that paracellular transport plays a minor role compared to transcellular transport. In the model, LEC results from increased Ca2+-ATPase activity in combination with increased metabolism. Implementing OA increases the concentration of CO2 throughout the entire tissue, thereby increasing the availability of CO3− in the ECM. As a result, the model finds that calcification becomes more energy-demanding and the calcification rate increases.

Continue reading ‘Testing hypotheses on the calcification in scleractinian corals using a spatio-temporal model that shows a high degree of robustness’

Climate & ecosystems coordinator

About the Position

The Northeastern Regional Association of Coastal Ocean Observing Systems (NERACOOS) is seeking to hire a Climate & Ecosystems Coordinator to manage and grow a portfolio of work on emerging issues that affect ecological integrity, coastal resilience, livelihoods, and human health in coastal and ocean environments of the Northeastern U.S. A particular focus will be advancing and integrating existing initiatives addressing Ocean & Coastal Acidification (OCA), specifically the Northeast Coastal Acidification Network and the Ocean Acidification Information Exchange. Additionally, the position will scope and develop new initiatives related to Harmful Algal Blooms (HABs), Marine Heat Waves (MHWs), marine Carbon Dioxide Removal (mCDR), and other issues, including the intersections of those issues with one another and with OCA. For all of the issues considered, the position will also determine how to most effectively capitalize on and evolve the regional ocean observing systems managed by NERACOOS to better track critical climate and ecosystem indicators. Across this portfolio of work, the position will work at the intersection of ecosystem science and end-user engagement.

Primary Responsibilities

Northeast Coastal Acidification Network (NECAN)

  • Organize regular meetings of the NECAN Steering Committee and the NECAN thematic work groups (education & outreach, science, management & policy, and industry).
  • Continue the popular NECAN webinar program by recruiting speakers, publicizing events, and synthesizing outcomes.
  • Lead the development of a Regional OCA Monitoring Plan in collaboration with the Northeast Regional Ocean Council and other partners, and work to begin its implementation.
  • Participate in meetings, conferences, and other events as part of the national system of Coastal Acidification Networks (CANs) and other initiatives organized by the NOAA Ocean Acidification Program (OAP).
  • Plan and execute research, monitoring, and user engagement activities at regional and national scales in collaboration with OAP, other CANs, and other partners.
  • Coordinate and support outreach activities such as workshops, webinars, and educational collaterals.
  • Maintain the NECAN implementation plan, website, and newsletter.

Ocean Acidification Information Exchange (OAIE)

  • Manage the OAIE online platform, including responding to new member requests, tracking technical issues, managing work of the site developer, ensuring regular member updates, and other tasks.
  • Work with web developer to implement website transition to new content management system and website improvements that better serve the community.
  • Grow the community of OAIE users by publicizing the platform through social media channels, OCA-related events and publications, direct outreach to prospective users, and other tactics.
  • Foster community engagement on the OAIE platform with content, both directly and by encouraging members to share questions, ideas, and news of interest to the community.
  • Organize the OAIE community through teams convened through the platform.
  • Convene and organize quarterly meetings of the Steering Committee.
  • Work closely with OAP and CANs to identify ways that OAIE can better serve the community of practitioners focused on OCA.

Applying Instructions: Submit CV, 1-page cover letter, and contact information for three professional references as a PDF to Rob Cardeiro ( The search committee will review applications beginning February 1, 2023, and will continue until the position is filled.

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Vulnerability of red sea urchins to climate change depends on location

Red sea urchins are an important commercial fishery species along the California coast. Emily Donham and other UCSC researchers studied how different populations of red sea urchins respond to changes in their environments. (Photo by Kate Vylet)

A new study of red sea urchins, a commercially valuable species, investigated how different populations respond to changes in their environments. The results show that red sea urchin populations in Northern and Southern California are adapted to their local conditions but differ in their vulnerability to the environmental changes expected to occur in the future due to global climate change and ocean acidification.

The new findings, published January 20 in Science Advances, indicate that red sea urchin populations in Southern California may be more vulnerable to climate change than those in Northern California. Although the sea urchins in Southern California are already adapted to warmer conditions, the researchers suspect that further warming of their environment may be more than they can tolerate.

“Red sea urchins from the Southern California population were much more sensitive to environmental changes than those from Northern California, and we think that is likely because they are already closer to some kind of thermal limit,” said senior author Kristy Kroeker, professor of ecology and evolutionary biology at UC Santa Cruz.

First author Emily Donham led the study as a UCSC graduate student and is now a postdoctoral scholar at UC Santa Barbara. “Red sea urchins are an important fishery species along our coast, so understanding how they are likely to be impacted by climate change is very important,” she said.

The study looked at the effects of three key environmental variables in the sea urchins’ coastal habitat: water temperature, dissolved oxygen, and pH (a measure of ocean acidification). Climate change driven by increased carbon dioxide in the atmosphere is warming the oceans and reducing oxygen levels in the water, while increased absorption of carbon dioxide by seawater leads to ocean acidification.

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Population-specific vulnerability to ocean change in a multistressor environment

Variation in environmental conditions across a species’ range can alter their responses to environmental change through local adaptation and acclimation. Evolutionary responses, however, may be challenged in ecosystems with tightly coupled environmental conditions, where changes in the covariance of environmental factors may make it more difficult for species to adapt to global change. Here, we conduct a 3-month-long mesocosm experiment and find evidence for local adaptation/acclimation in populations of red sea urchins, Mesocentrotus franciscanus, to multiple environmental drivers. Moreover, populations differ in their response to projected concurrent changes in pH, temperature, and dissolved oxygen. Our results highlight the potential for local adaptation/acclimation to multivariate environmental regimes but suggest that thresholds in responses to a single environmental variable, such as temperature, may be more important than changes to environmental covariance. Therefore, identifying physiological thresholds in key environmental drivers may be particularly useful for preserving biodiversity and ecosystem functioning.

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Metabolic adaptation of fishes under different consequences of climate change

Aquaculture sustainability is affected by climate change which regulated livelihood, nutrition and world food security. The most important contributor to climate change is documented by a human due to deforestation and industries that release GHGs (greenhouse gases) accumulated in the surrounding environment such as methane, nitrous oxide, fluorinated gases and carbon dioxide. Climate change affected fisheries adversely but it is overshadowing the positive one. The effects of climate change on fishes can be directed by water quality parameters such as temperature, dissolve oxygen, pH (acidification) etc. which affected fish physiology and behavioural changes through metabolic adaptation. Due to the changes in climate fishes are adapting to a novel environment like high temperatures (higher to lower latitude or lower to higher latitude), a hypoxic condition due to evolutionary effect and adapting to low pH which is caused by high carbon dioxide released in the environment by human activities. This chapter mainly focuses on how fishes are adapting to the novel climatic condition such as a high or low temperature, hypoxic conditions and low pH through the metabolic activity through enzymatic action (fish physiology) and morphological changes like gill structure to cope with low oxygen and acidification of natural water body.

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Effect of pH on the early development of the biofouling ascidian Ciona robusta

Ocean acidification (OA) impacts the survival, fertilization, and community structure of marine organisms across the world. However, some populations or species are considered more resilient than others, such as those that are invasive, globally distributed, or biofouling. Here, we tested this assumption by investigating the effect of pH on the larval development of one such tunicate, Ciona robusta, which is currently exposed to a wide range of pH levels. Consistent with our hypothesis, C. robusta larvae developed and metamorphosed at a rate comparable to control (pH 8.0) at modest near-future conditions (pH 7.7) over a 58-hour period. However, development was stunted at the extreme low pH of 6.8 such that no embryo progressed beyond late cleavage after 58 hours. Interestingly, piecewise regression of the proportion of embryos at the most advanced stage at a given time point against pH identified a breakpoint with the highest pH (~pH 7.6) at around hatching. The variation in breakpoint pH throughout ontogeny highlighted that the sensitivity to decreasing pH differs significantly between developmental stages. More broadly, our results show that even a cosmopolitan, biofouling, invasive species could be negatively impacted by decreasing pH.

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