Posts Tagged 'reproduction'

Understanding the impacts of environment and parasitism on Eastern oyster (Crassostrea virginica) vulnerability to ocean acidification

The global process of ocean acidification caused by the absorption of increased atmospheric carbon dioxide decreases the concentration of carbonate ions and reduces the associated seawater saturation state (ΩCaCO3) – making it more energetically costly for marine calcifying organisms to build their shells or skeletons. Bivalves are particularly vulnerable to the adverse effects of ocean acidification on calcification, and they inhabit estuaries and coastal zones – regions most susceptible to ocean acidification. However, the response of an individual to elevated pCO2 can depend on the carbonate chemistry dynamics of its current environment and the environment of its parents. Additionally, an organism’s response to ocean acidification can depend on its ability to control the chemistry at the site of calcification. Biotic and abiotic stressors can modify bivalves’ control of calcifying fluid chemistry – known as extrapallial fluid (EPF). Understanding the responses of bivalves – which are foundation species – to ocean acidification is essential for predicting the impacts of oceanic change on marine communities. This dissertation uses a culturally, ecologically, and economically important bivalve in the northwest Atlantic – the Eastern oyster (Crassostrea virginica) – to explore the effects of environment and species interactions on responses to elevated pCO2.

Chapter 2 describes a field study that characterized diurnal and seasonal carbonate chemistry dynamics of two estuaries in the Gulf of Maine that support Eastern oyster populations. The estuaries were monitored at high temporal resolution (half-hourly) over four years (2018-2021) using pH and conductivity loggers. Measured pH, salinity, and temperature were used to calculate carbonate chemistry parameters. Both estuaries exhibited strong seasonal and diurnal fluctuations in carbonate chemistry. They also experienced pCO2 values that greatly exceeded current atmospheric carbon dioxide levels and those projected for the year 2100.

Chapter 3 describes a laboratory experiment that examined the capacity of intergenerational exposure to mitigate the adverse effects of ocean acidification on larval growth, shell morphology, and survival. Adult oysters were cultured in control or elevated pCO2 conditions for 30 days then crossed using a North Carolina II cross design. Larvae were grown for three days under control and elevated pCO2 conditions. Intergenerational exposure to elevated pCO2 conditions benefited early larval growth and shell morphology, but not survival. However, parental exposure was insufficient to completely counteract the adverse effects of the elevated pCO2 treatment on shell formation and survival.

Chapter 4 describes a laboratory experiment that examined the interplay between ocean acidification and parasite-host dynamics. Eastern oysters infested and not infested with bioeroding sponge (Cliona sp.) were cultured under three pCO2 conditions (539, 1040, 3294 ppm) and two temperatures (23, 27˚C) for 70 days to assess oyster control of EPF chemistry, growth, and survival. Bioeroding sponge infestation and elevated pCO2 reduced oyster net calcification and EPF pH but did not affect condition or survival. Infested oyster EPF pH was consistently lower than seawater pH, while EPF dissolved inorganic carbon was consistently elevated relative to seawater. These findings suggested that infested oysters effectively precipitated repair shell to prevent seawater intrusion into extrapallial fluid through bore holes across all treatments.

Chapter 5 characterizes the concentration of a suite of 56 elements normalized to calcium in EPF and shell of Crassostrea virginica grown under three pCO2 conditions (570, 990, 2912 ppm) and sampled at four timepoints (days 2, 9, 79, 101) to assess effects of pCO2 on organismal control of EPF and shell elemental composition and EPF-to-shell elemental partitioning. Elevated pCO2 significantly influenced the relative abundance of elements in the EPF (29) and shell (13) and altered EPF-to-shell elemental partitioning for 45 elements. Importantly, elevated pCO2 significantly influenced the concentration of several elements in C. virginica shell that are used in other biogenic carbonates as paleo-proxies for other environmental parameters. This result suggests that elevated pCO2 could influence the accuracy of paleo reconstructions.

Overall, this dissertation provides insights that can help improve our understanding of past, present, and future ocean environments. Understanding current local carbonate chemistry dynamics and the capacity for C. virginica to acclimate intergenerationally to elevated pCO2 can inform site and stock selection for aquaculture and restoration efforts. Studying parasite-host environment interactions provides critical insights into the potential for parasitism to alter responses to future ocean acidification. Finally, exploring the impact of elevated pCO2 on elemental composition of EPF and shell allowed us to understand better biomineralization processes, identify potential proxies for seawater pCO2 in bivalves, and offer insights that could help improve the accuracy of paleo reconstructions.

Continue reading ‘Understanding the impacts of environment and parasitism on Eastern oyster (Crassostrea virginica) vulnerability to ocean acidification’

Ocean acidification impacts fish larvae but warming could compensate juveniles

Related content

A related article has been published: Effects of ocean acidification over successive generations decrease resilience of larval European sea bass to ocean acidification and warming but juveniles could benefit from higher temperatures in the NE Atlantic

A 40 day old European sea bass (Dicentrarchus labrax) larva: Photo credit: Sarah Howald.

As we pump more CO2 into the atmosphere, the pH of the oceans is decreasing and although a reduction of 0.1 pH units may not sound much, the reality is that the acidity of the seas has increased by 30% since the start of the Industrial Revolution in the 18th century. But no one knew how much of an impact decreasing pH might have on long-lived fish species. ‘Fish had been thought to be less vulnerable to ocean acidification due to well-developed acid–base regulation systems’, says Sarah Howald from the Alfred Wegener Institute for Polar and Marine Research (AWI), Germany. However, scientists have recently discovered that fish larvae may be more vulnerable than thought. Some grew faster in more acidic waters, while others suffered tissue and hearing damage in addition to growing more slowly. Yet, no one knew how ocean acidification might impact subsequent generations. Felix Mark from AWI, with colleagues from Germany and France, embarked on an ambitious 5.5 year investigation to find out how European sea bass (Dicentrarchus labrax) larvae and their eventual offspring deal with acidic conditions.

In October 2013, at the Ifremer-Centre de Bretagne, France, Guy Claireaux (University of Brest, France), José Zambonino and David Mazurais (both from Ifremer), Myron Peck (University of Hamburg, Germany) and Mark allocated recently hatched sea bass larvae to small tanks of seawater pumped in from the Bay of Brest at summer temperatures (19°C) while other larvae lived in tanks of seawater where the acidity had been raised to 1700 μatm CO2, the IPCC’s prediction for seawater CO2 concentrations 120 years in the future. Once the larvae had developed into juveniles (∼2.5 months old), the team relocated the youngsters to larger cool (15°C) tanks, maintaining the two different pH levels until the fish were adult (spring 2017), when the researchers selected ∼30 adult fish each from the two water conditions to rehome in palatial 3000 l tanks. Then, in March 2018, the 5 year old adults spawned to produce the next generation of larvae. But this time the scientists added a twist, dividing the offspring of the parents from the modern day (current CO2) seawater conditions and those of the parents raised in the acidic future water conditions (1700 μatm CO2) into cool and warm tanks, to simulate climate change. Meanwhile, the team kept track of the first and the second generations as they grew and developed.

Initially, the first generation of sea bass youngsters didn’t seem to be affected by their acidic start in life and neither did their offspring. However, when the team altered the water temperature as the second generation developed in the acidic future water, they found the larvae from the warmer (20°C) tank were much smaller when they metamorphosed into juveniles than those in cool acidic seawater and those that developed in modern warm water. Mark suspects that the warmer high-CO2 conditions in the future could impair energy production by the youngsters’ mitochondria, limiting their growth. However, once the larvae developed into juvenile fish, they seemed to benefit, growing faster, although the team isn’t sure whether the warmth was accelerating the fish’s growth or whether the acidity failed to impair the growing juveniles.

The team warns that the faster growth of larvae in a warmer more acidic world could place them at risk if there is insufficient food for the rapidly growing youngsters. But it seems that if the youngsters develop successfully into juvenile fish, their chances may improve.

Continue reading ‘Ocean acidification impacts fish larvae but warming could compensate juveniles’

Adaptive potential of coastal invertebrates to environmental stressors and climate change

Climate change presents multiple stressors that are impacting marine life. As carbon dioxide emissions continue to increase in the atmosphere, atmospheric and sea water temperatures increase. In addition, more carbon dioxide is absorbed into the oceans, reducing pH and aragonite saturation state, resulting in ocean acidification (OA). Tightly coupled with OA is hypoxia due to deep stratified sea water becoming increasingly acidified and deoxygenated. The effects of these climate stressors have been studied in detail for only a few marine animal models. However, there are still many taxa and developmental stages in which we know very little about the impacts. Using genomic techniques, we examine the adaptive potential of three local marine invertebrates under three different climate stressors: marine disease exacerbated by thermal stress, OA, and combined stressors OA with hypoxia (OAH). As sea water temperatures rise, the prevalence of marine diseases increases, as seen in the sea star wasting syndrome (SSWS). The causation of SSWS is still widely debated; however reduced susceptibility to SSWS could aid in understanding disease progression. By examining genetic variation in Pisaster ochraceous collected during the SSWS outbreak, we observed weak separation between symptomatic and asymptomatic individuals. OA has been widely studied in many marine organisms, including Crassostrea gigas. However, limited studies have parsed the effects of OA during settlement, with no studies assessing the functionality of settlement and how it is impacted by OA. We investigated the effects of OA on settlement and gene expression during the transition from larval to juvenile stages in Pacific oysters. While OA and hypoxia are common climate stressors examined, the combined effects have scarcely examined. Further, the impacts of OAH have been narrowly focused on a select few species, with many economically important organisms having no baseline information on how they will persist as OAH severity increases. To address these gaps in our knowledge, we measured genetic variation in metabolic rates during OA for the species Haliotis rufescens to assess their adaptive potential through heritability measurements. We discuss caveats and considerations when utilizing similar heritability estimate methods for other understudied organisms. Together, these studies will provide novel information on the biological responses and susceptibility of difference coastal species to stressors associated with global climate change. These experiments provide information on both the vulnerability of current populations and their genetic potential for adaptation to changing ocean conditions.

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Caribbean king crab larvae and juveniles show tolerance to ocean acidification and ocean warming

Coastal habitats are experiencing decreases in seawater pH and increases in temperature due to anthropogenic climate change. The Caribbean king crab, Maguimithrax spinosissimus, plays a vital role on Western Atlantic reefs by grazing macroalgae that competes for space with coral recruits. Therefore, identifying its tolerance to anthropogenic stressors is critically needed if this species is to be considered as a potential restoration management strategy in coral reef environments. We examined the effects of temperature (control: 28 °C and elevated: 31 °C) and pH (control: 8.0 and reduced pH: 7.7) on the king crab’s larval and early juvenile survival, molt-stage duration, and morphology in a fully crossed laboratory experiment. Survival to the megalopal stage was reduced (13.5% lower) in the combined reduced pH and elevated temperature treatment relative to the control. First-stage (J1) juveniles delayed molting by 1.5 days in the reduced pH treatment, while second-stage (J2) crabs molted 3 days earlier when exposed to elevated temperature. Juvenile morphology did not differ among treatments. These results suggests that juvenile king crabs are tolerant to changes associated with climate change. Given the important role of the king crab as a grazer of macroalgae, its tolerance to climate stressors suggests that it could benefit restoration efforts aimed at making coral reefs more resilient to increasingly warm and acidic oceans into the future.

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Otolith development and elemental incorporation in response to seawater acidification in the flounder Paralichthys olivaceus at early life stages


  • Ocean acidification promoted otolith growth but not changed otolith shape.
  • Ocean acidification did not alter somatic growth or otolith elemental incorporation.
  • Ocean acidification induced and increased the occurrence of irregular calcitic otoliths.
  • Elemental incorporation is higher in aragonitic otoliths than in calcitic otoliths.


Ocean acidification can influence the formation, development and functions of calcified structures in marine organisms, such as otoliths, which are mainly composed of calcium carbonate (CaCO3) and function in orientation, balance, sensory perception and locomotion in fish. This study investigated the impacts of seawater acidification (pH 8.10, 7.70 and 7.30, roughly corresponding to the ocean acidification under RCP 8.5 scenario predicted by the IPCC) on somatic growth, otolith (aragonite) morphology and microchemistry in the flounder Paralichthys olivaceus at early life stages (ELSs, exposed to acidified seawater via pCO2 from embryonic to juvenile stages for 52 days). The results demonstrated that seawater acidification promoted otolith growth (mass and size) but did not change their geometric outlines. Seawater acidification did not alter the somatic growth or otolith elemental incorporation (Sr, Ba and Mg) in the flounder. Seawater acidification increased the occurrence of abnormally developed calcitic otoliths (calcite) which considerably differed from the aragonitic otoliths in surface and crystal structures. Additionally, elemental incorporation (Sr:Ca and Ba:Ca) appeared to be higher in aragonitic otoliths than in calcitic otoliths, which was likely related to their unique manners of formation. Our results agreed with the broad literature, in that seawater acidification showed species-specific influences (positive or no effect) on otolith size but did not affect somatic growth, otolith shape or elemental incorporation of fish at ELSs. These findings provide knowledge for evaluating the ecological effects of ocean acidification on the recruitment and population dynamics of fish in the wild.

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Impact of microplastics and ocean acidification on critical stages of sea urchin (Paracentrotus lividus) early development


  • Ocean acidification and microplastics altered the morphology of P. lividus larvae.
  • Ocean acidification and microplastics reduce growth of P. lividus larvae.
  • Alterations occurred before and after larvae start to feed exogenously.
  • The combined effect of both stressors on P. lividus morphology is non additive.
  • SET is an ideal method to study the impact of ocean acidification at a lab scale.


One of the major consequences of increasing atmospheric CO2 is a phenomenon known as ocean acidification. This alteration of water chemistry can modulate the impact on marine organisms of other stressors also present in the environment, such as microplastics (MP). The objective of this work was to determine the combined impact of microplastic pollution and ocean acidification on the early development of Paracentrotus lividus. To study these multi-stressor impacts on development P. lividus the sea urchin embryo test (SET) was used. Newly fertilised embryos of P. lividus were exposed to a control treatment (filtered natural seawater), MP (3000 particles/mL), acidified sea water (pH = 7.6), and a combination of MP and acidification (3000 particles/mL + pH = 7.6). After 48, 72, and 96 h measurements of growth and morphometric parameters were taken. Results showed that ocean acidification and MP cause alterations in growth and larval morphology both before and after the larvae start to feed exogenously. The exposure to MP under conditions of ocean acidification did not produce any additional effect on growth, but differences were observed at the morphological level related to a decrease in the width of larvae at 24 h. Overall, changes in larvae shape observed at three key points of their development could modify their buoyancy affecting their ability to obtain and ingest food. Therefore, ocean acidification and MP pollution might compromise the chances of P. lividus to survive in the environment under future scenarios of global climate change.

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Metabolic effect of ocean acidification on common cuttlefish Sepia officinalis early stages

Atmospheric carbon dioxide (CO2) emissions are continuously increasing due to the growing anthropogenic activities, causing a rise in the sea-surface partial pressure of CO2 (pCO2). This change in turn leads to decreased ocean pH, named ocean acidification, and affects the carbonate-silicate cycle. Such modification of seawater chemistry also affects the physiology and behaviour of marine organisms, impacting their metabolism, growth and development during vulnerable early-life stages. Among them, the embryo of the cephalopod cuttlefish develops for ~2 months) in encapsulated eggs with harsh conditions of hypoxia and hypercapnia, potentially worsen by the environmental ocean acidification. In this study, the development and the growth of early-life stages of Sepia officinalis were followed during the whole embryonic developmental period up to 10 days post-hatchling juveniles. Embryos and juveniles were exposed to five elevated pCO2 conditions controlled with a continuous pH-stat system (pH 8.08; 7.82; 7.65; 7.54; 7.43). Metabolites were determined in ready-to-hatch embryos, just hatched embryos and 10 d-old juveniles, using a 1H nuclear magnetic resonance (NMR) spectroscopy as a platform for untargeted metabolomics analysis. Consistent with previous studies, our results showed longer embryonic development and decreased hatching success at the lowest pH, but no effect on juvenile weight upon hatching. Metabolomics analysis revealed a metabolic depression in embryos reared at pH 7.43, non-monotonic changes to pH in 10 d-old juveniles, and no clear pH effect in newly hatched juvenile cuttlefish, likely due to the metabolic stress associated with hatching. Those results reveal possible effect of ocean acidification on the cuttlefish recruitment.

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Multigenerational life-history responses to pH in distinct populations of the copepod Tigriopus californicus

Intertidal zones are highly dynamic and harsh habitats: organisms that persist there must face many stressors, including drastic changes in seawater pH, which can be strongly influenced by biological processes. Coastal ecosystems are heterogeneous in space and time, and populations can be exposed to distinct selective pressures and evolve different capacities for acclimation to changes in pH. Tigriopus californicus is a harpacticoid copepod found in high-shore rock pools on the west coast of North America. It is a model system for studying population dynamics in diverse environments, but little is known about its responses to changes in seawater pH. I quantified the effects of pH on the survivorship, fecundity, and development of four T. californicus populations from San Juan Island, Washington, across three generations. For all populations and generations, copepod cultures had lower survivorship and delayed development under extended exposure to higher pH treatments (pH 7.5 and pH 8.0), whereas cultures maintained in lower pH (7.0) displayed stable population growth over time. Reciprocal transplants between treatments demonstrated that these pH effects were reversible. Life histories were distinct between populations, and there were differences in the magnitudes of pH effects on development and culture growth that persisted through multiple generations. These results suggest that T. californicus might not have the generalist physiology that might be expected of an intertidal species, and it could be adapted to lower average pH conditions than those that occur in adjacent open waters.

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Ocean futures for the world’s largest yellowfin tuna population under the combined effects of ocean warming and acidification

The impacts of climate change are expected to have profound effects on the fisheries of the Pacific Ocean, including its tuna fisheries, the largest globally. This study examined the combined effects of climate change on the yellowfin tuna population using the ecosystem model SEAPODYM. Yellowfin tuna fisheries in the Pacific contribute significantly to the economies and food security of Pacific Island Countries and Territories and Oceania. We use an ensemble of earth climate models to project yellowfin populations under a high greenhouse gas emissions (IPCC RCP8.5) scenario, which includes, the combined effects of a warming ocean, increasing acidification and changing ocean chemistry. Our results suggest that the acidification impact will be smaller in comparison to the ocean warming impact, even in the most extreme ensemble member scenario explored, but will have additional influences on yellowfin tuna population dynamics. An eastward shift in the distribution of yellowfin tuna was observed in the projections in the model ensemble in the absence of explicitly accounting for changes in acidification. The extent of this shift did not substantially differ when the three-acidification induced larval mortality scenarios were included in the ensemble; however, acidification was projected to weaken the magnitude of the increase in abundance in the eastern Pacific. Together with intensive fishing, these potential changes are likely to challenge the global fishing industry as well as the economies and food systems of many small Pacific Island Countries and Territories. The modelling framework applied in this study provides a tool for evaluating such effects and informing policy development.

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A framework for assessing harvest strategy choice when considering multiple interacting fisheries and a changing environment: the example of eastern Bering Sea crab stocks

Ecosystem Based Fisheries Management aims to broaden the set of factors included in assessments and management decision making but progress with implementation remains limited. We developed a framework that examines the consequences of temporal changes in temperature and ocean pH on yield and profit of multiple interacting stocks including eastern Bering Sea (EBS) snow, southern Tanner, and red king crab. Our analyses integrate experimental work on the effects of temperature and ocean pH on growth and survival of larval and juvenile crab and monitoring data from surveys, fishery landings, and at-sea observer programs. The impacts of future changes in temperature and ocean pH on early life history have effects that differ markedly among stocks, being most pessimistic for Bristol Bay red king crab and most optimistic for EBS snow crab. Our results highlight that harvest control rules that aim to maximize yield lead to lower profits than those that aim to maximize profit. Similarly, harvest control rules that aim to maximize profit lead to lower yields than those that aim to maximize yield, but differences are less pronounced. Maximizing profits has conservation benefits, especially when the implemented harvest control rule reduces fishing mortality if population biomass is below a threshold level.

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Effects of ocean acidification on Lythrypnus dalli reproductive output and behavior

Reproduction in fishes is an energetically costly but vital process that is important to nearshore fisheries and proper ecosystem functioning. Successful fish reproduction is generally limited to a narrow breadth of specific environmental conditions, and variation in these conditions may affect the ability of fish to allocate energy towards reproduction. In particular, ocean acidification (OA) is generally assumed to be a major threat to fish reproduction, but past studies on the effects of OA have produced variable results. To examine how OA affects bluebanded goby (Lythrypnus dalli) reproduction, female reproductive output and male reproductive behaviors were quantified under two experimental treatments that represent differences between present-day (ambient) and future OA (decreased by 0.2 pH units) conditions. To do this, sexually mature bluebanded gobies were placed in laboratory mesocosms for continuous seven-day trials and allowed to reproduce in artificial nests. Four artificial nests were placed in each of the four mesocosms to provide fish with similar nesting habitats to encourage reproduction. Each mesocosm included similar fish size structures and numbers of female gobies to control for any size- or sex-dependent responses. Male reproductive behavior was quantified daily through visual assessment of their movement patterns within each mesocosm. Female reproductive output was quantified by checking the nests for the presence of eggs, which were photographed to evaluate egg quantity, size, and development. Results indicate that future OA conditions did not significantly affect any of the reproducti on metrics examined in this study. These results suggest that future changes in environmental factors such as seawater pH may not have dramatic effects on the reproductive output and behavior of bluebanded gobies.

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Raw data concerning the carbonate system and the sensory behaviour of juvenile Dicentrarchus labrax in response to mechano-acoustic and visual cues under ocean warming and acidification

This data set is linked to a study that sought to investigate whether a mid-term 92-days exposure to warming and/or acidification alters the visual or mechano-acoustic sensory channels of the European sea bass Dicentrarchus labrax when it comes to detect and avoid simulated avian predator cues. Juveniles, aged between 283 to 316 days post hatching, were challenged in separate behavioural trials to assess their reaction facing either a shadow (visual cue) or a falling object (mechano-acoustic cue). These cues were intended to mimic an overflying bird or a bird swoop attack, respectively.

To follow the best practices of ocean acidification, the 1st and 2nd tabs show daily measurements of temperature and pH (in NIST scale). The 3rd tab shows weekly measurements of temperature and pH (in NIST and total scale), salinity, oxygen and total alkalinity that were used to calculate the carbonate system parameters, which is also shown in the 3rd tab.

Total body length (in cm, from the nose tip to end of caudal fin) was measured in a sample of 74 alive individuals upon arrival (4th tab) or in 379 dead individuals once the behavioural tests were ended (5th tab).

Abbreviations for the kinematic behavioural variables evaluated during the behavioural tests are available in the 6th tab. Data set for both the visual behavioural tests (7th tab) and the mechano-acoustic behavioural tests (8th tab) were used to run the linear mixed-effects models.

Continue reading ‘Raw data concerning the carbonate system and the sensory behaviour of juvenile Dicentrarchus labrax in response to mechano-acoustic and visual cues under ocean warming and acidification’

Partial raw data of the carbonate system after years of transgenerational exposure to ocean acidification in the European sea bass Dicentrarchus labrax

This data set is linked to a study that sought to investigate the impacts of long-term ocean acidification on the olfactory rosette transcriptome of the European sea bass (Dicentrarchus labrax) and on viral resistance.  We exposed two generations of the D. labrax to end-of-century predicted pH levels (IPCC RCP8.5), with parents being exposed for 53 months (F1) and their offspring for 18 months (F2). Our design included a transcriptomic analysis of the olfactory rosette (collected from the F2) and a viral challenge (exposing F2 to betanodavirus) where we assessed survival rates.
This data set contains physico-chemical parameters of the rearing sea water including the carbonate system components as well as survival data and temperature measurements during the viral challenge.
The rearing periods extends as follows:
F1 parents: 24 October 2013 – 26 March 2018; in duplica tanks per treatment
F2 eggs phase: 27 March 2018 – 31 March 2018; in a simplica per treatment
F2 larval phase: 1 April 2018 – 1 June 2018; in triplica tanks per treatment
F2 juvenile phase: 2 April 2018 – 17 October 2019; in a duplica per treatment
However, since this study extends over 7 years, some data is not available in digital form but in paper form. Therefore, here we provide digitalized data for the following periods.
F1 parents: 8 February 2016 – 6 March 2018; monthly data showing physico-chemical and carbonate parameters of the sea water
F2 eggs phase: 27 March 2018 – 31 March 2018; daily data showing the pH and temperature of the sea water
F2 larval phase: 1 April 2018 – 1 June 2018; monthly data showing physico-chemical and carbonate parameters of the sea water and daily data showing the pH and temperature of the sea water
F2 juvenile phase:   2 April 2018 – 24 October 2018; daily data showing the pH and temperature of the sea water
F2 juvenile phase:   2 April 2018 – 11 February 2019; monthly data showing physico-chemical and carbonate parameters of the sea water
pH in NIST scale and temperature were daily measured with a WTW 3110 pH meter (Xylem Analytics Germany, Weilheim, Germany; with electrode: WTW Sentix 41) calibrated daily with pH4.0 and pH7.0 buffers (WTW, Germany). Total alkalinity was measured following the adapted protocol of Strickland and Parsons: a 50 ml sample of filtered tank seawater was mixed with 15 ml HCl (0.01 M) and pH was measured immediately. The software CO2SYS using the constants from Mehrbach et al. refitted by Dickson and Millero were used to calculate pH in NIST scale to total scale and the carbonate chemistry components.
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CO2 induced seawater acidification impacts survival and development of European eel embryos

Fish embryos may be vulnerable to seawater acidification resulting from anthropogenic carbon dioxide (CO2) emissions or from excessive biological CO2 production in aquaculture systems. This study investigated CO2 effects on embryos of the European eel (Anguilla anguilla), a catadromous fish that is considered at risk from climate change and that is targeted for hatchery production to sustain aquaculture of the species. Eel embryos were reared in three independent recirculation systems with different pH/CO2 levels representing “control” (pH 8.1, 300 μatm CO2), end-of-century climate change (“intermediate”, pH 7.6, 900 μatm CO2) and “extreme” aquaculture conditions (pH 7.1, 3000 μatm CO2). Sensitivity analyses were conducted at 4, 24, and 48 hours post-fertilization (hpf) by focusing on development, survival, and expression of genes related to acute stress response (crhr1crfr2), stress/repair response (hsp70hsp90), water and solute transport (aqp1aqp3), acid-base regulation (nkcc1ancccar15), and inhibitory neurotransmission (GABAAα6bGabra1). Results revealed that embryos developing at intermediate pH showed similar survival rates to the control, but egg swelling was impaired, resulting in a reduction in egg size with decreasing pH. Embryos exposed to extreme pH had 0.6-fold decrease in survival at 24 hpf and a 0.3-fold change at 48 compared to the control. These observed effects of acidification were not reflected by changes in expression of any of the here studied genes. On the contrary, differential expression was observed along embryonic development independent of treatment, indicating that the underlying regulating systems are under development and that embryos are limited in their ability to regulate molecular responses to acidification. In conclusion, exposure to predicted end-of-century ocean pCO2 conditions may affect normal development of this species in nature during sensitive early life history stages with limited physiological response capacities, while extreme acidification will negatively influence embryonic survival and development under hatchery conditions.

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Effects of ocean acidification over successive generations decrease larval resilience to ocean acidification & warming but juvenile European sea bass could benefit from higher temperatures in the NE Atlantic

European sea bass (Dicentrarchus labrax) is a large, economically important fish species with a long generation time whose long-term resilience to ocean acidification (OA) and warming (OW) is not clear. We incubated sea bass from Brittany (France) for two generations (>5 years in total) under ambient and predicted OA conditions (PCO2: 650 and 1700 µatm) crossed with ambient and predicted ocean OW conditions in F1 (temperature: 15-18°C and 20-23°C) to investigate the effects of climate change on larval and juvenile growth and metabolic rate.

We found that in F1, OA as single stressor at ambient temperature did not affect larval or juvenile growth and OW increased developmental time and growth rates, but OAW decreased larval size at metamorphosis. Larval routine and juvenile standard metabolic rates were significantly lower in cold compared to warm conditioned fish and also lower in F0 compared to F1 fish. We did not find any effect of OA as a single stressor on metabolic rates. Juvenile PO2crit was not affected by OA or OAW in both generations.

We discuss the potential underlying mechanisms resulting in the resilience of F0 and F1 larvae and juveniles to OA and in the beneficial effects of OW on F1 larval growth and metabolic rate, but on the other hand in the vulnerability of F1, but not F0 larvae to OAW. With regard to the ecological perspective, we conclude that recruitment of larvae and early juveniles to nursery areas might decrease under OAW conditions but individuals reaching juvenile phase might benefit from increased performance at higher temperatures.

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A calcification-related calmodulin-like protein in the oyster Crassostrea gigas mediates the enhanced calcium deposition induced by CO2 exposure


  • A novel and calcification-related gene CgCaLP was identified.
  • The protein level of CgCaLP in hemocytes increased, but decreased in gill and mantle after CO2 exposure.
  • CgCaLP translocated to the outer mantle epithelium cells under CO2 exposure.
  • Calcium-rich deposites were observed in the outer mantle epithelium cells.


Calcium transportation and homeostasis are essential for marine bivalves to maintain basic metabolism and build their shells. Calmodulin-like proteins (CaLPs) are important calcium sensors and buffers and can respond to ocean acidification (OA) in marine calcifiers. However, no further study of their physiological function in calcium metabolism under elevated CO2 has been performed. Here, we identified a novel CaLP (designated CgCaLP) in the Pacific oyster Crassostrea gigas and demonstrated its participation in the calcification process: the mRNA expression level of CgCaLP peaked at the trochophore larval stage and remained high at stages when shells were shaped; the mRNA and protein of CgCaLP were more highly expressed in mantle tissue than in other tissues. Under elevated CO2 levels, the protein expression level of CgCaLP in hemocytes increased, while in contrast, significantly decreased protein levels were detected in gill and mantle tissues. Shell dissolution caused the imbalance of calcium in hemocytes and decreased calcium absorption and transportation demand in gill and mantle tissues, inducing the molecular function allocation of CgCaLP under CO2 exposure. Despite the decreased protein level in mantle tissue, CgCaLP was found to translocate to outer mantle epithelium (OME) cells where condensed calcium-rich deposits (CRDs) were detected. We further demonstrated that CgCaLP mRNA and protein expression levels could respond to seawater Ca2+ availability, suggesting that the calcium deposition capacity of oysters might be enhanced to fight against shell dissolution problems and that CgCaLP might serve as an essential participator of the process. In summary, CgCaLP might enhance calcium deposition under CO2 exposure and thus play a significant and flexible molecular function involved in a compensation strategy of oysters to fight against the acidified ocean.

Continue reading ‘A calcification-related calmodulin-like protein in the oyster Crassostrea gigas mediates the enhanced calcium deposition induced by CO2 exposure’

Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance Ammodytes dubius

Rising oceanic pCO2 levels could affect many traits in fish early life stages, but only few species to date have shown direct CO2-induced survival reductions. This might partly be because species from less CO2-variable, offshore environments in higher latitudes are currently underrepresented in the literature. We conducted new experimental work on northern sand lance Ammodytes dubius, a keystone forage fish on offshore Northwest Atlantic sand banks, which was recently suggested to be highly CO2-sensitive. In two complementary trials, we produced embryos from wild, Gulf of Maine (GoM) spawners and reared them at several pCO2 levels (~400–2000 µatm) in combination with static (6, 7, 10°C) and dynamic (10 → 5°C) temperature treatments. Again, we consistently observed large, CO2-induced reductions in hatching success (–23% at 1000 µatm, -61% at ~2000 µatm), and the effects were temperature-independent. To distinguish pCO2 effects during development from potential impacts on hatching itself, some embryos were switched between high and control pCO2 treatments just prior to hatch. This indeed altered hatching patterns consistent with the CO2-impaired hatching hypothesis. High CO2 also delayed the day of first hatch in one trial and peak hatch in the other, where later-hatched larvae were of similar size but with progressively less endogenous energy reserves. For context, we extracted seasonal pCO2 projections for Stellwagen Bank (GoM) from regional ensemble simulations, which indicated a CO2-induced reduction in sand lance hatching success to 71% of contemporary levels by 2100. The species’ unusual CO2 sensitivity has large ecological and scientific ramifications that warrant future in-depth research.

Continue reading ‘Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance Ammodytes dubius’

Ocean acidification alters sperm responses to egg-derived chemicals in a broadcast spawning mussel

The continued emissions of anthropogenic carbon dioxide are causing progressive ocean acidification (OA). While deleterious effects of OA on biological systems are well documented in the growth of calcifying organisms, lesser studied impacts of OA include potential effects on gamete interactions that determine fertilization, which are likely to influence the many marine species that spawn gametes externally. Here, we explore the effects of OA on the signalling mechanisms that enable sperm to track egg-derived chemicals (sperm chemotaxis). We focus on the mussel Mytilus galloprovincialis, where sperm chemotaxis enables eggs to bias fertilization in favour of genetically compatible males. Using an experimental design based on the North Carolina II factorial breeding design, we test whether the experimental manipulation of seawater pH (comparing ambient conditions to predicted end-of-century scenarios) alters patterns of differential sperm chemotaxis. While we find no evidence that male–female gametic compatibility is impacted by OA, we do find that individual males exhibit consistent variation in how their sperm perform in lowered pH levels. This finding of individual variability in the capacity of ejaculates to respond to chemoattractants under acidified conditions suggests that climate change will exert considerable pressure on male genotypes that can withstand an increasingly hostile fertilization environment.

Continue reading ‘Ocean acidification alters sperm responses to egg-derived chemicals in a broadcast spawning mussel’

Dynamic energy budget modeling of Atlantic surfclam, Spisula solidissima, under future ocean acidification and warming


  • Surfclams were exposed to OA levels inducing effects on physiological rates
  • A DEB model was calibrated integrating effects on ingestion and maintenance costs
  • The model was validated on Georges Bank and Mid-Atlantic Bight population data
  • Effects of future OA and warming conditions projected by RCP scenarios were simulated
  • Under high pCO2 emissions, DEB projects effects on growth and reproduction by 2100


A dynamic energy budget (DEB) model integrating pCO2 was used to describe ocean acidification (OA) effects on Atlantic surfclam, Spisula solidissima, bioenergetics. Effects of elevated pCO2 on ingestion and somatic maintenance costs were simulated, validated, and adapted in the DEB model based upon growth and biological rates acquired during a 12-week laboratory experiment. Temperature and pCO2 were projected for the next 100 years following the intergovernmental panel on climate change representative concentration pathways scenarios (2.6, 6.0, and 8.5) and used as forcing variables to project surfclam growth and reproduction. End-of-century water warming and acidification conditions resulted in simulated faster growth for young surfclams and more energy allocated to reproduction until the beginning of the 22nd century when a reduction in maximum shell length and energy allocated to reproduction was observed for the RCP 8.5 scenario.

Continue reading ‘Dynamic energy budget modeling of Atlantic surfclam, Spisula solidissima, under future ocean acidification and warming’

Severe seawater acidification causes a significant reduction in pulse rate, bell diameter, and acute deterioration in feeding apparatus in the scyphozoan medusa Cassiopeia sp

The detrimental effect of ocean acidification (OA) on marine animals with carbonate exoskeletons or shells is an issue drawing increased attention in marine biology and ecology, yet few studies have focused on the impact on gelatinous organisms like scyphozoan medusae. Here, we examined the physiological tolerance of Cassiopea sp., an abundant genus of scyphozoans valuable for their role as bioindicators and for having similarities to other cnidarians, to OA by conducting three, 12-week trials using CO2 diffusers and electronic pH controllers to incrementally lower the water to test pHs of 7.5 and 7.0. The impact of reduced pH on the survival, pulse rate, bell diameter, and reorientation and settlement abilities of Cassiopea sp. medusae were measured weekly. Cassiopea sp. was tolerant to pH 7.5 while further reduction of the pH to 7.0 resulted in 22.22% mortality rate, which was significantly different from the control and treatment pH 7.5. Significant differences between the treatment pH 7.0 and control first occurred on day 23.5 with a 50% reduction in the pulse rate, and on day 36 with a 16.6% reduction in bell diameter, while pH 7.5 had no effect. By the final time point of 66 days in treatment pH 7.0, there was an 87% reduction in pulse rate and a 36% reduction in bell diameter versus control. Reduced pH 7.0 caused bell malformations, inhibited swimming abilities, and deterioration of the oral arm feeding apparatus, but had no effect on the orientation and settlement assay. Observations indicate that asexual reproduction via planuloid production and strobilation was unaffected by pH reduction, though polyps in treatment pH 7.0 gave rise to ephyrae with inverted bells. Combined, findings from this study demonstrate Cassiopea sp. to be resilient to the end of century ocean acidity prediction of pH 7.6, and vulnerable to more severe OA to pH 7.0.

Continue reading ‘Severe seawater acidification causes a significant reduction in pulse rate, bell diameter, and acute deterioration in feeding apparatus in the scyphozoan medusa Cassiopeia sp’

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