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Ocean warming and acidification are a threat to calcifying marine invertebrates such as Echinoderms. Transgenerational plasticity may allow animals to respond to these conditions, but few studies exposing marine invertebrates to climate stressors over multiple generations exist. Here, data from the final (F2 post-settlement, F3 larvae and juveniles) generations in a long-term (> 6 yrs) experiment on the tropical sea urchin Echinometra sp. A. This commenced with exposing wild collected animals (F0 generation) and subsequent generations (larvae and adults both for F1 and F2) to control (present-day ambient) and climate change (CC) conditions (2 °C above ambient temperatures, 940 ppm pCO2). Survivorship in all F2 treatments (ranging from all generations being held at ambient conditions to all at elevated conditions) was high (> 50%). Some significant differences in survivorship existed among treatments, although there was no apparent relationship to CC conditions exposure time. There was also no difference in size among treatment groups in the F2 sea urchins up to 720d post-settlement. As in previous generations, the largest effect on adults was that males exposed to CC conditions have reduced reproductive potential, and there was a significant negative relationship with the number of generations exposed to future ocean conditions and spawning performance. Effects were extreme, in that we could only raise larvae from the control treatment, or those individuals kept for 0.5 generations (only F2 adults under climate change conditions). Larvae from both parental groups only reached settlement when raised under control conditions. Larval morphology also responded to treatment (reduced arm length under CC conditions) and exhibited negative parental effects (smaller arm and body lengths from parents under CC conditions). Thus, negative parental effects observed in earlier publications did not diminish over the following generations but, in some traits, increased. We therefore detected no evidence of transgenerational acclimation to future ocean conditions. [ABSTRACT FROM AUTHOR]

The eastern North Pacific is simultaneously experiencing ocean warming (OW) and ocean acidification (OA), which may negatively affect fish early life stages. Pacific cod (Gadus macrocephalus) is an economically and ecologically important species with demonstrated sensitivity to OW and OA, but their combined impacts are unknown. Through a ~ 9-week experiment, Pacific cod embryos and larvae were reared at one of six combinations of three temperatures (3, 6, 10 °C) and two CO2 levels (ambient: ~ 360 μatm; high: ~ 1560 μatm) in a factorial design. Both embryonic and larval mortality were highest at the warmest temperature. Embryonic daily mortality rates were lower under elevated CO2 and there was no effect of CO2 level on larval daily mortality rates. Growth rates of young larvae (0 to 11 days post-hatch) were faster at warmer temperatures and at high CO2 levels, but growth during the 11–28 days post-hatch interval increased by temperature alone. The condition of larvae decreased with age, but less markedly under high CO2 levels. However, at 6 °C, fish incubated in ambient CO2 remained in higher condition than fish in the high CO2 treatment throughout the experiment. Overall, temperature had the greater influence on Pacific cod early life stages across each measurement endpoint, while CO2 effects were more modest and inconsistent. Subtle developmental differences in larval Pacific cod could be magnified later in life and important in the context of recruitment. These results show the complexity of stage- and trait-specific responses to and value of investigating the combined effects of co-occurring climatic stressors. [ABSTRACT FROM AUTHOR]

Ocean acidification and warming could affect animal physiology, key trophic interactions and ecosystem functioning in the long term. This study investigates the effects of four pH−temperature combination treatments simulating ocean acidification (OA), ocean warming (OW) and combined OA and OW conditions (FUTURE) relative to ambient present-day conditions (PRESENT) on the grazing of the juveniles of two seagrass-associated invertebrates namely the sea cucumber Stichopus cf. horrens and topshell Trochus maculatus over a 5-day exposure period. Diel and feeding activity of both species increased under OW and FUTURE to some extent, while the nighttime activity of Trochus but not Stichopus decreased under OA relative to PRESENT during the first 2 days. Fecal production of Stichopus did not differ among treatments, while the lowest fecal production of Trochus was observed under OA during the first 24 h of grazing. These responses suggest that Trochus may be initially more sensitive to OA compared with Stichopus. Interestingly, fecal production of Trochus in FUTURE was significantly higher than OA, suggesting that warming may ameliorate the negative effect of acidification. Diel activity, feeding and fecal production after 5 days did not differ among treatments for both species, suggesting acclimation to the acute changes in temperature and pH after a few days, although Stichopus acclimated rapidly than Trochus. The ability of the two juvenile invertebrate grazers to rapidly acclimate to increased temperature and lowered pH conditions after short-term exposure may favor their survival under projected changes in ocean conditions. [ABSTRACT FROM AUTHOR]

Structural and mechanical properties of the decapod exoskeleton affect foraging, defense, and locomotion. Ocean acidification (OA) poses a threat to marine biomes and their inhabitants, particularly calcifying organisms. Vulnerability of the snow crab, Chionecetes opilio, a commercially important, high-latitude species, to OA has not been explored. Although all oceans are experiencing acidification, abiotic factors in high-latitude areas increase the rate of acidification. We examined the effect of long-term (2 year) exposure to decreased seawater pH (7.8 and 7.5, PCO2 ~ 760 and 1550 µatm, respectively) on exoskeletal properties in post-terminal-molt female C. opilio. Since the effects of OA vary among body regions in decapods, exoskeletal properties (microhardness, thickness, and elemental composition) were measured in five body regions: the carapace, both claws, and both third walking legs. Overall, adult C. opilio exoskeletons were robust to OA in all body regions. Decreased pH had no effect on microhardness or thickness of the exoskeleton, despite a slight (~ 6%) reduction in calcium content in crabs held at pH 7.5. In contrast, exoskeletal properties varied dramatically among body regions regardless of pH. The exoskeleton of the claws was harder, thicker, and contained more calcium but less magnesium than that of other body regions. Exoskeleton of the legs was thinner than that of other body regions and contained significantly greater magnesium concentrations (~ 2.5 times higher than the claws). Maintenance of exoskeletal properties after long-term OA exposure, at least down to pH 7.5, in adult C. opilio suggests that wild populations may tolerate future ocean pH conditions. [ABSTRACT FROM AUTHOR]

Ocean acidification alters the dissolved inorganic carbon chemistry of seawater and can reduce the calcification rates of tropical corals. Here we explore the effect of altering seawater pCO2 on the skeletal morphology of 4 genotypes of massive Porites spp. which display widely different calcification rates. Increasing seawater pCO2 causes significant changes in in the skeletal morphology of all Porites spp. studied regardless of whether or not calcification was significantly affected by seawater pCO2. Both the median calyx size and the proportion of skeletal surface occupied by the calices decreased significantly at 750 µatm compared to 400 µatm indicating that polyp size shrinks in this genus in response to ocean acidification. The coenosteum, connecting calices, expands to occupy a larger proportion of the coral surface to compensate for this decrease in calyx area. At high seawater pCO2 the spines deposited at the skeletal surface became more numerous and the trabeculae (vertical skeletal pillars) became significantly thinner in 2 of the 4 genotypes. The effect of high seawater pCO2 is most pronounced in the fastest growing coral and the regular placement of trabeculae and synapticulae is disturbed in this genotype resulting in a skeleton that is more randomly organised. The study demonstrates that ocean acidification decreases the polyp size and fundamentally alters the architecture of the skeleton in this major reef building species from the Indo-Pacific Ocean. [ABSTRACT FROM AUTHOR]

Extreme reef environments have become useful natural laboratories to investigate physiological specificities of species chronically exposed to future-like climatic conditions. The lagoon of Bouraké in New Caledonia (21°56′56.16′′ S; 125°59′36.82′′ E) is one of the only reef environments studied where the three main climatic stressors predicted to most severely impact corals occur. In this lagoon, temperatures, seawater pHT and dissolved oxygen chronically fluctuate between extreme and close-to-normal values (17.5–33.85 °C, 7.23–7.92 pHT units and 1.87–7.24 mg O2 L−1, respectively). In March 2020, the endosymbiont functions (chl a, cell density and photosynthesis) and respiration rates were investigated in seven coral species from this lagoon and compared with those of corals from an adjacent reference site using hour-long incubations mimicking present-day and future conditions. Corals originating from Bouraké displayed significant differences in these variables compared to reference corals, but these differences were species-specific. Photosynthetic rates of Bouraké corals were all significantly lower than those of reference corals but were partially compensated by higher chlorophyll contents. Respiration rates of the Bouraké corals were either lower or comparable to those of reference corals. Conversely, photosynthesis and respiration rates of most studied species were similar regardless of the incubation conditions, which mimicked either present-day or future conditions. This study supports previous work indicating that no unique response can explain corals' tolerance to sub-optimal conditions and that a variety of mechanisms will be at play for corals in a changing world. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Brooding in bivalves is a reproductive strategy that benefits larvae by protecting them from predators and adverse ambient conditions. Recent studies on brooding oysters (Ostrea spp.) have shown, however, that chemical conditions in the pallial cavity, in which the brood is held, rapidly decline soon after valve closure, representing an inescapable prison for larvae. Conditions in the pallial cavity among open, ventilating females are less well understood. This study examined how conditions in the pallial cavities of non-brooding O. chilensis females respond to prevailing environmental conditions and female valve gaping and respiration. Two separate microsensors (O2 and pH) were placed in the pallial cavities of 12 non-brooding females while valve gapes were recorded. The experiments were carried out in December 2019 using oysters collected from the Quempillén estuary in southern Chile (41° 52ʹ S, 73° 46ʹ W). As in previous studies, pallial cavity conditions were influenced by ambient O2, pH, and temperature. There were clear, quantifiable relationships between valve movement, respiration, and pallial cavity pH. Even among ventilating oysters, the pallial cavities can acidify the fluid bathing larvae. Thus, there is the potential for larvae in brooding females to be exposed to carbonate conditions predicted for the future—hence a time machine. These data suggest that brooding can apply evolutionary pressure on larvae to develop traits that help them cope with conditions in the pallial cavity, which may also be exapted to confer fitness under ocean acidification. [ABSTRACT FROM AUTHOR]

Reef-building corals are subject to multi-day periods of reduced light and progressive ocean acidification. We experimentally assessed how adult and early post-settlement Acropora tenuis and A. hyacinthus corals responded to contrasting daily light integrals (DLI) and to multi-day variability in DLI, and whether contrasting DLIs altered the effects of ocean acidification. Four light treatments—three with stable DLIs (12.6, 7.6, 2.5 mol photons m−2 d−1) and one with variable DLI that averaged 7.6 mol photons m−2 d−1 were fully crossed with two levels of pCO2 (400 and 900 ppm) in a 63-day aquarium experiment. Adult coral growth and protein content declined as average DLI declined, regardless of whether DLI was stable or variable. In both species, photoacclimation was insufficient to compensate for low DLI, although both effective (φPSII) and maximum (Fv/Fm) quantum yields of photosystem two varied by < 5% between all stable DLI treatments. Under variable DLI, both species adjusted their φPSII on the day of change in DLI, whereas Fv/Fm remained relatively constant despite five-fold difference in DLI between days. Elevated CO2 increased protein content in adult A. tenuis at all DLIs, but otherwise had little effect on measured parameters. For juveniles, both species had reduced survival at low DLI due to overgrowth by Peyssonnelia algae, and A. tenuis growth was fastest at low DLI. Our study shows that the effects of multi-day periods of DLI reductions accumulate over time for corals, negatively affecting Acropora adult growth rates and juvenile survival, and hence slowing reef recovery after disturbance. [ABSTRACT FROM AUTHOR]

Under the ocean acidification (OA) conditions predicted for 2100, the larval stages of temperate sea urchins are smaller, with reduced and abnormal skeleton and changes in metabolic rate. Here, we measure the impact of near-future and long-term predictions of atmospheric pCO2 levels on the early development of the echinometrid sea urchin Evechinus chloroticus using single male:female crosses, effect sizes and a within-study meta-analysis. Using the developmental signpost of the 16-cell stage, we show a mean delay of 5.11 min at pH 7.7 and 11.85 min at pH 7.5, which may have flow-on effects to later embryo and larval stages. Echinopluteus larvae raised in OA conditions (pH 7.7, 7.5) were ~ 5–10% smaller in body length and 10–12% smaller in arm length than controls. Metabolic rate was highly variable between single male:female crosses—increasing in some crosses, decreasing in others—with a non-significant effect size in the meta-analysis. Preliminary experiments suggest that metabolic rate changes may be impacted by loss of mitochondrial function at low pH. Single male:female crosses showed variable OA responses in all measurements, suggesting that when assessing the population-level impacts of OA on early development of sea urchins there is a need to include high levels of biological replication. [ABSTRACT FROM AUTHOR]

To study the effects of ocean warming and acidification on the immune response of octopuses, 24 Octopus rubescens were collected from Driftwood Park, Washington (48°09′48.9"N 122°38′14.1"W) April–July 2018. Following 3 weeks in elevated pCO2, elevated temperature, or the combination thereof, immunological parameters were measured including total hemocyte count, phagocytosis activity, superoxide production, and lysozyme activity. Increased pCO2 elicited an increase in the number of circulating hemocytes, which are responsible for the cellular immune response, indicating a stress response. As a result, total phagocytosis also increased. This is the first study examining the effects of climate change on the immune system of cephalopods. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) will decrease shellfish growth and survival, with ecological and economic consequences for fisheries and aquaculture. However, the high variability of results among experiments, and the lack of long-term studies, make it difficult to predict the effect that OA will have on bivalve species. We tested the long-term effect of high CO2 on growth, calcification rates, and survival of juveniles of the commercial bivalve species Chamelea gallina from Southern Portugal. The local high alkalinity of seawater probably buffered the negative effect of the pH drop, and after 75 days juveniles increased their growth and calcification rates with CO2. However, after 217 days, the situation reversed, bivalves under control conditions had the highest growth and calcification rates, while individuals under high CO2 presented negative calcification rates. The biometric variable that responded first was the width of the individuals, followed by the height and length of the shells. Survival was unaffected except for a mortality peak of juveniles under control and intermediate conditions as a consequence of a temperature drop. In the short term, C. gallina will increase their calcification rates to compensate for OA. However, in the long term, the additional energy expended will be translated into growth losses with negative repercussions for the fisheries and aquaculture. The cultivation of shellfish on high alkaline seawater should be further explored as a bioremediation measure to mitigate the negative effect of OA on shellfish aquaculture. [ABSTRACT FROM AUTHOR]

Ocean acidification, a reduction in the pH of the oceans caused by increasing CO2, can have negative physiological effects on marine species. In this study, we examined how CO2-driven acidification affected the growth and survival of juvenile golden king crab (Lithodes aequispinus), an important fishery species in Alaska. Juveniles were reared from larvae in surface ambient pH seawater at the Kodiak Laboratory. Newly molted early benthic instar crabs were randomly assigned to one of three pH treatments: (1) surface ambient pH ~ 8.2, (2) likely in situ ambient pH 7.8, and (3) pH 7.5. Thirty crabs were held in individual cells in each treatment for 127 days and checked daily for molting or death. Molts and dead crabs were photographed under a microscope and measured using image analysis to assess growth and morphology. Mortality was primarily associated with molting in all treatments, differed among all treatments, and was highest at pH 7.5 and lowest at ambient pH. Crabs at pH 7.5 were smaller than crabs at ambient pH at the end of the experiment, both in terms of carapace length and wet mass; had a smaller growth increment after molting; had a longer intermolt period. Carapace morphology was not affected by pH treatment. Decreased growth and increased mortality in laboratory experiments suggest that lower pH could affect golden king crab stocks and fisheries. Future work should examine if larval rearing conditions affect the juvenile response to low pH. [ABSTRACT FROM AUTHOR]

Responses of marine populations to climate conditions reflect the integration of a suite of complex and interrelated physiological and behavioral responses at the individual level. Many of these responses are not immediately reflected in changes to survival, but may impact growth or survival at later life stages. Understanding the broad range of impacts of rising CO2 concentrations on marine fishes is critical to predicting the consequences of ongoing ocean acidification. Walleye pollock (Gadus chalcogrammus) support the largest single-species fishery in the world and provide a critical forage base throughout north Pacific ecosystems. Previous studies of high CO2 effects on early life stages of walleye pollock have suggested a general resiliency in this species, but those studies focused primarily on growth and survival rates. Here, we expand on earlier studies with an independent experiment focused on walleye pollock larval development, swimming behavior, and lipid composition from fertilization to 4 weeks post-hatch at ambient (~ 425 µatm) and elevated (~ 1230 µatm) CO2 levels. Consistent with previous observations, size metrics of walleye pollock were generally insensitive to CO2 treatment. However, 4-week post-hatch larvae had significantly reduced rates of swim bladder inflation. A modest change in the swimming behavior of post-feeding larvae was observed at four, but not at 2 weeks post-hatch. Although there were no differences in overall lipid levels between CO2 treatments, the ratio of energy storage lipids (triacylglycerols) to structural membrane lipids (sterols) was lower among larvae reared at high CO2 levels. Although we observed higher survival to 4 weeks post-hatch among fish reared at high CO2 levels, the observations of reduced swim bladder inflation rates and changes in lipid cycling suggest the presence of sub-lethal effects of acidification that may carry over and manifest in later life stages. These observations support the continued need to evaluate the impacts of ocean acidification on marine fishes across a wide range of traits and life stages with replicated, independent experiments. [ABSTRACT FROM AUTHOR]

Recognition that ocean acidification (OA) alters calcification rates in many tropical corals and photosynthetic processes in some has motivated research into coral's carbon processing systems. Here, a multi-compartment coral model is used to assess inorganic carbon fluxes, accounting for carbon uptake, photosynthesis, transport across and between coral tissue and calcification. The increased complexity of this model is enabled by incorporating recent measurements of carbonic anhydrase activity and dissolved inorganic carbon (DIC) related photosynthetic parameters, allowing the model to respond to changes in external inorganic carbon chemistry. The model reproduced measured gross photosynthesis, calcification rates and calcifying fluid pH from Orbicella faveolata at current oceanic conditions. Model simulations representing OA conditions showed an increase in net photosynthesis and modest decreases in calcification which fall within trends seen in experimental data. Photosynthesis increased due to higher diffusive influx of CO2 into the oral tissue layers, increasing DIC where symbiotic algae reside. The model suggests that decreases in calcification result from increased fluxes of CO2 into the calcifying fluid from the aboral tissue layer and the bulk seawater, lowering its pH and reducing the aragonite saturation state. However, modeled pH drops in the calcifying fluid exceed those observed, pointing to the need for additional empirical constraints on DIC fluxes associated with calcification and coelenteron transport. [ABSTRACT FROM AUTHOR]

Although benthic foraminifera are an important component of meiofauna and contribute to carbonate production and carbon/nitrogen cycles, their role in bioturbation processes remains poorly known. Five dominant intertidal benthic foraminiferal species were recently classified into functional bioturbator groups according to their sediment reworking mode and intensity. Our study aimed at identifying potential drivers (i.e. size and/or travelled distance) of species-specific surface sediment reworking rate. The travelled distance and surface sediment reworking rate of Haynesina germanica, Cribroelphidium williamsoni, Ammonia tepida, Quinqueloculina seminulum and Miliammina fusca were assessed through image analysis. Our results show that the surface sediment reworking performed by these species is not size-dependent, but dependent on their motility traits through interspecific differences in the travelled distance. Smaller species (i.e. Quinqueloculina seminulum and Haynesina germanica) contributed more to surface sediment reworking than larger ones (i.e. Ammonia tepida, Cribroelphidium williamsoni and Miliammina fusca). These observations stress the critical role of motion behaviour in surface sediment reworking processes by intertidal foraminifera. Finally, we stress that the high inter-individual variability observed in conspecific motion behaviour may be important to decipher the role of foraminifera in sediment bioturbation. Noticeably, the species characterized by a strong inter-individual variability are also the species that have the highest surface sediment reworking rates. This last observation may inform on the species-specific phenotypic plasticity and, therefore, the potential for the functional role of these species to be maintained in their natural environment. This is particularly relevant in an era of global change where ecosystem balance is increasingly threatened by various stressors such as heat-waves, ocean acidification and pollution. [ABSTRACT FROM AUTHOR]

Under predicted future ocean conditions, reefs exposed to elevated nutrients will simultaneously experience ocean acidification and elevated temperature. We evaluated if moderate nutrients mitigate, minimize, or exacerbate negative effects of predicted future ocean conditions on coral physiology. For 30 days, Acropora millepora and Turbinaria reniformis were exposed to a fully factorial experiment of eight treatments including two seawater temperatures (26.4 °C and 29.8 °C), pCO2 levels (401 μatm pCO2 and 760 μatm pCO2), and nutrient concentrations (ambient: 0.40 μmol L−1 NO3− and 0.22 μmol L−1 PO43−, and moderate: 3.56 μmol L−1 NO3− and 0.31 μmol L−1 PO43−). Added nitrate was taken up by the algal endosymbionts and transferred to the coral hosts in both species, though to a much higher degree in A. millepora. When exposed to elevated temperature, elevated pCO2, or both, effects observed for chlorophyll a, calcification, biomass, and energy reserves were not compounded by the moderate nutrient concentrations in either species. Moderate nutrients enabled A. millepora to continue to meet daily metabolic demand via photosynthesis under predicted future ocean conditions and T. reniformis to greatly exceed daily metabolic demand via photosynthesis and heterotrophy. Our results suggest that balanced moderate nutrients are not detrimental to corals under predicted future ocean conditions and may even provide some benefits. [ABSTRACT FROM AUTHOR]

Krill are abundant and ecologically important zooplankton that inhabit dynamic environments characterized by strong natural variability, but global ocean change is shifting the range of conditions that they experience. Laboratory tests reveal that krill are sensitive to ocean acidification despite residing in naturally low pH areas, showing the importance of modulating factors for determining their responses. This study combines laboratory manipulations with field observations across a strong natural water chemistry gradient in Puget Sound, Washington, USA to investigate the effects of pH and oxygen on adult female North Pacific krill, Euphausia pacifica. Enzyme activities of the Electron Transport System (ETS) and aminoacyl-tRNA synthetases (AARS) were used as indices of zooplankton metabolism and growth, respectively, and were paired with traditional incubation methods. Acclimation to pH and oxygen conditions in the laboratory did not reveal effects on respiration rate, ETS, or AARS activity of krill. However, field observations showed that respiratory potential, as estimated by ETS activity, decreased with decreasing oxygen, declining 9% (95% confidence interval 2.5–15%) over the range of conditions we observed (3.9–8.1 mg O2 L−1). This reduction would depress the metabolic potential of krill in areas of stressful conditions (concurrent low pH), though krill also displayed a high degree of inter-individual variability. Although differences in age structure suggest different patterns of recruitment between E. pacifica populations in areas with stressful conditions and those without, populations persist at stressful sites. Lower temperature of waters with low oxygen and pH, as well as high food concentrations, may contribute to these populations' success. [ABSTRACT FROM AUTHOR]

Ocean acidification is a consequence of chemical changes driven mainly by a continuous uptake of carbon dioxide, resulting in pH decrease. This phenomenon represents an additional threat to marine life, with expected effects ranging from changes in behavioral responses and calcification rates to the potential promotion of oxidative stress. To unravel the impacts of ocean acidification on the antioxidant system of sharks, we performed a long-term exposure (9 months, since early embryogenesis) to high CO2 conditions (pCO2 ~ 900 μatm) on a temperate shark (Scyliorhinus canicula). The following biomarkers were measured: enzymatic antioxidant defense (superoxide dismutase, catalase and glutathione peroxidase), protein repair and removal (heat shock proteins and ubiquitin), and oxidative damage on lipids (malondialdehyde) and DNA (8-hydroxy-2′-deoxyguanosine). Changes in the antioxidant enzyme defense were restricted to an increase in catalase activity in the muscle, an enzyme that plays a major role in oxidative stress mitigation. On the other hand, no evidence of oxidative damage was found, indicating that the observed increase in catalase activity may be enough to neutralize the effects of potentially higher reactive oxygen species. These results further indicate that these sharks' antioxidant system can successfully cope with the levels of carbon dioxide projected for the end of the century. Nonetheless, the interaction between ocean acidification and the rise in temperature expected to occur in a near future may disturb their antioxidant capacity, requiring further investigation. [ABSTRACT FROM AUTHOR]

Ocean warming and increasing incidence of marine heatwaves (MHW) challenge the survival of marine organisms. While the impacts of climate scenario-based ocean warming are well investigated, the response of organisms to extreme events such as MHW is less understood. In this study, the thermal tolerance of the amphipod Hyale niger, an ecologically important amphipod in southeast Australia, and its algal host Sargassum linearifolium, were determined. For H. niger, a broad temperature range (2–33 °C) was tested in 6-day exposures in three seasons (summer, autumn and winter) and extended to 11 days in summer. Despite the 7 °C difference in mean habitat temperature across seasons, H. niger had a similar broad thermal optimum (Topt) range with ≥ 90% survival across a 17–20 degree temperature range. The upper lethal temperature with 50% mortality in the 6-day tests was also similar across seasons (LT50 29–30 °C). In 11-day tests in summer, the LT50 was reduced to 26 °C. Cold tolerance of H. niger indicated potential for poleward migration. Sargassum linearifolium had a similar broad thermal tolerance with a 50% reduction in the photosynthetic capacity at 33 °C. Temperature significantly affected survival of H. niger depending on the size and sex. The decrease in the Topt range over time pointed to the deleterious influence of prolonged heatwaves. The broad thermal tolerance of H. niger and S. linearifolium suggests that this important amphipod–host system may be resilient to habitat warming. [ABSTRACT FROM AUTHOR]

Trans-generational plasticity (TGP) represents a primary mechanism for guaranteeing species persistence under rapid global changes. To date, no study on TGP responses of marine organisms to global change scenarios in the ocean has been conducted on phylogenetically closely related species, and we thus lack a true appreciation for TGP inter-species variation. Consequently, we examined the tolerance and TGP of life-history and physiological traits in two annelid species within the genus Ophryotrocha: one rare (O. robusta) and one common (O. japonica). Both species were exposed over two generations to ocean acidification (OA) and warming (OW) in isolation and in combination (OAW). Warming scenarios led to a decrease in energy production together with an increase in energy requirements, which was lethal for O. robusta before viable offspring could be produced by the F1. Under OA conditions, O. robusta was able to reach the second generation, despite showing lower survival and reproductive performance when compared to control conditions. This was accompanied by a marked increase in fecundity and egg volume in F2 females, suggesting high capacity for TGP under OA. In contrast, O. japonica thrived under all scenarios across both generations, maintaining its fitness levels via adjusting its metabolomic profile. Overall, the two species investigated show a great deal of difference in their ability to tolerate and respond via TGP to future global changes. We emphasize the potential implications this can have for the determination of extinction risk, and consequently, the conservation of phylogenetically closely related species. [ABSTRACT FROM AUTHOR]

The abundance and distribution of many benthic marine organisms are shaped by the success of their dispersive larval life-history stage. An increasing number of studies have shown that ocean acidification negatively impacts the larval life-history stage, including those of echinoids which are commercially and ecologically important. However, little is known about the behavioral responses of echinoid larvae to different pH levels in the water column. Changes in vertical movement in response to the naturally occurring pH variations caused by biological activities and/or physical conditions could affect dispersal and recruitment. In this study, we quantified the vertical distribution of larval sand dollars, Dendraster excentricus (Echinodermata), in water columns with stratified layers of seawater varying in salinity and pH. When larval sand dollars swimming upwards in ambient seawater (pHNBS 7.86 ± 0.04) encountered a layer of low pH (pHNBS 7.54 ± 0.04) seawater, about half of the individuals (53 ± 28%) were aggregated near the transition layer 60 min after the start of the experiment. Preliminary video analysis showed larvae reversed their direction of travel and altered the shape of their helical swimming trajectories, upon encountering the transition layer moving from ambient to low pH water. In contrast, when larval sand dollars swimming upwards in acidified seawater encountered ambient seawater, they continued to swim upward to aggregate near the top of the column. In control water columns with uniform pH, larvae did not change swimming behavior regardless of whether pH was ambient or acidified and whether salinity was uniform or stratified. These results indicate that stratification itself did not strongly affect the vertical distributions of larvae. These observations suggest that echinoid larvae, and perhaps many other types of planktonic larvae, may use behavioral plasticity to reduce exposure to stresses from ocean acidification. The presence and effectiveness of these responses may improve the ability of larvae to cope with stressful, dynamic habitats, and hence may be significant to prediction of potential impacts of global climate change. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) is a major global driver that leads to substantial changes in seawater carbonate chemistry, with potentially serious consequences for calcifying organisms. Marine shelled molluscs are ecologically and economically important species, providing essential ecosystem services and food sources for other species. Due to their physiological characteristics and their use of calcium carbonate (CaCO3) to build their shells, molluscs are among the most vulnerable invertebrates with regard to OA, with early developmental stages being particularly sensitive to pH changes. This study investigated the effects of CO2-induced OA on juveniles of the European abalone Haliotis tuberculata, a commercially important gastropod species. Six-month-old juvenile abalones were cultured for 3 months at four pH levels (8.1, 7.8, 7.7, 7.6) representing current and predicted near-future conditions. Survival, growth, shell microstructure, thickness, and strength were compared across the four pH treatments. After 3 months of exposure, significant reductions in juvenile shell length, weight, and strength were revealed in the pH 7.6 treatment. Scanning electron microscopy observations also revealed modified texture and porosity of the shell mineral layers as well as alterations of the periostracum at pH 7.6 which was the only treatment with an aragonite saturation state below 1. It is concluded that low pH induces both general effects on growth mechanisms and corrosion of deposited shell in H. tuberculata. This will impact both the ecological role of this species and the costs of its aquaculture. [ABSTRACT FROM AUTHOR]

Elevated temperature and decreased ocean pH (ocean acidification) are associated with anthropogenic climate change and can adversely affect fertilization and development in marine invertebrates. However, the potential synergistic impact of these stressors on fertilization success remains unresolved for many ecologically and economically important species including giant clams of the genus Tridacna. Individual and interactive effects of warming and acidification on fertilization (successful first cleavage) were investigated in the small giant clam, Tridacna maxima. Experiments were performed on gametes of T. maxima (collected in October 2015 from the island of Moorea, French Polynesia; 17.54° S, 149.83° W) fertilized under ambient conditions (27 °C, pH 8.1) and under conditions congruent with temperature and pH projections for the coming century (31 °C, pH 7.6). Fertilization success was low, but within previously reported levels, under ambient conditions (47.7 ± 3.4%) and was significantly reduced at elevated temperature per se and in combination with lowered pH (18.5 ± 4.4% and 21.2 ± 4.6%, respectively). However, acidification alone had no effect on fertilization success in T. maxima (48.2 ± 3.1%). These results indicate that although fertilization in T. maxima is resilient to lowered pH, it is strongly inhibited by elevated temperature. Populations of T. maxima may, therefore, be at risk of low reproductive success over the coming century as a result of rising ocean temperature. [ABSTRACT FROM AUTHOR]

As climate change advances, coastal marine ecosystems are predicted to experience increasingly frequent and intense heatwaves. At the same time, already variable CO2 levels in coastal habitats will be exacerbated by ocean acidification. High temperature and elevated CO2 levels can be stressful to marine organisms, especially during critical early life stages. Here, we used a fully cross-factored experiment to test the effects of simulated heatwave conditions (+ 4 °C) and elevated CO2 (1000 µatm) on the aerobic physiology and swimming performance of juvenile Australasian snapper, Chrysophrys auratus, an ecologically and economically important mesopredatory fish. Both elevated temperature and elevated CO2 increased resting metabolic rate of juvenile snapper, by 21–22% and 9–10%, respectively. By contrast, maximum metabolic rate was increased by elevated temperature (16–17%) and decreased by elevated CO2 (14–15%). The differential effects of elevated temperature and elevated CO2 on maximum metabolic rate resulted in aerobic scope being reduced only in the elevated CO2 treatment. Critical swimming speed also increased with elevated temperature and decreased with elevated CO2, matching the results for maximum metabolic rate. Periods of elevated CO2 already occur in the coastal habitats occupied by juvenile snapper, and these events will be exacerbated by ongoing ocean acidification. Our results show that elevated CO2 has a greater effect on metabolic rates and swimming performance than heatwave conditions for juvenile snapper, and could reduce their overall performance and potentially have negative consequences for population recruitment. [ABSTRACT FROM AUTHOR]

Environmental conditions experienced by parents can have lasting effects on offspring. For some marine organisms, parental acclimation may attenuate the negative effects observed in offspring exposed to the same conditions. Here, development of the coral reef sea urchin Echinometra sp. A was examined in larvae derived from parents acclimated for 20 months in either present-day conditions or those predicted for the year 2100 (+ 2 °C/pH 7.8). Egg size was measured, and larval morphology, survival and respiration were quantified in larvae raised in present-day (26 °C/pH 8.1) and 2100 (28 °C/pH 7.8) treatments to near settlement to determine whether parental acclimation promotes greater resilience to climate change stressors. Although there was no difference in egg size, larvae from 2100 parents were generally larger and more developmentally advanced than those derived from present-day parents. However, negative carryover effects reduced survival in offspring of parents acclimated to 2100 conditions. At 15 days post-fertilization, survival of offspring derived from 2100 parents was 50.6% and 43.7% when raised in present-day and 2100 conditions, respectively, compared to 59.9% and 64.6% in offspring derived from present-day parents. When raised in 2100 conditions, respiration declined by 36.8% in larvae derived from present-day parents, while respiration rates of larvae from 2100 parents increased by 109%, suggesting that carryover effects may be associated with higher energy consumption and physiological stress in larvae from 2100 parents. Although parental acclimation enhanced growth of larvae in early development, overall, negative carryover effects outweighed potential benefits of parental acclimation to ocean warming and acidification in this species. [ABSTRACT FROM AUTHOR]

Early life stages of marine calcifiers are particularly vulnerable to climate change. In the Southern Ocean aragonite undersaturation events and areas of rapid warming already occur and are predicted to increase in extent. Here, we present the first study to successfully hatch the polar pteropod Limacina helicina antarctica and observe the potential impact of exposure to increased temperature and aragonite undersaturation resulting from ocean acidification (OA) on the early life stage survival and shell morphology. High larval mortality (up to 39%) was observed in individuals exposed to perturbed conditions. Warming and OA induced extensive shell malformation and dissolution, respectively, increasing shell fragility. Furthermore, shell growth decreased, with variation between treatments and exposure time. Our results demonstrate that short-term exposure through passing through hotspots of OA and warming poses a serious threat to pteropod recruitment and long-term population viability. [ABSTRACT FROM AUTHOR]

High pCO environments, such as volcanic carbon dioxide (CO) vents, which mimic predicted near-future scenarios of ocean acidification (OA), offer an opportunity to examine effects of low pH conditions on marine biodiversity and adaptation/acclimatization of marine organisms to such conditions. Based on previous field studies in these systems, it is predicted that the stress owing to increasing CO concentrations favours the colonization by invertebrate species with a brooding habit. The goal of this study was to investigate the relative occurrence of the two sibling species Platynereis dumerilii (Audouin & Milne-Edwards, 1834) (free spawner) and Platynereis massiliensis (Moquin-Tandon, 1869) (egg brooder) in two shallow CO vents off Ischia and Vulcano islands (Italy, Tyrrhenian Sea), and in various areas with ambient pH conditions, where they represent one of the dominant genera. Phylogeographic analyses were integrated with reproductive biology and life-history observations on some selected populations thriving in the vent areas. This approach revealed the presence of four distinct Platynereis clades. Whereas two clades primarily inhabit CO vents and are presumably all brooders, the other two clades dominate the non-acidified sites and appear to be epitokous free spawners. We postulate that one of the brooding, vent-inhabiting clades represents P. massiliensis and one of the free spawning, non-vent-inhabiting clades represents P. dumerilii, although confirmation of the species status with sequence data from the respective-type localities would be desirable. [ABSTRACT FROM AUTHOR]

Evaluating the relative effects of local (e.g. eutrophication) and global (e.g. ocean acidification, OA) environmental change is important to predict how marine macroalgae might respond to future oceanic conditions. In this study, the effects of nitrate supply, and hence tissue nitrogen status, and OA on the N metabolism, growth and photosynthetic rates of the kelp Macrocystis pyrifera were examined. We hypothesized that (1) NO uptake and assimilation processes will depend on nitrate supply and (2) tissue N status modulates the physiological response of Macrocystis to OA. Macrocystis blades were grown for 3 days under replete or deplete NO concentrations. Thereafter, the NO replete and deplete blades were grown for 3 days under current and future pCO/pH conditions, with NO enriched SW. After the initial pre-experimental incubation, total tissue N content, nitrate reductase (NR) activity and internal NO pools were reduced under low [NO ], while NO uptake rates increased. Initial tissue N status did not modulate the physiological response to OA. However, NO uptake rates and NR activity were enhanced under the OA treatment regardless of the initial tissue N status, suggesting that increases in [H]/reduced pH might play a regulating role in the N metabolism of this species. [ABSTRACT FROM AUTHOR]

Naturally acidified environments, such as CO vents, are important sites to evaluate the potential effects of increased ocean acidification on marine ecosystems and biota. Here we assessed the effect of high CO/low pH on otolith shape and chemical composition of six coastal fish species ( Chromis chromis, Coris julis, Diplodus vulgaris, Gobius bucchichi, Sarpa salpa, Symphodus ocellatus) in a Mediterranean shallow CO vent. Taking into consideration the major and trace elements found near the vent and the gradient of dissolved inorganic carbon, we compared the otolith chemical signatures of fish exposed long-term to elevated CO emissions and reduced pH (mean pH 7.8) against fish living in two control sites (mean pH 8.2). A number of element:Ca ratios (Na:Ca, Mg:Ca, Mn:Ca, Cu:Ca, Zn:Ca, Sr:Ca, Ba:Ca and Pb:Ca), along with isotope ratios, were measured in otoliths (δC and δO) and water (δC) samples. Additionally, we performed otolith outline shape and morphometric analysis to evaluate the effect of high CO/low pH. We observed species-specific responses with regards to both shape and chemical signatures. Significant differences among sites were found in otolith shape (elliptical Fourier descriptors) of G. bucchichi and D. vulgaris. Elemental and isotopic signatures were also significantly different in these site attached species, though not for the other four. Overall, the carbon isotopic composition seems a good proxy to follow pH gradient in naturally acidified area. Ultimately, besides improving our knowledge of the effects of high CO/low pH on otoliths, the present results contribute to our understanding on their use as natural tags. [ABSTRACT FROM AUTHOR]

Ocean acidification is a recognized consequence of anthropogenic carbon dioxide (CO) emission in the atmosphere. Despite its threat to marine ecosystems, little is presently known about the capacity for fish to respond efficiently to this acidification. In adult fish, acid-base regulatory capacities are believed to be relatively competent to respond to hypercapnic conditions. However, fish in early life stage could be particularly sensitive to environmental factors as organs and important physiological functions become progressively operational during this period. In this study, the response of European sea bass ( Dicentrarchus labrax) larvae reared under three ocean acidification scenarios, i.e., control (present condition, $$P_{{{\text{CO}}_{2} }}$$ = 590 µatm, pH total = 7.9), low acidification (intermediate IPCC scenario, $$P_{{{\text{CO}}_{2} }}$$ = 980 µatm, pH total = 7.7), and high acidification (most severe IPCC scenario, $$P_{{{\text{CO}}_{2} }}$$ = 1520 µatm, pH total = 7.5) were compared across multiple levels of biological organizations. From 2 to 45 days-post-hatching, the chronic exposure to the different scenarios had limited influence on the survival and growth of the larvae (in the low acidification condition only) and had no apparent effect on the digestive developmental processes. The high acidification condition induced both faster mineralization and reduction in skeletal deformities. Global (microarray) and targeted (qPCR) analysis of transcript levels in whole larvae did not reveal any significant changes in gene expression across tested acidification conditions. Overall, this study suggests that contemporary sea bass larvae are already capable of coping with projected acidification conditions without having to mobilize specific defense mechanisms. [ABSTRACT FROM AUTHOR]

Elevated temperature (ocean warming) and reduced oceanic pH (ocean acidification) are products of increased atmospheric pCO, and have been shown in many marine taxa to alter morphology, impede development, and reduce fitness. Here, we investigated the effects of high pCO and elevated temperature on developmental rate, hatching success, and veliger morphology of embryos of the tropical sea hare, Stylocheilus striatus. Exposure to high pCO resulted in significant developmental delays, postponing hatching by nearly 24 h, whereas exposure to elevated temperature (in isolation or in combination with high pCO) resulted in accelerated development, with larvae reaching several developmental stages approximately 48 h in advance of controls. Hatching success was reduced by ~20 and 55% under high pCO and warming, respectively, while simultaneous exposure to both conditions resulted in a nearly additive 70% reduction in hatching. In addition to these ontological and lethal effects, exposure of embryos to climate change stressors resulted in significant morphological effects. Larval shells were nearly 40% smaller under high pCO and warming in isolation and up to 53% smaller under multi-stressor conditions. In general, elevated temperature had the largest impact on development, with temperature-effects nearly 3.5-times the magnitude of high pCO-effects. These results indicate that oceanic conditions congruent with climate change predictions for the end of the twenty-first century suppress successful development in S. striatus embryos, potentially reducing their viability as pelagic larvae. [ABSTRACT FROM AUTHOR]

Despite efforts to understand marine organismal responses to ocean acidification (gradual change in pH/ $${p_{{\text{C}}{{\text{O}}_2}}}$$ over decades), there is a lack of information about the capabilities of coastal organisms to endure rapid and extreme pH change (often full units within hours). We predicted that gastropods faced with estuarine acidification avoid extreme pH exposure through isolation and/or escape behavior, and energetically compensate for feeding and energy uptake limitations by facultative metabolic depression (FMD). To test this, we studied behavioral (organism activity) and aerobic (cardiac performance) responses to acidification in two closely related tropical intertidal species, the estuarine Indothais gradata (two populations) and the open-shore Reishia bitubercularis. Snails were exposed in the laboratory to either acutely declining or stable low pH conditions, using two acidification modes (HNO-acidification and CO-aeration). Under acutely declining pH, aerobic performance was regulated to unexpectedly low pH levels (4.5), effectively extending the field pH range for activity. This pH performance threshold marked the onset of behavioral isolation and FMD (as opposed to respiratory stress) and was lower in Indothais than Reishia snails during mineral acidification. Behavioral (in isolated gastropods) and environmental hypercapnic acidosis complicates interpretation of lowered metabolic performance. Stable reduced pH exposures resulted in different behavioral and physiological responses by the Indothais populations, including more prominent escape from water in the seaward population. Overall, these results suggest that aerobic and behavioral flexibility are crucial to organismal fitness in widely fluctuating pH circumstances. They further warn against overgeneralizing marine acidification consequences across physiological dispositions, taxonomic levels, and ecological systems. [ABSTRACT FROM AUTHOR]

Sediment acidification is known to influence the burrowing behaviour of juvenile marine bivalves. Unlike the alteration of behaviour by ocean acidification (OA) observed in many marine organisms, this burrowing response to present-day variation in sediment pH is likely adaptive in that it allows these organisms to avoid shell dissolution and mortality. However, the consequences of global climate stressors on these burrowing responses have yet to be tested. Further, while neurotransmitter interference appears to be linked to the alteration of behaviour by OA in marine vertebrates, the mechanism(s) controlling the burrowing responses of juvenile bivalves in response to present-day variation in sediment acidification remain unknown. We tested the interactive effects of elevated seawater temperature and sediment acidification on juvenile soft-shell clam burrowing behaviour (measured as the proportion of clams burrowed into sediment) to test for effects of elevated temperature on bivalve burrowing responses to sediment acidification. We also examined whether GABA-like receptor interference could act as a potential biological mechanism underpinning the burrowing responses of these clams to present-day variation in sediment acidification. Results showed that both elevated temperature and gabazine administration reduced the proportion of clams that avoided burrowing into low pH sediment. These results suggest that CO effects on neurophysiology (GABA receptors) can act to mediate adaptive behaviours in juvenile marine bivalves to elevated CO, but that these behaviours may be adversely affected by elevated temperature. [ABSTRACT FROM AUTHOR]

Anthropogenic atmospheric emissions of CO are responsible for simultaneous ocean warming (OW) and ocean acidification (OA). These global events can have important impacts on marine fleshy macroalgae and coastal ecosystems. To understand the effects of OW and OA on the early life history stages of native ( Macrocystis pyrifera) and invasive ( Undaria pinnatifida) macroalgae, a multi-factorial experiment was performed to determine the independent and interactive effects of the drivers and the corresponding species-specific responses. Meiospores of M. pyrifera and U. pinnatifida were separately exposed to a 4 × 2 factorial design of seawater pH (pH 7.20, extreme OA predicted for 2300; pH 7.65, OA predicted for 2100; pH 8.03, ambient pH; and pH 8.40, pre-industrial pH) and temperature (12 °C, seasonal average temperature; and 16 °C, OW predicted for 2100). Over 15 days, different physiological parameters (i.e. meiospore germination, germling growth rate, gametophyte development and sex ratio) were measured. Reduced seawater pH and elevated temperature had independent and significant effects on developmental processes (germling growth rate, and male and female gametophyte sizes were independently greater under OA and OW conditions), but the interaction of the abiotic factors had no effect on any stage of meiospore development of either species. Despite some small differences between species (e.g. sex ratio), results of this experiment suggest that microscopic stages of the native M. pyrifera and the invasive U. pinnatifida will respond similarly to OA and OW. [ABSTRACT FROM AUTHOR]

Breeding designs such as the North Carolina II can be used to identify the sources of genetic and environmental variances in embryo performance. Here this approach is used for the Antarctic sea urchin S. neumayeri to explore how the contribution of sire and dam can influence the performance of cleavage stage embryos and blastulae, and how these contributions differ when exposed to stress from increased temperature and acidification. The interrelationship of sire-dam effects was also compared across developmental stages. The effects of warming (+3 °C) and acidification (−0.3 and −0.5 pH units) on 24 sire-dam crosses were investigated. These stressors decreased cleavage success and the percentage of normal blastulae, with a negative interactive effect between stressors. The response to these factors differed among the sire-dam pairs indicating the influence of gamete compatibility. A positive genetic correlation indicated that genotypes that performed well as blastulae in low pH also performed well at increased temperatures. Performance at cleavage was a good predictor of performance at the later blastula stage. Significant dam by temperature interactions indicated differential performance among maternal half-siblings in response to increased temperature. Adaptation depends on additive genetic variance for stress tolerance being present in populations; however, there were no sire by stressor interactions found. This indicates that S. neumayeri will need to rely on phenotypic plasticity to persist through an ocean decreasing in pH and warming, at least with respect to early development. [ABSTRACT FROM AUTHOR]

Ocean acidification is already having measurable impacts on marine ecosystems. Intraspecific variation in the responses of marine organisms to ocean acidification can reveal genetic differences in tolerance to low pH conditions and determine the potential for a species to adapt to a changing environment. This study tests for the existence of genetic variation in both the transmission success of the trematode Maritrema novaezealandense to its second intermediate amphipod host, Paracalliope novizealandiae, and the extent of parasite-induced mortality in that host, in response to decreasing pH. Eight parasite genotypes were tested in a custom-built ocean acidification simulation system, at 8.1 pH (current ocean conditions) and under conditions of 7.4 pH (worst-case scenario future prediction). The parasites had significantly higher infection success in the more acidic treatment, but there was no significant difference among genotypes in how infection success was affected by pH. In contrast, some parasite genotypes induced higher mortality in amphipods than other genotypes, but this genetic effect was also independent of pH. Overall, our results reveal no significant intergenotype variation in how the parasite responds to ocean acidification with respect to two key traits, infection success and parasite-induced host mortality, suggesting limited potential for adaptation in the face of acidifying conditions. [ABSTRACT FROM AUTHOR]

Thecosomatous pteropods are pelagic molluscs with aragonitic shells. They are considered to be especially vulnerable among plankton to ocean acidification, but to recognize changes due to anthropogenic forcing a baseline understanding of their life history is needed. In the present study, adult Limacina retroversa were collected on five cruises from multiple sites in the Gulf of Maine (between 42°22.1′-42°0.0′N and 69°42.6′-70°15.4′W; water depths of ca. 45-260 m) from October 2013 to November 2014. They were maintained in the laboratory under continuous light at 8 °C. There was evidence of year-round reproduction and an individual life span in the laboratory of 6 months. Eggs laid in captivity were observed throughout development. Hatching occurred after 3 d, the veliger stage was reached after 6-7 d, and metamorphosis to the juvenile stage was after ~1 month. Reproductive individuals were first observed after 3 months. Calcein staining of embryos revealed calcium storage beginning in the late gastrula stage. Staining was observed in the shell gland, shell field, mantle and shell margin in later stages. Exposure of two batches of larvae at the gastrula stage to elevated CO levels (800 and 1200 ppm) resulted in significantly increased mortality in comparison with individuals raised under ambient (~400 ppm) conditions and a developmental delay in the 1200 ppm treatment compared with the ambient and 800 ppm treatments. [ABSTRACT FROM AUTHOR]

Polyplacophoran molluscs show low morphological diversity compared to other marine invertebrate clades, yet chitons are ecologically important grazers that occupy a range of distinct ecological niches. We investigated a potential functional correlate of niche separation in three species of co-occurring mopallid chitons that have total ranges across differing environments ( Mopalia muscosa, Mopalia lignosa, Katharina tunicata). We found that the force needed to fracture the protective valves varied significantly among species. K. tunicata, whose valves have a relatively reduced exposed dorsal surface, was significantly more resistant to fracture than the two Mopalia species (mean force: K. tunicata = 31.9 ± 4.5 N; M. lignosa = 12.5 ± 0.8 N; M. muscosa = 20.2 ± 0.8 N). In Mopalia spp., the terminal valves were significantly stronger than intermediate valves (i.e. higher force to fracture), whereas all valves in K. tunicata appeared to be functionally equivalent. To assess whether future chemical changes predicted under ocean acidification (OA) will affect these species differently, we measured the force to fracture of valves after 10 days of exposure to elevated pCO (control = 8.0 pH [407 ± 104, pCO], elevated = 7.5 pH [1544 ± 249, pCO]) for both live animals and dissected individual valves. Although previous experimental OA work found significant impacts of elevated pCO on adult mollusc shells over similar timescales, we saw no reduction in total strength related to treatment. Our data demonstrate that diversity in chiton valve morphology has functional implications and that physical changes in local topology and wave exposure may have stronger impacts on adult chitons than changes in ocean chemistry under future climate change. [ABSTRACT FROM AUTHOR]

Ocean acidification is causing changes to the chemistry and biology of the marine environment, in ways that we are only just beginning to understand. Growing evidences demonstrate that ocean acidification can influence the survival, growth, development, and physiology of marine invertebrates. Here, we assessed the impact of ocean acidification on the sea urchin Paracentrotus lividus larval development (from embryos exposed to experimental conditions from the 24 h gastrula stage to 35 days) and settlement. Samples were collected from the Canary Islands (28°24′N, 16°18′W) in March 2012. Three pH treatments were tested: (1) pH 8.1, the present average pH; (2) pH 7.7, the average predicted for the year 2100, but already experienced in the natural environment during extremes of variability; and (3) pH 7.4, predicted extremes of natural variability by 2100. The mortality rate was significantly increased by 40 % at the lowest pH. Time required by larvae to achieve each developmental stage (from gastrula to competent stage) was decreased at pH 7.7 (larval development speed increased by 18 %), but larval morphology at a given size did not differ from the other pH treatments. Settlement was delayed by 8 days at pH 7.7 compared to pH 8.1, and no settlement was observed at pH 7.4. Overall, only sublethal effects were observed in larvae exposed to pH 7.7, while pH 7.4 induced both lethal and sublethal effects. Our results support the hypothesis that P. lividus is robust to survive in an environment with the present natural variation. However, the species is sensitive to extreme levels of pH that are predicted within the next 90 years. [ABSTRACT FROM AUTHOR]

Warming of the world's oceans is predicted to have many negative effects on organisms as they have optimal thermal windows. In coastal waters, however, both temperatures and pCO (pH) exhibit diel variations, and biological performances are likely to be modulated by physical and chemical environmental changes. To understand how coastal zooplankton respond to the combined impacts of heat shock and increased pCO, the benthic copepod Tigriopus japonicus were treated at temperatures of 24, 28, 32 and 36 °C to simulate natural coastal temperatures experienced in warming events, when acclimated in the short term to either ambient (LC, 390 μatm) or future CO (HC, 1000 μatm). HC and heat shock did not induce any mortality of T. japonicus, though respiration increased up to 32 °C before being depressed at 36 °C. Feeding rate peaked at 28 °C but did not differ between CO treatments. Expression of heat shock proteins ( hsps mRNA) was positively related to temperature, with no significant differences between the CO concentrations. Nauplii production was not affected across all treatments. Our results demonstrate that T. japonicus responds more sensitively to heat shocks rather than to seawater acidification; however, ocean acidification may synergistically act with ocean warming to mediate the energy allocation of copepods. [ABSTRACT FROM AUTHOR]

A large percentage of CO emitted into the atmosphere is absorbed by the oceans, causing chemical changes in surface waters known as ocean acidification (OA). Despite the high interest and increased pace of OA research to understand the effects of OA on marine organisms, many ecologically important organisms remain unstudied. Calcidiscus is a heavily calcified coccolithophore genus that is widespread and genetically and morphologically diverse. It contributes substantially to global calcium carbonate production, organic carbon production, oceanic carbon burial, and ocean-atmosphere CO exchange. Despite the importance of this genus, relatively little work has examined its responses to OA. We examined changes in growth, morphology, and carbon allocation in multiple strains of Calcidiscus leptoporus in response to ocean acidification. We also, for the first time, examined the OA response of Calcidiscus quadriperforatus, a larger and more heavily calcified Calcidiscus congener. All Calcidiscus coccolithophores responded negatively to OA with impaired coccolith morphology and a decreased ratio of particulate inorganic to organic carbon (PIC:POC). However, strains responded variably; C. quadriperforatus showed the most sensitivity, while the most lightly calcified strain of C. leptoporus showed little response to OA. Our findings suggest that calcium carbonate production relative to organic carbon production by Calcidiscus coccolithophores may decrease in future oceans and that Calcidiscus distributions may shift if more resilient strains and species become dominant in assemblages. This study demonstrates that variable responses to OA may be strain or species specific in a way that is closely linked to physiological traits, such as cellular calcite quota. [ABSTRACT FROM AUTHOR]

Anthropogenic emissions cause the global CO partial pressure (pCO) to increase, and atmospheric models predict a pCO of ~1,000 µatm by the year 2100. About one-third of emitted CO is absorbed by the world's oceans, causing a decrease in ocean pH. Experiments show varying effects of this so-called ocean acidification (OA) on marine animals, and it has proven exceedingly difficult to establish general rules for OA effects among species. In the present study, we found different energetic OA effects in populations from Svalbard and Skagerrak of the same calanoid copepod species, Pseudocalanus acuspes. In the Svalbard population, ingestion rates showed an inverted U-shaped hormesis-like response with higher rates at pH 7.80 than at pH 7.95 and pH 7.61 at medium and high prey concentrations. On the other hand, ingestion rates were lower at pH 7.70 and pH 7.47 than at pH 7.95 only at high prey concentrations in the Skagerrak population. Secondly, we found significant interactions between the effects of pH and prey concentration on both ingestion rate and respiration rate in the Skagerrak population, which indicates that OA may influence the way ingestion and respiration relate to prey concentration. In conclusion, the results suggest that OA effects may be far from linearly related to pH in copepods, and moreover, the effects may vary within species between populations from different regions. [ABSTRACT FROM AUTHOR]

Larvae of the Mediterranean pteropod Cavolinia inflexa were maintained at controlled pH.sub.T values of 8.1, 7.82 and 7.51, equivalent, respectively, to pCO.sub.2 levels of 380, 857 and 1,713 [mu]atm. At pH.sub.T 7.82, larvae exhibited malformations and lower shell growth, compared to the control condition. At pH.sub.T 7.51, the larvae did not make shells but were viable and showed a normal development. However, smaller shells or no shells will have both ecological (food web) and biogeochemical (export of carbon and carbonate) consequences. These results suggest that pteropod larvae, as well as the species dependent upon them or upon adults as a food resource, might be significantly impacted by ocean acidification., Author(s): S. Comeau [sup.1] [sup.2] , G. Gorsky [sup.1] [sup.2] , S. Alliouane [sup.1] [sup.2] , J.-P. Gattuso [sup.1] [sup.2] Author Affiliations: (1) grid.452348.c, 0000 0001 2154 1736, INSU-CNRS, Laboratoire [...]

Changes in seawater carbonate chemistry that accompany ongoing ocean acidification have been found to affect calcification processes in many marine invertebrates. In contrast to the response of most invertebrates, calcification rates increase in the cephalopod Sepia officinalis during long-term exposure to elevated seawater pCO.sub.2. The present trial investigated structural changes in the cuttlebones of S. officinalis calcified during 6 weeks of exposure to 615 Pa CO.sub.2. Cuttlebone mass increased sevenfold over the course of the growth trail, reaching a mean value of 0.71 ± 0.15 g. Depending on cuttlefish size (mantle lengths 44-56 mm), cuttlebones of CO.sub.2-incubated individuals accreted 22-55% more CaCO.sub.3 compared to controls at 64 Pa CO.sub.2. However, the height of the CO.sub.2-exposed cuttlebones was reduced. A decrease in spacing of the cuttlebone lamellae, from 384 ± 26 to 195 ± 38 [mu]m, accounted for the height reduction The greater CaCO.sub.3 content of the CO.sub.2-incubated cuttlebones can be attributed to an increase in thickness of the lamellar and pillar walls. Particularly, pillar thickness increased from 2.6 ± 0.6 to 4.9 ± 2.2 [mu]m. Interestingly, the incorporation of non-acid-soluble organic matrix (chitin) in the cuttlebones of CO.sub.2-exposed individuals was reduced by 30% on average. The apparent robustness of calcification processes in S. officinalis, and other powerful ion regulators such as decapod cructaceans, during exposure to elevated pCO.sub.2 is predicated to be closely connected to the increased extracellular [HCO.sub.3.sup.-] maintained by these organisms to compensate extracellular pH. The potential negative impact of increased calcification in the cuttlebone of S. officinalis is discussed with regard to its function as a lightweight and highly porous buoyancy regulation device. Further studies working with lower seawater pCO.sub.2 values are necessary to evaluate if the observed phenomenon is of ecological relevance., Author(s): Magdalena A. Gutowska [sup.1] [sup.4] , Frank Melzner [sup.2] , Hans O. Pörtner [sup.1] , Sebastian Meier [sup.3] Author Affiliations: (1) grid.10894.34, 0000000110337684, Alfred-Wegener-Institute for Polar and Marine Research, [...]

Many tropical corals have declined in abundance in the last few decades, and evaluating the causal basis of these losses is critical to understanding how coral reefs will change in response to ongoing environmental challenges. Motivated by the likelihood that marine environments will become increasingly unfavorable for coral growth as they warm and become more acidic (i.e., ocean acidification), it is reasonable to evaluate whether specific phenotypic traits of the coral holobiont are associated with ecological success (or failure) under varying environmental conditions including those that are adverse to survival. Initially, we asked whether it was possible to identify corals that are resistant or sensitive to such conditions by compiling quantitative measures of their phenotypic traits determined through empirical studies, but we found only weak phenotypic discrimination between ecological winners and losers, or among taxa. To reconcile this outcome with ecological evidence demonstrating that coral taxa are functionally unequal, we looked beyond the notion that phenotypic homogeneity arose through limitations of empirical data. Instead, we examined the validity of contemporary means of categorizing corals based on ecological success. As an alternative means to distinguish among functional groups of corals, we present a demographic approach using integral projection models (IPMs) that link organismal performance to demographic outcomes, such as the rates of population growth and responses to environmental stress. We describe how IPMs can be applied to corals so that future research can evaluate within a quantitative framework the extent to which changes in physiological performance influence the demographic underpinnings of ecological performance. [ABSTRACT FROM AUTHOR]

Among bivalves, scallops are exceptional due to their capacity to escape from predators by swimming which is provided by rapid and strong claps that are produced by the phasic muscle interspersed with tonic muscle contractions. Based on the concept of oxygen and capacity-limited thermal tolerance, the following hypothesis was tested: ocean warming and acidification (OWA) would induce disturbances in aerobic metabolic scope and extracellular acid-case status and impair swimming performance in temperate scallops. Following long-term incubation under near-future OWA scenarios [20 vs. 10 °C (control) and 0.112 kPa CO (hypercapnia) vs. 0.040 kPa CO (normocapnic control)], the clapping performance and metabolic rates (MR) were measured in resting (RMR) and fatigued (maximum MR) king scallops, Pecten maximus, from Roscoff, France. Exposure to OA, either alone or combined with warming, left MR and swimming parameters such as the total number of claps and clapping forces virtually unchanged. Only the duration of the escape response was affected by OA which caused earlier exhaustion in hyper- than in normocapnic scallops at 10 °C. While maximum MR was unaffected, warm exposure increased RMR in both normocapnic and hypercapnic P. maximus resulting in similar Q values of ~2.2. The increased costs of maintenance and the observation of strongly reduced haemolymph PO levels indicate that at 20 °C scallops have reached the upper thermal pejus range with unbalanced capacities for aerobic energy metabolism. As a consequence, warming to 20 °C decreased mean phasic force during escape performance until fatigue. The observed prolonged recovery time in warm incubated scallops might be a consequence of elevated metabolic costs at reduced oxygen availability in the warmth. [ABSTRACT FROM AUTHOR]

Ocean acidification is predicted to have negative effects on marine biota, resulting in the loss of biodiversity and changes in marine ecosystem structure and function. However, some species and life stages may be capable of thriving in low pH conditions, either due to their natural ability to tolerate stressful low pH-high pCO conditions and/or alteration of species interactions caused by changes in pH profiles, or due to evolutionary trade-offs. A better understanding of which species may be capable of tolerating ocean acidification can guide future research into the mechanisms for physiological and ecological resilience to future carbon dioxide (CO) conditions. We investigated the colonization of selected polychaete species along a pH gradient originating from shallow, coastal volcanic CO vents (Ischia, Italy). Colonization was quantified by exposing artificial invertebrate collectors attached to the substratum for 30 days during different periods of the year (late spring, fall and late winter). Three species, Amphiglena mediterranea, Platynereis dumerilii and Syllis prolifera, were present and abundant along the gradient throughout the year. All three species were significantly more abundant in the most acidified areas, confirming their high tolerance and capacity to cope with very low pH. Abundances of all three species were compared to data previously collected via collectors suspended in the water column. More individuals were found in the collectors attached to the substratum, suggesting that abundances may have previously been underestimated. This is likely due to the close proximity of these collectors with the natural rocky substratum. All three species exhibited similar temporal variability, consistent with their life cycle and reproductive biology. Our results demonstrate high tolerance of the species for low and variable pH and corroborate their use as robust models to explore the capacity to cope with low pH-high pCO conditions, both in the natural vent systems and in the laboratory. [ABSTRACT FROM AUTHOR]

Ocean acidification, a process caused by the continuous rise of atmospheric CO levels, is expected to have a profound impact on marine invertebrates. Findings of the numerous studies conducted in this field indicate high variability in species responses to future ocean conditions. This study aimed at understanding the effects of long-term exposure to elevated pCO conditions on the performance of adult Echinometra sp. EE from the Gulf of Aqaba (Red Sea). During an 11-month incubation under high pCO (1,433 μatm, pH 7.7) and control (435 μatm, pH 8.1) conditions, we examined the urchins' somatic and gonadal growth, gametogenesis and skeletal microstructure. Somatic and gonadal growths were exhibited with no significant differences between the treatments. In addition, all urchins in the experiment completed a full reproductive cycle, typical of natural populations, with no detectable impact of increased pCO on the timing, duration or progression of the cycle. Furthermore, scanning electron microscopy imaging of urchin tests and spines revealed no signs of the usual observed effects of acidosis, such as skeletal dissolution, widened stereom pores or non-smoothed structures. Our results, which yielded no significant impact of the high pCO treatment on any of the examined processes in the urchins studied, suggest high resistance of adult Echinometra sp. EE to near future ocean acidification conditions. With respect to other findings in this area, the outcome of this study provides an example of the complicated and diverse responses of echinoids to the predicted environmental changes. [ABSTRACT FROM AUTHOR]

Surprisingly little is known about potential effects of ocean acidification on krill of the Northern Hemisphere as ecologically very important food web component. Sub-adult individuals of the northern Atlantic krill species Nyctiphanes couchii (caught at Austevoll near Bergen, Norway, in January 2013) were exposed in the laboratory to four different levels of pCO (430, 800, 1,100, and 1,700 µatm) for 5 weeks in order to assess potential changes in a set of biological response variables. Survival decreased and the frequency of moulting-related deaths increased with increasing pCO. Survival was considerably reduced at relatively high pCO of 1,700 µatm and tended to be negatively affected at 1,100 µatm pCO. However, the experimental results show no significant effects of pCO on inter-moult period and growth at pCO levels below 1,100 µatm. No differences in length measurements of the carapace and uropod were observed across pCO levels, indicating no effect of changing carbonate chemistry on the morphology of those calciferous parts of the exoskeleton. The results suggest that sub-adult N. couchii may not suffer dramatically from predicted near-future changes in pCO. However, potential detrimental effects on the moulting process and associated higher mortality at 1,100 µatm pCO cannot be excluded. Further experiments are needed in order to investigate whether early life stages of N. couchii show a different sensitivity to elevated sea water pCO and whether those results are transferable to other krill species of the Northern Hemisphere. [ABSTRACT FROM AUTHOR]