Posts Tagged 'pathogens'

Wild oyster population resistance to ocean acidification adversely affected by bacterial infection

Published 22 December 2022 Science Closed
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Graphical abstract.

The carbon dioxide induced ocean acidification (OA) process is well known to have profound effects on physiology, survival and immune responses in marine organisms, and particularly calcifiers including edible oysters. At the same time, some wild populations could develop a complex and sophisticated immune system to cope with multiple biotic and abiotic stresses, such as bacterial infections and OA, over the long period of coevolution with the environment. However, it is unclear how immunological responses and the underlying mechanisms are altered under the combined effect of OA and bacterial infection, especially in the ecologically and economically important edible oysters. Here, we collected the wild population of oyster species Crassostrea hongkongensis (the Hong Kong oyster) from their native estuarine area and carried out a bacterial challenge with the worldwide pervasive pathogen of human foodborne disease, Vibrio parahaemolyticus, to investigate the host immune responses and molecular mechanisms under the high-CO2 and low pH-driven OA conditions. The wild population had a high immune resistance to OA, but the resistance is compromised under the combined effect of OA and bacterial infection both in vivo or in vitro. We classified all transcriptomic genes based on expression profiles and functional pathways and identified the specifically switched on and off genes and pathways under combined effect. These genes and pathways were mainly involved in multiple immunological processes including pathogen recognition, immune signal transduction and effectors. This work would help understand how the immunological function and mechanism response to bacterial infection in wild populations and predict the dynamic distribution of human health-related pathogens to reduce the risk of foodborne disease under the future climate change scenario.

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Impacts of seawater pH buffering on the larval microbiome and carry-over effects on later-life disease susceptibility in Pacific oysters

Published 11 November 2022 Science Closed
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Ocean acidification upwelling events and the resulting lowered aragonite saturation state of seawater have been linked to high mortality of marine bivalve larvae in hatcheries. Major oyster seed producers along North America’s west coast have mitigated impacts via seawater pH buffering (e.g., addition of soda ash). However, little consideration has been given to whether such practice may impact the larval microbiome, with potential carry-over effects on immune competency and disease susceptibility in later-life stages. To investigate possible impacts, Pacific oysters (Crassostrea gigas) were reared under soda ash pH buffered or ambient pH seawater conditions for the first 24 h of development. Both treatment groups were then reared under ambient pH conditions for the remainder of the developmental period. Larval microbiome, immune status (via gene expression), growth, and survival were assessed throughout the developmental period. Juveniles and adults arising from the larval run were then subjected to laboratory-based disease challenges to investigate carry-over effects. Larvae reared under buffered conditions showed an altered microbiome, which was still evident in juvenile animals. Moreover, reduced survival was observed in both juveniles and adults of the buffered group under a simulated marine heatwave and Vibrio exposure compared with those reared under ambient conditions. Results suggest that soda ash pH buffering during early development may compromise later-life stages under stressor conditions, and illustrate the importance of a long-view approach with regard to hatchery husbandry practices and climate change mitigation.

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Coral reef fishes in a multi-stressor world

Published 1 November 2022 Science Closed
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Coral reef fishes and the ecosystems they support represent some of the most biodiverse and productive ecosystems on the planet yet are under threat as they face dramatic increases in multiple, interacting stressors that are largely intensified by anthropogenic influences, such as climate change. Coral reef fishes have been the topic of 875 studies between 1979 and 2020 examining physiological responses to various abiotic and biotic stressors. Here, we highlight the current state of knowledge regarding coral reef fishes’ responses to eight key abiotic stressors (i.e., pollutants, temperature, hypoxia and ocean deoxygenation, pH/CO2, noise, salinity, pressure/depth, and turbidity) and four key biotic stressors (i.e., prey abundance, predator threats, parasites, and disease) and discuss stressors that have been examined in combination. We conclude with a horizon scan to discuss acclimation and adaptation, technological advances, knowledge gaps, and the future of physiological research on coral reef fishes. As we proceed through this new epoch, the Anthropocene, it is critical that the scientific and general communities work to recognize the issues that various habitats and ecosystems, such as coral reefs and the fishes that depend on and support them, are facing so that mitigation strategies can be implemented to protect biodiversity and ecosystem health.

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Adaption potential of Crassostrea gigas to ocean acidification and disease caused by Vibrio harveyi

Published 7 July 2020 Science Closed
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The survival and development of bivalve larvae is adversely impacted by ocean acidification and Vibrio infection, indicating that bivalves need to simultaneously adapt to both stressors associated with anthropogenic climate change. In this study, we use a half-dial breeding design to estimate heritability (h2) for survival to Vibrio harveyi infection and larval shell length to aragonite undersaturated and normal conditions in laboratory-reared Crassostrea gigas. Phenotypic differences were observed between families for these traits with heritability estimated to be moderate for survival to V. harveyi challenge (h2 = 0.25) and low for shell length in corrosive (Ωaragonite = 0.9, h2 = 0.15) and normal conditions (Ωaragonite = 1.6, h2 = 0.15). Predicted breeding values for larval shell length are correlated between aragonite-undersaturated and normal conditions (Spearman r = 0.63, p < 0.05), indicating that larger larvae tend to do better in corrosive seawater. Aquaculture hatcheries routinely cull slow-growing larvae to reduce and synchronize time taken for larvae to metamorphose to spat, thus inadvertently applying size-related selection for larger larvae. This indirect selection in the hatchery populations provides a plausible explanation why domesticated oyster populations are less sensitive to ocean acidification.

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Positive genetic associations among fitness traits support evolvability of a reef‐building coral under multiple stressors

Published 29 August 2019 Science Closed
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Climate change threatens organisms in a variety of interactive ways that requires simultaneous adaptation of multiple traits. Predicting evolutionary responses requires an understanding of the potential for interactions among stressors and the genetic variance and covariance among fitness‐related traits that may reinforce or constrain an adaptive response. Here we investigate the capacity of Acropora millepora, a reef‐building coral, to adapt to multiple environmental stressors: rising sea surface temperature, ocean acidification, and increased prevalence of infectious diseases. We measured growth rates (weight gain), coral color (a proxy for Symbiodiniaceae density), and survival, in addition to nine physiological indicators of coral and algal health in 40 coral genets exposed to each of these three stressors singly and combined. Individual stressors resulted in predicted responses (e.g., corals developed lesions after bacterial challenge and bleached under thermal stress). However, corals did not suffer substantially more when all three stressors were combined. Nor were trade‐offs observed between tolerances to different stressors; instead, individuals performing well under one stressor also tended to perform well under every other stressor. An analysis of genetic correlations between traits revealed positive covariances, suggesting that selection to multiple stressors will reinforce rather than constrain the simultaneous evolution of traits related to holobiont health (e.g., weight gain and algal density). These findings support the potential for rapid coral adaptation under climate change and emphasize the importance of accounting for corals’ adaptive capacity when predicting the future of coral reefs.

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Low pH reduced survival of the oyster Crassostrea gigas exposed to the Ostreid herpesvirus 1 by altering the metabolic response of the host

Published 26 December 2018 Science Closed
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Highlights

  • The susceptibility of Crassostrea gigas to OsHV-1 increased at pH 7.8 in comparison to pH 8.1
  • The amount of OsHV-1 in oyster tissues was the same at both pH, suggesting the role of host metabolic response in differential survival
  • A lower activity of SOD and a basal activity of iNOS at pH 7.8, in comparison to pH 8.1, may have impaired the defence of oysters to OsHV-1 explaining the lower survival

Abstract

Environmental change in the marine realm has been accompanied by emerging diseases as new pathogens evolve to take advantage of hosts weakened by environmental stress. Here we investigated how an exposure to reduced seawater pH influenced the response of the oyster Crassostrea gigas to an infection by the Ostreid herpesvirus type I (OsHV-1). Oysters were acclimated at pH 8.1 or pH 7.8 and then exposed to OsHV-1. Their survival was monitored and oyster tissues were sampled for biochemical analyses. The survival of oysters exposed to OsHV-1 at pH 7.8 was lower (33.5%) than that of their counterparts at pH 8.1 (44.8%) whereas levels of OsHV-1 DNA were similar. Energetic reserves, fatty acid composition and prostaglandin levels in oyster did not vary consistently with pH, infection or their interactions. However, there was a reduction in the activities of superoxide dismutase (SOD) and nitric oxide synthase (iNOS) in oysters at low pH, which is associated with the observed difference in survival.

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Oysters and eelgrass: potential partners in a high pCO2 ocean

Published 16 August 2018 Science Closed
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Climate change is affecting the health and physiology of marine organisms and altering species interactions. Ocean acidification (OA) threatens calcifying organisms such as the Pacific oyster, Crassostrea gigas. In contrast, seagrasses, such as the eelgrass Zostera marina, can benefit from the increase in available carbon for photosynthesis found at a lower seawater pH. Seagrasses can remove dissolved inorganic carbon from OA environments, creating local daytime pH refugia. Pacific oysters may improve the health of eelgrass by filtering out pathogens such as Labyrinthula zosterae (LZ), which causes eelgrass wasting disease (EWD). We examined how co-culture of eelgrass ramets and juvenile oysters affected the health and growth of eelgrass and the mass of oysters under different pCO(2) exposures. In Phase I, each species was cultured alone or in co-culture at 12 degrees C across ambient, medium, and high pCO(2) conditions, (656, 1,158 and 1,606 mu atm pCO(2), respectively). Under high pCO(2), eelgrass grew faster and had less severe EWD (contracted in the field prior to the experiment). Co-culture with oysters also reduced the severity of EWD. While the presence of eelgrass decreased daytime pCO(2), this reduction was not substantial enough to ameliorate the negative impact of high pCO(2) on oyster mass. In Phase II, eelgrass alone or oysters and eelgrass in co-culture were held at 15 degrees C under ambient and high pCO(2) conditions, (488 and 2,013atm pCO(2), respectively). Half of the replicates were challenged with cultured LZ. Concentrations of defensive compounds in eelgrass (total phenolics and tannins), were altered by LZ exposure and pCO(2) treatments. Greater pathogen loads and increased EWD severity were detected in LZ exposed eelgrass ramets; EWD severity was reduced at high relative to low pCO(2). Oyster presence did not influence pathogen load or EWD severity; high LZ concentrations in experimental treatments may have masked the effect of this treatment. Collectively, these results indicate that, when exposed to natural concentrations of LZ under high pCO(2) conditions, eelgrass can benefit from co-culture with oysters. Further experimentation is necessary to quantify how oysters may benefit from co-culture with eelgrass, examine these interactions in the field and quantify context-dependency.

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Seawater acidification reduced the resistance of Crassostrea gigas to Vibrio splendidus challenge: an energy metabolism perspective

Published 12 July 2018 Science Closed
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Negative physiological impacts induced by exposure to acidified seawater might sensitize marine organisms to future environmental stressors, such as disease outbreak. The goal of this study was to evaluate if ocean acidification (OA) could reduce the resistance capability of the Pacific oyster (Crassostrea gigas) to Vibrio splendidus challenge from an energy metabolism perspective. In this study, the Pacific oyster was exposed to OA (pH 7.6) for 28 days and then challenged by V. splendidus for another 72 h. Antioxidative responses, lipid peroxidation, metabolic (energy sensors, aerobic metabolism, and anaerobic metabolism) gene expression, glycolytic enzyme activity, and the content of energy reserves (glycogen and protein) were investigated to evaluate the environmental risk of pathogen infection under the condition of OA. Our results demonstrated that following the exposure to seawater acidification, oysters exhibited an energy modulation with slight inhibition of aerobic energy metabolism, stimulation of anaerobic metabolism, and increased glycolytic enzyme activity. However, the energy modulation ability and antioxidative regulation of oysters exposed to seawater acidification may be overwhelmed by a subsequent pathogen challenge, resulting in increased oxidative damage, decreased aerobic metabolism, stimulated anaerobic metabolism, and decreased energy reserves. Overall, although anaerobic metabolism was initiated to partially compensate for inhibited aerobic energy metabolism, increased oxidative damage combined with depleted energy reserves suggested that oysters were in an unsustainable bioenergetic state and were thereby incapable of supporting long-term population viability under conditions of seawater acidification and a pathogen challenge from V. splendidus.

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Influence of bacteria on shell dissolution in dead gastropod larvae and adult Limacina helicina pteropods under ocean acidification conditions

Published 6 February 2018 Science Closed
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Ocean acidification (OA) increases aragonite shell dissolution in calcifying marine organisms. It has been proposed that bacteria associated with molluscan shell surfaces in situ could damage the periostracum and reduce its protective function against shell dissolution. However, the influence of bacteria on shell dissolution under OA conditions is unknown. In this study, dissolution in dead shells from gastropod larvae and adult pteropods (Limacina helicina) was examined following a 5-day incubation under a range of aragonite saturation states (Ωarag; values ranging from 0.5 to 1.8) both with and without antibiotics. Gastropod and pteropod specimens were collected from Puget Sound, Washington (48°33′19″N, 122°59′49″W and 47°41′11″N, 122°25′23″W, respectively), preserved, stored, and then treated in August 2015. Environmental scanning electron microscopy (ESEM) was used to determine the severity and extent of dissolution, which was scored as mild, severe, or summed (mild + severe) dissolution. Shell dissolution increased with decreasing Ωarag. In gastropod larvae, there was a significant interaction between the effects of antibiotics and Ωarag on severe dissolution, indicating that microbes could mediate certain types of dissolution among shells under low Ωarag. In L. helicina, there were no significant interactions between the effects of antibiotics and Ωarag on dissolution. These findings suggest that bacteria may differentially influence the response of some groups of shelled planktonic gastropods to OA conditions. This is the first assessment of the microbial–chemical coupling of dissolution in shells of either gastropod larvae or adult L. helicina under OA.

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CO2-induced ocean acidification impairs the immune function of the Pacific oyster against Vibrio splendidus challenge: an integrated study from a cellular and proteomic perspective

Published 15 January 2018 Science Closed
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Highlights

• Combined effects of elevated pCO2 and Vibrio splendidus challenge on the Pacific oyster are investigated.
• Vibrio infection aggravates the oyster immunosuppressive effect caused by ocean acidification.
• Vibrio infection aggravates the oyster immunosuppressive effect caused by ocean acidification.
• Ocean acidification may increase the risk of enhanced disease of marine mollusks.

Abstract

Ocean acidification (OA) and pathogenic diseases pose a considerable threat to key species of marine ecosystem. However, few studies have investigated the combined impact of reduced seawater pH and pathogen challenge on the immune responses of marine invertebrates. In this study, Pacific oysters, Crassostrea gigas, were exposed to OA (~2000 ppm) for 28 days and then challenged with Vibrio splendidus for another 72 h. Hemocyte parameters showed that V. splendidus infection exacerbated the impaired oyster immune responses under OA exposure. An iTRAQ-based quantitative proteomic analysis revealed that C. gigas responded differently to OA stress and V. splendidus challenge, alone or in combination. Generally, OA appears to act via a generalized stress response by causing oxidative stress, which could lead to cellular injury and cause disruption to the cytoskeleton, protein turnover, immune responses and energy metabolism. V. splendidus challenge in oysters could suppress the immune system directly and lead to a disturbed cytoskeleton structure, increased protein turnover and energy metabolism suppression, without causing oxidative stress. The combined OA- and V. splendidus-treated oysters ultimately presented a similar, but stronger proteomic response pattern compared with OA treatment alone. Overall, the impaired oyster immune functions caused by OA exposure may have increased the risk of V. splendidus infection. These results have important implications for the impact of OA on disease outbreaks in marine invertebrates, which would have significant economic and ecological repercussions.

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Ocean acidification and pathogen exposure modulate the immune response of the edible mussel Mytilus chilensis

Published 6 September 2017 Science Closed
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Highlights

  • Exposure to futuristic concentration of pCO2 modulates innate immune response.
  • After OA-stress, gene expression is partially counteracted after pathogen challenge.
  • pCO2 might trigger specific immune-related genes at early stages of infection.
  • Combination of OA and bacterial infection seems to have partial antagonistic effects.

Abstract

Ocean acidification (OA) is one of the main consequences of increasing atmospheric carbon dioxide (CO2), impacting key biological processes of marine organisms such as development, growth and immune response. However, there are scarce studies on the influence of OA on marine invertebrates’ ability to cope with pathogens. This study evaluated the single and combined effects of OA and bacterial infection on the transcription expression of genes related to antioxidant system, antimicrobial peptides and pattern recognition receptors in the edible mussel Mytilus chilensis. Individuals of M. chilensis were exposed during 60 days at two concentrations of pCO2 (550 and 1200 μatm) representing respectively current and future scenario of OA and were then injected with the pathogenic bacterium Vibrio anguillarum. Results evidenced an immunomodulation following the OA exposure with an up-regulation of C-type Lectin and Mytilin B and a down-regulation of Myticin A and PGRP. This immunomodulation pattern is partially counteracted after challenge with V. anguillarum with a down-regulation of the C-type lectin and Mytilin B and the up-regulation of Myticin A. In turn, these results evidence that pCO2-driven OA scenarios might triggers specific immune-related genes at early stages of infection, promoting the transcription of antimicrobial peptides and patterns recognition receptors. This study provides new evidence of how the immune response of bivalves is modulated by higher CO2 conditions in the ocean, as well one factor for the resilience of marine population upon global change scenarios.

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Parasitic infection alters the physiological response of a marine gastropod to ocean acidification

Published 31 May 2016 Science Closed
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Increased hydrogen ion concentration and decreased carbonate ion concentration in seawater are the most physiologically relevant consequences of ocean acidification (OA). Changes to either chemical species may increase the metabolic cost of physiological processes in marine organisms, and reduce the energy available for growth, reproduction and survival. Parasitic infection also increases the energetic demands experienced by marine organisms, and may reduce host tolerance to stressors associated with OA. This study assessed the combined metabolic effects of parasitic infection and OA on an intertidal gastropod, Zeacumantus subcarinatus. Oxygen consumption rates and tissue glucose content were recorded in snails infected with one of three trematode parasites, and an uninfected control group, maintained in acidified (7·6 and 7·4 pH) or unmodified (8·1 pH) seawater. Exposure to acidified seawater significantly altered the oxygen consumption rates and tissue glucose content of infected and uninfected snails, and there were clear differences in the magnitude of these changes between snails infected with different species of trematode. These results indicate that the combined effects of OA and parasitic infection significantly alter the energy requirements of Z. subcarinatus, and that the species of the infecting parasite may play an important role in determining the tolerance of marine gastropods to OA.

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Parasitic infection: a buffer against ocean acidification?

Published 20 May 2016 Science Closed
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Recently, there has been a concerted research effort by marine scientists to quantify the sensitivity of marine organisms to ocean acidification (OA). Empirical data generated by this research have been used to predict changes to marine ecosystem health, biodiversity and productivity that will be caused by continued acidification. These studies have also found that the effects of OA on marine organisms can be significantly modified by additional abiotic stressors (e.g. temperature or oxygen) and biotic interactions (e.g. competition or predation). To date, however, the effects of parasitic infection on the sensitivity of marine organisms to OA have been largely ignored. We show that parasitic infection significantly altered the response of a marine gastropod to simulated OA conditions by reducing the mortality of infected individuals relative to uninfected conspecifics. Without the inclusion of infection data, our analysis would not have detected the significant effect of pH on host mortality. These results strongly suggest that parasitic infection may be an important confounding factor in OA research and must be taken into consideration when assessing the response of marine species to OA.

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Photosynthetic responses of ‘Neosiphonia sp. epiphyte-infected’ and healthy Kappaphycus alvarezii (Rhodophyta) to irradiance, salinity and pH variations

Published 5 April 2016 Science Closed
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Understanding the physiological condition of seaweeds as influenced by biotic and abiotic stress is vital from the perspective of massive expansion and sustainability of seaweed-based industries. The photosynthetic responses of Neosiphonia sp. epiphyte-infected (INF) and healthy (HEA) Kappaphycus alvarezii under various combinations of irradiance, salinity and pH were studied using photosynthesis-irradiance (P-E) curves. Measurements of algal photosynthetic rates, expressed in terms of amount of oxygen production per fresh weight biomass per unit time (mg O2 g−1 FW h−1), were carried out using the light-dark bottle technique. Neosiphonia-infected K. alvarezii (INF) had lower photosynthetic rates than healthy ones (HEA). Similarities (p > 0.05) in light-saturated photosynthesis rates (P max) and significant differences (p < 0.05) in initial slope of curve (α) between INF and HEA K. alvarezii suggest that both samples are adapted to similar light conditions and differs only on photosynthetic efficiency. Low P max (0.7–2.0 mg O2 g−1 FW h−1) and high initial saturation irradiances (E k  = 90–519 μmol photons m−2 s−1) of INF seaweeds resulted to their low photosynthetic efficiency (α = 0.002–0.010). Such decline in α is attributed to the epiphyte, as Neosiphonia sp. covered almost the entire surface of K. alvarezii. An increase in chlorophyll-a (35–42.1 vs. 27.7–31.5 μg g−1 FW, HEA) and phycobilin (1.96–2.39 vs. 1.16–1.58 mg g−1 FW, HEA) contents was also observed in INF samples, suggesting acclimation to low-irradiance conditions, as a result of competition for light between the epiphyte and host. Both INF and HEA K. alvarezii also exhibited broad photosynthetic tolerance to short-term changes in irradiance, with no photoinhibition at the highest irradiance of 850 μmol photons m−2 s−1. K. alvarezii had a euryhaline photosynthetic response, with optimum salinity of 35 psu. Photosynthetic rates increased with decreasing pH, revealing K. alvarezii’s ability to modify its photosynthetic affinity for acidic seawater conditions; yet, their underlying mechanism of response to pH shifts still need to be further examined.

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Interactive effects of parasitic infection and ocean acidification on the calcification of a marine gastropod

Published 29 October 2015 Science Closed
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The interactive effects of ocean acidification (OA) and parasitic infection have the potential to alter the performance of many marine organisms. Parasitic infection can affect host organisms’ response to abiotic stressors, and vice versa, while the response of marine organisms to stressors associated with OA can vary within and between taxonomic groups (host or parasite). Accordingly, it seems likely that the combination of infection stress and the novel stressors associated with OA could alter previously stable host–parasite interactions. This study is a detailed investigation into the changes to shell growth, dissolution, and tensile strength in the New Zealand mud snail Zeacumantus subcarinatus caused by trematode infection in combination with exposure to simulated OA conditions. This study also tests the effects of reduced pH on snails infected by 3 different trematode species to investigate potential species-specific effects of infection. After a 90 d exposure to 3 pH treatments (pH 8.1, 7.6, and 7.4), acidified seawater caused significant reductions in shell growth, length, and tensile strength in all snails. Trematode infected snails displayed increased shell growth and dissolution and reduced shell strength relative to uninfected conspecifics. In all measured variables, there were also significant differences between snails maintained at the same pH but infected by different species of parasite. These results indicate that parasitic infection has the potential to alter host organisms’ response to OA and that the magnitude of this effect varies among parasite species.

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Technical note: maximising accuracy and minimising cost of a potentiometrically regulated ocean acidification simulation system (update)

Published 5 February 2015 Science Closed
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This article describes a potentiometric ocean acidification simulation system which automatically regulates pH through the injection of 100% CO2 gas into temperature-controlled seawater. The system is ideally suited to long-term experimental studies of the effect of acidification on biological processes involving small-bodied (10–20 mm) calcifying or non-calcifying organisms. Using hobbyist-grade equipment, the system was constructed for approximately USD 1200 per treatment unit (tank, pH regulation apparatus, chiller, pump/filter unit). An overall tolerance of ±0.05 pHT units (SD) was achieved over 90 days in two acidified treatments (7.60 and 7.40) at 12 °C using glass electrodes calibrated with synthetic seawater buffers, thereby preventing liquid junction error. The performance of the system was validated through the independent calculation of pHT (12 °C) using dissolved inorganic carbon and total alkalinity data taken from discrete acidified seawater samples. The system was used to compare the shell growth of the marine gastropod Zeacumantus subcarinatus infected with the trematode parasite Maritrema novaezealandensis with that of uninfected snails at pH levels of 7.4, 7.6, and 8.1.

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Viral attack exacerbates the susceptibility of a bloom-forming alga to ocean acidification

Published 29 September 2014 Science Closed
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Both ocean acidification and viral infection bring about changes in marine phytoplankton physiological activities and community composition. However, little information is available on how the relationship between phytoplankton and viruses may be affected by ocean acidification and what impacts this might have on photosynthesis-driven marine biological CO2 pump. Here we show that when the harmful bloom alga Phaeocystis globosa is infected with viruses under future ocean conditions, its photosynthetic performance further decreased and cells became more susceptible to stressful light levels, showing enhanced photoinhibition and reduced carbon fixation, up-regulation of mitochondrial respiration and decreased virus burst size. Our results indicate that ocean acidification exacerbates the impacts of viral attack on P. globosa, which implies that, while ocean acidification directly influences marine primary producers, it may also affect them indirectly by altering their relationship with viruses. Therefore, viruses as a biotic stressor need to be invoked when considering the overall impacts of climate change on marine productivity and carbon sequestration.

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Technical note: maximising accuracy and minimising cost of a potentiometrically regulated ocean acidification simulation system

Published 3 June 2014 Science Closed
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This article describes a potentiometric ocean acidification simulation system which automatically regulates pH through the injection of 100% CO2 gas into temperature-controlled seawater. The system is ideally suited to long-term experimental studies of the effect of acidification on biological processes involving small-bodied (10–20 mm) calcifying or non-calcifying organisms. Using hobbyist grade equipment, the system was constructed for approximately USD 1200 per treatment unit (tank, pH regulation apparatus, chiller, pump/filter unit). An overall accuracy of ±0.05 pHT units (SD) was achieved over 90 days in two acidified treatments (7.60 and 7.40) at 12 °C using glass electrodes calibrated with salt water buffers, thereby preventing liquid junction error. The accuracy of the system was validated through the independent calculation of pHT (12 °C) using dissolved inorganic carbon (DIC) and total alkalinity (AT) data taken from discrete acidified seawater samples. The system was used to compare the shell growth of the marine gastropod Zeacumantus subcarinatus infected with the trematode parasite Maritrema novaezealandensis with that of uninfected snails, at pH levels of 7.4, 7.6, and 8.1.

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1H-NMR metabolomics reveals contrasting response by male and female mussels exposed to reduced seawater pH, increased temperature and a pathogen

Published 27 May 2014 Science Closed
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Human activities are fundamentally altering the chemistry of the world’s oceans. Ocean acidification (OA) is occurring against a background of warming and an increasing occurrence of disease outbreaks, posing a significant threat to marine organisms, communities and ecosystems. In the current study 1H NMR spectroscopy was used to investigate the response of the blue mussel, Mytilus edulis, to a 90 day exposure to reduced seawater pH and increased temperature, followed by a subsequent pathogenic challenge. Analysis of the metabolome revealed significant differences between male and female organisms. Furthermore, males and females are shown to respond differently to environmental stress. Whilst males were significantly affected by reduced seawater pH, increased temperature and a bacterial challenge, it was only a reduction in seawater pH that impacted females. Despite impacting males and females differently, stressors seem to act via a generalised stress response impacting both energy metabolism and osmotic balance in both sexes. This study therefore has important implications for the interpretation of metabolomic data in mussels, as well as the impact of environmental stress in marine invertebrates in general.

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Projected marine climate change: effects on copepod oxidative status and reproduction

Published 17 December 2013 Science Closed
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Zooplankton are an important link between primary producers and fish. Therefore, it is crucial to address their responses when predicting effects of climate change on pelagic ecosystems. For realistic community-level predictions, several biotic and abiotic climate-related variables should be examined in combination. We studied the combined effects of ocean acidification and global warming predicted for year 2100 with toxic cyanobacteria on the calanoid copepod, Acartia bifilosa. Acidification together with higher temperature reduced copepod antioxidant capacity. Higher temperature also decreased egg viability, nauplii development, and oxidative status. Exposure to cyanobacteria and its toxin had a negative effect on egg production but, a positive effect on oxidative status and egg viability, giving no net effects on viable egg production. Additionally, nauplii development was enhanced by the presence of cyanobacteria, which partially alleviated the otherwise negative effects of increased temperature and decreased pH on the copepod recruitment. The interactive effects of temperature, acidification, and cyanobacteria on copepods highlight the importance of testing combined effects of climate-related factors when predicting biological responses.

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