Posts Tagged 'physiology'

The effects of climate change on the heart rates & growth of sea slugs in the Gulf of Maine

In the next 80 years, sea surface temperatures are expected to increase by 1.5o to 2oC and ocean pH is expected to drop by 0.06 to 0.32 units, with exacerbated effects seen in coastal waters. Temperature increase has already forced organisms to shift their range polewards and ocean acidification has negatively affected calcifying organisms. Interactive effects, only more recently studied, vary depending on phylum and life cycle stage. This study examined both the upper thermal tolerance and interactive effect of temperature and acidification on the heart rate of five cold-water species of nudibranchs (Aeolidia papillosa, Cuthona gymnota, Dendronotus frondosus, Flabellina verrucosa, and Onchidoris bilamellata) and one species of sacoglossan (Placida dendritica) from the Gulf of Maine. Thermal tolerance was determined by recording heart rate for each organism starting at 4oC and increasing the temperature by increments of 4oC until the organism’s heartbeat slowed or ceased. For interactive effects, pH levels used were pH 8 (control) and pH 7 at temperatures: 4o, 8o (control), 12o, and 16oC. Upper thermal tolerance limits ranged from 16o to 20oC for the nudibranchs and 24oC for the sacoglossan. The combined effects of increasing temperature and lower pH were neutral, negatively additive, and antagonistic. Only F. verrucosa exhibited an interactive effect, with higher temperature and lower pH leading to decreased heart rate. Although no interactive effect was demonstrated in C. xgymnota, D. frondosus, and O. bilamellata, lower pH slowed heart rates across all temperatures. Subsequently, the relationship between temperature and growth rates was examined in D. frondosus and F. verrucosa. The nudibranchs were reared for eight weeks at 4o, 10o, or 16oC and growth was measured weekly. The ideal temperature for growth appeared to be 10oC, whereas 16oC was lethal. Additionally, an unsuccessful attempt was made to culture A. papillosa, but the number of embryos per egg capsule and larval growth rates were examined. Size of adult sea slug positively impacted the number of embryos per egg capsule, with embryos increasing in length by 50% over the first week and 10% over subsequent weeks. With an interactive effect only seen in one species and upper temperatures being lethal if held constant for a month, temperature appears to be the greatest threat to survival. What is happening to these sea slugs in the GOM is likely happening to other snails and marine invertebrates throughout the ocean. Knowing how organisms will react to the projected changes can help inform future policies and practices.

Continue reading ‘The effects of climate change on the heart rates & growth of sea slugs in the Gulf of Maine’

Effects of multiple climate change stressors on gene expression in blue rockfish (Sebastes mystinus)


  • Marine fishes will be exposed to multiple stressors under climate change.
  • Hypoxia and high pCO2 are both expected to cause shifts in energy metabolism.
  • No signs of energetic shifts were observed at transcriptomic or enzymatic levels.
  • Multiple stressor transcriptomes are not predictable based on responses to single stressors.
  • Blue rockfish may be relatively tolerant to intensified upwelling conditions.


Global climate change is predicted to increase the co-occurrence of high pCO2 and hypoxia in upwelling zones worldwide. Yet, few studies have examined the effects of these stressors on economically and ecologically important fishes. Here, we investigated short-term responses of juvenile blue rockfish (Sebastes mystinus) to independent and combined high pCO2 and hypoxia at the molecular level, using changes in gene expression and metabolic enzymatic activity to investigate potential shifts in energy metabolism. Fish were experimentally exposed to conditions associated with intensified upwelling under climate change: high pCO2 (1200 μatm, pH~7.6), hypoxia (4.0 mg O2/L), and a combined high pCO2/hypoxia treatment for 12 h, 24 h or two weeks. Muscle transcriptome profiles varied significantly among the three treatments, with limited overlap among genes responsive to both the single and combined stressors. Under elevated pCO2, blue rockfish increased expression of genes encoding proteins involved in the electron transport chain and muscle contraction. Under hypoxia, blue rockfish up-regulated genes involved in oxygen and ion transport and down-regulated transcriptional machinery. Under combined high pCO2 and hypoxia, blue rockfish induced a unique set of ionoregulatory and hypoxia-responsive genes not expressed under the single stressors. Thus, high pCO2 and hypoxia exposure appears to induce a non-additive transcriptomic response that cannot be predicted from single stressor exposures alone, further highlighting the need for multiple stressor studies at the molecular level. Overall, lack of a major shift in cellular energetics indicates that blue rockfish may be relatively resistant to intensified upwelling conditions in the short term.

Continue reading ‘Effects of multiple climate change stressors on gene expression in blue rockfish (Sebastes mystinus)’

Changes in the metabolic potential of the sponge microbiome under ocean acidification

Anthropogenic CO2 emissions are causing ocean acidification, which can affect the physiology of marine organisms. Here we assess the possible effects of ocean acidification on the metabolic potential of sponge symbionts, inferred by metagenomic analyses of the microbiomes of two sponge species sampled at a shallow volcanic CO2 seep and a nearby control reef. When comparing microbial functions between the seep and control sites, the microbiome of the sponge Stylissa flabelliformis (which is more abundant at the control site) exhibits at the seep reduced potential for uptake of exogenous carbohydrates and amino acids, and for degradation of host-derived creatine, creatinine and taurine. The microbiome of Coelocarteria singaporensis (which is more abundant at the seep) exhibits reduced potential for carbohydrate import at the seep, but greater capacity for archaeal carbon fixation via the 3-hydroxypropionate/4-hydroxybutyrate pathway, as well as archaeal and bacterial urea production and ammonia assimilation from arginine and creatine catabolism. Together these metabolic features might contribute to enhanced tolerance of the sponge symbionts, and possibly their host, to ocean acidification.

Continue reading ‘Changes in the metabolic potential of the sponge microbiome under ocean acidification’

Flow-driven micro-scale pH variability affects the physiology of corals and coralline algae under ocean acidification

Natural variability in pH in the diffusive boundary layer (DBL), the discrete layer of seawater between bulk seawater and the outer surface of organisms, could be an important factor determining the response of corals and coralline algae to ocean acidification (OA). Here, two corals with different morphologies and one coralline alga were maintained under two different regimes of flow velocities, pH, and light intensities in a 12 flumes experimental system for a period of 27 weeks. We used a combination of geochemical proxies, physiological and micro-probe measurements to assess how these treatments affected the conditions in the DBL and the response of organisms to OA. Overall, low flow velocity did not ameliorate the negative effect of low pH and therefore did not provide a refugia from OA. Flow velocity had species-specific effects with positive effects on calcification for two species. pH in the calcifying fluid (pHcf) was reduced by low flow in both corals at low light only. pHcf was significantly impacted by pH in the DBL for the two species capable of significantly modifying pH in the DBL. The dissolved inorganic carbon in the calcifying fluid (DICcf) was highest under low pH for the corals and low flow for the coralline, while the saturation state in the calcifying fluid and its proxy (FWHM) were generally not affected by the treatments. This study therefore demonstrates that the effects of OA will manifest most severely in a combination of lower light and lower flow habitats for sub-tropical coralline algae. These effects will also be greatest in lower flow habitats for some corals. Together with existing literature, these findings reinforce that the effects of OA are highly context dependent, and will differ greatly between habitats, and depending on species composition.

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Effects of elevated carbon dioxide on the growth and welfare of Juvenile tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid


• High CO2 impair the growth performance and health of hybrid grouper, TGGG juveniles.

• Blood haematological and biochemical indicate TGGG juveniles are unwell when being cultured in high CO2.

• The release of glucose and cortisol in stress condition (high CO2) may include a disturbance of the metabolic balance which inhibit growth and affect the gill structure.

• The stressor (high CO2) may increase the susceptibility to disease in fish as indicated by the swollen gill structure in TGGG juveniles.


Increasing carbon dioxide (CO2) in the ocean are predicted to affect vital physiological functions and possibly reduce growth of marine fish. Yet, studies on the impacts on marine fish with the increasing CO2 is still limited. Therefore, this study aimed to explore the elevated CO2 effect on the growth and welfare (condition factor, blood parameters, stress analysis, gill histology) of newly developed commercially important marine fish, tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid or TGGG. TGGG juveniles were exposed for 120 days in a laboratory condition of CO2 groups: 390 μatm (control-current CO2), 610 μatm (moderate) and 1010 μatm (high) consistent with projections for CO2 concentrations in the ocean over the next 50–100 years. The experiments were done in triplicate (20 fish/tank; N = 180, total length = 20.0 ± 0.5 cm, weight = 94.0 ± 3.0 g). Results showed that the lowest specific growth rate (SGR) (0.65 ± 0.05% day−1) and condition factor (1.12 ± 0.01) were observed in high CO2. Unfavourable blood haematological and biochemical parameters were observed in high CO2 group. The highest stress level measured by glucose (102 ± 8 mg dL−1) and cortisol concentration (1.0 ± 0.1 ng mL−1) were also observed in the high CO2. Gill lesions were histologically observed in high CO2 treatment. The results suggested that high CO2 negatively affected the growth and welfare of TGGG. Outputs of this study would offers a simple tool to evaluate the potential risk of elevated CO2 to an important commercial marine grouper.

Continue reading ‘Effects of elevated carbon dioxide on the growth and welfare of Juvenile tiger grouper (Epinephelus fuscoguttatus) × giant grouper (E. lanceolatus) hybrid’

CO2 and HCl-induced seawater acidification impair the ingestion and digestion of blue mussel Mytilus edulis


1. The effect of two acidifying treatments, CO2 enrichment and HCl addition, on Mytilus edulis manifests different degrees of damage.

2. The effect of seawater acidification on mussels is not from a single factor (H+) but other action factors related to CO2.

3. Seawater acidification might inhibit the energy intake of mussels through interfering with the processes of ingestion and digestion.


Anthropogenic CO2 emissions lead to seawater acidification that reportedly exerts deleterious impacts on marine organisms, especially on calcifying organisms such as mussels. A 21-day experiment focusing on the impacts of seawater acidification on the blue mussel, Mytilus edulis, was performed in this study, within which two acidifying treatments, CO2 enrichment and HCl addition, were applied. Two acidifying pH values (7.7 and 7.1) and the alteration of the key physiological processes of ingestion and digestion were estimated. To thoroughly investigate the impact of acidification on mussels, a histopathological study approach was adopted. The results showed that: (1) Seawater acidification induced either by CO2 enrichment or HCl addition impaired the gill structure. Transmission electron microscope (TEM) results suggested that the most obvious impacts were inflammatory lesions and edema, while more distinct alterations, including endoplasmic reticulum edema, nuclear condensation and chromatin plate-like condensation, were placed in the CO2-treated groups compared to HCl-treated specimens. The ciliary activity of the CO2 group was significantly inhibited simultaneously, leading to an obstacle in food intake. (2) Seawater acidification prominently damaged the structure of digestive glands, and the enzymatic activities of amylase, protease and lipase significantly decreased, which might indicate that the digestion was suppressed. The negative impacts induced by the CO2 group were more severe than that by the HCl group. The present results suggest that acidification interferes with the processes of ingestion and digestion, which potentially inhibits the energy intake of mussels.

Continue reading ‘CO2 and HCl-induced seawater acidification impair the ingestion and digestion of blue mussel Mytilus edulis’

Neurobiological and behavioural responses of cleaning mutualisms to ocean warming and acidification

Cleaning interactions are textbook examples of mutualisms. On coral reefs, most fishes engage in cooperative interactions with cleaners fishes, where they benefit from ectoparasite reduction and ultimately stress relief. Furthermore, such interactions elicit beneficial effects on clients’ ecophysiology. However, the potential effects of future ocean warming (OW) and acidification (OA) on these charismatic associations are unknown. Here we show that a 45-day acclimation period to OW (+3 °C) and OA (980 μatm pCO2) decreased interactions between cleaner wrasses (Labroides dimidiatus) and clients (Naso elegans). Cleaners also invested more in the interactions by providing tactile stimulation under OA. Although this form of investment is typically used by cleaners to prolong interactions and reconcile after cheating, interaction time and client jolt rate (a correlate of dishonesty) were not affected by any stressor. In both partners, the dopaminergic (in all brain regions) and serotoninergic (forebrain) systems were significantly altered by these stressors. On the other hand, in cleaners, the interaction with warming ameliorated dopaminergic and serotonergic responses to OA. Dopamine and serotonin correlated positively with motivation to interact and cleaners interaction investment (tactile stimulation). We advocate that such neurobiological changes associated with cleaning behaviour may affect the maintenance of community structures on coral reefs.

Continue reading ‘Neurobiological and behavioural responses of cleaning mutualisms to ocean warming and acidification’

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Ocean acidification in the IPCC AR5 WG II

OUP book