Posts Tagged 'fish'

Effects of bicarbonate on cardiac function in fish

An entirely novel mechanism to modulate heart rate was recently discovered in the Pacific hagfish (Eptatretus stoutii): a soluble adenylyl cyclase (sAC)-mediated pathway that increases cyclic adenosine monophosphate (cAMP) production upon stimulation by HCO₃₋ to increase heart rate. However, still unknown is whether this cardiac control pathway is present in other species as well. The objective of my study was to determine the effects of increasing extracellular [HCO₃₋] on the in vitro cardiac function of other fish species and whether the sAC-mediated pathway is associated with recovery of cardiac function during debilitating conditions. Exposure to severe hypoxia (100% N₂) and hypercapnic acidosis (7.5% or 15% CO₂) significantly decreased the heart rate of isolated, freely beating hearts and reduced the isometric tension (contractility) of electrically paced ventricular strips from Pacific lamprey (Lampetra richardsoni), Pacific spiny dogfish (Squalus suckleyi), Asian swamp eel (Monopterus albus), white sturgeon (Acipenser transmontanus), zebrafish (Danio rerio), and starry flounder (Platichthys stellatus). Spontaneous recovery in heart rate or contractility was not observed during severe hypoxia or hypercapnic acidosis for any of the species tested. Addition of HCO₃₋ (up to 50 mM) was associated with a complete and dose-dependent recovery of control heart rate in lamprey, dogfish, and swamp eel hearts during severe hypoxia, and in dogfish, sturgeon, and swamp eel hearts during hypercapnic acidosis. A partial recovery of control heart rate was observed in lamprey and zebrafish hearts during hypercapnic acidosis. However, HCO₃₋ had no effect on the heart rate or contractility in flounder hearts and had little to no effect on restoring control contractility in dogfish, swamp eel, and flounder ventricular strips. The addition of KH7 (sAC blocker) abolished the HCO₃₋-induced recovery of heart rate during severe hypoxia only in the lamprey heart. Thus, the sAC-mediated pathway in cardiac control appears to be unique to the cyclostomes and not present in the other species tested. While the sAC-mediated pathway was associated with the recovery of heart rate in the lamprey heart, the specific mechanisms behind how HCO₃₋ was associated with the recovery of heart rate in the other species still needs to be determined.

Continue reading ‘Effects of bicarbonate on cardiac function in fish’

Community composition in mangrove ponds with pulsed hypoxic and acidified conditions

The potential resilience of biological communities to accelerating rates of global change has received considerable attention. We suggest that some shallow aquatic ecosystems, where temperature, dissolved oxygen (DO), and pH can exhibit extreme variation on short timescales of hours or days, provide an opportunity to develop a mechanistic understanding of species persistence and community assembly under harsh environmental conditions. Extreme diel swings in DO and pH have been observed in eutrophic temperate ecosystems, and here, we describe a similar phenomenon consistently occurring across tropical sites that included relatively remote atolls on the Meso-American barrier reefs in Belize and oligotrophic coastal lagoons in Panama. In particular, we documented large daily swings in temperature, DO, and pH within shallow ponds of Caribbean mangrove forests. Water in seven of 13 ponds went hypoxic (<2 mg/L DO) during the multiday sampling period, and pH dipped nightly to low levels, falling below 7.0 in some ponds. Minimum pH and minimum DO were correlated, and showed a similar relationship in Belize and Panama, suggesting a common mechanism produced diel cycles. Remarkably, most ponds exhibited high abundance of macroalgae, macroinvertebrates, and fish, despite potentially stressful abiotic conditions. Although fish diversity was negatively correlated with pH range, our overall results from the ponds suggest that many species are sufficiently resistant such that a functionally complex community can persist in the midst of pulsed stressful conditions. We propose that the mangrove ponds could serve as a model ecosystem for investigating resistance and resilience of coastal marine communities to global change factors such as climate change, hypoxia, and ocean acidification.

Continue reading ‘Community composition in mangrove ponds with pulsed hypoxic and acidified conditions’

Early development of the threespine stickleback in relation to water pH

Ocean acidification is a growing environmental problem, and there is a need to investigate how the decreasing pH will affect marine organisms. Here we studied the effects of lowered pH on the growth and development of the threespine stickleback (Gasterosteus aculeatus) eggs. Adult fish, collected from the natural environment, were allowed to mate in aquaria and the newly produced eggs were incubated in an experiment. Eggs and larvae from ambient conditions (produced in the laboratory) were reared at three different pH concentrations (control: pH 7.8; and reduced pH treatments: pH 7.5 and 7.0) for 21 days in the laboratory. Dissolved oxygen concentration (8.1 ± 0.1 mg l−1) and temperature (18.6 ± 0.02°C) were monitored regularly. Then, egg diameter, larval length, weight and survival were measured. There was no relationship between egg diameter and pH or oxygen, but a negative relationship was found with temperature. Survival of larvae was not affected by pH or temperature, whereas dissolved oxygen concentration had a positive effect on number of survivors. The pH did not have a significant effect on the final larval length on day 21, but interacted significantly with dissolved oxygen. Higher temperatures were found to have a positive effect on the final larval length and weight. Larval weight, on the other hand, was not related to pH nor oxygen. Coastal zones are characterized by pH levels that fluctuate due to natural processes, such as upwelling and river runoff. Our results suggest that the threespine stickleback larvae are well adapted to the different pHs tested, and egg development will likely not be affected by decreasing pH, but even slight temperature and oxygen changes can have a great impact on the threespine stickleback development.

Continue reading ‘Early development of the threespine stickleback in relation to water pH’

An interplay between plasticity and parental phenotype determines impacts of ocean acidification on a reef fish

The impacts of ocean acidification will depend on the ability of marine organisms to tolerate, acclimate and eventually adapt to changes in ocean chemistry. Here, we use a unique transgenerational experiment to determine the molecular response of a coral reef fish to short-term, developmental and transgenerational exposure to elevated CO2, and to test how these responses are influenced by variations in tolerance to elevated CO2 exhibited by the parents. Within-generation responses in gene expression to end-of-century predicted CO2 levels indicate that a self-amplifying cycle in GABAergic neurotransmission is triggered, explaining previously reported neurological and behavioural impairments. Furthermore, epigenetic regulator genes exhibited a within-generation specific response, but with some divergence due to parental phenotype. Importantly, we find that altered gene expression for the majority of within-generation responses returns to baseline levels following parental exposure to elevated CO2 conditions. Our results show that both parental variation in tolerance and cross-generation exposure to elevated CO2 are crucial factors in determining the response of reef fish to changing ocean chemistry.

Continue reading ‘An interplay between plasticity and parental phenotype determines impacts of ocean acidification on a reef fish’

Potential for maternal effects on offspring CO2 sensitivities in the Atlantic silverside (Menidia menidia)


• Offspring produced by different females varied in their sensitivity to high CO2 conditions.
• Specific fatty acids in eggs were correlated to the log-transformed CO2 response ratio of embryo survival and hatch length.
• Maternal provisioning might be an additional determinant of CO2 sensitivity in fish early life stages.


For marine fish, the influence of maternal provisioning on offspring sensitivity to high carbon dioxide (CO2) conditions remains unknown. We separately reared offspring obtained from five wild-caught Atlantic silverside (Menidia menidia) females from fertilization to 16 days post hatch under contrasting CO2 conditions (ambient: ~ 400 μatm, acidified: ~ 2,300 μatm), testing whether average survival during the embryo and larval stage, hatch length, final length, and growth rates were affected by CO2, female identity, or their interaction. Average trait responses did not significantly differ between treatments (CO2 or female identity), however, significant CO2 × female identity interactions indicated that females produced offspring with different average CO2 sensitivities. We then examined whether differential egg provisioning with fatty acids (FA) may partially explain the observed differences in offspring CO2 sensitivities. Concentrations of 27 FAs in the unfertilized eggs of each female were measured. Cumulative absolute FA levels were negatively related to hatch length and to the log-transformed CO2 response ratio of hatch length. Eggs with lower concentrations of 20:1n9 and 22:5n3 resulted in offspring where embryo survival was negatively impacted by high CO2. Eggs with higher concentrations of 18:3n3, 18:4n3, and 22:6n3 produced shorter offspring at hatching under high CO2 conditions. These results indicate that maternal provisioning might be an additional determinant of CO2 sensitivity in fish early life stages. Acidification experiments should therefore utilize large numbers of parents from different natural conditions and, where possible, track heritage.

Continue reading ‘Potential for maternal effects on offspring CO2 sensitivities in the Atlantic silverside (Menidia menidia)’

Effects of high pCO2 on early life development of pelagic spawning marine fish

The present study investigated the effect of elevated pCO2 on the development of early stages of the pelagic spawning marine fish Solea senegalensis, Diplodus sargus and Argyrosomus regius. Eggs and larvae were reared under control (pH 8.0, ~570 μatm) and two elevated pCO2 conditions (pH 7.8, ~1100 μatm; pH 7.6, ~1900 μatm) until mouth opening (3 days post-hatching). Egg size did not change with exposure to elevated pCO2, but hatching rate was significantly reduced under high pCO2 for all three species. Survival rate was not affected by exposure to increased pCO2, but growth rate was differently affected across species, with A. regius growing faster in the mid-level pCO2 treatment compared with control conditions. S. senegalensis and A. regius hatched with smaller yolk sacs under increased pCO2 but endogenous reserves of D. sargus were not affected. Otoliths were consistently larger under elevated pCO2 conditions for all the three species. Differences among egg batches and a significant interaction between batch and pCO2 suggest that other factors, such as egg quality, can influence the response to increased pCO2. Overall, the results support the occurrence of a species-specific response to pCO2, but highlight the need for cautious analysis of potential sensitivity of species from unreplicated observations.

Continue reading ‘Effects of high pCO2 on early life development of pelagic spawning marine fish’

Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)


• Atmospheric and water conditions/contaminants influence animal physiology status.
• Scarcely studied multi-stressor effects were extricated via full-factorial design.
• Warming stimulated mercury accumulation, but was offset by acidification.
• Co-occurring acidification countered oxidative stress elicited by other stressors.
• Enhanced mitigation pathways or chemical dynamics may underpin stressor antagonism.


Increases in carbon dioxide (CO2) and other greenhouse gases emissions are changing ocean temperature and carbonate chemistry (warming and acidification, respectively). Moreover, the simultaneous occurrence of highly toxic and persistent contaminants, such as methylmercury, will play a key role in further shaping the ecophysiology of marine organisms. Despite recent studies reporting mostly additive interactions between contaminant and climate change effects, the consequences of multi-stressor exposure are still largely unknown. Here we disentangled how Argyrosomus regius physiology will be affected by future stressors, by analysing organ-dependent mercury (Hg) accumulation (gills, liver and muscle) within isolated/combined warming (ΔT = 4 °C) and acidification (ΔpCO2 = 1100 μatm) scenarios, as well as direct deleterious effects and phenotypic stress response over multi-stressor contexts. After 30 days of exposure, although no mortalities were observed in any treatments, Hg concentration was enhanced under warming conditions, especially in the liver. On the other hand, elevated CO2 decreased Hg accumulation and consistently elicited a dampening effect on warming and contamination-elicited oxidative stress (catalase, superoxide dismutase and glutathione-S-transferase activities) and heat shock responses. Thus, potentially unpinned on CO2-promoted protein removal and ionic equilibrium between hydrogen and reactive oxygen species, we found that co-occurring acidification decreased heavy metal accumulation and contributed to physiological homeostasis. Although this indicates that fish can be physiologically capable of withstanding future ocean conditions, additional experiments are needed to fully understand the biochemical repercussions of interactive stressors (additive, synergistic or antagonistic).

Continue reading ‘Ocean acidification dampens physiological stress response to warming and contamination in a commercially-important fish (Argyrosomus regius)’

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Ocean acidification in the IPCC AR5 WG II

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