Posts Tagged 'fish'

Ocean acidification alters morphology of all otolith types in Clark’s anemonefish (Amphiprion clarkii)

Ocean acidification, the ongoing decline of surface ocean pH and [CO32-] due to absorption of surplus atmospheric CO2, has far-reaching consequences for marine biota, especially calcifiers. Among these are teleost fishes, which internally calcify otoliths, critical elements of the inner ear and vestibular system. There is evidence in the literature that ocean acidification increases otolith size and alters shape, perhaps impacting otic mechanics and thus sensory perception. However, existing analyses of otolith morphological responses to ocean acidification are limited to 2-dimensional morphometrics and shape analysis. Here, we reared larval Clark’s anemonefish, Amphiprion clarkii (Bennett, 1830), in various seawater pH treatments analogous to future ocean scenarios in a 3x-replicated experimental design. Upon settlement, we removed all otoliths from each individual fish and analyzed them for treatment effects on morphometrics including area, perimeter, and circularity; further, we used scanning electron microscopy to screen otoliths visually for evidence of treatment effects on lateral development, surface roughness, and vaterite replacement. Our results corroborate those of other experiments with other taxa that observed otolith growth with elevated pCO2, and provide evidence that lateral development and surface roughness increased as well; we observed at least one of these effects in all otolith types. Finally, we review previous work investigating ocean acidification impacts on otolith morphology and hypotheses concerning function, placing our observations in context. These impacts may have consequences teleost fitness in the near-future ocean.

Continue reading ‘Ocean acidification alters morphology of all otolith types in Clark’s anemonefish (Amphiprion clarkii)’

Juvenile rockfish show resilience to CO2-acidification and hypoxia across multiple biological scales

California’s coastal ecosystems are forecasted to undergo shifting ocean conditions due to climate change, some of which may negatively impact recreational and commercial fish populations. To understand if fish populations have the capacity to respond to multiple stressors, it is critical to examine interactive effects across multiple biological scales, from cellular metabolism to species interactions. This study examined the effects of CO2-acidification and hypoxia on two naturally co-occurring species, juvenile rockfish (genus Sebastes) and a known predator, cabezon (Scorpaenichthys marmoratus). Fishes were exposed to two PCO2 levels at two dissolved oxygen (DO) levels: ~600 (ambient) and ~1600 (high) μatm PCO2 and 8.0 (normoxic) and 4.5 mg l−1 DO (hypoxic) and assessments of cellular metabolism, prey behavior and predation mortality rates were quantified after 1 and 3 weeks. Physiologically, rockfish showed acute alterations in cellular metabolic enzyme activity after 1 week of acclimation to elevated PCO2 and hypoxia that were not evident in cabezon. Alterations in rockfish energy metabolism were driven by increases in anaerobic LDH activity, and adjustments in enzyme activity ratios of cytochrome c oxidase and citrate synthase and LDH:CS. Correlated changes in rockfish behavior were also apparent after 1 week of acclimation to elevated PCO2 and hypoxia. Exploration behavior increased in rockfish exposed to elevated PCO2 and spatial analysis of activity indicated short-term interference with anti-predator responses. Predation rate after 1 week increased with elevated PCO2; however, no mortality was observed under the multiple-stressor treatment suggesting negative effects on cabezon predators. Most noteworthy, metabolic and behavioral changes were moderately compensated after 3 weeks of acclimation, and predation mortality rates also decreased suggesting that these rockfish may be resilient to changes in environmental stressors predicted by climate models. Linking physiological and behavioral responses to multiple stressors is vital to understand impacts on populations and community dynamics.

Continue reading ‘Juvenile rockfish show resilience to CO2-acidification and hypoxia across multiple biological scales’

CO2 emissions boost the benefits of crop production by farming damselfish

Farming is a technique employed by both humans and animals to enhance crop yields, allowing their populations to increase beyond the natural carrying capacity of the environment. Using volcanic CO2 vents, we investigate how a species of herbivorous fish (the black scalyfin Parma alboscapularis) may use increasing anthropogenic CO2 emissions to enhance its crop yields. We found that these farming fish can take advantage of this resource enrichment, to grow crops within smaller territories and increase the capacity of the environment to support more densely packed fish populations.

Continue reading ‘CO2 emissions boost the benefits of crop production by farming damselfish’

CO2 induced pHi changes in the brain of polar fish: a TauCEST application

Chemical exchange saturation transfer (CEST) from taurine to water (TauCEST) can be used for in vivo mapping of taurine concentrations as well as for measurements of relative changes in intracellular pH (pHi) at temperatures below 37°C. Therefore, TauCEST offers the opportunity to investigate acid–base regulation and neurological disturbances of ectothermic animals living at low temperatures, and in particular to study the impact of ocean acidification (OA) on neurophysiological changes of fish. Here, we report the first in vivo application of TauCEST imaging. Thus, the study aimed to investigate the TauCEST effect in a broad range of temperatures (1–37°C) and pH (5.5–8.0), motivated by the high taurine concentration measured in the brains of polar fish. The in vitro data show that the TauCEST effect is especially detectable in the low temperature range and strictly monotonic for the relevant pH range (6.8–7.5). To investigate the specificity of TauCEST imaging for the brain of polar cod (Boreogadus saida) at 1.5°C simulations were carried out, indicating a taurine contribution of about 65% to the in vivo expected CEST effect, if experimental parameters are optimized. B. saida was acutely exposed to three different CO2 concentrations in the sea water (control normocapnia; comparatively moderate hypercapnia OAm = 3300 μatm; high hypercapnia OAh = 4900 μatm). TauCEST imaging of the brain showed a significant increase in the TauCEST effect under the different CO2 concentrations of about 1.5–3% in comparison with control measurements, indicative of changes in pHi or metabolite concentration. Consecutive recordings of 1H MR spectra gave no support for a concentration induced change of the in vivo observed TauCEST effect. Thus, the in vivo application of TauCEST offers the possibility of mapping relative changes in pHi in the brain of polar cod during exposure to CO2.

Continue reading ‘CO2 induced pHi changes in the brain of polar fish: a TauCEST application’

Exposure to elevated carbon dioxide does not impair short‐term swimming behaviour or shelter‐seeking in a predatory coral‐reef fish

Adult bluespotted rockcod Cephalopholis cyanostigma, a coral‐reef grouper, were acclimated to either ambient (mean ± S.D. 41.12 ± 2.13 Pa;) or high pCO2 (95.75 ± 11.75 Pa) conditions in a laboratory for 8–9 days, then released at the water surface directly above a reef (depth c. 5 m) and followed on video camera (for 191 ± 21 s) by scuba divers until they sought cover in the reef. No differences were detected between groups in any of the six measured variables, which included the time fish spent immobile after release, tail beat frequency during swimming and the time required to locate and enter the protective shelter of the reef.

Continue reading ‘Exposure to elevated carbon dioxide does not impair short‐term swimming behaviour or shelter‐seeking in a predatory coral‐reef fish’

Integrated multi-biomarker responses of juvenile seabass to diclofenac, warming and acidification co-exposure


• An integrated multi-biomarker approach was used to assess ecotoxicological responses of D. labrax under the co-exposure to DCF, warming and acidification.
• DCF decreased HSI, BBratio, erythrocyte viability and HSP70/HSC70 content in fish brain.
• DCF induced ENAs, oxidative stress, Ub synthesis in muscle, brain AChE activity and liver VTG synthesis.
• DCF deleterious effects were either enhanced or reversed/inhibited by the co-exposure to acidification and/or warming.
• IBR showed that DCF and warming co-exposure resulted in an overall higher degree of stress.
• Results highlighted the need to consider interactions between different stressors in future ecotoxicological studies.


Pharmaceutical drugs, such as diclofenac (DCF), are frequently detected in the marine environment, and recent evidence has pointed out their toxicity to non-target marine biota. Concomitantly, altered environmental conditions associated with climate change (e.g. warming and acidification) can also affect the physiology of marine organisms. Yet, the underlying interactions between these environmental stressors (pharmaceutical exposure and climate change-related stressors) still require a deeper understanding. Comprehending the influence of abiotic variables on chemical contaminants’ toxicological attributes provides a broader view of the ecological consequences of climate change. Hence, the aim of this study was to assess the ecotoxicological responses of juvenile seabass Dicenthrachus labrax under the co-exposure to DCF (from dietary sources, 500 ± 36 ng kg-1 dw), warming (ΔTºC = +5 °C) and acidification (ΔpCO2 ~1000 µatm, equivalent to ΔpH = -0.4 units), using an “Integrated Biomarker Response” (IBR) approach. Fish were exposed to these three stressors, acting alone or combined, for 28 days in a full cross-factorial design, and blood, brain, liver and muscle tissues were subsequently collected in order to evaluate: i) animal/organ fitness; ii) hematological parameters and iii) molecular biomarkers. Results not only confirmed the toxicological attributes of dietary exposure to DCF in marine fish species at the tissue (e.g. lower HSI), cellular (e.g. increased ENAs and lower erythrocytes viability) and molecular levels (e.g. increased oxidative stress, protein degradation, AChE activity and VTG synthesis), but also showed that such attributes are altered by warming and acidification. Hence, while acidification and/or warming enhanced some effects of DCF exposure (e.g. by further lowering erythrocyte viability, and increasing brain GST activity and Ub synthesis in muscle), the co-exposure to these abiotic stressors also resulted in a reversion/inhibition of some molecular responses (e.g. lower CAT and SOD inhibition and VTG synthesis). IBRs evidenced that an overall higher degree of stress (i.e. high IBR index) was associated with DCF and warming co-exposure, while the effects of acidification were less evident. The distinct responses observed when DCF acted alone or the animals were co-exposed to the drug together with warming and acidification not only highlighted the relevance of considering the interactions between multiple environmental stressors in ecotoxicological studies, but also suggested that the toxicity of pharmaceuticals can be aggravated by climate change-related stressors (particularly warming), thus, posing additional biological challenges to marine fish populations.

Continue reading ‘Integrated multi-biomarker responses of juvenile seabass to diclofenac, warming and acidification co-exposure’

Behavioral responses of a coastal flatfish to predation-associated cues and elevated CO2


• Understanding behavior will improve interpretations of climate effects on fishes.
• Sanddab responded differently to damaged skin cues and the sight of a predator.
• Elevated CO2 appeared to have little effect on most behaviors of juvenile sanddab.


The direct and indirect effects of ocean acidification (OA) on marine ecosystems are a growing concern. Studies with marine fishes suggest that elevated CO2 may affect behavior by interfering with an important brain neurotransmitter. OA effects on fish behavior are comparatively understudied in temperate and boreal species. In laboratory experiments, we first characterized speckled sanddab (Citharichthys stigmaeus) behavioral responses to potential predation cues (predator odor, damaged skin cues from injured conspecifics, and sight of a predator) under ambient CO2 levels (~400 μatm). Sanddab reduced conspicuousness and foraging at the sight of a predator, but increased activity and conspicuousness when exposed to damaged skin cues. We then examined the effects of elevated CO2 levels (~900 μatm and ~1500 μatm) on posture, activity, and foraging of sanddab, and the behavioral responses to damaged skin cues. Sanddab behavior appeared generally resilient to the effects of elevated CO2 levels, but there were non-significant trends of fish from the medium CO2 treatment exhibiting lower posture and activity scores, and reduced feeding activity. The resiliency of speckled sanddab to OA conditions may be related to their distribution in a coastal upwelling region with seasonally elevated CO2 levels. Alternatively, prolonged acclimation to elevated CO2 may have mitigated the effects observed in other fishes following shorter-term exposures. Additional studies of ecologically relevant behaviors across diverse species assemblages are necessary to evaluate the impact of ocean acidification on marine food webs.

Continue reading ‘Behavioral responses of a coastal flatfish to predation-associated cues and elevated CO2’

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Ocean acidification in the IPCC AR5 WG II

OUP book