Damselfish in distress: on ocean acidification and suicidal reef fish

Munday L., Cheal A. L., Dixson D. L., Rummer J. L. & Fabricius K. E., 2014. Behavioural impairment in reef fishes caused by ocean acidification at CO2 seeps. Nature Climate Change 4:487-492.

Background

In Finding Nemo, the despondent protagonist Nemo wanders away from a school fieldtrip after his father Marlin mocks his impaired swimming ability, the result of a congenital lame fin. At least that is Pixar’s take on what happened. Science might say it was something in the water that emboldened the little talking clownfish to leave the safety of his reef to embark on a feature length adventure of a lifetime.

That something might have been carbon dioxide, the main culprit of ocean acidification, and prime suspect in anthropogenic climate change. When atmospheric carbon dioxide dissolves in water, it equilibrates to form carbonic acid. Acidification due to dissolved carbon dioxide is the same reason your dentist might have told you to avoid carbonated beverages. Sugar aside, just like the carbonation in a can of soda weakens your teeth, increases in acidity (decreases in pH) due to dissolved carbon dioxide can compromise coral structure, or otherwise alter the physiology of, for example, Nemo.

A study recently published by Munday et al. in Nature Climate Change suggests that reef fish exposed to higher levels of carbon dioxide exhibit reckless and vagrant behavior as compared to their more conservative counterparts in waters with lower concentrations of carbon dioxide. Past studies meant to simulate the effects of ocean acidification on fish behavior have shown that elevated exposure to the greenhouse gas desensitizes laboratory-reared fish to danger, such as predation. However, the question remains: how are native ecological communities affected by behavioral changes due to continuous exposure to elevated levels of carbon dioxide?

Continue reading ‘Damselfish in distress: on ocean acidification and suicidal reef fish’

Tough as a rock-boring urchin: adult Echinometra sp. EE from the Red Sea show high resistance to ocean acidification over long-term exposures

Ocean acidification, a process caused by the continuous rise of atmospheric CO2 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 pCO2 conditions on the performance of adult Echinometra sp. EE from the Gulf of Aqaba (Red Sea). During an 11-month incubation under high pCO2 (1,433 μatm, pHNBS 7.7) and control (435 μatm, pHNBS 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 pCO2 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 pCO2 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.

Continue reading ‘Tough as a rock-boring urchin: adult Echinometra sp. EE from the Red Sea show high resistance to ocean acidification over long-term exposures’

Ocean acidification reduces the crystallographic control in juvenile mussel shells

Global climate change threatens the oceans as anthropogenic carbon dioxide causes ocean acidification and reduced carbonate saturation. Future projections indicate under saturation of aragonite, and potentially calcite, in the oceans by 2100. Calcifying organisms are those most at risk from such ocean acidification, as carbonate is vital in the biomineralisation of their calcium carbonate protective shells. This study highlights the importance of multi-generational studies to investigate how marine organisms can potentially adapt to future projected global climate change. Mytilus edulis is an economically important marine calcifier vulnerable to decreasing carbonate saturation as their shells comprise two calcium carbonate polymorphs: aragonite and calcite. M. edulis specimens were cultured under current and projected pCO2 (380, 550, 750 and 1000 μatm), following 6 months of experimental culture, adults produced second generation juvenile mussels. Juvenile mussel shells were examined for structural and crystallographic orientation of aragonite and calcite. At 1000 μatm pCO2, juvenile mussels spawned and grown under this high pCO2 do not produce aragonite which is more vulnerable to carbonate under-saturation than calcite. Calcite and aragonite were produced at 380, 550 and 750 μatm pCO2. Electron back scatter diffraction analyses reveal less constraint in crystallographic orientation with increased pCO2. Shell formation is maintained, although the nacre crystals appear corroded and crystals are not so closely layered together. The differences in ultrastructure and crystallography in shells formed by juveniles spawned from adults in high pCO2 conditions may prove instrumental in their ability to survive ocean acidification.

Continue reading ‘Ocean acidification reduces the crystallographic control in juvenile mussel shells’

Shell condition and survival of Puget Sound pteropods are impaired by ocean acidification conditions

We tested whether the thecosome pteropod Limacina helicina from Puget Sound, an urbanized estuary in the northwest continental US, experiences shell dissolution and altered mortality rates when exposed to the high CO2, low aragonite saturation state (Ωa) conditions that occur in Puget Sound and the northeast Pacific Ocean. Five, week-long experiments were conducted in which we incubated pteropods collected from Puget Sound in four carbon chemistry conditions: current summer surface (~460–500 µatm CO2, Ωa≈1.59), current deep water or surface conditions during upwelling (~760 and ~1600–1700 µatm CO2, Ωa≈1.17 and 0.56), and future deep water or surface conditions during upwelling (~2800–3400 µatm CO2, Ωa≈0.28). We measured shell condition using a scoring regime of five shell characteristics that capture different aspects of shell dissolution. We characterized carbon chemistry conditions in statistical analyses with Ωa, and conducted analyses considering Ωa both as a continuous dataset and as discrete treatments. Shell dissolution increased linearly as aragonite saturation state decreased. Discrete treatment comparisons indicate that shell dissolution was greater in undersaturated treatments compared to oversaturated treatments. Survival increased linearly with aragonite saturation state, though discrete treatment comparisons indicated that survival was similar in all but the lowest saturation state treatment. These results indicate that, under starvation conditions, pteropod survival may not be greatly affected by current and expected near-future aragonite saturation state in the NE Pacific, but shell dissolution may. Given that subsurface waters in Puget Sound’s main basin are undersaturated with respect to aragonite in the winter and can be undersaturated in the summer, the condition and persistence of the species in this estuary warrants further study.

Continue reading ‘Shell condition and survival of Puget Sound pteropods are impaired by ocean acidification conditions’

Workshop to tackle big threat of ocean acidification (audio)

Ahead of next week’s Small Island Developing States conference, experts have been meeting to discuss the problem of ocean acidification.

It’s considered to be one of the biggest threats to small island developing nations – with the potential to impact on local fisheries and in turn, the livelihoods of many people in the Pacific.

Presenter: Bruce Hill

Speaker: Dr Melchio Mataki, Solomon Islands Permanent Secretary for Climate Change

Continue reading ‘Workshop to tackle big threat of ocean acidification (audio)’

Proteomic and metabolomic responses of Pacific oyster Crassostrea gigas to elevated pCO2 exposure

The gradually increased atmospheric CO2 partial pressure (pCO2) has thrown the carbonate chemistry off balance and resulted in decreased seawater pH in marine ecosystem, termed ocean acidification (OA). Anthropogenic OA is postulated to affect the physiology of many marine calcifying organisms. However, the susceptibility and metabolic pathways of change in most calcifying animals is still far from been well understood. In this work, the effects of exposure to elevated pCO2 were characterized in gills and hepatopancreas of Crassostrea gigas using integrated proteomic and metabolomic approaches. Metabolic responses indicated that high CO2 exposure mainly caused disturbances in energy metabolism and osmotic regulation marked by differentially altered ATP, glucose, glycogen, amino acids and organic osmolytes in oysters, and the depletions of ATP in gills and the accumulations of ATP, glucose and glycogen in hepatopancreas accounted for the difference in energy distribution between these two tissues. Proteomic responses suggested that OA could affect energy and primary metabolisms, stress responses and calcium homeostasis in both tissues, but also influence the nucleotide metabolism in gills and cytoskeleton structure in hepatopancreas. This study demonstrated that the combination of proteomics and metabolomics could provide an insightful view into the effects of OA on oyster C. gigas.

Continue reading ‘Proteomic and metabolomic responses of Pacific oyster Crassostrea gigas to elevated pCO2 exposure’

Protect our oceans, urges Samoa minister

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Scientists at the Ocean Acidification workshop aboard the P&O cruiseliner Pacific Jewel in Apia, Samoa– Samisoni Pareti

Small Island states need to do more to rehabilitate, protect and preserve their threatened marine environment. That advice came from Samoa’s Environment Minister Faamoetauloa-Lealaiauloto Taito Dr Faale Tumaalii when he opened a two-day workshop on ocean acidification in Apia today. It’s being held aboard the luxurious cruise-liner, the Pacific Jewel docked at the Apia Port to assist accommodate delegates who will be attending the United Nations Conference on Small Islands Developing States (SIDS).

Continue reading ‘Protect our oceans, urges Samoa minister’


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