Archive for October, 2013

Some like it hot: Temperature and pH modulate larval development and settlement of the sea urchin Arbacia lixula

We studied the effects of temperature and pH on larval development, settlement and juvenile survival of a Mediterranean population of the sea urchin Arbacia lixula. Three temperatures (16, 17.5 and 19 °C) were tested at present pH conditions (pHT 8.1). At 19 °C, two pH levels were compared to reflect present average (pHT 8.1) and near-future average conditions (pHT 7.7, expected by 2100). Larvae were reared for 52-days to achieve the full larval development and complete the metamorphosis to the settler stage. We analyzed larval survival, growth, morphology and settlement success. We also tested the carry-over effect of acidification on juvenile survival after 3 days. Our results showed that larval survival and size significantly increased with temperature. Acidification resulted in higher survival rates and developmental delay. Larval morphology was significantly altered by low temperatures, which led to narrower larvae with relatively shorter skeletal rods, but larval morphology was only marginally affected by acidification. No carry-over effects between larvae and juveniles were detected in early settler survival, though settlers from larvae reared at pH 7.7 were significantly smaller than their counterparts developed at pH 8.1. These results suggest an overall positive effect of environmental parameters related to global change on the reproduction of A. lixula, and reinforce the concerns about the increasing negative impact on shallow Mediterranean ecosystems of this post-glacial colonizer.

Continue reading ‘Some like it hot: Temperature and pH modulate larval development and settlement of the sea urchin Arbacia lixula’

Is the perceived resiliency of fish larvae to ocean acidification masking more subtle effects?

Ocean acidification, caused by rising concentrations of carbon dioxide (CO2), is widely considered to be a major global threat to marine ecosystems. To investigate the potential effects of ocean acidification on the early life stages of a commercially important fish species, European sea bass (Dicentrarchus labrax), 12 000 larvae were incubated from hatch through metamorphosis under a matrix of two temperatures (17 and 19 °C) and two seawater pCO2s (400 and 750 μatm) and sampled regularly for 42 days. Calculated daily mortality was significantly affected by both temperature and pCO2, with both increased temperature and elevated pCO2 associated with lower daily mortality and a significant interaction between these two factors. There was no significant pCO2 effect noted on larval morphology during this period but larvae raised at 19 °C possessed significantly larger eyes and lower carbon:nitrogen ratios at the end of the study compared to those raised under 17 °C. These results suggest that D. labrax larvae are resilient to near-future oceanic conditions. However, when the incubation was continued to post-metamorphic (juvenile) animals (day 67–69), fish raised under a combination of 19 °C and 750 μatm pCO2 were significantly heavier and exhibited lower aerobic scopes than those incubated at 19 °C and 400 μatm. Most other studies investigating the effects of near-future oceanic conditions on the early life stages of marine fish have used incubations of relatively short durations and suggested these animals are resilient to ocean acidification. We propose the durations of these other studies may be insufficient for more subtle effects, such as those observed in this study, to become apparent. These findings may have important implications for both sea bass in a changing ocean and also for the interpretation of results from other studies that have shown resiliency in marine teleosts exposed to higher atmospheric concentrations of CO2.

Continue reading ‘Is the perceived resiliency of fish larvae to ocean acidification masking more subtle effects?’

Action plan and covering new ground (audio)

This week West Coast leaders signed the Pacific Coast Action Plan on Climate and Energy. In doing so Governor Jay Inslee, California Governor Ed Brown Jr., Oregon Governor John Kitzhaber, and British Columbia’s Premier Christy Clark have committed their governments to combatting climate change and promoting clean energy. The agreement is based on the recognition that the West Coast is bounded together by a common geography, shared infrastructure and a regional economy with a combined GDP of $2.8 trillion, making it the world’s fifth largest economy. Bill Dewey, Manager of Public Affairs for Taylor Shellfish Farms a family owned business in Shelton, was also on hand to speak at the event.

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Nutrient availability affects the response of the calcifying chlorophyte Halimeda opuntia (L.) J.V. Lamouroux to low pH

Atmospheric carbon dioxide emissions cause a decrease in the pH and aragonite saturation state of surface ocean water. As a result, calcifying organisms are expected to suffer under future ocean conditions, but their physiological responses may depend on their nutrient status. Because many coral reefs experience high inorganic nutrient loads or seasonal changes in nutrient availability, reef organisms in localized areas will have to cope with elevated carbon dioxide and changes in inorganic nutrients. Halimeda opuntia is a dominant calcifying primary producer on coral reefs that contributes to coral reef accretion. Therefore, we investigated the carbon and nutrient balance of H.opuntia exposed to elevated carbon dioxide and inorganic nutrients. We measured tissue nitrogen, phosphorus and carbon content as well as the activity of enzymes involved in inorganic carbon uptake and nitrogen assimilation (external carbonic anhydrase and nitrate reductase, respectively). Inorganic carbon content was lower in algae exposed to high CO2, but calcification rates were not significantly affected by CO2 or inorganic nutrients. Organic carbon was positively correlated to external carbonic anhydrase activity, while inorganic carbon showed the opposite correlation. Carbon dioxide had a significant effect on tissue nitrogen and organic carbon content, while inorganic nutrients affected tissue phosphorus and N:P ratios. Nitrate reductase activity was highest in algae grown under elevated CO2 and inorganic nutrient conditions and lowest when phosphate was limiting. In general, we found that enzymatic responses were strongly influenced by nutrient availability, indicating its important role in dictating the local responses of the calcifying primary producer H.opuntia to ocean acidification.

Continue reading ‘Nutrient availability affects the response of the calcifying chlorophyte Halimeda opuntia (L.) J.V. Lamouroux to low pH’

Geologic history of seawater: A MAGic approach to carbon chemistry and ocean ventilation

We explore the relationship between atmospheric O2 and CO2 evolution and seawater chemistry, with particular focus on the CO2-carbonic acid system and ocean ventilation, over the Phanerozoic Eon using a coupled biogeochemical Earth system model (MAGic). This model describes the biogeochemical cycles involving the major components of seawater (Ca, Mg, Na, K, Cl, SO4, CO2 − HCO3 − CO3), as well as components (O2, Fe, P, organic C, reduced S) central to long-term ecosystem productivity. The MAGic calculations show that the first-order input fluxes from weathering of continental rocks of Ca, Mg, and dissolved inorganic carbon (DIC) to the ocean varied in a cyclical manner over the Phanerozoic. The cyclicity is mainly the result of the impact of changing atmospheric CO2 levels, and hence temperature and runoff, on these fluxes, reflecting the nature of hothouse (greenhouse, high CO2 and warm) versus icehouse (low CO2, cool, and continental glaciation) conditions during the Phanerozoic. Uptake of DIC by seafloor basalt-seawater reactions also varied in a corresponding fashion to the weathering fluxes. The fluxes of Ca, Mg, DIC and other seawater constituents removed in oceanic sinks were also calculated and hence with calculated inputs and outputs of seawater constituents, the changes in seawater chemistry through Phanerozoic time could be obtained. Seawater pH increased irregularly during the Phanerozoic from just above 7 in the Cambrian Period, approaching modern average values in the most recent several millions of years. Calcite saturation state also increased with decreasing age. Both pH and calcite saturation state trends exhibited a cyclic overprint of hothouse and icehouse environmental conditions. Dissolved sulfate changed in a cyclical manner reflecting mainly variations in weathering and accretion rates and redox conditions, whereas dissolved potassium exhibited little variation in concentration.

Using our “standard” model results for the chemistry of seawater and changes in atmospheric CO2 and O2 as the basis for a series of sensitivity experiments, we vary the ventilation rate of the global ocean, and quantify the resulting changes in terms of processes such as net primary production, organic carbon burial and oxidation, pyrite weathering, and sulfate reduction. We use these preliminary results to discuss how changes in ocean ventilation affect atmospheric CO2 and O2, and in turn exert changes in the sulfur, organic carbon, and inorganic carbon systems. We postulate that periods of slow plate accretion rates, associated with lower atmospheric CO2, vigorous deep water formation, cooler, drier climatic conditions and greater poleward temperature gradients are more likely to be associated with a strong thermohaline circulation, and thus “enhanced” global ocean mixing. Conversely, periods of higher accretion rates, higher CO2, higher average global temperatures with more equable poleward gradients, and higher sea levels resulting in extensive continental inundation, would be more likely to be coincident with times of reduced mixing of the global ocean. It is important to recognize that the scale of these changes depends on how major tectonic cycles (controlling chemical weathering, CO2 and temperature) in turn affect nutrient supply, global ocean productivity, and global ocean thermohaline circulation. The key to elucidating these changes lies in an understanding of the relationship between long-term tectonic evolution, which leads to changes in climate, sea level, and the global distribution of continental landmasses and the sedimentary environments they host, and the circulation of the global ocean.

Continue reading ‘Geologic history of seawater: A MAGic approach to carbon chemistry and ocean ventilation’

Irukandji threat to southern waters

A Griffith University led study has made the surprising discovery that ocean acidification may provide some protection for South East Queenslanders from the Irukandji jellyfish.

Researchers from Griffith University’s Australian Rivers Institute have conducted a series of climate change simulation experiments to investigate whether the dangerous tropical jellyfish, the Irukandji, is likely to establish breeding populations in the South East.

It was found that while higher sea temperatures could provide an opportunity for adult Irukandji to expand their range south, increasing ocean acidification may inhibit the development of juveniles.

The research is the first step towards assessing if Irukandji pose a significant threat to tourism and human health in the South East. The findings have been published in the journal Global Change Biology.

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Irukandji jellyfish polyps exhibit tolerance to interacting climate change stressors

Increasing ocean temperatures and strengthening boundary currents have caused the poleward migration of many marine species. Cubozoan jellyfish known to cause Irukandji syndrome have historically been confined to tropical waters but may be expanding into subtropical regions. Here, we examine the interactive effects of warming and acidification on the population dynamics of polyps of an Irukandji jellyfish, Alatina nr mordens, and the formation of statoliths in newly metamorphosed medusae, to determine if this jellyfish could tolerate future conditions predicted for southeast Queensland (SEQ), Australia. Two experiments, examining the orthogonal factors of temperature and pH, were undertaken. Experiment 1 mimicked the current, ca. 2050 and ca. 2100 summer temperature and pH conditions predicted for SEQ using A1F1 scenarios (temperature: 25, 27, 29 °C; pH: 7.9, 7.8, 7.6) and Experiment 2 mimicked current and future winter conditions (18 and 22 °C, pH 7.9, 7.8, 7.6). All polyps in Experiment 1 survived and budded. Fewer polyps budded in the lower pH treatments; however, patterns varied slightly among temperature treatments. Statoliths at pH 7.6 were 24% narrower than those at pH 7.8 and 7.9. Most polyps survived the winter conditions mimicked by Experiment 2 but only polyps in the 22 °C, pH 7.9 treatment increased significantly. The current absence of A. nr mordens medusae in SEQ, despite the polyps’ ability to tolerate the current temperature and pH conditions, suggests that ecological, rather than abiotic factors currently limit their distribution. Observations that budding was lower under low pH treatments suggest that rates of asexual reproduction will likely be much slower in the future. We consider that A. nr mordens polyps are likely to tolerate future conditions but are unlikely to thrive in the long term. However, if polyps can overcome potential ecological boundaries and acidification proceeds slowly A. nr mordens could expand polewards in the short term.

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How shifting ocean chemistry threatens Maine

An environmental crisis is looming on the marine horizon. Ocean acidification threatens Maine’s inshore fisheries, growing aquaculture industry and the jobs that rely on them.

The culprit in this story is carbon dioxide. It’s changing the chemistry of the ocean and endangering shellfish like lobster, oysters, clams and sea urchins.

The oceans are naturally slightly basic, or alkaline. But as the oceans absorb more carbon dioxide resulting from fossil fuels use, they move toward the other end of the pH scale, becoming acidic. The acidity level of the oceans has increased 30 percent since the Industrial Revolution.

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Australia’s marine resources in a warm, acid ocean

One of the distinguishing features of our planet is the presence of an ocean that covers 71% of its surface. This vast ocean nurtured life’s beginnings and continues to support the biosphere and ultimately humanity. Approximately a quarter of the world’s population lives along coastlines where people extract food, building materials, energy, cultural significance and income (Seto and Shepherd, 2009).

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Predicting evolutionary responses to climate change in the sea

An increasing number of short-term experimental studies show significant effects of projected ocean warming and ocean acidification on the performance on marine organisms. Yet, it remains unclear if we can reliably predict the impact of climate change on marine populations and ecosystems, because we lack sufficient understanding of the capacity for marine organisms to adapt to rapid climate change. In this review, we emphasise why an evolutionary perspective is crucial to understanding climate change impacts in the sea and examine the approaches that may be useful for addressing this challenge. We first consider what the geological record and present-day analogues of future climate conditions can tell us about the potential for adaptation to climate change. We also examine evidence that phenotypic plasticity may assist marine species to persist in a rapidly changing climate. We then outline the various experimental approaches that can be used to estimate evolutionary potential, focusing on molecular tools, quantitative genetics, and experimental evolution, and we describe the benefits of combining different approaches to gain a deeper understanding of evolutionary potential. Our goal is to provide a platform for future research addressing the evolutionary potential for marine organisms to cope with climate change.

Continue reading ‘Predicting evolutionary responses to climate change in the sea’

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Ocean acidification in the IPCC AR5 WG II

OUP book