Archive for November, 2016

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New study shows ocean acidification accelerates erosion of coral reefs

Published 23 November 2016 Press releases Closed

MIAMI—Scientists studying naturally high carbon dioxide coral reefs in Papua New Guinea found that erosion of essential habitat is accelerated in these highly acidified waters, even as coral growth continues to slow. The new research by the University of Miami Rosenstiel School’s Cooperative Institute for Marine and Atmospheric Studies (CIMAS),  NOAA, and the Australian Institute of Marine Science has important implications for coral reefs around the world as the ocean become more acidic as a result of global change.

The study, published in the journal Proceedings of the Royal Society B, measured changes in the structural habitat at two reefs situated in volcanically acidified water off remote Papau New Guinea and, for the first time, found increased activity of worms and other organisms that bore into the reef structure, resulting in a loss of the framework that is the foundation of coral reef ecosystems.

These ‘champagne reefs’ are natural analogs of how coral reefs may look in 100 years if carbon dioxide continues to rise and ocean acidification conditions continue to worsen.

Continue reading ‘New study shows ocean acidification accelerates erosion of coral reefs’

A chalkier ocean? Multi-decadal increases in North Atlantic coccolithophore populations

Published 23 November 2016 Science Closed
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Increasing atmospheric CO2 concentrations are resulting in both warmer sea surface temperatures due to the greenhouse effect and increasingly carbon-rich surface waters. The ocean has absorbed roughly one third of anthropogenic carbon emissions (1), causing a shift in carbon chemistry equilibrium to more acidic conditions with lower calcium carbonate saturation states (ocean
acidification). Organisms that produce calcium carbonate structures are thought to be particularly susceptible to these changes (2-4).

Coccolithophores are the most abundant type of calcifying unicellular micro-algae in the ocean, producing microscopic calcium carbonate plates called coccoliths (5). Low-pH conditions have been shown to disrupt the formation of coccoliths (calcification; e.g., (6)). Therefore, it is generally expected that a higher-CO2 ocean will cause a reduction in calcification rates or a decrease in the abundance of these calcifiers. Such changes could have far-reaching consequences for marine ecosystems, as well as global carbon cycling and carbon export to the deep sea. (…)

Continue reading ‘A chalkier ocean? Multi-decadal increases in North Atlantic coccolithophore populations’

Shell dissolution observed in Limacina helicina antarctica from the Ross Sea, Antarctica: paired shell characteristics and in situ seawater chemistry

Published 23 November 2016 Science Closed
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The euthecosome (shelled) Antarctic pteropod, Limacina helicina antarctica, is a dominant member of the Southern Ocean macrozooplankton community, and due to its aragonitic shell, is thought to be particularly vulnerable to ocean acidification and under-saturation conditions that are predicted in the future. Notably, pteropods in surface waters and near the continental shelf in the Ross Sea are highly vulnerable as these regions are predicted to be seasonally under-saturated within 2–3 decades. Carbonate chemistry data are rare for this region and here we present the results of a 6-week field study and report patterns of dissolution of juvenile pteropods along with carbonate chemistry of seawater at the time of collection. Conducted in McMurdo Sound in the south Ross Sea in the Pacific sector of the Southern Ocean, L. h. antarctica was successfully collected in plankton tows through the fast sea ice at a single station at 50 m. During the 6-week field study, ocean pH was relatively stable, ranging from 7.988 in October to 8.029 by early December. Calculated saturation states for aragonite (Ωarag) over the 6-week study period ranged from 1.16 to 1.24. Pteropods collected at each sampling time point were prepared for SEM and analysis revealed that roughly 63 % of the shells displayed some degree of shell irregularities suggesting that active dissolution of the aragonitic shell was ongoing under in situ conditions. These results add to the accumulating evidence that shelled pteropods of the Southern Ocean are experiencing aragonite under-saturation events in the present-day that lead to a majority of individuals displaying shell dissolution. Predicted changes to the carbonate system in the Southern Ocean from ocean acidification will likely expand the intensity and duration of these under-saturation events, increasing the need to better understand how pteropods will fare in response to ocean acidification.

Continue reading ‘Shell dissolution observed in Limacina helicina antarctica from the Ross Sea, Antarctica: paired shell characteristics and in situ seawater chemistry’

Which habitats will thrive or die in acidifying oceans?

Published 23 November 2016 Media coverage Closed

Our oceans are acidifying as carbon dioxide levels rise, and some marine habitats will wither away. But it’s not all bad news – others such as seagrass meadows will flourish, new research suggests.

Whether the species that live within them will too is another story.

Jennifer Sunday from the University of British Columbia in Canada and a team of international researchers investigated how changing ocean chemistry affected coral reefs, mussel beds, seagrass meadows and seaweed habitats.

In Nature Climate Change, they found some habitats could grow perfectly well in acidified water, and might provide refuge for their resident species.

Ocean acidification – caused by dissolved carbon dioxide in seawater making carbonic acid – spells doom for many marine species by making it difficult for them to grow and reproduce.

Continue reading ‘Which habitats will thrive or die in acidifying oceans?’

Seasonal variation of CaCO3 saturation state in bottom water of a biological hotspot in the Chukchi Sea, Arctic Ocean (update)

Published 23 November 2016 Science Closed
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Distribution of calcium carbonate saturation state (Ω) was observed in the Chukchi Sea in autumn 2012 and early summer 2013. Ω in bottom water ranged from 0.3 to 2.0 for aragonite and from 0.5 to 3.2 for calcite in 2012. In 2013, Ω in bottom water was 1.1–2.8 for aragonite and 1.7–4.4 for calcite. Aragonite and calcite undersaturation was found in high productivity regions in autumn 2012 but not in early summer 2013. Comparison with other parameters has indicated that biological processes – respiration and photosynthesis – are major factors controlling the regional and temporal variability of Ω. From these ship-based observations, we have obtained empirical equations to reconstruct Ω from temperature, salinity and apparent oxygen utilization. Using 2-year-round mooring data and these equations, we have reconstructed seasonal variation of Ω in bottom water in Hope Valley, a biological hotspot in the southern Chukchi Sea. Estimated Ω was high in spring and early summer, decreased in later summer, and remained relatively low in winter. Calculations indicated a possibility that bottom water could have been undersaturated for aragonite on an intermittent basis even in the pre-industrial period, and that anthropogenic CO2 has extended the period of aragonite undersaturation to more than 2-fold longer by now.

Continue reading ‘Seasonal variation of CaCO3 saturation state in bottom water of a biological hotspot in the Chukchi Sea, Arctic Ocean (update)’

On location with ocean acidification

Published 22 November 2016 Media coverage , Projects Closed
Photo credit: Ryan Ono

Photo credit: Ryan Ono

Last week, two filmmakers and I went to South Florida to document how ocean acidification can touch communities, like Miami’s, that don’t depend heavily on shellfish harvests. Known for its marine life, beaches, coral reefs and sunny weather, Miami and much of Florida rely on these natural assets to drive the local fishing and tourist industry. Coral reefs are the key link, because they provide habitat for vast numbers of fish—including many of the sport fish that make Florida’s charter fishing industry a must-visit for thousands of tourists each year.

Corals live in shallow and deep waters all the way around Florida—from the Gulf of Mexico and Caribbean Sea around to the Atlantic coast. They provide nurseries for young fish, where food and protection abound. Shallow-water corals also protect Florida’s coasts from hurricane waves, and the skeletons of coral reefs from thousands of years ago create Florida’s actual bedrock. But ocean acidification doesn’t care—it’s wearing away at coral reefs new and old.

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Ocean acidification study offers warnings for marine life, habitats

Published 22 November 2016 Press releases Closed
Photo credit: C. Harley (UBC)

Photo credit: C. Harley (UBC)

Acidification of the world’s oceans could drive a cascading loss of biodiversity in some marine habitats, according to research published today in Nature Climate Change.

The work by biodiversity researchers from the University of British Columbia (UBC) and colleagues in the U.S., Europe, Australia, Japan and China, combines dozens of existing studies to paint a more nuanced picture of the impact of ocean acidification.

While most research in the field focuses on the impact of ocean acidification on individual species, the new work predicts how acidification will affect the living habitats, such as corals, seagrasses, and kelp forests, that form the homes of other ocean species.

“Not too surprisingly, species diversity in calcium carbonate-based habitats like coral reefs and mussel beds were projected to decline with increased ocean acidification,” said UBC zoologist and biodiversity researcher Jennifer Sunday, who led the study. Species that use calcium carbonate to build their shells and skeletons, like mussels and corals, are expected to be particularly vulnerable to acidification.

Continue reading ‘Ocean acidification study offers warnings for marine life, habitats’

Ocean acidification can mediate biodiversity shifts by changing biogenic habitat

Published 22 November 2016 Science Closed
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The effects of ocean acidification (OA) on the structure and complexity of coastal marine biogenic habitat have been broadly overlooked. Here we explore how declining pH and carbonate saturation may affect the structural complexity of four major biogenic habitats. Our analyses predict that indirect effects driven by OA on habitat-forming organisms could lead to lower species diversity in coral reefs, mussel beds and some macroalgal habitats, but increases in seagrass and other macroalgal habitats. Available in situ data support the prediction of decreased biodiversity in coral reefs, but not the prediction of seagrass bed gains. Thus, OA-driven habitat loss may exacerbate the direct negative effects of OA on coastal biodiversity; however, we lack evidence of the predicted biodiversity increase in systems where habitat-forming species could benefit from acidification. Overall, a combination of direct effects and community-mediated indirect effects will drive changes in the extent and structural complexity of biogenic habitat, which will have important ecosystem effects.

Continue reading ‘Ocean acidification can mediate biodiversity shifts by changing biogenic habitat’

Elevated pCO2 effects on the macroalgal genus Halimeda: Potential roles of photophysiology and morphology

Published 22 November 2016 Science Closed
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While ocean acidification (OA) is predicted to inhibit calcification in marine macroalgae, species whose photosynthesis is limited by current dissolved inorganic carbon (DIC) levels may benefit. Furthermore, variations in macroalgal morphology will likely give rise to a range of OA tolerance in calcifying macroalgae. One genus of calcifying macroalgae that has shown varying species’ tolerance to OA is Halimeda, a major carbonate sediment producer on tropical reefs. Species within this genus occupy a range of habitats within tropical environments (reefs and lagoons), illustrating their ability to adapt to diverse environmental conditions (e.g. carbonate chemistry, irradiance). To date it is not clear if morphological and photophysiological diversity in Halimeda will translate to different tolerances to OA conditions (elevated pCO2 and lower pH).

In this dissertation, aquaria experiments were conducted to examine growth, calcification, and aragonite crystal formation in 7 Halimeda species using year 2100 pCO2 levels (∼1000 µatm) compared to controls (∼400 µatm) under low (sub-saturating) and high (saturating) irradiance. Elevated pCO2 effects on dissolution in non-living segments of 4 Halimeda species were also assessed. Each species’ photophysiology and primary utricle morphology were characterized to determine their potential role in experimental responses to OA conditions.

Net calcification rates varied among species, but were unaffected by elevated pCO2, regardless of irradiance. The lack of a pCO2 effect on calcification was attributed to photosynthesis that was maintained or enhanced at [DIC] above current levels. Low irradiance stimulated growth of new segments with aragonite crystals that were indistinguishable across pCO2 treatments. In contrast, aragonite needles in non-living segments became narrower under elevated pCO2 relative to controls in weakly calcified species, unlike those that were heavily cemented with micro-anhedral crystals. Inter-species’ variations in inorganic content and crystal microstructure were related to differences in primary utricle morphology. Although these diverse utricle morphologies were predicted to influence variable OA tolerances, this thesis was rejected based on experimental evidence that all 7 Halimeda species maintained their ability to calcify and precipitate aragonite crystals under elevated pCO2. Thus, it is proposed that these 7 Halimeda species will continue their roles as carbonate sediment producers on future tropical reefs.

Continue reading ‘Elevated pCO2 effects on the macroalgal genus Halimeda: Potential roles of photophysiology and morphology’

Physiological responses of coastal and oceanic diatoms to diurnal fluctuations in seawater carbonate chemistry under two CO2 concentrations (update)

Published 22 November 2016 Science Closed
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Diel and seasonal fluctuations in seawater carbonate chemistry are common in coastal waters, while in the open-ocean carbonate chemistry is much less variable. In both of these environments, ongoing ocean acidification is being superimposed on the natural dynamics of the carbonate buffer system to influence the physiology of phytoplankton. Here, we show that a coastal Thalassiosira weissflogii isolate and an oceanic diatom, Thalassiosira oceanica, respond differentially to diurnal fluctuating carbonate chemistry in current and ocean acidification (OA) scenarios. A fluctuating carbonate chemistry regime showed positive or negligible effects on physiological performance of the coastal species. In contrast, the oceanic species was significantly negatively affected. The fluctuating regime reduced photosynthetic oxygen evolution rates and enhanced dark respiration rates of T. oceanica under ambient CO2 concentration, while in the OA scenario the fluctuating regime depressed its growth rate, chlorophyll a content, and elemental production rates. These contrasting physiological performances of coastal and oceanic diatoms indicate that they differ in the ability to cope with dynamic pCO2. We propose that, in addition to the ability to cope with light, nutrient, and predation pressure, the ability to acclimate to dynamic carbonate chemistry may act as one determinant of the spatial distribution of diatom species. Habitat-relevant diurnal changes in seawater carbonate chemistry can interact with OA to differentially affect diatoms in coastal and pelagic waters.

Continue reading ‘Physiological responses of coastal and oceanic diatoms to diurnal fluctuations in seawater carbonate chemistry under two CO2 concentrations (update)’

Limited impact of ocean acidification on phytoplankton community structure and carbon export in an oligotrophic environment: Results from two short-term mesocosm studies in the Mediterranean Sea

Published 21 November 2016 Science Closed
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Modifications in the strength of the biological pump as a consequence of ocean acidification, whether positive or negative, have the potential to impact atmospheric CO2 and therefore climate. So far, most plankton community perturbation studies have been performed in nutrient-rich areas although there are some indications that CO2-dependent growth could differ in nutrient-replete vs. -limited regions and with different community compositions. Two in situ mesocosm experiments were performed in the NW Mediterranean Sea during two seasons with contrasted environmental conditions: summer oligotrophic stratified waters in the Bay of Calvi vs. winter mesotrophic well-mixed waters in the Bay of Villefranche. Nine mesocosms were deployed for 20 and 12 d, respectively, and subjected to seven CO2 levels (3 controls, 6 elevated levels). Both phytoplankton assemblages were dominated by pico- and nano-phytoplankton cells. Although haptophyceae and dinoflagellates benefited from short-term CO2 enrichment in summer, their response remained small with no consequences on organic matter export due to strong environmental constraints (nutrient availability). In winter, most of the plankton growth and associated nutrient consumption occurred during the 4-day acidification period (before the experimental phase). During the remaining experimental period, characterized by low nutrient availability, plankton growth was minimal and no clear CO2-dependency was found for any of the tested parameters. While there is a strong confidence on the absence of significant effect of short-term CO2 addition under oligotrophic conditions, more investigations are needed to assess the response of plankton communities in winter when vertical mixing and weather conditions are major factors controlling plankton dynamics.

Continue reading ‘Limited impact of ocean acidification on phytoplankton community structure and carbon export in an oligotrophic environment: Results from two short-term mesocosm studies in the Mediterranean Sea’

Exploring foraminiferal Sr/Ca as a new carbonate system proxy

Published 21 November 2016 Science Closed
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In present day paleoclimate research one of the most pressing challenges is the reconstruction of atmospheric CO2 concentrations. A variety of proxies for several components of the marine inorganic carbon system have been developed in this context (e.g. B isotopes, B/Ca, U/Ca) to allow reconstruction of past seawater pH, alkalinity etc., and thereby facilitate estimates of past atmospheric pCO2. Based on culture experiments using the benthic foraminifera Ammonia sp. we describe a positive correlation between Sr/Ca and the carbonate system, namely DIC/ bicarbonate ion concentration. Foraminiferal Sr/Ca ratios provide potentially additional constraints on the carbonate system proxy, because the analysis of foraminiferal carbonate Sr/Ca is straightforward and not easily contaminated. Applying our calibration to a published dataset of paleo-Sr/Ca suggests the validity of Sr/Ca as a carbonate system proxy. Furthermore, we explore how our data can be used to advance conceptual understanding of the foraminiferal biomineralization mechanism.

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Acidification alters predator-prey interactions of blue crab Callinectes sapidus and soft-shell clam Mya arenaria

Published 21 November 2016 Science Closed
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Acidification due to anthropogenic CO2 pollution, along with episodic or persistent acidification that occurs in coastal environments, will likely result in severe seasonal acidification in estuarine environments. Acidification decreases the fitness of individual species, but the degree to which predator-prey interactions will be impacted is largely unknown. This mesocosm study examined the effect of CO2 acidification on crab-bivalve predator-prey interactions involving two commercially important Chesapeake Bay species, the blue crab Callinectes sapidus and the soft-shell clam Mya arenaria. In particular, the direct effects of CO2 acidification on clam growth and behavior, and the indirect effects of CO2 acidification on interactions between crabs and clams were examined. Mya arenaria were grown in CO2-acidified water (pH 7.2) or ambient conditions (pH 7.8) for 30 days. To determine the effect of acidification on clam responsiveness to mechanical disturbance, a probe was slowly moved towards clams until they ceased pumping (a behavior to avoid detection by predators), and the distance between the probe and the clam’s siphon was noted. Clams were exposed to predation by C. sapidus, which were held under acidified or ambient conditions for 48 h. Callinectes sapidus handling time, search time, and encounter rate were measured from video. Acidified clams had lighter shells than ambient clams, indicating that shell dissolution occurred. Acidification reduced the responsiveness of M. arenaria to a mechanical disturbance that simulated an approaching predator. As compared to ambient trials, crabs in acidified trials had higher encounter rates; however, this was offset by crabs taking longer to find the first clam in trials, and by increased occurrence of crabs eating only a portion of the prey available. As a result, there was no net change in predation-related clam mortality in acidified trials as compared to ambient conditions. Understanding how acidification will impact food webs in productive estuarine environments requires an examination of the direct impacts of acidification on organism behavior and physiology, as well as indirect effects of acidification mediated through predator-prey interactions.

Continue reading ‘Acidification alters predator-prey interactions of blue crab Callinectes sapidus and soft-shell clam Mya arenaria’

Calcium carbonate composition and other measures of vulnerability of the skeletons and shells of echinoderms and gastropods challenged by ocean acidification or climate warming

Published 21 November 2016 Science Closed
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Marine invertebrate calcium carbonate (CaCO3) composition will likely be impacted by climate warming and ocean acidification (OA). Elevated temperature alters physiological processes that can induce stress, and OA alters the ability of calcareous marine invertebrates to maintain acid-base balances, calcify, and repair skeletal dissolution. The first of three chapters of this dissertation exploits a natural CO2 seep to evaluate impacts of chronic exposure to OA on the shells of four gastropods: the limpets Patella caerulea and P. rustica, top-shell snail Osilinus turbinatus, and whelk Hexaplex trunculus. All four gastropods experienced shell dissolution to various degrees and reduced shell integrity as pH decreased. The limpet P. rustica demonstrated altered CaCO3 composition of the shell with reduced pH, and there was evidence of altered shell microstructure in both limpets. The second chapter documents the variability of CaCO3 composition of skeletal components of high latitude Antarctic echinoderms to further evaluate the hypothesis that skeletal magnesium content is inversely correlated with latitude in the Echinodermata. Significant inverse correlations were observed in echinoderms collected between 62° and 76°S, but not when the correlation analysis was restricted to those collected south of 70°S where seawater temperature is comparatively constant. This suggests that temperature may be an important factor driving this global relationship in echinoderms. This also suggests that climate warming may lead to increasing levels of magnesium in skeletal components, rendering them more susceptible to dissolution under conditions of OA. The third chapter examines variability of the CaCO3 composition of skeletal components of the model sea urchin Lytechinus variegatus exposed to ambient and near-future seawater temperature. Over the 90-day experiment, there was no increase in skeletal magnesium content in the test, spines, or Aristotle’s lantern in the elevated temperature treatment. This result was likely related to thermal stress and individuals allocating their resources elsewhere. It appears that elevated temperatures may not alter CaCO3 composition or impact skeletal solubility in L. variegatus as OA intensifies. The mineralogy of gastropods and echinoderms investigated herein exemplifies the variable nature of susceptibility to OA and the difficulty of predicting impacts of climate change without a focus at the species level.

Continue reading ‘Calcium carbonate composition and other measures of vulnerability of the skeletons and shells of echinoderms and gastropods challenged by ocean acidification or climate warming’

Responses of the sea anemone, Exaiptasia pallida, to ocean acidification conditions and zinc or nickel exposure

Published 21 November 2016 Science Closed
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Ocean acidification, caused by increasing atmospheric carbon dioxide (CO2), is a growing concern in marine environments. Land-based sources of pollution, such as metals, have also been a noted problem; however, little research has addressed the combined exposure of both pollutants to coral reef organisms. In this study we examined tissue metal accumulation and physiological effects (activity of anti-oxidant enzymes, catalase and glutathione reductase) in the sea anemone, Exaiptasia pallida after exposure to increased CO2, as well as zinc (Zn) or nickel (Ni). After exposure to four concentrations (nominal values = control, 10, 50, 100 μg/L) of Zn or Ni over 7 days, both metals accumulated in the tissues of E. pallida in a concentration-dependent manner. Anemones exposed to elevated CO2 (1000 ppm) accumulated significant tissue burdens of Zn or Ni faster (by 48 h) than those exposed to the same metal concentrations at ambient CO2. No differences were observed in catalase activity due to Zn exposure; however, 50 μg/L Ni caused a significant increase in catalase activity at ambient CO2. No significant effect on catalase activity from CO2 exposure alone was observed. Glutathione reductase activity was affected by increased Zn or Ni exposure and those effects were influenced by increased CO2. Results of this study provide insight into the toxic mechanisms and environmental implications of CO2 and Zn or Ni exposure to the cnidarian E. pallida.

Continue reading ‘Responses of the sea anemone, Exaiptasia pallida, to ocean acidification conditions and zinc or nickel exposure’

Oceanographer Position Open: Coral Reef Ecosystem Program, Honolulu

Published 21 November 2016 Jobs Closed

Closing date for applications: 28 November 2016!

Regular, Full-Time, RCUH Non-Civil Service position with the School of Ocean and Earth Science and Technology (SOEST), Joint Institute for Marine and Atmospheric Research (JIMAR), located at the National Marine Fisheries Service (NMFS), Pacific Islands Fisheries Science Center (PIFSC) in Honolulu, Hawai‘i.

Continuation of employment is dependent upon program/operational needs, satisfactory work performance, availability of funds, and compliance with applicable Federal/State laws.

Salary commensurate with qualifications.

DUTIES: Plans and implements oceanographic surveys and field operations. Processes, analyzes, and interprets oceanographic data with the purpose of examining the relationship between oceanographic processes and coral reef ecosystem dynamics. Develops graphical and other synthesized data products for presentation in reports, scientific articles, and outreach/educational materials. Designs and develops software tools and data management procedures to analyze, integrate, and visualize ecosystem data. Develops, implements, and maintains procedures to process and produce data products for current and historical data. Contributes to scientific manuscripts for publication and presents research at various conferences or relevant settings. Participates in research cruises, marine ecosystem surveys and observation networks to assess and monitor coral reefs, which involves field surveys, the deployment and recovery oceanographic instrument platforms, and data transmission, analysis, and creation of data products. Provides training and guidance in operating equipment, conducting field surveys and processing data.

Continue reading ‘Oceanographer Position Open: Coral Reef Ecosystem Program, Honolulu’

Sea Talk: “Ocean Acidification – Science and Policy”, 22 November 2016, The Aquarium of Hawaii

Published 21 November 2016 Events Closed

Date & time: 22 November 2016, 6-7 pm

Location: Open Ocean Exhibit, Maui Ocean Center, 192 Ma’alaea Rd, Wailuku, Hawaii, HI 96793

“Ocean Acidification – Global Scientific and Policy Challenges” will be presented by Dr. Will Howard.

Today, ocean acidification poses growing risks to marine assets ranging from the tropical reefs to polar oceans. Join Dr. Will Howard and learn about ocean acidification and discover which natural science and social disciplines will be vital in the coming years for policymakers, the public and the scientific community.

Dr. Will Howard is the Head of Science at the Office of the Chief Scientist in Canberra and has a Ph.D in Geological Sciences from Brown University in Providence, Rhode Island. His research work focuses on marine climate change, with particular emphasis on ocean acidification and its impacts on the past, current and future ocean. He is particularly interested in the ocean carbon cycle and the responses of marine ecosystems to climate change.

Sea Talks are held in the Open Ocean Exhibit. Admission is FREE and open to the public. Seating is limited. Reservations are recommended, please call (808) 270-7075.

Further information about the event venue.

The metabolic response of thecosome pteropods from the North Atlantic and North Pacific oceans to high CO2 and low O2 (update)

Published 21 November 2016 Science Closed
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As anthropogenic activities directly and indirectly increase carbon dioxide (CO2) and decrease oxygen (O2) concentrations in the ocean system, it becomes important to understand how different populations of marine animals will respond. Water that is naturally low in pH, with a high concentration of carbon dioxide (hypercapnia) and a low concentration of oxygen, occurs at shallow depths (200–500 m) in the North Pacific Ocean, whereas similar conditions are absent throughout the upper water column in the North Atlantic. This contrasting hydrography provides a natural experiment to explore whether differences in environment cause populations of cosmopolitan pelagic calcifiers, specifically the aragonitic-shelled pteropods, to have a different physiological response when exposed to hypercapnia and low O2. Using closed-chamber end-point respiration experiments, eight species of pteropods from the two ocean basins were exposed to high CO2 ( ∼  800 µatm) while six species were also exposed to moderately low O2 (48 % saturated, or  ∼  130 µmol kg−1) and a combined treatment of low O2/high CO2. None of the species tested showed a change in metabolic rate in response to high CO2 alone. Of those species tested for an effect of O2, only Limacina retroversa from the Atlantic showed a response to the combined treatment, resulting in a reduction in metabolic rate. Our results suggest that pteropods have mechanisms for coping with short-term CO2 exposure and that there can be interactive effects between stressors on the physiology of these open ocean organisms that correlate with natural exposure to low O2 and high CO2. These are considerations that should be taken into account in projections of organismal sensitivity to future ocean conditions.

Continue reading ‘The metabolic response of thecosome pteropods from the North Atlantic and North Pacific oceans to high CO2 and low O2 (update)’

Lethal and sublethal responses in the clam Scrobicularia plana exposed to different CO2-acidic sediments

Published 18 November 2016 Science Closed
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One of the main impacts expected in CO2 leakage scenarios from carbon capture and storage in sub-seabed geological structures is the acidification of the environment. In the present work, laboratory-scale experiments were performed to investigate the effects of seawater acidification (pH 7.0, 6.5, 6.0, and control) in native clams (Scrobicularia plana) over 21 days of exposure. For this purpose, a battery of biomarkers (GSI, EROD, GST, GPX, LPO, and DNA damage) were analysed in the digestive glands of individuals collected on days 7, 14 and 21. Seawater acidification significantly affected the average life span of S. plana, and both the biomarkers analysed and the multivariate analysis approach demonstrated that seawater acidification induced a strong oxidative stress response in the clam. Oxidative stress overwhelmed the capacity of S. plana to defend its cells against it, resulting in DNA damage. Furthermore, the decline in the population of S. plana in their natural habitat could lead to a reduction in available food resources for avifauna, ichthyofauna, and for the local economy because this clam is a commercial species in the south of Europe.

Continue reading ‘Lethal and sublethal responses in the clam Scrobicularia plana exposed to different CO2-acidic sediments’

Study shows ocean acidification is two-front assault on coral reefs

Published 18 November 2016 Press releases Closed

Scientists studying coral reefs in volcanically acidified water of the southwestern Pacific Ocean measured a net loss of coral reef skeletons due to increased bio-erosion by worms and other organisms, according to new research by NOAA, the Cooperative Institute for Marine and Atmospheric Studies (CIMAS) and Australian scientists.

The study, published in the Proceedings of the Royal Society B, measured changes in the reef framework in several naturally high-carbon dioxide settings near Papua New Guinea. For the first time, scientists found increased activity of worms and other organisms that bore into the reef structure resulting in a net loss of the framework that is the foundation of coral reef ecosystems.

This two-year study used cutting edge technology to analyze the combined influences of organisms that add to and break down reef framework. Micro-CT scans and specialized software allowed scientists to peer inside the coral skeletons to see the bore holes left by worms. They created three-dimensional digital models to precisely measure the net difference between new coral material added by calcifying organisms and coral material lost through bio-erosion by worms and other organisms.

Continue reading ‘Study shows ocean acidification is two-front assault on coral reefs’

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