Archive for August, 2014

Metabolic suppression during protracted exposure to hypoxia in the jumbo squid, Dosidicus gigas, living in an oxygen minimum zone

The jumbo squid, Dosidicus gigas, can survive extended forays into the oxygen minimum zone (OMZ) of the Eastern Pacific Ocean. Previous studies have demonstrated reduced oxygen consumption and a limited anaerobic contribution to ATP production, suggesting the capacity for substantial metabolic suppression during hypoxic exposure. Here, we provide a more complete description of energy metabolism and explore the expression of proteins indicative of transcriptional and translational arrest that may contribute to metabolic suppression. We demonstrate a suppression of total ATP demand under hypoxic conditions (1% oxygen, PO2=0.8 kPa) in both juveniles (52%) and adults (35%) of the jumbo squid. Oxygen consumption rates are reduced to 20% under hypoxia relative to air-saturated controls. Concentrations of arginine phosphate (Arg-P) and ATP declined initially, reaching a new steady state (~30% of controls) after the first hour of hypoxic exposure. Octopine began accumulating after the first hour of hypoxic exposure, once Arg-P breakdown resulted in sufficient free arginine for substrate. Octopine reached levels near 30 mmol g−1 after 3.4 h of hypoxic exposure. Succinate did increase through hypoxia but contributed minimally to total ATP production. Glycogenolysis in mantle muscle presumably serves to maintain muscle functionality and balance energetics during hypoxia. We provide evidence that post-translational modifications on histone proteins and translation factors serve as a primary means of energy conservation and that select components of the stress response are altered in hypoxic squids. Reduced ATP consumption under hypoxia serves to maintain ATP levels, prolong fuel store use and minimize the accumulation of acidic intermediates of anaerobic ATP-generating pathways during prolonged diel forays into the OMZ. Metabolic suppression likely limits active, daytime foraging at depth in the core of the OMZ, but confers an energetic advantage over competitors that must remain in warm, oxygenated surface waters. Moreover, the capacity for metabolic suppression provides habitat flexibility as OMZs expand as a result of climate change.

Continue reading ‘Metabolic suppression during protracted exposure to hypoxia in the jumbo squid, Dosidicus gigas, living in an oxygen minimum zone’

Living in warmer more acidic oceans retards physiological recovery from tidal emersion in the velvet swimming crab Necora puber (L.)

The distribution patterns of many species in the intertidal zone are partly determined by their ability to survive and recover from tidal emersion. During emersion most crustaceans experience gill-collapse impairing gas-exchange. Such collapse generates a state of hypoxemia and a hypercapnia-induced respiratory acidosis, leading to hyperlactaemia and metabolic acidosis. However, how such physiological responses to emersion are modified by prior exposure to elevated CO2 and temperature combinations, indicative of future climate change scenarios, is not known. We therefore investigated key physiological responses of velvet swimming crabs, Necora puber, kept for 14 days at one of four pCO2/temperature treatments (400 μatm/10 °C, 1000 μatm/10 °C, 400 μatm/15 °C, 1000 μatm/15 °C), to experimental emersion and recovery. Pre-exposure to elevated pCO2 and temperature increased pre-emersion bicarbonate ion concentrations [HCO3-], increasing resistance to short periods of emersion (90 min). However, there was still a significant acidosis following 180 min emersion in all treatments. The recovery of extracellular acid base via the removal of extracellular pCO2 (PCO2) and lactate after emersion was significantly retarded by exposure to both elevated temperature and pCO2. If elevated environmental pCO2 and temperature lead to slower recovery after emersion, then some predominantly subtidal species that also inhabit the low to mid shore, such as N. puber, may have a reduced physiological capacity to retain their presence in the low intertidal zone, ultimately affecting their bathymetric range of distribution, as well as the structure, and diversity of intertidal assemblages.

Continue reading ‘Living in warmer more acidic oceans retards physiological recovery from tidal emersion in the velvet swimming crab Necora puber (L.)’

Characterization of the Antarctic sea urchin (Sterechinus neumayeri) transcriptome and mitogenome: a molecular resource for phylogenetics, ecophysiology and global change biology

This is the first de novo transcriptome and complete mitochondrial genome of an Antarctic sea urchin species sequenced to date. Sterechinus neumayeri is an Antarctic sea urchin and a model species for ecology, development, physiology, and global change biology. To identify transcripts important to ocean acidification and thermal stress, this transcriptome was created pooling thirteen larval samples representing developmental stages on day 11 (late gastrula), 19 (early pluteus), and 30 (mid pluteus) maintained at three CO2 levels (421, 652, and 1071 μatm) as well as four additional heat shocked samples. The normalized cDNA pool was sequenced using emulsion PCR (pyrosequencing) resulting in 1.34M reads with an average read length of 492 base pairs. 40,994 isotigs were identified, averaging 1188bp with a median coverage of 11x. Additional primer design and gap sequencing was required to complete the mitochondrial genome. The mitogenome of S. neumayeri is a circular DNA molecule with a length of 15,684 bp that contains all 37 genes normally found in metazoans. We detail the main features of the transcriptome and the mitogenome architecture and investigate the phylogenetic relationships of S. neumayeri within Echinoidea. In addition, we provide comparative analyses of S. neumayeri with its closest relative, Strongylocentrotus purpuratus, including a list of potential ocean acidification gene targets. The resources described here will support a variety of quantitative (genomic, proteomic, multistress and comparative) studies to interrogate physiological responses to OA and other stressors in this important Antarctic calcifier.

Continue reading ‘Characterization of the Antarctic sea urchin (Sterechinus neumayeri) transcriptome and mitogenome: a molecular resource for phylogenetics, ecophysiology and global change biology’

Health and population-dependent effects of ocean acidification on the marine isopod Idotea balthica

Three populations of the grazing isopod Idotea balthica were exposed to high CO2 treatment for a period of 20 days to investigate the effect of ocean acidification (OA) on animal health and immunocompetence. The results of the populations from more saline habitats were comparable and showed a 60–80 % decrease in immune response as a result of the high CO2 treatment. Analysis of protein carbonyls showed no treatment effect, indicating that short-term OA does not increase oxidative protein damage. Meanwhile, the third tested population from the lower saline Baltic Sea had higher background protein carbonyl levels. Ocean acidification in addition to this resulted in 100 % mortality. The results of this study show that OA reduced immunocompetence of this marine isopod. In addition, populations and individuals in poor health are potentially at greater risk to succumb under OA.

Continue reading ‘Health and population-dependent effects of ocean acidification on the marine isopod Idotea balthica’

Long Island Sound becoming more acidic, scientists say

Long Island Sound, already choked with nitrogen, may also be becoming more acidic — a state that could threaten marine life.

Scientists are turning their attention to the phenomenon of ocean acidification — and its potential impact on the hard clams, oysters and other shellfish that make the Sound their home. Acidic water could threaten Long Island’s shellfish population during the most vulnerable stages of their lives — when they are beginning to form shells, said Christopher Gobler, a professor at Stony Brook University’s School of Marine and Atmospheric Sciences who has been studying the issue. “The very earliest stages of life for all the shellfish commercially important to Long Island are very sensitive to acidification,” Gobler said. “We see high levels of mortality and very poor survival when acidification happens.” The Sound has been experiencing summer algal blooms, fed by high levels of nitrogen from wastewater and runoff from fertilizers. Those blooms are thought to feed a chemical process that ends in increased acidification, scientists say.

Continue reading ‘Long Island Sound becoming more acidic, scientists say’

Ocean acidification and policy failure

The Melbourne Sustainable Society Institute (MSSI) invites everyone to a free public lecture as part of the Sustainability in the Anthropocene series.

Event date: Wednesday, 10 September 2014
Event time: 1-2pm
Event location: Theatre C, Old Arts Building, University of Melbourne

Ocean acidification is potentially one of the most pervasive and persistent global environmental problems we face. Yet despite its widespread economic, social and ecological consequences, the issue is poorly understood by the public and by politicians and wrongly seen as merely one among the many adverse impacts of climate change. This talk first reviews the current science of ocean acidification. Then, using Australia as its focus, it addresses the puzzle of why ocean acidification has been poorly recognised as a policy issue to date and considers remedies to its obscurity.

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Diverse coral communities in mangrove habitats suggest a novel refuge from climate change

Risk analyses indicate that more than 90% of the world’s reefs will be threatened by climate change and local anthropogenic impacts by the year 2030 under “business-as-usual” climate scenarios. Increasing temperatures and solar radiation cause coral bleaching that has resulted in extensive coral mortality. Increasing carbon dioxide reduces seawater pH, slows coral growth, and may cause loss of reef structure. Management strategies include establishment of marine protected areas with environmental conditions that promote reef resiliency. However, few resilient reefs have been identified, and resiliency factors are poorly defined.

Here we characterize the first natural, non-reef coral refuge from thermal stress and ocean acidification and identify resiliency factors for mangrove–coral habitats. We measured diurnal and seasonal variations in temperature, salinity, photosynthetically active radiation (PAR), and seawater chemistry; characterized substrate parameters; and examined water circulation patterns in mangrove communities where scleractinian corals are growing attached to and under mangrove prop roots in Hurricane Hole, St. John, US Virgin Islands. Additionally, we inventoried the coral species and quantified incidences of coral bleaching, mortality, and recovery for two major reef-building corals, Colpophyllia natans and Diploria labyrinthiformis, growing in mangrove-shaded and exposed (unshaded) areas.

Over 30 species of scleractinian corals were growing in association with mangroves. Corals were thriving in low-light (more than 70% attenuation of incident PAR) from mangrove shading and at higher temperatures than nearby reef tract corals. A higher percentage of C. natans colonies were living shaded by mangroves, and no shaded colonies were bleached. Fewer D. labyrinthiformis colonies were shaded by mangroves, however more unshaded colonies were bleached. A combination of substrate and habitat heterogeneity, proximity of different habitat types, hydrographic conditions, and biological influences on seawater chemistry generate chemical conditions that buffer against ocean acidification. This previously undocumented refuge for corals provides evidence for adaptation of coastal organisms and ecosystem transition due to recent climate change. Identifying and protecting other natural, non-reef coral refuges is critical for sustaining corals and other reef species into the future.

Continue reading ‘Diverse coral communities in mangrove habitats suggest a novel refuge from climate change’

Interactive comment on “Comparison of seven packages that compute ocean carbonate chemistry” by J. C. Orr et al.

Response to Referee, Richard Zeebe

The comments from Drs. Zeebe and Wolf-Gladrow are repeated below in gray (here marked with “…”); our response follows in black. We thank them for the effort that they put into providing this comment.

“Errors and typos in numerical routines that lead to differences in CO2 system calculations should of course be rigorously eliminated. Ideally, numerical routines using the same equations should agree within round-off error. Actual fundamental / systematic differences between packages may be eliminated in the future by agreeing on a common approach.”

For the most part, the packages that we compared in the Discussion paper did follow the same approach, as outlined in the guide for best practices (Dickson et al., 2007). Although that guide did not specify how to perform pressure adjustments of equilibrium constants, packages still followed the same basic approach. They usually differed due to slight variations or errors in implementations.

Please read the whole article here.

Continue reading ‘Interactive comment on “Comparison of seven packages that compute ocean carbonate chemistry” by J. C. Orr et al.’

Organic matter production response to CO2 increase in open subarctic plankton communities: Comparison of six microcosm experiments under iron-limited and -enriched bloom conditions

Increase in seawater pCO2 and the corresponding decrease in pH caused by the increasing atmospheric CO2 concentration (i.e., ocean acidification) may affect organic matter production by phytoplankton communities. Organic matter production forms the basis of marine food webs and plays a crucial role in oceanic CO2 uptake through the biological carbon pump, and hence will potentially affect future marine ecosystem dynamics. However, responses of organic matter production in open ocean plankton ecosystems to CO2 increase have not been fully examined. We conducted on-deck microcosm experiments using high nutrient, low chlorophyll (HNLC) waters in the western subarctic Pacific and oceanic Bering Sea basin in summer 2008 and 2009, respectively, to examine the impacts of elevated CO2 on particulate and dissolved organic matter (i.e., POM and DOM, respectively) production. Iron deficient natural plankton communities were incubated for 7–14 days under multiple CO2 levels with and without iron enrichments (hereafter +Fe and −Fe treatments, respectively). By combining with our previous experiments at two sites, we created a comprehensive dataset on responses of organic matter production to CO2 increase during macronutrient replete conditions in HNLC waters. Significant differences in net particulate organic carbon production among CO2 treatments were observed only in the −Fe treatments, whereas that in net dissolved organic carbon production were mainly observed in the +Fe treatments, suggesting that CO2 may affect different processes depending on the Fe nutritional status. However, impacts of CO2 were not consistent among experiments and were much smaller than the consistent positive effects of Fe enrichment. In contrast, no significant differences among the CO2 treatments were observed for organic carbon partitioning into POM and DOM, and carbon to nitrogen ratio of net produced POM. We conclude that CO2 does not play a primary role, but could have secondary effects on controlling the organic matter production under macronutrient replete conditions in HNLC waters. On the other hand, in a nutrient-depleted, declining phase of the phytoplankton bloom induced by Fe enrichment, carbon overconsumption was found in an experiment with elevated CO2 conditions suggesting that CO2 impacts might become more significant in such environments.

Continue reading ‘Organic matter production response to CO2 increase in open subarctic plankton communities: Comparison of six microcosm experiments under iron-limited and -enriched bloom conditions’

Ocean acidification threatens economies and cultures around the world (text & video)

Ocean Conservancy intern Alexis Valauri-Orton spent the last three months on a journey around the world learning about ocean acidification.

She visited marine communities most at risk from ocean acidification and saw firsthand how dire the need is for more research, guidance and infrastructure to prepare for the challenges ahead. She produced a video, shown below, to help make the stories from her blog posts come alive.

Valauri-Orton encourages you to watch her video and “Listen to Waiaria talk about the value of shellfish to the identity of people in New Zealand … Watch fishermen in Peru celebrate El Dia de Pescadores … Tag along as a shellfish farmer in Thailand hand dredges the bay in the middle of the night … See the faces and the places that continue to drive my conviction that we have more work to do … And share them with your friends, so we can do good on what Peter, a cod-fisherman in Norway who can trace fishing back 1,000 years in his family, said to me: ‘The whole world has to know. Not only in this small place, but the whole world has to know what is happening.’”
Continue reading ‘Ocean acidification threatens economies and cultures around the world (text & video)’

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Ocean acidification in the IPCC AR5 WG II

OUP book