Archive for October, 2019

OA-ICC bibliographic database updated

An updated version of the OA-ICC bibliographic database is available online.

The database currently contains over 5,800 references and includes citations, abstracts and assigned keywords. Updates are made every month.

The database is available as groups on Mendeley and Zotero. Subscribe online or, for a better user experience, download the Mendeley or Zotero desktop applications and sync with the group Ocean Acidification (OA-ICC) in Mendeley, or OA-ICC in Zotero. Please see the “User instructions” for further details.

Continue reading ‘OA-ICC bibliographic database updated’

Perspectives on in situ sensors for ocean acidification research

As ocean acidification (OA) sensor technology develops and improves, in situ deployment of such sensors is becoming more widespread. However, the scientific value of these data depends on the development and application of best practices for calibration, validation, and quality assurance as well as on further development and optimization of the measurement technologies themselves. Here, we summarize the results of a 2-day workshop on OA sensor best practices held in February 2018, in Victoria, British Columbia, Canada, drawing on the collective experience and perspectives of the participants. The workshop on in situ Sensors for OA Research was organized around three basic questions: 1) What are the factors limiting the precision, accuracy and reliability of sensor data? 2) What can we do to facilitate the quality assurance/quality control (QA/QC) process and optimize the utility of these data? and 3) What sort of data or metadata are needed for these data to be most useful to future users? A synthesis of the discussion of these questions among workshop participants and conclusions drawn is presented in this paper.

Continue reading ‘Perspectives on in situ sensors for ocean acidification research’

Climate change puts oyster industry on edge (video)

Climate change is putting shellfish at risk as increases in carbon emissions and agricultural runoff are altering ocean ecosystems.

Now oyster farmers are adapting before going extinct.

“It’s not that they grow more slowly, it’s that they’re less likely to grow at all,” said Todd Van Herpe of Humboldt County Oyster Co.

Van Herpe has been farming northern California’s Humboldt Bay for years.

Now his livelihood is at risk after scientists say a change in ocean acidification is making it more difficult for oysters to form their shells and ultimately survive.

Continue reading ‘Climate change puts oyster industry on edge (video)’

Lipid biochemistry and physiology of Antarctic krill (Euphausia superba) in the present day and under future ocean acidification scenarios

Antarctic krill (Euphausia superba, hereafter ‘krill’) are lipid-rich euphausiids with an important role in the Southern Ocean, including as the primary prey of Antarctic megafauna (whales, seals, penguins), fish, squid and seabirds. They contain high levels of nutritious long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA), specifically eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). The sheer abundance of krill in the Southern Ocean means that the ecosystem is largely driven by energy derived from krill lipids. In addition to their ecological importance, a Scotia Sea krill fishery harvests krill, including for commercial use of their LC-PUFA. The existence of this year-round krill fishery provides a unique opportunity to collect krill samples for research over large spatial and temporal scales, which is unfeasible using scientific research vessels.

In this thesis, fishery caught krill samples were used to investigate the fatty acid content and composition of krill, during all seasons and over consecutive years (2013 – 2016). This research (presented in Chapter 2) aimed to fill knowledge gaps on the seasonal diet of krill (particularly in winter) in the Scotia Sea region, using fatty acids as dietary biomarkers. Krill were primarily herbivorous in summer (higher levels of 20:5n-3 and 22:6n-3, and low 18:1n-9c/18:1n-7c ratios) and became more omnivorous from autumn to spring (increasing ratios of 18:1n-9c/18:1n-7c and percentages of Σ 20:1 + 22:1 isomers). Seasonal proportions of herbivory and omnivory differed between years, and fatty acid composition differed between fishing locations. Selected samples were also used to investigate the composition of fatty acids in the structural (phospholipids) and storage lipids (triacylglycerols) of krill (Chapter 3). Triacylglycerol fatty acids (thought to better represent recent diet), reflected omnivorous feeding with highest percentages of flagellate biomarkers (18:4n-3) occurring in summer, diatom biomarkers (16:1n-7c) from autumn-spring, and greater carnivory (higher Σ 20:1 + 22:1 and 18:1n-9c/18:1n-7c ratios) in autumn. Phospholipid fatty acids were less variable and were higher in the essential membrane fatty acids 20:5n-3 and 22:6n-3. Percentages of the major krill sterol, cholesterol, were significantly higher in winter and spring compared with summer and autumn. Results presented in Chapters 2 and 3 highlighted the dynamic nature of krill lipids, and the flexible diet of krill, which likely contributes to their huge biomass and success as one of the most abundant organisms on Earth.

Because krill are so important in the Southern Ocean food web, any decreases in krill biomass could result in a major ecological regime shift. Very little is known about how climate change will affect krill. Increasing anthropogenic carbon dioxide (CO2) emissions are causing ocean acidification, as absorption of atmospheric CO2 in seawater alters ocean chemistry. Ocean acidification increases mortality and negatively affects physiological functioning in some marine invertebrates, and is predicted to occur most rapidly at high latitudes. Long-term laboratory studies are needed to understand how keystone species such as krill may respond to predicted future pCO2 levels. A long term experiment was conducted to test whether rising ocean pCO2 is likely to impact krill physiology and biochemistry (Chapters 4 and 5). Adult krill were exposed to near-future ocean acidification (1000 – 2000 μatm pCO2) for one year in the laboratory. Krill reared in near-future pCO2 conditions were able to survive, grow, store fat, mature, and maintain normal respiration rates. Haemolymph pH, lipid and fatty acid composition were also maintained at the same levels as krill in ambient pCO2 (400 μatm). Negative effects on physiology and lipid biochemistry were only observed in extreme pCO2 conditions (4000 μatm), which krill will not experience in the wild. These results place adult krill among the most resilient species in ocean acidification studies to date.

In summary, results in this thesis highlight the remarkable adaptability of krill in a changing environment, from short-term seasonal or annual scales, to longer-term decadal scales. Their flexible phenotype may aid their survival in an ocean that is rapidly changing with increasing anthropogenic CO2 emissions. The data obtained in this thesis can be used for fisheries management to guide fishing activities, and in fisheries models to predict how krill biomass may be affected by climate change. Krill lipid energy fuels the Southern Ocean ecosystem and to date, lipid data has not been included in Antarctic ecosystem models. The large scale of lipid data in this study makes it ideal for inclusion in such models, and it has important implications for the health of the wider Southern Ocean ecosystem.

Continue reading ‘Lipid biochemistry and physiology of Antarctic krill (Euphausia superba) in the present day and under future ocean acidification scenarios’

Explore ocean and coastal acidification with NOAA Data in the Classroom

A screenshot of a map for the new Data in the Classroom ocean and coastal acidification module. NOAA’s Data in the Classroom uses story maps to help students explore today’s most pressing environmental issues through interactive narratives. Now, teachers and students can learn about ocean and coastal acidification through a new module.

Can ocean conditions support the growth and survival of marine life, both now and into the future?

With this new NOAA Data in the Classroom module, students can dig into this question and the relationships between carbon dioxide, ocean pH and aragonite saturation state. This educational resource introduces students to ocean and coastal acidification through a series of interactive web maps, apps, and videos, allowing students to explore authentic research questions and scaled data interactions that use near real‐time data from NOAA.

Continue reading ‘Explore ocean and coastal acidification with NOAA Data in the Classroom’

Impact of ocean acidification and warming on the feeding behaviour of two gastropod species

Increased atmospheric CO2 produced by anthropogenic activities will be absorbed by the oceans over the next century causing ocean acidification and changes in the seawater carbonate chemistry. Elevated CO2 causes sublethal physiological and behavioural responses on the locomotion and foraging behaviour of marine organisms. This study aims to investigate the independent and synergistic effects of long term exposure to low pH and increased temperature on the feeding behaviour of two gastropod species, Hexaplex trunculus and Nassarius nitidus, both in adults and juveniles. Gastropods were maintained under controlled conditions of temperature (ambient = 20°C, increased = 23°C) and pH (ambient = 8, low = 7.6) for 2.5 years. The percentage of animals which successfully reached their food, the response time until gastropods began moving, the total duration until they reached food and the total distance covered, were measured. Speed and path index (i.e how straightforward the movement is) were estimated as means of foraging efficiency. Increased temperature (under ambient pH) resulted in faster responses, a shorter duration until food was reached and a higher speed in H. trunculus adults. H. trunculus (both adults and juveniles) were less successful in reaching their food source under low pH and ambient temperature in comparison to all other treatments. The response time, duration, speed and path index were not affected by low pH (at ambient or increased temperature) for H. trunculus adults and juveniles, as well as for N. nitidus. The foraging performance of juveniles hatched and developed under low pH (either at ambient or increased temperature) was more effective than adults of the same species, thus indicating a degree of acclimation. Also, the scavenger N. nitidus was more successful and responded faster in reaching carrion than the predator H. trunculus, whereas no significant effects were observed for N. nitidus under low pH.

Continue reading ‘Impact of ocean acidification and warming on the feeding behaviour of two gastropod species’

The development and validation of a profiling glider deep ISFET-based pH sensor for high resolution observations of coastal and ocean acidification

Coastal and ocean acidification can alter ocean biogeochemistry, with ecological consequences that may result in economic and cultural losses. Yet few time series and high resolution spatial and temporal measurements exist to track the existence and movement of water low in pH and/or carbonate saturation. Past acidification monitoring efforts have either low spatial resolution (mooring) or high cost and low temporal and spatial resolution (research cruises). We developed the first integrated glider platform and sensor system for sampling pH throughout the water column of the coastal ocean. A deep ISFET (Ion Sensitive Field Effect Transistor)-based pH sensor system was modified and integrated into a Slocum glider, tank tested in natural seawater to determine sensor conditioning time under different scenarios, and validated in situ during deployments in the U.S. Northeast Shelf (NES). Comparative results between glider pH and pH measured spectrophotometrically from discrete seawater samples indicate that the glider pH sensor is capable of accuracy of 0.011 pH units or better for several weeks throughout the water column in the coastal ocean, with a precision of 0.005 pH units or better. Furthermore, simultaneous measurements from multiple sensors on the same glider enabled salinity-based estimates of total alkalinity (AT) and aragonite saturation state (ΩArag). During the Spring 2018 Mid-Atlantic deployment, glider pH and derived AT/ΩArag data along the cross-shelf transect revealed higher pH and ΩArag associated with the depth of chlorophyll and oxygen maxima and a warmer, saltier water mass. Lowest pH and ΩArag occurred in bottom waters of the middle shelf and slope, and nearshore following a period of heavy precipitation. Biofouling was revealed to be the primary limitation of this sensor during a summer deployment, whereby offsets in pH and AT increased dramatically. Advances in anti-fouling coatings and the ability to routinely clean and swap out sensors can address this challenge. The data presented here demonstrate the ability for gliders to routinely provide high resolution water column data on regional scales that can be applied to acidification monitoring efforts in other coastal regions.

Continue reading ‘The development and validation of a profiling glider deep ISFET-based pH sensor for high resolution observations of coastal and ocean acidification’

Photosynthesis and light-dependent proton pumps increase boundary layer pH in tropical macroalgae: a proposed mechanism to sustain calcification under ocean acidification

Highlights

• Tropical calcifying macroalgae raise boundary layer pH due to photosynthesis

• Different mechanisms of inorganic carbon uptake control pH increase

• Proton pumps in light without photosynthesis appear important calcification

• Photosynthesis-driven pH increase allows calcification with ocean acidification

Abstract

Ocean acidification (OA) projections predict ocean pH to decline between 0.2 and 0.4 by 2100 with potential negative consequences for marine calcifiers without acclimation or adaption strategies to accomodate greater [H+] in seawater. Biotic control of calcified reef macroalgae thalli surface diffusive boundary layer (DBL) chemistry may overcome low pH in seawater as one strategy to accommodate OA conditions. To investigate this strategy, we examined surface DBL O2 and pH dynamics in five calcifying macroalgae (Halimeda, Udotea, Jania, Neogoniolithon, crustose coralline algae [CCA]) from the Florida Reef Tract under ambient (8.1) and low (7.65) pH using microsensors (100 μm) at the thalli surface in a flow-through flume. The role of photosynthesis and photosystem II (PSII)-independent proton pumps in controlling DBL pH were examined. Four of the five macroalgae exhibited a strong positive linear relationship between O2 production and increasing pH in the first 15–30 s of irradiance. Once a quasi-steady-state O2 concentration was reached (300 s), all species had DBL pH that were higher (0.02–0.32) than bulk seawater. The DBL pH increase was greatest at low pH and dependent on PSII. Some evidence was found for a light-dependent, but PSII-independent, proton pump. High DBL Δ pH upon illumination was likely in response to carbon concentrating mechanisms (CCMs) for photosynthesis. CCMs may be a HCO3−–H+ symport, OH– antiport or other DIC transport system, accompanied by proton efflux. HCO3– dehydration by external carbonic anhydrase (CAext) also produces OH– that can neutralize H+ in the DBL. CO2 or HCO3– uptake for photosynthesis may also engage H+/OH– fluxes as part of intracellular acid-base regulation changing DBL pH. A higher Δ pH within the DBL at low pH could be accounted for by greater CO2 diffusion and/or lower efficiencies in exporting cellular H+ across a lower concentration gradient, and/or a more efficient removal of H+ by CAext-driven dehydration of HCO3−. In the dark, Δ pH was less than in the light as these dynamics were primarily due to photosynthesis. We present a conceptual model of inorganic carbon uptake and ion transport pathways, as well as other processes associated with photosynthesis that drive DBL Δ pH and sustain tropical macroalgal calcification in the light under OA. In the dark, unless PSII-independent proton pumps are present, which do not appear to be ubiquitous amongst species, acidification processes likely dominate, resulting in CaCO3 net dissolution, particularly under OA conditions.

Continue reading ‘Photosynthesis and light-dependent proton pumps increase boundary layer pH in tropical macroalgae: a proposed mechanism to sustain calcification under ocean acidification’

Ocean acidification and hypoxia can have opposite effects on rockfish otolith growth

Highlights

• Elevated CO2 and reduced dissolved oxygen have opposite effects on otolith (earstone) development in juvenile copper and blue rockfish.

• Increased CO2 levels resulted in otoliths being larger in area for a relative fish body size in blue rockfish.

• Reduced dissolved oxygen levels results in otoliths being smaller in area for a relative fish body size in both species.

Abstract

Climate change is predicted to alter ocean chemistry through warming temperatures, increases in CO2 (i.e., ocean acidification), and reductions in dissolved oxygen (DO) (i.e., hypoxia). Past research has shown that early life stages of marine fishes are sensitive to all three stressors, but with sometimes different directions of response. In this study, we examined the separate effects of ocean acidification and hypoxia on otolith growth in two species of juvenile rockfish (copper rockfish, Sebastes caurinus, and blue rockfish, Sebastes mystinus). Fishes were collected at settlement stage from kelp forests on the central California coast and reared in the laboratory for up to 6 months in 4 separate pH treatments (pH = 7.3, 7.6, 7.8, and a control of 8.0), simulating the effects of ocean acidification through the addition of CO2, and 4 separate dissolved oxygen treatments (DO = 2.2, 4.1, 6.0, and a control of 8.7 mg/L), simulating the effects of hypoxia. For both species, otoliths were smaller for a given fish length in response to hypoxia but were larger (trend was non-significant for copper rockfish) in response to elevated CO2. The results suggest that otolith growth may respond differently to ocean acidification and hypoxia for some species, which has implications for sensory development, ecological performance, and interpretations of the permanent record of fish growth in hard parts such as otoliths.

Continue reading ‘Ocean acidification and hypoxia can have opposite effects on rockfish otolith growth’

Antioxidant responses to seawater acidification in an invasive fouling mussel are alleviated by transgenerational acclimation

Highlights

• Neither pH nor transgeneration elicited lipid peroxidation.

• Antioxidant responses occurred in CO2-exposed mussels.

• Transgenerational effects alleviated oxidative stress responses.

• Transgenerational immunity may occur rapidly in an acidifying ocean.

Abstract

Ocean acidification and marine biofouling, which may interact in the future, pose two major threats to global coastal ecosystems. Yet, the fate of highly invasive fouling species in a rapidly acidifying ocean remains poorly understood, due to lack of information on multigenerational consequences at different levels of biological organization. Here, we investigated antioxidant responses of the mussel, Musculista senhousia, a swiftly spreading invasive fouling species in global coastal waters, following transgenerational exposure to elevated pCO2. In the face of seawater acidification, M. senhousia without a prior history of transgenerational exposure to elevated pCO2 showed resistance to lipid peroxidation, but significantly increased activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), indicated oxidative stress responses. However, enhanced transgenerational immunity occurred, as exemplified by observations that mussels originating from parents exposed to elevated pCO2 exhibited significantly lower activities of SOD, CAT and GPx in comparison to those spawn from parents exposed to ambient pCO2. Rapid transgenerational acclimation of M. senhousia in terms of reduced oxidative stress responses can likely be linked to the enhanced capacity of maintaining acid-base homeostasis previously demonstrated. These findings provide the first evidence of transgenerational plasticity at the biochemical level in highly invasive fouling bivalve species, and represent a step forward in understanding how they respond and acclimate in an acidifying ocean.

Continue reading ‘Antioxidant responses to seawater acidification in an invasive fouling mussel are alleviated by transgenerational acclimation’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

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