Archive for the 'Science' Category

Nitrogen availability modulates the effects of ocean acidification on biomass yield and food quality of a marine crop Pyropia yezoensis

Highlights

• Higher pCO2 reduces growth of Pyropia yezoensis.
• Higher pCO2 induces synthesis of phycobiliprotein and flavor amino acids.
• Higher nitrate alleviates the negative effect of ocean acidification on growth.
• Higher nitrate and pCO2 synergistically stimulate phycobiliprotein synthesis.
• Higher nitrate and higher pCO2 synergistically stimulate amino acid synthesis.

Abstract

Pyropia yezoensis is an important marine crop in the world. We cultured it under two levels of partial pressure of carbon dioxide (pCO2) (408 (LC), 998 (HC) μatm) and nitrate (30 (LN) and 500 (HN) μmol L-1) to investigate the effect of ocean acidification on its growth and food quality under changing nitrogen supply. HC decreased growth rate of P. yezoensis under LN but did not affect it under HN. Phycoerythrin and phycocyanin were enhanced by HC, particularly at HN, which contributed to the darker color. HC stimulated the synthesis of sweat amino acids regardless of nitrate condition and umami amino acid only under LN. HN increased the content of umami amino acids regardless of pCO2 condition and sweet amino acids only under LC. Our findings indicate that future ocean acidification may reduce biomass yield of P. yezoensis but increase its color and flavor, which was regulated by nitrate availability.

Continue reading ‘Nitrogen availability modulates the effects of ocean acidification on biomass yield and food quality of a marine crop Pyropia yezoensis’

Ocean acidification alters morphology of all otolith types in Clark’s anemonefish (Amphiprion clarkii)

Ocean acidification, the ongoing decline of surface ocean pH and [CO32-] due to absorption of surplus atmospheric CO2, has far-reaching consequences for marine biota, especially calcifiers. Among these are teleost fishes, which internally calcify otoliths, critical elements of the inner ear and vestibular system. There is evidence in the literature that ocean acidification increases otolith size and alters shape, perhaps impacting otic mechanics and thus sensory perception. However, existing analyses of otolith morphological responses to ocean acidification are limited to 2-dimensional morphometrics and shape analysis. Here, we reared larval Clark’s anemonefish, Amphiprion clarkii (Bennett, 1830), in various seawater pH treatments analogous to future ocean scenarios in a 3x-replicated experimental design. Upon settlement, we removed all otoliths from each individual fish and analyzed them for treatment effects on morphometrics including area, perimeter, and circularity; further, we used scanning electron microscopy to screen otoliths visually for evidence of treatment effects on lateral development, surface roughness, and vaterite replacement. Our results corroborate those of other experiments with other taxa that observed otolith growth with elevated pCO2, and provide evidence that lateral development and surface roughness increased as well; we observed at least one of these effects in all otolith types. Finally, we review previous work investigating ocean acidification impacts on otolith morphology and hypotheses concerning function, placing our observations in context. These impacts may have consequences teleost fitness in the near-future ocean.

Continue reading ‘Ocean acidification alters morphology of all otolith types in Clark’s anemonefish (Amphiprion clarkii)’

Version 6 of the Surface Ocean CO2 Atlas (SOCAT) now available

More than than 100 contributing scientists worldwide have contributed to Version 6 of the Surface Ocean CO2 Atlas (SOCAT). SOCAT (www.socat.info) is a synthesis activity by international marine carbon scientists with annual public releases. SOCAT version 6 has 23.4 million quality-controlled in situ surface ocean fCO2 (fugacity of carbon dioxide) measurements from 1957 to 2017 for the global oceans and coastal seas, as well as additional calibrated sensor fCO2 measurements.

Continue reading ‘Version 6 of the Surface Ocean CO2 Atlas (SOCAT) now available’

Comparing model parameterizations of the biophysical impacts of ocean acidification to identify limitations and uncertainties

Highlights

• We explored model approaches for ocean acidification effects on marine organisms.
• Modelled effects on aerobic performance were scaled up to population level dynamics.
• Results were sensitive to model structure, then scenario and parameter uncertainty.
• Sensitivity was variable across species and the source of uncertainty.
• Integrated global change models progress development of future scenarios.

Abstract

Ocean acidification (OA) driven by anthropogenic CO2 emissions affects marine ecosystems, fisheries and aquaculture. Assessing the impacts of OA using projection models facilitates the development of future scenarios and potential solutions. Here, we explored various ways to incorporate OA impacts into a multi-stressor dynamic bioclimatic envelope model to project biogeographic changes of ten commercially exploited invertebrate species. We examine three dimensions of uncertainties in modelling biophysical OA effects: model structure, parameterization, and scenario uncertainty. Our results show that projected OA impacts are most sensitive to the choice of structural relationship between OA and biological responses, followed by the choice of climate change emission scenarios and parameterizations of the size of OA effects. Species generally showed negative effects to OA but sensitivity to the various sources of uncertainty were not consistent across or within species. For example, some species showed higher sensitivity to structural uncertainty and very low sensitivity to parameter uncertainty, while others showed greatest sensitivity to parameter uncertainty. This variability is largely due to geographic variability and difference in life history traits used to parameterize model simulations. Our model highlights the variability across the sources of uncertainty and contributes to the development of integrating OA impacts in species distribution models. We further stress the importance of defining the limitations and assumptions, as well as exploring the range of uncertainties associated with modelling OA impacts.

Continue reading ‘Comparing model parameterizations of the biophysical impacts of ocean acidification to identify limitations and uncertainties’

Seasonal variability of carbonate chemistry and decadal changes in waters of a marine sanctuary in the Northwestern Gulf of Mexico

Highlights

• Temperature dominated seawater carbonate system variations in FGBNMS.
• Subsurface acidification is caused by anthropogenic CO2 uptake and higher respiration.
• The FGBNMS is currently a negligible atmospheric CO2 sink.

Abstract

We report seasonal water column carbonate chemistry data collected over a three-year period (late 2013 to 2016) at Flower Garden Banks National Marine Sanctuary (FGBNMS) located on the subtropical shelf edge of the northwestern Gulf of Mexico. The FGBNMS hosts the northernmost tropical coral species in the contiguous United States, with over 50% living coral cover. Presented here are results from samples of the upper 25 m of the water column collected from September 2013 to November 2016. Additionally, following a localized mortality event likely associated with major continental flooding in summer 2016, water samples from up to ~250 m depth were collected in the broader FGBNMS area on a rapid response cruise to examine the seawater carbonate system. Both surface (<5 m) total alkalinity (TA) and total dissolved inorganic carbon (DIC) vary over small ranges (2391 ± 19 μmol kg−1 and 2060 ± 19 μmol kg−1, respectively) for all times-series samples. Temperature and salinity both played an important role in controlling the surface water carbonate system dynamics, although temperature was the sole significant factor when there was no flooding. The FGBNMS area acted as a sink for atmospheric CO2 in winter and a CO2 source in summer, while the time-integrated CO2 flux is close to zero (−0.14 ± 1.96 mmol-C m−2 yr−1). Results from three cruises, i.e., the Gulf of Mexico and East Coast Carbon Project (GOMECC-1) in 2007, the rapid response study, and the Gulf of Mexico Ecosystems and Carbon Cruise (GOMECC-3), revealed decreases in both pH and saturation state with respect to aragonitearag) in subsurface waters (~100–250 m) over time. These decreases are larger than those observed in other tropical and subtropical waters. Based on reaction stoichiometry, calculated anthropogenic CO2 contributed 30–41% of the overall DIC increase, while elevated respiration accounted for the rest.

Continue reading ‘Seasonal variability of carbonate chemistry and decadal changes in waters of a marine sanctuary in the Northwestern Gulf of Mexico’

Ocean acidification and molluscan shell taphonomy: can elevated seawater pCO2 influence taphonomy in a naticid predator–prey system?

Highlights

• Tested for taphonomic effects of elevated pCO2 in a naticid predator-prey system
• High pCO2 induced greater shell dissolution rates, which differed across species
• Breakage force differed across species and drill hole category
• No pCO2 effect on shell breakage force
• Limited species-specific drill hole diameter increase under high pCO2

Abstract

The size and frequency of gastropod drill holes in shells of their prey are common indicators of predator-prey ecology in the fossil record. Taphonomic processes occurring after predation, however, can influence the preservation of shells in a given fossil assemblage and can thus influence ecological inferences based on preserved shells. To determine if ocean acidification (OA) has the capacity to influence prey shell taphonomy in a gastropod drilling predation system, we tested for effects of elevated pCO2 on dissolution rates, breakage force, and drill hole diameters in non-fragmented shells of two prey species of the cannibalistic naticid gastropod, Euspira heros. Drilled and non-drilled shells of Littorina littorea and E. heros were exposed to control (~300 μatm) and elevated (~800 and 4000 μatm) pCO2 treatments for five weeks. Dry shell weight and drill hole diameter (outer and inner) were recorded for individual shells before and after exposure; the force required for shell breakage was recorded at the end of the exposure period. Shell mass loss in 800 and 4000 μatm, respectively, were ~1 and 7% for E. heros, and ~0 and 4% for L. littorea, compared to ~0% in the control for both species. Shell breakage force was unaffected by elevated pCO2, but was affected by species and drill hole presence, with E. heros shells requiring a force of ~220 and 269 Newtons in drilled and non-drilled shells, respectively, compared to ~294 and 415 Newtons in L. littorea. At 4000 μatm, outer drill hole diameter significantly increased by ~12% for E. heros, while inner drill hole diameter significantly increased by ~13% in E. heros and ~10% in L. littorea. Ultimately, this study provides the first documentation of molluscan shell taphonomy in the context of OA for a gastropod drilling predation system and sets the stage for future research.

 

Continue reading ‘Ocean acidification and molluscan shell taphonomy: can elevated seawater pCO2 influence taphonomy in a naticid predator–prey system?’

Impacts of shifts in phytoplankton community on clouds and climate via the sulfur cycle

Dimethyl sulfide (DMS), primarily produced by marine organisms, contributes significantly to sulfate aerosol loading over the ocean after being oxidized in the atmosphere. In addition to exerting a direct radiative effect, the resulting aerosol particles act as cloud condensation nuclei, modulating cloud properties and extent, with impacts on atmospheric radiative transfer and climate. Thus, changes in pelagic ecosystems, such as phytoplankton physiology and community structure, may influence organosulfur production, and subsequently affect climate via the sulfur cycle. A fully coupled Earth system model, including explicit marine ecosystems and the sulfur cycle, is used here to investigate the impacts of changes associated with individual phytoplankton groups on DMS emissions and climate. Simulations show that changes in phytoplankton community structure, DMS production efficiency, and interactions of multielement biogeochemical cycles can all lead to significant differences in DMS transfer to the atmosphere. Subsequent changes in sulfate aerosol burden, cloud condensation nuclei number, and radiative effect are examined. We find the global annual mean cloud radiative effect shifts up to 0.21 W/m2, and the mean surface temperature increases up to 0.1 °C due to DMS production changes associated with individual phytoplankton group in simulations with radiative effects at the 2,100 levels under an 8.5 scenario. However, changes in DMS emissions, radiative effect, and surface temperature are more intensive on regional scales. Hence, we speculate that major uncertainties associated with future marine sulfur cycling will involve strong region‐to‐region climate shifts. Further understanding of marine ecosystems and the relevant phytoplankton‐aerosol‐climate linkage are needed for improving climate projections.

Continue reading ‘Impacts of shifts in phytoplankton community on clouds and climate via the sulfur cycle’


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Ocean acidification in the IPCC AR5 WG II

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