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- OPEN ACCESSMercury (Hg) is a global pollutant emitted primarily as gaseous Hg0 that is deposited in aquatic and terrestrial ecosystems following its oxidation to HgII. From that point, microbes play a key role in determining Hg’s fate in the environment by participating in sequestration, oxidation, reduction, and methylation reactions. A wide diversity of chemotrophic and phototrophic microbes occupying oxic and anoxic habitats are known to participate directly in Hg cycling. Over the last few years, new findings have come to light that have greatly improved our mechanistic understanding of microbe-mediated Hg cycling pathways in the environment. In this review, we summarize recent advances in microbially mediated Hg cycling and take the opportunity to compare the relatively well-studied chemotrophic pathways to poorly understood phototrophic pathways. We present how the use of genomic and analytical tools can be used to understand Hg transformations and the physiological context of recently discovered cometabolic Hg transformations supported in anaerobes and phototrophs. Finally, we propose a conceptual framework that emphasizes the role that phototrophs play in environmental Hg redox cycling and the importance of better characterizing such pathways in the face of the environmental changes currently underway.
- OPEN ACCESS
- Julio Mercader,
- Tolutope Akeju,
- Melisa Brown,
- Mariam Bundala,
- Matthew J. Collins,
- Les Copeland,
- Alison Crowther,
- Peter Dunfield,
- Amanda Henry,
- Jamie Inwood,
- Makarius Itambu,
- Joong-Jae Kim,
- Steve Larter,
- Laura Longo,
- Thomas Oldenburg,
- Robert Patalano,
- Ramaswami Sammynaiken,
- María Soto,
- Robert Tyler, and
- Hermine Xhauflair
Ancient starch research illuminates aspects of human ecology and economic botany that drove human evolution and cultural complexity over time, with a special emphasis on past technology, diet, health, and adaptation to changing environments and socio-economic systems. However, lapses in prevailing starch research demonstrate the exaggerated expectations for the field that have been generated over the last few decades. This includes an absence of explanation for the millennial-scale survivability of a biochemically degradable polymer, and difficulties in establishing authenticity and taxonomic identification. This paper outlines new taphonomic and authenticity criteria to guide future work toward designing research programs that fully exploit the potential of ancient starch while considering growing demands from readers, editors, and reviewers that look for objective compositional identification of putatively ancient starch granules. - OPEN ACCESS
- Krishna K. Thakur,
- Raphaël Vanderstichel,
- Shaorong Li,
- Emilie Laurin,
- Strahan Tucker,
- Chrys Neville,
- Amy Tabata, and
- Kristina M. Miller
Infectious diseases are likely contributing to large-scale declines in chinook salmon stocks in the Pacific Northwest, but the specific agents and diseases involved, and the prevalences in migratory salmon, are mostly unknown. We applied a high-throughput microfluidics platform to screen for 45 infectious agents in 556 out-migrating juvenile chinook salmon, collected from freshwater (FW) and saltwater (SW) locations in the Cowichan River system on Vancouver Island, Canada, during 2014. Nineteen agents (5 bacterial, 2 viral, and 12 parasitic) were detected, with prevalences ranging from 0.2% to 57.6%. Co-infections between Candidatus Branchiomonas cysticola Toenshoff, Kvellestad, Mitchell, Steinum, Falk, Colquhoun & Horn, 2012, Paranucleospora theridion Nylund, Nylund, Watanabe, Arnesen & Kalrsbakk, 2010, and gill chlamydia, all associated with gill disease, were observed in SW samples. We detected agents known to cause large-scale mortalities in Pacific salmon (Ceratonova shasta (Noble, 1950), Parvicapsula minibicornis Kent, Whitaker & Dawe, 1977), and agents only recently reported in Pacific salmon in BC (Ca. B. cysticola, P. theridion, Facilispora margolisi Jones, Prosperi-Porta & Kim, 2012 and Parvicapsula pseudobranchicola Karlsbakk, Saether, Hostlund, Fjellsoy & Nylund, 2002). Wild and hatchery fish were most divergent in agent profiles in FW, with higher agent diversity in wild fish. Differences in prevalence largely dissipated once they converged in the marine environment, although hatchery fish may be infected by a greater diversity of agents sooner after ocean entry by virtue of their more rapid migration from nearshore to offshore environments. - OPEN ACCESS
- Emiliano Di Cicco,
- Hugh W. Ferguson,
- Karia H. Kaukinen,
- Angela D. Schulze,
- Shaorong Li,
- Amy Tabata,
- Oliver P. Günther,
- Gideon Mordecai,
- Curtis A. Suttle, and
- Kristina M. Miller
Piscine orthoreovirus Strain PRV-1 is the causative agent of heart and skeletal muscle inflammation (HSMI) in Atlantic salmon (Salmo salar Linnaeus, 1758). Given its high prevalence in net pen salmon, debate has arisen on whether PRV poses a risk to migratory salmon, especially in British Columbia (BC) where commercially important wild Pacific salmon are in decline. Various strains of PRV have been associated with diseases in Pacific salmon, including erythrocytic inclusion body syndrome (EIBS), HSMI-like disease, and jaundice/anemia in Japan, Norway, Chile and Canada. We examined the developmental pathway of HSMI and jaundice/anemia associated with PRV-1 in farmed Atlantic and chinook (Oncorhynchus tshawytscha (Walbaum, 1792)) salmon in BC, respectively. In situ hybridization localized PRV-1 within developing lesions in both diseases. The two diseases showed dissimilar pathological pathways, with inflammatory lesions in heart and skeletal muscle in Atlantic salmon and degenerative-necrotic lesions in kidney and liver in chinook salmon, plausibly explained by differences in PRV load tolerance in red blood cells. Viral genome sequencing revealed no consistent differences in PRV-1 variants intimately involved in the development of both diseases suggesting that migratory chinook salmon may be at more than a minimal risk of disease from exposure to the high levels of PRV occurring in salmon farms. - OPEN ACCESSNickel (Ni) leaching from oil sands petroleum coke can have toxicological effects on aquatic organisms. However, geochemical controls on Ni release, transport, and attenuation within coke deposits remains limited. We examined the geochemistry of fluid coke and associated pore waters from two deposits at an oil sands mine near Fort McMurray, Alberta, Canada. Synchrotron-based micro-X-ray fluorescence (μXRF) and micro-X-ray absorption near edge structure (μXANES) spectroscopy show that Ni(II)-porphyrin complexes dominate, but inorganic phases including Ni(II)-sulfide and Ni(II)-oxide comprise a minor component of fluid coke. Sequential chemical extractions suggested that sorption–desorption reactions may influence Ni mobility within fluid coke deposits. Although only a small proportion of total Ni (<4%) is susceptible to leaching under environmentally relevant concentrations, dissolved Ni concentrations (n = 65) range from 2 to 120 μg·L−1 (median 7.8 μg·L−1) within the two deposits and generally decrease with depth below the water table. Pore water Ni concentrations are negatively correlated with pH, but not with dissolved sulfate, bicarbonate, or chloride. Overall, our findings suggest that pore water pH and sorption–desorption reactions are principal controls on dissolved Ni concentrations within oil sands fluid petroleum coke deposits.
- OPEN ACCESS
- Leonora King,
- Lucy MacKenzie,
- Marc Tadaki,
- Sara Cannon,
- Kiely McFarlane,
- David Reid, and
- Michele Koppes
Effective policies promoting diversity in geoscience require understanding of how the values and practices of the community support the inclusion of different social groups. As sites of knowledge exchange and professional development, academic conferences are important culturing institutions that can alleviate or reproduce barriers to diversity in geoscience. This study examines diversity at a 2017 geoscience conference, the joint Canadian Geophysical Union and Canadian Society of Agricultural and Forest Meteorology annual meeting, through observation of participation, presentation content, and behaviour in conference sessions. Across 256 observed presentations, women constituted 28% of speakers, whereas women of colour made up only 5%. Participation rates differed between disciplinary sections, with the most populous sessions (Hydrology and Earth Surface) having the lowest percentage of women. Examination of presentation content reveals that the methods and scholarly contributions of both women and people of colour differed from the majority, suggesting an intellectual division of labour in geoscience. Examination of audience behaviours between presenters reveals how a “chilly climate” can be experienced by women and other marginalized demographics in conferences. We argue that there is more to be done than simply increasing numbers of women or other minorities in geoscientific spaces, and we suggest pathways to making geoscience a more inclusive and democratic pursuit. - OPEN ACCESSMultiparameter data with both spatial and temporal components are critical to advancing the state of environmental science. These data and data collected in the future are most useful when compared with each other and analyzed together, which is often inhibited by inconsistent data formats and a lack of structured documentation provided by researchers and (or) data repositories. In this paper we describe a linked table-based structure that encodes multiparameter spatiotemporal data and their documentation that is both flexible (able to store a wide variety of data sets) and usable (can easily be viewed, edited, and converted to plottable formats). The format is a collection of five tables (Data, Locations, Params, Data Sets, and Columns), on which restrictions are placed to ensure data are represented consistently from multiple sources. These tables can be stored in a variety of ways including spreadsheet files, comma-separated value (CSV) files, JavaScript object notation (JSON) files, databases, or objects in a software environment such as R or Python. A toolkit for users of R statistical software was also developed to facilitate converting data to and from the data format. We have used this format to combine data from multiple sources with minimal metadata loss and to effectively archive and communicate the results of spatiotemporal studies. We believe that this format and associated discussion of data and data storage will facilitate increased synergies between past, present, and future data sets in the environmental science community.
- OPEN ACCESSThe identification of sustainably managed fisheries is problematic for marketers and consumers of Pacific salmon food products owing to lack of well-defined and robust criteria that take into account current ecosystem science of salmon. We present the rationale for an alternative conceptual framework for salmon management that supports the development of sustainable sourcing criteria. Our approach contrasts with current large-scale fisheries certification programs such as that of the Marine Stewardship Council (MSC) and general consumer recommendation services such as Monterey Bay Aquarium’s Seafood Watch (SFW) program. Our framework is based on the “place-based” character of salmon populations and recognition of fundamental aspects of salmon ecology, particularly the evolution of population life histories that are locally adapted to freshwater spawning and rearing habitats. We describe how this framework underpins development of science-based sourcing criteria and how it differs in important respects from the industrial approach that historically and currently is the basis for most salmon management. We conclude with a discussion of how the framework and its application may provide a model for redirecting salmon management, in general, towards a more science- and place-based approach and why that is likely to be sustainable in the long term in a way that most contemporary salmon management is not.
- OPEN ACCESSAn increase in greenhouse gas emissions has led to a rise in average global air and ocean temperatures. Increased sea surface temperatures can cause changes in species’ distributions, particularly those species close to their thermal tolerance limits. We use a bioclimate envelope approach to assess potential shifts in the range of marine macroalgae harvested in North American waters: rockweed (Fucus vesiculosus Linnaeus, 1753), serrated wrack (Fucus serratus Linnaeus, 1753), knotted wrack (Ascophyllum nodosum (Linnaeus) Le Jolis, 1863), carrageen moss (Chondrus crispus Stackhouse, 1797), and three kelp species (Laminaria digitata (Hudson) J.V. Lamouroux, 1813; Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl et G.W. Saunders, 2006; and Saccharina longicruris (Bachelot de la Pylaie) Kuntze, 1891). We determined species’ thermal limits from the current sea surface temperatures associated with their geographical distributions. Future distributions were based on sea surface temperatures projected for the year ∼2100 by four atmosphere-ocean general circulation models and earth system models for regional concentration pathways (RCPs) 4.5 and 8.5. Future distributions based on RCP 8.5 indicate that the presence of all but rockweed (F. vesiculosus) is likely to be threatened by warming waters in the Gulf of St. Lawrence and along the Atlantic coast of Nova Scotia. Range retractions of macroalgae will have significant ecological and economic effects including impacts on commercial fisheries and harvest rates and losses of floral and faunal biodiversity and production, and should be considered in the designation of marine protected areas.
- OPEN ACCESSIn 1956, Shell Oil Company geologist M. King Hubbert published a model for the growth and decline over time of the production rates of oil extracted from the land mass of the continental US. Employing an estimate for the amount of ultimately recoverable oil and a logistic curve for the oil production rate, he accurately predicted a peak in US oil production for 1970. His arguments and the success of his prediction have been much celebrated, and the original paper has 1400 publication citations to date. The theory of “peak oil” (and subsequently, of natural resource scarcity in general) has consequently become associated with Hubbert and “Hubbert” curves and models. However, his prediction for the timing of a world peak oil production rate and the subsequent predictions of many others have proven inaccurate. We revisit the Hubbert model for oil extraction and provide an analysis of it and several variants in the language of (time) autonomous differential equations.
- OPEN ACCESS
- Michael R.S. Coffin,
- Simon C. Courtenay,
- Kyle M. Knysh,
- Christina C. Pater, and
- Michael R. van den Heuvel
In this study, we examined the effects of dissolved oxygen, via metrics based on hourly measurements, and other environmental variables on invertebrate assemblages in estuaries spanning a gradient of nutrient loading and geography in the southern Gulf of St. Lawrence, Canada. Upper areas (15–25 practical salinity units (PSU)) of 13 estuaries that were dominated by either seagrass (Zostera marina Linnaeus, 1753) or macroalgae (Ulva spp. Linnaeus, 1753) were sampled from June to September 2013. Macroinvertebrate assemblages from Z. marina were found to be distinct from Ulva assemblages for both epifauna and infauna. Small snails dominated each vegetation type, specifically cerithids in Z. marina and hydrobids in Ulva. Although Z. marina had higher species richness, approximately 70% of species were common to both habitats. Faunal communities differed among estuaries with large, within-estuary, temporal variance only observed at Ulva sites impacted by hypoxia and particularly at sites with long water residence time. Indeed, abundances varied by several orders of magnitude in Ulva ranging from zero to thousands of macroinvertebrates. There was a strong negative correlation between hypoxic or anoxic water, 48 h prior to sampling, with relative abundances of amphipods, and a positive correlation with the relative abundances of snails. As one of the first studies to use high-frequency oxygen monitoring, this study revealed probable impacts and the transient nature of hypoxia in eutrophication. - OPEN ACCESS
- Mathieu Guillemette,
- Catherine Potvin,
- Lauliano Martinez,
- Bonarge Pacheco,
- Dioniz Caño, and
- Ignacio Pérez
Natural forest management and conservation projects such as reducing emissions from deforestation and forest degradation, and enhancing forest carbon stocks (REDD+) face many challenges in the field. Implementation of these projects depends on such factors as clarity of information among stakeholders, legal security of territories, and local decision-making power. These challenges have been previously identified in the Upper Bayano watershed of eastern Panama, where a long history of land cover and land-use conflicts is present between three different human groups. With a long-term objective of natural forest conservation, this study aims to develop and test participatory approaches (participatory mapping and participatory 3D modelling) for the Upper Bayano watershed in an attempt to create a consensus among all stakeholders on current land cover and land-use conflicts to overcome challenges faced by projects as REDD+. We found that the third dimension allows a common understanding over the landscape, creates a common ground discussion, and leads towards a consensus, while the participatory approach brings discussion and positive effects among the stakeholders and the bridging institutions bring equity and transparency. Finally, we discuss implications of this knowledge generation and common agreement over the landscape for future forest management projects such as REDD+’s implementation. - OPEN ACCESSWith increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.
- OPEN ACCESSWe examine the importance of the rock weathering feedback mechanism during the last deglacial period (∼16 000–4000 BCE) using an Earth system model of intermediate complexity (the University of Victoria Earth System Climate Model (UVic ESCM)) with four box-model parameterizations of terrestrial weathering. The deglacial climate change is driven by changes in orbital parameters, ice core reconstructions of atmospheric CO2 variability, and prescribed removal of continental ice sheets. Over the course of the 12 000 year simulation period, increases in weathering provide a mechanism that slowly removes CO2 from the atmosphere, in opposition to the observed atmospheric CO2 increase during this period. These processes transfer both carbon and alkalinity to the ocean, the combination of which results in as much as a 1000 Pg C increase in total ocean carbon, relative to a control simulation with constant weathering. However, the rapid expansion of northern hemisphere vegetation introduces a significant uncertainty among the weathering parameterizations. Further experiments to test the individual impacts of weathering dissolved inorganic carbon and alkalinity fluxes on ocean biogeochemistry suggest that the worldwide distribution of rock types and the ratio of carbonate to silicate weathering may be crucially important in obtaining an accurate estimate of changes in global weathering rates.
- OPEN ACCESSTadpoles are important prey items for many aquatic organisms and often represent the largest vertebrate biomass in many fishless wetland ecosystems. Neurotoxic mercury (Hg) can, at elevated levels, decrease growth, lower survival, and cause developmental instability in amphibians. We compared total Hg (THg) body burden and concentration in boreal chorus frog (Pseudacris maculata) and wood frog (Rana sylvatica) tadpoles. Overall, body burden and concentration were lower in boreal chorus frog tadpoles than wood frog tadpoles, as expected, because boreal chorus frog tadpoles consume at lower trophic levels. The variables species, stage, and mass explained 21% of total variation for body burden in our models but had negligible predictive ability for THg concentration. The vast majority of the remaining variation in both body burden and THg concentration was attributable to differences among ponds; tadpoles from ponds in three areas had considerably higher THg body burden and concentration. The pond-to-pond differences were not related to any water chemistry or physical parameter measured, and we assumed that differences in wetland geomorphology likely played an important role in determining Hg levels in tadpoles. This is the first report of Hg in frog tadpoles in the Prairie Pothole Region of North America.
- OPEN ACCESSOceanic circulation patterns shape both the distribution of species and spatial patterns of intraspecific genetic variation by influencing passively dispersed marine invertebrates. In the northwest Atlantic, strong and consistent currents at the mouth of the Bay of Fundy are expected to restrict dispersal in this region, but the relationship between populations of high dispersal species along the surrounding coastal regions has been largely underrepresented in the phylogeographic literature. We analyzed phylogeographic patterns in two intertidal invertebrates with high dispersal abilities, Tritia obsoleta (Mollusca: Gastropoda) and Macoma petalum (Mollusca: Bivalvia), between Cape Cod and the Gulf of St. Lawrence using mitochondrial DNA (mtDNA). Hierarchical analysis of molecular variance revealed population structuring among regions defined by circulation patterns, highly divergent lineages within M. petalum, and strong concordant genetic subdivision in both species between the Bay of Fundy and Gulf of Maine. Our results suggest that the gyre at the mouth of the bay is influential in restricting alongshore dispersal, allowing genetic divergence between regions to arise through genetic drift. These findings are concordant with biogeographic and phylogeographic studies of other marine organisms, suggesting that the genetic isolation of widely distributed species may be a common feature of intertidal invertebrate communities in the Bay of Fundy.
- OPEN ACCESSAn ordinary differential equation describing the transverse profiles of U-shaped glacial valleys has two formal analogies, which we explore in detail, bridging these different areas of research. First, an analogy with point particle mechanics completes the description of the solutions. Second, an analogy with the Friedmann equation of relativistic cosmology shows that the analogue of a glacial valley profile is a universe with a future singularity of interest in theoretical models of cosmology. A Big Freeze singularity, which was not previously observed for positive curvature index, is also contained in the dynamics.
- OPEN ACCESSOften the Before-After-Control-Impact (BACI) design is suggested as being a statistically powerful experimental design in environmental impact studies. If the timing and location of the impact are known and adequate pre-data are collected, the BACI design is considered optimal to help isolate the effect of the development from natural variability. This paper presents 9 years of results from a long-term BACI experiment tested using a range of statistical models and post-impact monitoring designs. To explore suboptimal designs that are often utilized in environmental effects monitoring, the same data were also explored assuming either no control system was available (Before-After only), or that no pre-impact data were available (Control-Impact only). The results of the BACI design were robust to the statistical model used, and the BACI design was able to detect effects from the impact that the two suboptimal designs failed to detect. However, the BACI design demonstrated different conclusions depending on the number and configuration of post-impact years included in the analysis. Our results reinforce the idea that caution should be employed when using, or interpreting results from, a BACI design in an environmental impact study, but demonstrate that a well-designed BACI remains one of the best models for environmental effects monitoring programs.
- OPEN ACCESSAmmonium deposition at the International Institute for Sustainable Development Experimental Lakes Area (IISD–ELA), in northwestern Ontario, Canada, has doubled in the last 45 years and thus is no longer among the low nitrogen (N) deposition sites in North America. This may be related to the concurrent intensification of Manitoba agriculture to the west and upwind of the ELA. Large increases in ammonium deposition at the ELA were important in driving the observed trend and increased the NH4 + to NO3 − ratio of input to aquatic and terrestrial systems. Stable isotope analyses of two years of bulk (wet and dry) atmospheric deposition revealed very large ranges in δ15N−NH4 + (22‰ range), δ15N−NO3 − (18‰), and δ18O–NO3 − (19‰). Few other δ15N−NH4 +, δ15N−NO3 −, and δ18O–NO3 − values have been published for Canadian precipitation. Increases in δ15N of NH4 + and NO3 − in July occurred with increases in total N deposition. The wide range and seasonal trends of δ15N and δ18O values in ELA precipitation mean that studies characterizing N inputs to watersheds and lakes require an ongoing and comprehensive annual sampling regime. Global trends of declining δ15N of N deposition evident in lake sediment records may be a result of increases in NH4 + deposition with lower δ15N−NH4 + values. Similarly, the relationship in Lake Superior between increasing NO3 − and lower δ15N−NO3 − values may be explained by increased atmospheric deposition of N with low δ15N values.
- OPEN ACCESSA reliable marker of early coral response to environmental stressors can help guide decision-making to mitigate global coral reef decline by detecting problems before the development of clinically observable disease. We document the accumulation of acrylic acid in two divergent coral taxa, stony small polyp coral (Acropora sp.) and soft coral (Lobophytum sp.), in response to deteriorating water quality characterized by moderately increased ammonia (0.25 ppm) and phosphate (0.15 ppm) concentrations and decreased calcium (360 ppm) concentration, using nuclear magnetic resonance spectroscopy (NMR)-based metabolomic techniques. Changes in acrylic acid concentration in polyp tissues free of zooxanthellae suggest that acrylic acid could be a product of animal metabolism and not exclusively a metabolic by-product of the osmolyte dimethylsulfoniopropionate (DMSP) in marine algae or bacteria. Our findings build on previously documented depletions of acrylic acid in wild coral potentially correlated to temperature stress and provide additional insight into approaches to further characterize the nature of the metabolic accumulation of acrylic acid under controlled experimental conditions.