Seibel Brad A.

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Brad A.

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Now showing 1 - 6 of 6
  • Article
    The metabolic response of pteropods to acidification reflects natural CO2-exposure in oxygen minimum zones
    (Copernicus Publications on behalf of the European Geosciences Union, 2012-02-15) Maas, Amy E. ; Wishner, Karen F. ; Seibel, Brad A.
    Shelled pteropods (Thecosomata) are a group of holoplanktonic mollusks that are believed to be especially sensitive to ocean acidification because their aragonitic shells are highly soluble. Despite this concern, there is very little known about the physiological response of these animals to conditions of elevated carbon dioxide. This study examines the oxygen consumption and ammonia excretion of five pteropod species, collected from tropical regions of the Pacific Ocean, to elevated levels of carbon dioxide (0.10%, 1000 ppm). Our results show that pteropods that naturally migrate into oxygen minimum zones, such as Hyalocylis striata, Clio pyramidata, Cavolinia longirostris and Creseis virgula, were not affected by carbon dioxide at the levels and duration tested. Diacria quadridentata, which does not migrate, responds to high carbon dioxide conditions with reduced oxygen consumption and ammonia excretion. This indicates that the natural chemical environment of individual species may influence their resilience to ocean acidification.
  • Article
    Ocean deoxygenation and zooplankton: Very small oxygen differences matter
    (American Association for the Advancement of Science, 2018-12-19) Wishner, Karen F. ; Seibel, Brad A. ; Roman, Chris ; Deutsch, Curtis ; Outram, Dawn ; Shaw, C. Tracy ; Birk, Matthew A. ; Mislan, K. A. S. ; Adams, T. J. ; Moore, D. ; Riley, S.
    Oxygen minimum zones (OMZs), large midwater regions of very low oxygen, are expected to expand as a result of climate change. While oxygen is known to be important in structuring midwater ecosystems, a precise and mechanistic understanding of the effects of oxygen on zooplankton is lacking. Zooplankton are important components of midwater food webs and biogeochemical cycles. Here, we show that, in the eastern tropical North Pacific OMZ, previously undescribed submesoscale oxygen variability has a direct effect on the distribution of many major zooplankton groups. Despite extraordinary hypoxia tolerance, many zooplankton live near their physiological limits and respond to slight (≤1%) changes in oxygen. Ocean oxygen loss (deoxygenation) may, thus, elicit major unanticipated changes to midwater ecosystem structure and function.
  • Article
    Comment on “Modern-age buildup of CO2 and its effects on seawater acidity and salinity” by Hugo A. Loáiciga
    (American Geophysical Union, 2007-09-25) Caldeira, Ken ; Archer, David ; Barry, James P. ; Bellerby, Richard G. J. ; Brewer, Peter G. ; Cao, Long ; Dickson, Andrew G. ; Doney, Scott C. ; Elderfield, Henry ; Fabry, Victoria J. ; Feely, Richard A. ; Gattuso, Jean-Pierre ; Haugan, Peter M. ; Hoegh-Guldberg, Ove ; Jain, Atul K. ; Kleypas, Joan A. ; Langdon, Chris ; Orr, James C. ; Ridgwell, Andy ; Sabine, Christopher L. ; Seibel, Brad A. ; Shirayama, Yoshihisa ; Turley, Carol ; Watson, Andrew J. ; Zeebe, Richard E.
  • Article
    Oxygen supply capacity breathes new life into critical oxygen partial pressure (Pcrit)
    (The Company of Biologists, 2021-04-30) Seibel, Brad A. ; Andres, Alyssa ; Birk, Matthew A. ; Burns, Alexandra L. ; Shaw, C. Tracy ; Timpe, Alexander W. ; Welsh, Christina J.
    The critical oxygen partial pressure (Pcrit), typically defined as the PO2 below which an animal's metabolic rate (MR) is unsustainable, is widely interpreted as a measure of hypoxia tolerance. Here, Pcrit is defined as the PO2 at which physiological oxygen supply (α0) reaches its maximum capacity (α; µmol O2 g−1 h−1 kPa−1). α is a species- and temperature-specific constant describing the oxygen dependency of the maximum metabolic rate (MMR=PO2×α) or, equivalently, the MR dependence of Pcrit (Pcrit=MR/α). We describe the α-method, in which the MR is monitored as oxygen declines and, for each measurement period, is divided by the corresponding PO2 to provide the concurrent oxygen supply (α0=MR/PO2). The highest α0 value (or, more conservatively, the mean of the three highest values) is designated as α. The same value of α is reached at Pcrit for any MR regardless of previous or subsequent metabolic activity. The MR need not be constant (regulated), standardized or exhibit a clear breakpoint at Pcrit for accurate determination of α. The α-method has several advantages over Pcrit determination and non-linear analyses, including: (1) less ambiguity and greater accuracy, (2) fewer constraints in respirometry methodology and analysis, and (3) greater predictive power and ecological and physiological insight. Across the species evaluated here, α values are correlated with MR, but not Pcrit. Rather than an index of hypoxia tolerance, Pcrit is a reflection of α, which evolves to support maximum energy demands and aerobic scope at the prevailing temperature and oxygen level.
  • Article
    And on top of all that… coping with ocean acidification in the midst of many stressors
    (The Oceanography Society, 2015-06) Breitburg, Denise L. ; Salisbury, Joseph E. ; Bernhard, Joan M. ; Cai, Wei-Jun ; Dupont, Sam ; Doney, Scott C. ; Kroeker, Kristy J. ; Levin, Lisa A. ; Long, W. Christopher ; Milke, Lisa M. ; Miller, Seth H. ; Phelan, Beth ; Passow, Uta ; Seibel, Brad A. ; Todgham, Anne E. ; Tarrant, Ann M.
    Oceanic and coastal waters are acidifying due to processes dominated in the open ocean by increasing atmospheric CO2 and dominated in estuaries and some coastal waters by nutrient-fueled respiration. The patterns and severity of acidification, as well as its effects, are modified by the host of stressors related to human activities that also influence these habitats. Temperature, deoxygenation, and changes in food webs are particularly important co-stressors because they are pervasive, and both their causes and effects are often mechanistically linked to acidification. Development of a theoretical underpinning to multiple stressor research that considers physiological, ecological, and evolutionary perspectives is needed because testing all combinations of stressors and stressor intensities experimentally is impossible. Nevertheless, use of a wide variety of research approaches is a logical and promising strategy for improving understanding of acidification and its effects. Future research that focuses on spatial and temporal patterns of stressor interactions and on identifying mechanisms by which multiple stressors affect individuals, populations, and ecosystems is critical. It is also necessary to incorporate consideration of multiple stressors into management, mitigation, and adaptation to acidification and to increase public and policy recognition of the importance of addressing acidification in the context of the suite of other stressors with which it potentially interacts.
  • Preprint
    Metabolic suppression in thecosomatous pteropods as an effect of low temperature and hypoxia in the eastern tropical North Pacific
    ( 2011-10) Maas, Amy E. ; Wishner, Karen F. ; Seibel, Brad A.
    Many pteropod species in the eastern tropical north Pacific Ocean migrate vertically each day, transporting organic matter and respiratory carbon below the thermocline. These migrations take species into cold (15-10ºC) hypoxic water (< 20 µmol O2 kg-1) at depth. We measured the vertical distribution, oxygen consumption and ammonia excretion for seven species of pteropod, some of which migrate and some which remain in oxygenated surface waters throughout the day. Within the upper 200 meters of the water column, changes in water temperature result in a ~60-75% reduction in respiration for most species. All three species tested under hypoxic conditions responded to low O2 with an additional ~35-50% reduction in respiratory rate. Combined, low temperature and hypoxia suppress the metabolic rate of pteropods by ~80-90%. These results shed light on the ways in which expanding regions of hypoxia and surface ocean warming may impact pelagic ecology.