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Marc Trudel - One of the best experts on this subject based on the ideXlab platform.
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marine growth patterns of southern british columbia chum salmon explained by interactions between density dependent competition and changing Climate
Canadian Journal of Fisheries and Aquatic Sciences, 2017Co-Authors: Allan J Debertin, James R Irvine, Carrie A Holt, Marc TrudelAbstract:Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon (Oncorhynchus keta) in southern British Columbia demonstrated that competition and Climate Variation affect marine growth and age-at-maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye (Oncorhynchus nerka), and pink salmon (Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate Variation influenced competition effects. For instance, density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation became more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by Climate change and high aggregat...
Allan J Debertin - One of the best experts on this subject based on the ideXlab platform.
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marine growth patterns of southern british columbia chum salmon explained by interactions between density dependent competition and changing Climate
Canadian Journal of Fisheries and Aquatic Sciences, 2017Co-Authors: Allan J Debertin, James R Irvine, Carrie A Holt, Marc TrudelAbstract:Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon (Oncorhynchus keta) in southern British Columbia demonstrated that competition and Climate Variation affect marine growth and age-at-maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye (Oncorhynchus nerka), and pink salmon (Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate Variation influenced competition effects. For instance, density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation became more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by Climate change and high aggregat...
Paul A Baker - One of the best experts on this subject based on the ideXlab platform.
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nature and causes of quaternary Climate Variation of tropical south america
Quaternary Science Reviews, 2015Co-Authors: Paul A Baker, Sherilyn C FritzAbstract:Abstract This selective review of the Quaternary paleoClimate of the South American summer monsoon (SASM) domain presents viewpoints regarding a range of key issues in the field, many of which are unresolved and some of which are controversial. (1) El Nino-Southern Oscillation variability, while the most important global-scale mode of interannual Climate Variation, is insufficient to explain most of the Variation of tropical South American Climate observed in both the instrumental and the paleoClimate records. (2) Significant Climate Variation in tropical South America occurs on seasonal to orbital (i.e. multi-millennial) time scales as a result of sea-surface temperature (SST) Variation and ocean–atmosphere interactions of the tropical Atlantic. (3) Decadal-scale Climate variability, linked with this tropical Atlantic variability, has been a persistent characteristic of Climate in tropical South America for at least the past half millennium, and likely, far beyond. (4) Centennial-to-millennial Climate events in tropical South America were of longer duration and, perhaps, larger amplitude than any observed in the instrumental period, which is little more than a century long in tropical South America. These were superimposed upon both precession-paced insolation changes that caused significant Variation in SASM precipitation and eccentricity-paced global glacial boundary conditions that caused significant changes in the tropical South American moisture balance. As a result, river sediment and water discharge increased and decreased across tropical South America, lake levels rose and fell, paleolakes arose and disappeared on the Altiplano, glaciers waxed and waned in the tropical Andes, and the tropical rainforest underwent significant changes in composition and extent. To further evaluate Climate forcing over the last glacial cycle (∼125 ka), we developed a Climate forcing model that combines summer insolation forcing and a proxy for North Atlantic SST forcing to reconstruct long-term precipitation Variation in the SASM domain. The success of this model reinforces our confidence in assigning causation to observed reconstructions of precipitation. In addition, we propose a critical correction for speleothem stable oxygen isotopic ratios, which are among the most significant of paleoClimate proxies in tropical South America for reconstruction of Variation of paleo-precipitation (or SASM intensity). However, it is already well known that any particular δ18O value observed in speleothem carbonate is affected by two processes that have nothing to do with changes in precipitation amount—the influence of temperature on carbonate-water isotopic fractionation in the cave and the influence of changing δ18O of seawater. Quantitatively accounting for both “artifacts” can significantly alter the interpretations of speleothem records. In tropical South America, both adjustments act in the same direction and have the tendency to increase the true amplitude of the paleo-hydrologic signal (but by different amounts in glacial and inter-glacial stages). These corrections have even graver implications for the interpretation of tropical Northern Hemisphere speleothem records (e.g. Chinese speleothems) where the combined adjustments tend to decrease or even eliminate the “true” signal amplitude.
Sherilyn C Fritz - One of the best experts on this subject based on the ideXlab platform.
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nature and causes of quaternary Climate Variation of tropical south america
Quaternary Science Reviews, 2015Co-Authors: Paul A Baker, Sherilyn C FritzAbstract:Abstract This selective review of the Quaternary paleoClimate of the South American summer monsoon (SASM) domain presents viewpoints regarding a range of key issues in the field, many of which are unresolved and some of which are controversial. (1) El Nino-Southern Oscillation variability, while the most important global-scale mode of interannual Climate Variation, is insufficient to explain most of the Variation of tropical South American Climate observed in both the instrumental and the paleoClimate records. (2) Significant Climate Variation in tropical South America occurs on seasonal to orbital (i.e. multi-millennial) time scales as a result of sea-surface temperature (SST) Variation and ocean–atmosphere interactions of the tropical Atlantic. (3) Decadal-scale Climate variability, linked with this tropical Atlantic variability, has been a persistent characteristic of Climate in tropical South America for at least the past half millennium, and likely, far beyond. (4) Centennial-to-millennial Climate events in tropical South America were of longer duration and, perhaps, larger amplitude than any observed in the instrumental period, which is little more than a century long in tropical South America. These were superimposed upon both precession-paced insolation changes that caused significant Variation in SASM precipitation and eccentricity-paced global glacial boundary conditions that caused significant changes in the tropical South American moisture balance. As a result, river sediment and water discharge increased and decreased across tropical South America, lake levels rose and fell, paleolakes arose and disappeared on the Altiplano, glaciers waxed and waned in the tropical Andes, and the tropical rainforest underwent significant changes in composition and extent. To further evaluate Climate forcing over the last glacial cycle (∼125 ka), we developed a Climate forcing model that combines summer insolation forcing and a proxy for North Atlantic SST forcing to reconstruct long-term precipitation Variation in the SASM domain. The success of this model reinforces our confidence in assigning causation to observed reconstructions of precipitation. In addition, we propose a critical correction for speleothem stable oxygen isotopic ratios, which are among the most significant of paleoClimate proxies in tropical South America for reconstruction of Variation of paleo-precipitation (or SASM intensity). However, it is already well known that any particular δ18O value observed in speleothem carbonate is affected by two processes that have nothing to do with changes in precipitation amount—the influence of temperature on carbonate-water isotopic fractionation in the cave and the influence of changing δ18O of seawater. Quantitatively accounting for both “artifacts” can significantly alter the interpretations of speleothem records. In tropical South America, both adjustments act in the same direction and have the tendency to increase the true amplitude of the paleo-hydrologic signal (but by different amounts in glacial and inter-glacial stages). These corrections have even graver implications for the interpretation of tropical Northern Hemisphere speleothem records (e.g. Chinese speleothems) where the combined adjustments tend to decrease or even eliminate the “true” signal amplitude.
Nicholas J. Clark - One of the best experts on this subject based on the ideXlab platform.
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Climate Variation influences host specificity in avian malaria parasites
Ecology letters, 2019Co-Authors: Alan Fecchio, Holly L. Lutz, Konstans Wells, Jeffrey A. Bell, Vasyl V. Tkach, Jason D. Weckstein, Sonya M. Clegg, Nicholas J. ClarkAbstract:Parasites with low host specificity (e.g. infecting a large diversity of host species) are of special interest in disease ecology, as they are likely more capable of circumventing ecological or evolutionary barriers to infect new hosts than are specialist parasites. Yet for many parasites, host specificity is not fixed and can vary in response to environmental conditions. Using data on host associations for avian malaria parasites (Apicomplexa: Haemosporida), we develop a hierarchical model that quantifies this environmental dependency by partitioning host specificity Variation into region- and parasite-level effects. Parasites were generally phylogenetic host specialists, infecting phylogenetically clustered subsets of available avian hosts. However, the magnitude of this specialisation varied biogeographically, with parasites exhibiting higher host specificity in regions with more pronounced rainfall seasonality and wetter dry seasons. Recognising the environmental dependency of parasite specialisation can provide useful leverage for improving predictions of infection risk in response to global Climate change.