Differences in reproductive allocation of male and female fishes could lead to sexual divergence in nutritional requirements, trophic ecologies, and metabolisms that may be reflected in isotopic ...compositions. We compared muscle C:N ratio, δ
13
C, and δ
15
N between mature females and males for eight fish species from 21 North American populations. We also compared isotopic compositions between muscle and ova in a subset of females to determine if observed sex differences may be associated with fractionation during oogenesis. Muscle δ
13
C and δ
15
N did not vary greatly between males and females for most species but significant differences were observed in walleye (
Sander vitreus
) and burbot (
Lota lota
). Among-individual variation in isotopic composition, estimated as dispersion in δ
13
C–δ
15
N space, did not differ significantly between the sexes. Ova had significantly higher C:N ratio and lower δ
13
C than female muscle in all species with the greatest contrast between tissues seen in burbot. Ova had significantly higher δ
15
N than female muscle in most species with the greatest contrast between tissues in walleye. Sex-based divergence in isotopic composition of northern fishes is most evident in lean-fleshed piscivores, and may be related to selective mobilization of nutrients from soma to ovaries.
Modern extensions of the theory of island biogeography (TIB) posit that the slope of the species−area relationship (SAR) reflects the insularity of ecological communities and is strongly influenced ...by species’ motility. We explore the relative insularity of crustacean, echinoderm and mollusk/Cirripedia assemblages in terms of both alpha diversity (species richness) and assemblage structure (relative biomass of species). These taxa/groups differ in adult motility and larval dispersal capacity. The habitats of interest were 10 offshore banks on the Scotian Shelf, Northwest Atlantic Ocean, a region dominated by the NE- to SW-flowing Nova Scotia Current (NSC). Banks in the NE tended to be larger, more heterogeneous, cooler, less saline, more retentive and more productive (higher chlorophyll a) than those in the SW. Only mollusks/Cirripedia, the least motile and dispersive group, had a significant SAR slope, supporting TIB. For crustaceans and echinoderms, temperature/salinity properties and habitat heterogeneity, respectively, were important predictors of alpha diversity. Inter-bank variation in crustacean assemblage structure was accounted for largely by bank location relative to the NSC; the leading variables accounting for echinoderm and mollusk/Cirripedia assemblage structure were retention time and mean annual chlorophyll concentration, respectively. Along the NE to SW axis of the NSC, there was a substantial loss of species (7 crustacean, 9 echinoderm and 13 mollusk/Cirripedia species) and decreases in the biomass of common cold-water species. A complex interplay of species motility/dispersal capacity, local oceanography and habitat properties determine the extent to which (1) TIB applies to submarine macroinvertebrate assemblages and (2) upstream and downstream assemblages are interconnected.
A significant difference, now of some 16 years' duration, has been shown to exist between the observed global surface temperature trend and that expected from the majority of climate simulations. For ...its own sake, and to enable better climate prediction for policy use, the reasons behind this mismatch need to be better understood. While an increasing number of possible causes have been proposed, the candidate causes have not yet converged.With this background, this paper reinvestigates the relationship between change in the level of CO2 and two of the major climate variables, atmospheric temperature and the El Niño–Southern Oscillation (ENSO).Using time-series analysis in the form of dynamic regression modelling with autocorrelation correction, it is shown that first-difference CO2 leads temperature and that there is a highly statistically significant correlation between first-difference CO2 and temperature. Further, a correlation is found for second-difference CO2 with the Southern Oscillation Index, the atmospheric-pressure component of ENSO. This paper also shows that both these correlations display Granger causality.It is shown that the first-difference CO2 and temperature model shows no trend mismatch in recent years.These results may contribute to the prediction of future trends for global temperature and ENSO.Interannual variability in the growth rate of atmospheric CO2 is standardly attributed to variability in the carbon sink capacity of the terrestrial biosphere. The terrestrial biosphere carbon sink is created by the difference between photosynthesis and respiration (net primary productivity): a major way of measuring global terrestrial photosynthesis is by means of satellite measurements of vegetation reflectance, such as the Normalized Difference Vegetation Index (NDVI). In a preliminary analysis, this study finds a close correlation between an increasing NDVI and the increasing climate model/temperature mismatch (as quantified by the difference between the trend in the level of CO2 and the trend in temperature).
There is evidence that a natural control system influences global atmospheric surface temperature (Leggett and Ball
2020
). The present paper sets up and tests a hypothesis concerning the physical ...makeup of the sequential elements of the control system and its outcomes. The final outcome that the control system influences is defined as global atmospheric surface temperature. The terms used for the control system element types in the hypothesis are, in sequence: leading element, controller and actuator. Actuators are hypothesised to affect, in turn, the final outcome - either directly, or via penultimate outcomes. The existence of the control system is evidenced by demonstration of statistically significant one-way Granger causality across each step of the hypothesised control system sequence. Evidence is presented that the leading element of the control system, represented by the Normalized Difference Vegetation Index, is the global biosphere. The biosphere as a control system has previously been referred to as Gaia (Lovelock and Margulis
1974
). A fourth, second-derivative, term is found to enhance the Proportional, Integral and Derivative process terms of the control system shown in Leggett and Ball (
2020
). The main actuators of the control system found are shown to be wind speed and cloud cover. Cloud cover is shown to influence the final outcome, global surface temperature, directly. It and wind speed also influence the penultimate outcomes found, those of enhanced ocean heat uptake and enhanced outgoing longwave radiation. These together lead to control system output to the final outcome, global atmospheric temperature. Overall, evidence for the activity of the control system is shown to be present across many major physical dimensions of the Earth's atmosphere.
Life history theory predicts that organisms inhabiting environments with relatively poor conditions for the growth and survival of their offspring should produce fewer and larger offspring. We ...examined egg size (an index of offspring size) of an iteroparous, broadcast-spawning, freshwater fish-the walleye (Stizostedion vitreum)-from 34 populations across 26° of latitude in order to determine whether egg size varied with respect to environmental indices of juvenile habitat quality. Variation among populations (among environments) was compared to variation within populations (among females). Within populations, egg size generally increased with maternal size and age. Slopes of these relationships were much more variable among populations (CV > 100%) than interannually within populations (CV < 50%). Egg size vs. female size/age correlations were stronger in populations closer to the northern and southern limits of the walleye range. Egg size was also related to maternal growth history, but the effects of recent growth (previous year) were inconsistent. Egg size varied much less than fecundity among females of the same population. For a standard size/age of female, predicted egg size was more variable among populations (CV > 10%) than interannually within populations (CV < 5%), but only slightly more variable than among females within populations (mean CV = 8.5%). Nevertheless, among-population variability in egg size was related to environmental conditions. Mean egg size decreased with increasing latitude/decreasing mean annual temperature, contrary to our predictions. However, as predicted, egg size decreased with increasing lake productivity following adjustment for the latitudinal/temperature effect. These results suggest that egg size in fishes may be influenced by multiple environmental factors across populations, as well as by maternal effects within populations.
A biokinetic model for manganese Leggett, R.W.
The Science of the total environment,
09/2011, Volume:
409, Issue:
20
Journal Article
Peer reviewed
The International Commission on Radiological Protection (ICRP) is updating its biokinetic models used to derive dose coefficients and assess bioassay data for intake of radionuclides. This paper ...reviews biokinetic data for manganese and proposes a biokinetic model for systemic manganese in adult humans. The proposed model provides a more detailed and physiologically meaningful description of the behavior of absorbed manganese in the body than the current ICRP model. The proposed model and current ICRP model yield broadly similar estimates of dose per unit activity of inhaled or ingested radio-manganese but differ substantially with regard to interpretation of bioassay data. The model is intended primarily for use in radiation protection but can also serve as a baseline model for evaluation of potentially excessive intakes of stable manganese in occupational settings.
► Manganese is an essential trace element but a neurotoxin when inhaled excessively. ► Manganese-54 is an important radiation hazard in and around nuclear reactors. ► Biokinetic data for manganese are reviewed and a new biokinetic model is developed. ► The main purpose is to update the manganese model used in radiation protection. ► The model can also be applied in evaluations of manganese as a chemical hazard.
Here we provide statistically significant observational evidence that a feedback control system moderating atmospheric temperature is presently operating coherently at global scale. Further, this ...control system is of a sophisticated type, involving the corrective feedback not only of a linear error term but also its derivative and its integral. This makes it of the same type as the most widely used control system developed by humans, the proportional-integral-derivative (PID) control system.
The trophic theory of island biogeography (TTIB) predicts that when predators are depleted, prey extinction rates decrease, leading to increases in prey alpha diversity and an increase in the slope ...of the species−area relationship (SAR). The TTIB has been tested and supported in a restricted set of systems at small spatial scales (0.25 m³ reef patches to 29 500 m² terrestrial). Across semi-insular fish communities on 10 offshore banks ranging in size from 534 to 10 537 km² on the Scotian Shelf (northwest Atlantic Ocean), we found support for the predictions of the TTIB. The prey SAR slope was significantly higher after the collapse of large predator populations than before the collapse, due largely to the immigration (or colonization) of many new prey species, principally on the largest banks. Coincident increases in core (resident) prey species densities, primarily on the largest banks, suggests that extinction risk decreased. The appearance of a strong SAR within the mesopredator trophic group in the post-predator collapse era (r² = 0.55 relative to 0.12 in the pre-collapse era) suggests that the TTIB may also apply to mesopredator release in insular marine communities. Increases in mesopredator densities coincident with the colonization of previously unoccupied banks by core mesopredator species suggests that range expansions contributed to the increased strength of the SAR. Our study contributes to our evolving understanding of island biogeography theory and suggests that TTIB may provide a useful framework for evaluating trophic alterations in large marine (and non-marine) ecosystems.
Updated analyses of mortality data are presented on 46,970 workers employed 1948–1999 at Rocketdyne (Atomics International). Overall, 5,801 workers were involved in radiation activities, including ...2,232 who were monitored for intakes of radionuclides, and 41,169 workers were engaged in rocket testing or other non-radiation activities. The worker population is unique in that lifetime occupational doses from all places of employment were sought, updated and incorporated into the analyses. Further, radiation doses from intakes of 14 different radionuclides were calculated for 16 organs or tissues using biokinetic models of the International Commission on Radiation Protection (ICRP). Because only negligible exposures were received by the 247 workers monitored for radiation activities after 1999, the mean dose from external radiation remained essentially the same at 13.5 mSv (maximum 1 Sv) as reported previously, as did the mean lung dose from external and internal radiation combined at 19.0 mSv (maximum 3.6 Sv). An additional 9 years of follow-up, from December 31,1999 through 2008, increased the person-years of observation for the radiation workers by 21.7% to 196,674 (mean 33.9 years) and the number of cancer deaths by 50% to 684. Analyses included external comparisons with the general population and the computation of standardized mortality ratios (SMRs) and internal comparisons using proportional hazards models and the computation of relative risks (RRs). A low SMR for all causes of death (SMR 0.82; 95% CI 0.78–0.85) continued to indicate that the Rocketdyne radiation workers were healthier than the general population and were less likely to die. The SMRs for all cancers taken together (SMR 0.88; 95% CI 0.81–0.95), lung cancer (SMR 0.87; 95% CI 0.76–1.00) and leukemia other than chronic lymphocytic leukemia (CLL) (SMR 1.04; 95% 0.67–1.53) were not significantly elevated. Cox regression analyses revealed no significant dose–response trends for any cancer. For all cancers excluding leukemia, the RR at 100 mSv was estimated as 0.98 (95% CI 0.82–1.17), and for all leukemia other than CLL it was 1.06 (95% CI 0.50–2.23). Uranium was the primary radionuclide contributing to internal exposures, but no significant increases in lung and kidney disease were seen. The extended follow-up reinforces the findings in the previous study in failing to observe a detectable increase in cancer deaths associated with radiation, but strong conclusions still cannot be drawn because of small numbers and relatively low career doses. Larger combined studies of early workers in the United States using similar methodologies are warranted to refine and clarify radiation risks after protracted exposures.
Polonium-210 is a naturally occurring radioactive element that decays by emitting an alpha particle. It is in the air we breathe and also a component of tobacco smoke. Polonium-210 is used as an ...anti-static device in printing presses and gained widespread notoriety in 2006 after the poisoning and subsequent death of a Russian citizen in London. More is known about the lethal effects of polonium-210 at high doses than about late effects from low doses. Cancer mortality was examined among 7,270 workers at the Mound nuclear facility near Dayton, OH where polonium-210 was used (1944–1972) in combination with beryllium as a source of neutrons for triggering nuclear weapons. Other exposures included external gamma radiation and to a lesser extent plutonium-238, tritium and neutrons. Vital status and cause of death was determined through 2009. Standardized mortality ratios (SMRs) were computed for comparisons with the general population. Lifetime occupational doses from all places of employment were sought and incorporated into the analysis. Over 200,000 urine samples were analyzed to estimate radiation doses to body organs from polonium and other internally deposited radionuclides. Cox proportional hazards models were used to evaluate dose-response relationships for specific organs and tissues. Vital status was determined for 98.7% of the workers of which 3,681 had died compared with 4,073.9 expected (SMR 0.90; 95% CI 0.88–0.93). The mean dose from external radiation was 26.1 mSv (maximum 939.1 mSv) and the mean lung dose from external and internal radiation combined was 100.1 mSv (maximum 17.5 Sv). Among the 4,977 radiation workers, all cancers taken together (SMR 0.86; 95% CI 0.79–0.93), lung cancer (SMR 0.85; 95% CI 0.74–0.98), and other types of cancer were not significantly elevated. Cox regression analysis revealed a significant positive dose-response trend for esophageal cancer relative risk (RR) and 95% confidence interval at 100 mSv of 1.54 (1.15–2.07) and a negative dose-response trend for liver cancer RR (95% CI) at 100 mSv of 0.55 (0.23–1.32). For lung cancer the RR at 100 mSv was 1.00 (95% CI 0.97–1.04) and for all leukemias other than chronic lymphocytic leukemia (CLL) it was 1.04 (95% CI 0.63–1.71). There was no evidence that heart disease was associated with exposures RR at 100 mSv of 1.06 (0.95–1.18). Assuming a relative biological effectiveness factor of either 10 or 20 for polonium and plutonium alpha particle emissions had little effect on the dose-response analyses. Polonium was the largest contributor to lung dose, and a relative risk of 1.04 for lung cancer at 100 mSv could be excluded with 95% confidence. A dose related increase in cancer of the esophagus was consistent with a radiation etiology but based on small numbers. A dose-related decrease in liver cancer suggests the presence of other modifying factors of risk and adds caution to interpretations. The absence of a detectable increase in total cancer deaths and lung cancer in particular associated with occupational exposures to polonium (mean lung dose 159.8 mSv), and to plutonium to a lesser extent (mean lung dose 13.7 mSv), is noteworthy but based on small numbers. Larger combined studies of U.S. workers are needed to clarify radiation risks following prolonged exposures and radionuclide intakes.
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