Peatland Initiation During the Holocene in Continental Western Canada

Today, the southern limit of peatlands in continental western Canada is largely limited by thermal seasonal aridity, although physiographic parameters of substrate texture, topography, and salinity also exsert important controls on the presence and absence of peatlands. Factors that control peatland distribution today also operated in the past, thus the initiation of peatlands during the Holocene was mainly limited by aridity and physiography. Calibrated radiocarbon dates of basal peat deposits from 90 locations across continental western Canada indicate that peat formation began approximately 8,000 to 9,000 years BP in nucleation zones along the upper elevations of the Montane region of Alberta and in northern Alberta uplands after an initial deglacial lag. Predictions of maximum early Holocene summer insolation by climate simulations provide a mechanism for limiting peatland establishment during the early Holocene. From 6,000 to 8,000 years ago, peat formation in continental western Canada expanded eastwards into Manitoba responding to decreases in summer insolation. Peatland expansion during the early Holocene was more extensive in Alberta than in Manitoba in response to a southwesterly shift in the Arctic front. The displacement of the Arctic front allowed for more frequent incursions of moist Pacific air into Alberta while limiting it in Manitoba. After 6,000 years BP, the trend of southeasterly peatland expansion continued. Peatlands are youngest in the southern Boreal Forest and Aspen Parkland Region as well as in the lower elevations of the Peace-Wapiti River drainage basin, forming over the last 3,000 to 4,000 years. Peatlands are also young in the lower elevations of the Hudson Bay Lowlands where peat initiation has been limited by timing of emergence from glacial rebound. The spatial and temporal distribution of peatland initiation during the Holocene is verified by existing pollen records and corroborates some simulated climate models.     

The COVID-19 pandemic and global environmental change: Emerging research needs

The outbreak of COVID-19 raised numerous questions on the interactions between the occurrence of new infections, the environment, climate and health. The European Union requested the H2020 HERA project which aims at setting priorities in research on environment, climate and health, to identify relevant research needs regarding Covid-19. The emergence and spread of SARS-CoV-2 appears to be related to urbanization, habitat destruction, live animal trade, intensive livestock farming and global travel. The contribution of climate and air pollution requires additional studies. Importantly, the severity of COVID-19 depends on the interactions between the viral infection, ageing and chronic diseases such as metabolic, respiratory and cardiovascular diseases and obesity which are themselves influenced by environmental stressors. The mechanisms of these interactions deserve additional scrutiny. Both the pandemic and the social response to the disease have elicited an array of behavioural and societal changes that may remain long after the pandemic and that may have long term health effects including on mental health. Recovery plans are currently being discussed or implemented and the environmental and health impacts of those plans are not clearly foreseen. Clearly, COVID-19 will have a long-lasting impact on the environmental health field and will open new research perspectives and policy needs.     

High-resolution cyclostratigraphic analysis from magnetic susceptibility in a Lower Kimmeridgian (Upper Jurassic) marl–limestone succession (La Méouge,Vocontian Basin,France)

High-resolution magnetic susceptibility (MS) analysis was carried out on a Lower Kimmeridgian alternating marl–limestone succession of pelagic origin that crops out at La Méouge (Vocontian Basin, southeastern France). The aim of the study was to characterize the strong, dm-scale sedimentary cyclicity of the succession at a very high resolution, and to analyze the cycles for evidence of astronomical forcing. From marl to limestone, MS varies progressively and closely tracks the highest frequency cyclicity corresponding to the basic marl–limestone couplets. Long-term wavelength cycling modulates the high-frequency cyclicity (couplets), and appears to be controlled by clay content. Spectral analysis of the MS record reveals the presence of the complete suite of orbital frequencies in the precession, obliquity, and eccentricity (95–128 ka and 405 ka) bands with very high amplitude of the precession index cycles originating from dm-scale couplets. 405 ka-eccentricity cycles are very pronounced in the MS maxima of the marl members of the couplets, suggesting eccentricity-driven detrital input to the basin. 405 ka-orbital tuning of the MS maxima further sharpens all of the orbital frequencies present in the succession. These results are similar to those of previous studies at La Méouge that used carbonate content observed in field. Our results are also in accordance with cyclostratigraphic studies in Spain and Canada that report dominant precession index forcing. By contrast, in the Kimmeridge Clay (Dorset, UK), obliquity forcing dominates cyclic sedimentation, with weaker influence from the precession index. Ammonite zone duration estimates are made by counting the interpreted precession cycles, and provide an ultra-high resolution assessment of geologic time. In sum, this study demonstrates the power of the MS as a proxy in characterizing the high-resolution cyclostratigraphy of Mesozoic sections, particularly in alternating marl–limestone successions, and for high-resolution correlation and astronomical calibration of the geologic time scale.     

Development and validation of an estuarine biotic integrity index

We tested hypotheses about how estuarine fish assemblages respond to habitat degradation and then integrated these responses into an overall index, the Estuarine Biotic Integrity Index (EBI), which summarized observed changes. Fish assemblages (based on trawl catches) and habitat quality were measured monthly or biweekly at nine sites in two estuaries from March 1988 to June 1990. Submerged aquatic vegetation habitats were classified as low or medium quality based on year-round measurements of chemical and physical characteristics (phytoplankton blooms; macroalgae; dissolved oxygen; nutrients; dredged channels). We tested 15 metrics and selected 8 for inclusion in the EBI: total number of species, dominance, fish abundance (number or biomass), number of nursery species, number of estuarine spawning species, number of resident species, proportion of benthic-associated fishes, and proportion abnormal or diseased. Fish assemblages in low-quality sites had lower number of species, density, biomass, and dominance compared with medium-quality sites. Fish abundance peaked in July and August, and was lowest in January to March. The seasonal cycle in low-quality sites was damped compared with medium-quality sites. Abundances of fishes using estuaries as a spawning and nursery area and of benthic species were lower in low-quality sites compared to medium-quality sites. The individual metrics and the overall index correlated with habitat degradation. The EBI based on biomass did not do better than the EBI based on number, indicating that the extra effort to obtain biomass may not be warranted. We suggest the EBI is a useful indicator of estuarine ecosystem status because it reflects the relationship between anthropogenic alterations in estuarine ecosystems and the status of higher trophic levels.