Roland I. Hall

Learn More
The annual population growth of the exotic invader Bythotrephes cederstroemi was calculated from the spatial distribution and rate of accumulation of its diagnostic caudal processes in the sediments of Harp Lake, Ontario. To our knowledge, this is the first use of the sediment record to quantify the annual population growth of a zooplankton species on a(More)
Growth of natural resource development in northern Canada has raised concerns about the effects on downstream aquatic ecosystems, but insufficient knowledge of pre-industrial baseline conditions continues to undermine ability of monitoring programs to distinguish industrial-derived contaminants from those supplied by natural processes. Here, we apply a(More)
Freshwater ecosystems are increasingly affected by human influences. Since the pre-industrial era, lakes of the Muskoka–Haliburton region of south-central Ontario have had increases in shoreline residential development and acid deposition. Previous research on 54 of these lakes, using sediment cores and diatom-based transfer functions, showed changes in(More)
A new spectroscopic technique, giving complete two-dimensional e(-)-e(-) coincidence spectra in single photon double photoionization, is presented. The technique resolves the states of doubly charged ions and provides spectra of the individual electrons emitted in formation of each final dication state. Complete spectra for double photoionization of Xe, Kr,(More)
BACKGROUND The extent to which Alberta oil sands mining and upgrading operations have enhanced delivery of bitumen-derived contaminants via the Athabasca River and atmosphere to the Peace-Athabasca Delta (200 km to the north) is a pivotal question that has generated national and international concern. Accounts of rare health disorders in residents of Fort(More)
Identifying potential regional contamination by Alberta oil sands industrial emissions on sensitive ecosystems like the Peace-Athabasca Delta, ~200 km to the north, requires knowledge of historical contaminant levels and trends. Here we provide some of these critically-needed data, based on analysis of metals in a sediment core from an upland(More)
Lake-level fluctuations are common in the North American Great Plains region, where large-scale climate systems (El Niño, the Pacific Decadal Oscillation) and periodic droughts cause substantial hydrologic variability in both summer and winter. To date, most such research has focused on the effects of summer droughts on prairie lake ecosystems; therefore,(More)
ROBERTO QUINLAN* , ANDREW M. PATERSON †, , ROLAND I. HALL § , PETER J. DILLON , ANNA N. WILKINSON , BRIAN F. CUMMING , MARIANNE S. V. DOUGLAS* AND JOHN P. SMOL † *Paleoecological Assessment Laboratory (PAL), Department of Geology, University of Toronto, Toronto, Ontario, Canada †Paleoecological Environmental Assessment and Research Laboratory (PEARL),(More)
Assessments of stream condition using benthic algal communities have traditionally relied on taxonomy-based approaches to compare community structure at sites exposed to a stressor versus reference sites. Taxonomy-based methods are often effective, but they require high levels of training and are relatively time consuming and expensive. We examined the(More)