Late Holocene climate and chemical change at high latitudes: case studies from contaminated sites... more Late Holocene climate and chemical change at high latitudes: case studies from contaminated sites in subarctic and arctic Canada Jennifer M. Galloway (1), Darryl Cooney (2), Carley Crann (2), Hendrik Falck (3), Dana Howell (4), Heather Jamieson (4), Andrew Macumber (2), Nawaf Nasser (2), Michael Palmer (5), R. Timothy Patterson (2), Michael Parsons (1), Helen M. Roe (6), Hamed Sanei (1), Christopher Spence (7), Drew Stavinga (4), and Graeme T. Swindles (8)
Testate lobose amoebae of the order Arcellinida are a diverse, cosmopolitan group of shelled prot... more Testate lobose amoebae of the order Arcellinida are a diverse, cosmopolitan group of shelled protists found in many environments, including freshwater habitats, peatlands, and soils. Their decay-resistant tests make them an important fossil group for reconstructing Quaternary environments. Within the family Difflugidae Stein, 1859 more than 300 species and 200 sub-species have been attributed to the genus Difflugia Leclerc, 1815. Although carried out on only a few taxa, molecular evidence has demonstrated that test morphology is more important than test composition in categorizing distinct taxa within the Arcellinida. The type species of Difflugia, D. proteiformis Lamarck, 1816, is characterized by a terminal aperture and an elongate acuminate test. The morphology of D. proteiformis is vastly different from most species assigned to Difflugia, explaining its polyphyletic status. We reclassify Difflugia bidens Penard, 1902 as type species of Erugomicula, a new genus within the Difflugidae, which is distinguished from other taxa within Difflugia by its broad, ovoid test, and distinct compression. Based on the compressed morphology of the test, which is not a characteristic of the Difflugiidae, we tentatively assign Erugomicula to the family Hyalospheniidae.
Arcellaceans (testate lobose amoebae) were examined for 61 sediment surface samples from lakes in... more Arcellaceans (testate lobose amoebae) were examined for 61 sediment surface samples from lakes in the vicinity of the Giant Mine near Yellowknife, Northwest Territories to; (1) quantify the impact of the mine on the Baker Creek Watershed region, (2) determine the utility of arcellaceans as indicators of arsenic and heavy metal contamination and gauge the success of remediation efforts. Several statistical methods, including cluster analysis, Deterended Correspondence Analysis (DCA), and Redundancy Analysis (RDA), were used to quantify the impact of mining activity on the arcellacean assemblages. Cluster analysis revealed five arcellacean assemblages associated with a range of environmental conditions (e.g. polluted, transitional and remediated). Partial RDA results confirm that arsenic has the greatest influence on the arcellacean distribution, explaining 10.7% of the total variance. Stress-indicating species (e.g. Centropyxids) correlate with high arsenic concentrations, while species characteristic of more healthy lake conditions (e.g. Difflugids) dominate sites with significantly lower arsenic concentrations.
We examined late Holocene (ca. 3300 yr BP to present-day) climate variability in the central Nort... more We examined late Holocene (ca. 3300 yr BP to present-day) climate variability in the central Northwest Territories (Canadian Subarctic) using a diatom and sedimentological record from Danny's Lake (63.48ºN, 112.54ºW), located 40 km southwest of the modern-day treeline. High-resolution sampling paired with a robust age model (25 radiocarbon dates) allowed for the examination of both lake hydroecological conditions (30-year intervals; diatoms) and sedimentological changes in the watershed (12-year intervals; grain size records) over the late Holocene. Time series analysis of key lake ecological indicators (diatom species Aulacoseira alpigena, Pseudostaurosira brevistriata and Achnanthidium minutissimum) and sedimentological parameters, reflective of catchment processes (coarse silt fraction), suggests significant intermittent variations in turbidity, pH and light penetration within the lake basin. In the diatom record, we observed discontinuous periodicities in the range of ca. 69, 88-100, 115-132, 141-188, 562, 750 and 900 years (>90% and >95% confidence intervals), whereas the coarse silt fraction was characterized by periodicities in the >901 and <61-year range (>95% confidence interval). Periodicities in the proxy data from the Danny's Lake sediment core align with changes in total solar irradiance over the past ca. 3300 yr BP and we hypothesize a link to the Suess Cycle, Gleissberg Cycle and Pacific Decadal Oscillation via occasional inland propagation of shifting air masses over the Pacific Ocean. This research represents an important baseline study of the underlying causes of climate variability in the Canadian Subarctic and provides details on the long-term climate variability that has persisted in this region through the past three thousand years.
Frame Lake, located within the city of Yellowknife, Northwest Territories, Canada, has been ident... more Frame Lake, located within the city of Yellowknife, Northwest Territories, Canada, has been identified as requiring significant remediation due to its steadily declining water quality and inability to support fish by the 1970s. Former gold mining operations and urbanization around the lake have been suspected as probable causes for the decline in water quality. While these land-use activities are well documented, little information is available regarding their impact on the lake itself. For this reason, Arcellinida, a group of shelled protozoans known to be reliable bioindicators of land-use change, were used to develop a hydroecological history of the lake. The purpose of this study was to use Arcellinida to: (1) document the contamination history of the lake, particularly related to arsenic (As) associated with aerial deposition from mine roaster stacks; (2) track the progress of water quality deterioration in Frame Lake related to mining, urbanization and other activities; and (3...
Arcellininids (testate amoebae) were examined from 61 surface sediment samples collected from 59 ... more Arcellininids (testate amoebae) were examined from 61 surface sediment samples collected from 59 lakes in the vicinity of former gold mines, notably Giant Mine, near Yellowknife, Northwest Territories, Canada to determine their utility as bioindicators of arsenic (As), which occurs both as a byproduct of gold extraction at mines in the area and ore-bearing outcrops. Cluster analysis (Q-R-mode) and detrended correspondence analysis (DCA) reveal five arcellininid assemblages, three of which are related to varying As concentrations in the sediment samples. Redundancy analysis (RDA) showed that 14 statistically significant environmental parameters explained 57 % of the variation in faunal distribution, while partial RDA indicated that As had the greatest influence on assemblage variance (10.7 %; p < 0.10). Stress-indicating species (primarily centropyxids) characterized the faunas of samples with high As concentrations (median = 121.7 ppm, max > 10000 ppm, min = 16.1 ppm, n = 32),...
This is a repository copy of Sediment accumulation rates in subarctic lakes: Insights into age-de... more This is a repository copy of Sediment accumulation rates in subarctic lakes: Insights into age-depth modeling from 22 dated lake records from the Northwest Territories, Canada.
A multiproxy analysis was carried out on diatom, foraminiferal and macrophyte assemblages across ... more A multiproxy analysis was carried out on diatom, foraminiferal and macrophyte assemblages across the saltmarsh at Zeballos, Vancouver Island, British Columbia. To determine which group, or combination of groups provided the most accurate elevational zonations, 36 stepwise multiple linear regressions (SMLR) were carried out using a variety of data transformations on an elevational training set. Adjusted R 2 values yielded statistically significant results in all analyses as follows: foraminifera (0.658-0.870); diatoms (0.888-0.974); macrophytes (0.671-0.844); foraminifera/diatoms (0.941-0.981); foraminifera/diatoms/macrophytes (0.958-0.993). The most realistic SMLR results were obtained when data transformations comprised of (ln) normalized fractional abundance data was carried out on species present in statistically significant numbers (NrfaEQ). Of the individual proxies assessed, diatoms yielded the most significant adjusted R 2 results, with the low marsh diatom Achnanthes hauckiana being one of the most important predictor variables (pv's). Amongst the foraminifera, the low marsh species Miliammina fusca and high marsh Balticammina pseudomacrescens were determined to be the most significant pv's. For macrophytes, the low marsh species Carex lyngbyei, the high marsh species Juncus balticus, Shannon-Wiener Diversity Index (SDI) and absence of plant cover on the tidal flat were the most important pv's. As SMLR analysis of all individual groups and combinations of groups yielded statistically significant results, the choice of proxies, or combinations of proxies that are suitable for paleo-sea level research is at the discretion of the researcher.
Proxy records derived from ombrotrophic peatlands provide important insights into climate change ... more Proxy records derived from ombrotrophic peatlands provide important insights into climate change over decadal to millennial timescales. We present mid-to late-Holocene humification data and testate amoebae-derived water table records from two peatlands in Northern Ireland. We examine the replication of periodicities in these proxy climate records, which have been precisely linked through tephrochronology. Age-depth models are constructed using a Bayesian piece-wise linear accumulation model and chronological errors are calculated for each profile. A Lomb-Scargle Fourier transform-based spectral analysis is used to test for statistically significant periodicities in the data. Periodicities of c. 130, 180, 260, 540 and 1160 years are present in at least one proxy record at each site. The replication of these periodicities provides persuasive evidence that they are a product of allogenic climate controls, rather than internal peatland dynamics. A technique to estimate the possible level of red-noise in the data is applied and demonstrates that the observed periodicities cannot be explained by a first-order autoregressive model. We review the periodicities in the light of those reported previously from other marine and terrestrial climate proxy archives to consider climate forcing parameters.
Testate amoebae have been used widely as a proxy of hydrological change in ombrotrophic peatlands... more Testate amoebae have been used widely as a proxy of hydrological change in ombrotrophic peatlands, although their response to abiotic controls in other types of mire and fenland palaeo-environments is less well understood. This paper examines the response of testate amoebae to hydroseral and other environmental changes at Mer Bleue Bog, Ontario, Canada, a large ombrotrophic peatland, which evolved from a brackish-water embayment in the early Holocene. Sediments, plant macrofossils and diatoms examined from a 5.99 m core collected from the dome of the bog record six stages of development: i) a quiet, brackish-water riverine phase (prior to ca. 8500 cal BP); ii) a shallow lake (ca. 8500 e8200 cal BP); iii) fen (8200e7600 cal BP); iv) transitional mire (7600e6900 cal BP); v) pioneer raised mire (6900e4450 cal BP); and vi) ombrotrophic bog (4450 cal BP-present). Testate amoebae, notably small (<25 mm diameter) specimens of Centropyxis aculeata type, first appear in low abundances in sediments ascribed to the lacustrine phase. Diatoms from the same horizons record a shallowing in water depth, a decline in salinity and the development of emergent macrophytic vegetation, which may have provided favourable conditions for testate amoeba colonization. The testate amoeba communities of the inferred fen phase are more diverse and include centropyxids, cyclopyxids, Arcellidae and Hyalospheniidae, although the assemblages show some differences to those recently reported in modern European fen environments. The FeneBog Transition (FBT) is also dominated by C. aculeata type. The change in testate amoeba communities around this key transition is apparent in the results of Detrended Correspondence Analysis (DCA), and appears to reflect a latent nutrient gradient and a secondary moisture gradient. DCA analyses of plant macrofossil remains around the FBT show a similar trend, although the sensitivity of the two proxies to the inferred environmental changes differs. Comparisons with other regional mid-Holocene peatland records confirm the important influence of reduced effective precipitation on the testate amoeba communities during the initiation and development of Sphagnum-dominated, raised bog communities.
Arcellacea (testate lobose amoebae) communities were assessed from 73 sediment-water interface sa... more Arcellacea (testate lobose amoebae) communities were assessed from 73 sediment-water interface samples collected from 33 lakes in urban and rural settings within the Greater Toronto Area (GTA), Ontario, Canada, as well as from forested control areas in the Lake Simcoe area, Algonquin Park and eastern Ontario. The results were used to: (1) develop a statistically rigorous arcellacean-based training set for sedimentary phosphorus (Olsen P (OP)) loading; and (2) derive a transfer function to reconstruct OP levels during the post-European settlement era (AD1870s onward) using a chronologically well-constrained core from Haynes Lake on the environmentally sensitive Oak Ridges Moraine, within the GTA. Ordination analysis indicated that OP most influenced arcellacean assemblages, explaining 6.5% (p b 0.005) of total variance. An improved training set where the influence of other important environmental variables (e.g. total organic carbon, total nitrogen, Mg) was reduced, comprised 40 samples from 31 lakes, and was used to construct a transfer function for lacustrine arcellaceans for sedimentary phosphorus (Olsen P) using tolerance downweighted weighted averaging (WA-Tol) with inverse deshrinking (RMSEP jack-77pp; r 2 jack= 0.68). The inferred reconstruction indicates that OP levels remained near presettlement background levels from settlement in the late AD 1970s through to the early AD 1970s. Since OP runoff from both forests and pasture is minimal, early agricultural land use within the lake catchment was as most likely pasture and/or was used to grow perennial crops such as Timothy-grass for hay. A significant increase in inferred OP concentration beginning~AD 1972 may have been related to a change in crops (e.g. corn production) in the catchment resulting in more runoff, and the introduction of chemical fertilizers. A dramatic decline in OP after AD 1985 probably corresponds to a reduction in chemical fertilizer use related to advances in agronomy, which permitted a more precise control over required fertilizer application. Another significant increase in OP levels after~AD 1995 may have been related to the construction of a large golf course upslope and immediately to the north of Haynes Lake in AD 1993, where significant fertilizer use is required to maintain the fairways. These results demonstrate that arcellaceans have great potential for reconstructing lake water geochemistry and will complement other proxies (e.g. diatoms) in paleolimnological research.
Coastal Western Hemlock biogeoclimatic zone Marine palynology Aleutian Low pressure system Sedime... more Coastal Western Hemlock biogeoclimatic zone Marine palynology Aleutian Low pressure system Sediments collected in a 12-m long core (VEC02A04) obtained from Frederick Sound in the Seymour-Belize Inlet Complex of British Columbia were deposited between ca. 4540 cal. yr BP and ca. 1090 cal. yr BP in primarily dysoxic conditions. The sediments are characterized by alternating intervals of fine grained massive and laminated units. Laminated sediments consist of light-coloured diatom-rich layers deposited during summer and dark-coloured mineral-rich layers deposited during winter. Laminated sediments are most common in portions of the core deposited between ca. 2840 cal. yr BP and ca. 1820 cal. yr BP, and correspond to a decline in the relative abundance and pollen accumulation rate of Cupressaceae pollen between ca. 3190 cal. yr BP and ca. 2250 cal. yr BP. The preservation of laminated units and decline of Cupressaceae pollen at this time suggest that a drier and possibly cooler climate punctuated otherwise wet and temperate late Holocene conditions in the Seymour-Belize Inlet Complex. We correlate the occurrence of the mid-late Holocene dry climate interval documented in Frederick Sound to dynamics in the relative position and intensity of the Aleutian Low pressure system and suggest that climate change associated with dynamics of this semi-permanent air mass affected primary productivity and vegetation of the Seymour-Belize Inlet Complex.
Foraminifera and thecamoebian distribution along two marsh transects, in the Waump (WIR 16) and W... more Foraminifera and thecamoebian distribution along two marsh transects, in the Waump (WIR 16) and Wawwat'l (WIR 12) Indian Reserves, in the Seymour-Belize Inlet Complex, north coastal British Columbia were investigated. Based on Q-and R-mode cluster analysis of the faunal distributions three high abundance, low diversity faunal assemblages were identified; the Freshwater, Brackish and High Salt Marsh Assemblages. The Freshwater Assemblage is dominated by the soil thecamoebian species Cyclopyxis kahli, a significant presence of centropyxids and Nebela collaris. The Brackish Assemblage is characterized by abundant centropyxids and less than 10% foraminifera. The High Salt Marsh Assemblage is characterized by the dominance of Balticammina pseudomacrescens. The results of this study show the high potential of combined thecamoebian/foraminifera analyses for paleo-sea level research under lower salinity marsh conditions.
A pollen‐based study from Tiny Lake in the Seymour‐Belize Inlet Complex of central coastal Britis... more A pollen‐based study from Tiny Lake in the Seymour‐Belize Inlet Complex of central coastal British Columbia, Canada, permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change. Open Pinus parklands grew at the site during the early Lateglacial when the climate was cool and dry, but more humid conditions in the later phases of the Lateglacial permitted mesophytic conifers to colonise the region. Early Holocene conditions were warmer than present and a successional mosaic of Tsuga heterophylla and Alnus occurred at Tiny Lake. Climate cooling and moistening at 8740 ± 70 14C a BP initiated the development of closed, late successional T. heterophylla–Cupressaceae forests, which achieved modern character after 6860 ± 50 14C a BP, when a temperate and very wet climate became established. The onset of early Holocene climate cooling and moistening at Tiny Lake may have preceded change at more southern locations, including within the Seymour‐B...
We examine mid-to late Holocene centennial-scale climate variability in Ireland using proxy data ... more We examine mid-to late Holocene centennial-scale climate variability in Ireland using proxy data from peatlands, lakes and a speleothem. A high degree of between-record variability is apparent in the proxy data and significant chronological uncertainties are present. However, tephra layers provide a robust tool for correlation and improve the chronological precision of the records. Although we can find no statistically significant coherence in the dataset as a whole, a selection of high-quality peatland water table reconstructions co-vary more than would be expected by chance alone. A locally weighted regression model with bootstrapping can be used to construct a 'best-estimate' palaeoclimatic reconstruction from these datasets. Visual comparison and cross-wavelet analysis of peatland water table compilations from Ireland and Northern Britain shows that there are some periods of coherence between these records. Some terrestrial palaeoclimatic changes in Ireland appear to coincide with changes in the North Atlantic thermohaline circulation and solar activity. However, these relationships are inconsistent and may be obscured by chronological uncertainties. We conclude by suggesting an agenda for future Holocene climate research in Ireland.
Pollen and plant macrofossils are often well-preserved in coastal sediments, providing a palaeoen... more Pollen and plant macrofossils are often well-preserved in coastal sediments, providing a palaeoenvironmental record of sea-level and landscape change. In this study, we examine the pollen and plant macrofossil assemblages of a well-dated saltmarsh sediment core from southwest Newfoundland, Canada, to establish recent coastal vegetation and land use change, to increase the knowledge of anthropogenic activities in the area and develop pollen chronozones for reconstructing marsh accumulation rates and to examine the representation of plant macrofossil remains in the wetland pollen profile. Grouping the pollen record into upland and wetland assemblages allows local events related to hydrological change to be separated from landscape-scale changes. The wetland pollen and plant macrofossil records indicate a general acceleration in sea-level rise ca.ad1700. The sedge pollen and plant macrofossil records attest to multiple phases of rhizome encroachment during inferred periods of marine re...
Late Holocene climate and chemical change at high latitudes: case studies from contaminated sites... more Late Holocene climate and chemical change at high latitudes: case studies from contaminated sites in subarctic and arctic Canada Jennifer M. Galloway (1), Darryl Cooney (2), Carley Crann (2), Hendrik Falck (3), Dana Howell (4), Heather Jamieson (4), Andrew Macumber (2), Nawaf Nasser (2), Michael Palmer (5), R. Timothy Patterson (2), Michael Parsons (1), Helen M. Roe (6), Hamed Sanei (1), Christopher Spence (7), Drew Stavinga (4), and Graeme T. Swindles (8)
Testate lobose amoebae of the order Arcellinida are a diverse, cosmopolitan group of shelled prot... more Testate lobose amoebae of the order Arcellinida are a diverse, cosmopolitan group of shelled protists found in many environments, including freshwater habitats, peatlands, and soils. Their decay-resistant tests make them an important fossil group for reconstructing Quaternary environments. Within the family Difflugidae Stein, 1859 more than 300 species and 200 sub-species have been attributed to the genus Difflugia Leclerc, 1815. Although carried out on only a few taxa, molecular evidence has demonstrated that test morphology is more important than test composition in categorizing distinct taxa within the Arcellinida. The type species of Difflugia, D. proteiformis Lamarck, 1816, is characterized by a terminal aperture and an elongate acuminate test. The morphology of D. proteiformis is vastly different from most species assigned to Difflugia, explaining its polyphyletic status. We reclassify Difflugia bidens Penard, 1902 as type species of Erugomicula, a new genus within the Difflugidae, which is distinguished from other taxa within Difflugia by its broad, ovoid test, and distinct compression. Based on the compressed morphology of the test, which is not a characteristic of the Difflugiidae, we tentatively assign Erugomicula to the family Hyalospheniidae.
Arcellaceans (testate lobose amoebae) were examined for 61 sediment surface samples from lakes in... more Arcellaceans (testate lobose amoebae) were examined for 61 sediment surface samples from lakes in the vicinity of the Giant Mine near Yellowknife, Northwest Territories to; (1) quantify the impact of the mine on the Baker Creek Watershed region, (2) determine the utility of arcellaceans as indicators of arsenic and heavy metal contamination and gauge the success of remediation efforts. Several statistical methods, including cluster analysis, Deterended Correspondence Analysis (DCA), and Redundancy Analysis (RDA), were used to quantify the impact of mining activity on the arcellacean assemblages. Cluster analysis revealed five arcellacean assemblages associated with a range of environmental conditions (e.g. polluted, transitional and remediated). Partial RDA results confirm that arsenic has the greatest influence on the arcellacean distribution, explaining 10.7% of the total variance. Stress-indicating species (e.g. Centropyxids) correlate with high arsenic concentrations, while species characteristic of more healthy lake conditions (e.g. Difflugids) dominate sites with significantly lower arsenic concentrations.
We examined late Holocene (ca. 3300 yr BP to present-day) climate variability in the central Nort... more We examined late Holocene (ca. 3300 yr BP to present-day) climate variability in the central Northwest Territories (Canadian Subarctic) using a diatom and sedimentological record from Danny's Lake (63.48ºN, 112.54ºW), located 40 km southwest of the modern-day treeline. High-resolution sampling paired with a robust age model (25 radiocarbon dates) allowed for the examination of both lake hydroecological conditions (30-year intervals; diatoms) and sedimentological changes in the watershed (12-year intervals; grain size records) over the late Holocene. Time series analysis of key lake ecological indicators (diatom species Aulacoseira alpigena, Pseudostaurosira brevistriata and Achnanthidium minutissimum) and sedimentological parameters, reflective of catchment processes (coarse silt fraction), suggests significant intermittent variations in turbidity, pH and light penetration within the lake basin. In the diatom record, we observed discontinuous periodicities in the range of ca. 69, 88-100, 115-132, 141-188, 562, 750 and 900 years (>90% and >95% confidence intervals), whereas the coarse silt fraction was characterized by periodicities in the >901 and <61-year range (>95% confidence interval). Periodicities in the proxy data from the Danny's Lake sediment core align with changes in total solar irradiance over the past ca. 3300 yr BP and we hypothesize a link to the Suess Cycle, Gleissberg Cycle and Pacific Decadal Oscillation via occasional inland propagation of shifting air masses over the Pacific Ocean. This research represents an important baseline study of the underlying causes of climate variability in the Canadian Subarctic and provides details on the long-term climate variability that has persisted in this region through the past three thousand years.
Frame Lake, located within the city of Yellowknife, Northwest Territories, Canada, has been ident... more Frame Lake, located within the city of Yellowknife, Northwest Territories, Canada, has been identified as requiring significant remediation due to its steadily declining water quality and inability to support fish by the 1970s. Former gold mining operations and urbanization around the lake have been suspected as probable causes for the decline in water quality. While these land-use activities are well documented, little information is available regarding their impact on the lake itself. For this reason, Arcellinida, a group of shelled protozoans known to be reliable bioindicators of land-use change, were used to develop a hydroecological history of the lake. The purpose of this study was to use Arcellinida to: (1) document the contamination history of the lake, particularly related to arsenic (As) associated with aerial deposition from mine roaster stacks; (2) track the progress of water quality deterioration in Frame Lake related to mining, urbanization and other activities; and (3...
Arcellininids (testate amoebae) were examined from 61 surface sediment samples collected from 59 ... more Arcellininids (testate amoebae) were examined from 61 surface sediment samples collected from 59 lakes in the vicinity of former gold mines, notably Giant Mine, near Yellowknife, Northwest Territories, Canada to determine their utility as bioindicators of arsenic (As), which occurs both as a byproduct of gold extraction at mines in the area and ore-bearing outcrops. Cluster analysis (Q-R-mode) and detrended correspondence analysis (DCA) reveal five arcellininid assemblages, three of which are related to varying As concentrations in the sediment samples. Redundancy analysis (RDA) showed that 14 statistically significant environmental parameters explained 57 % of the variation in faunal distribution, while partial RDA indicated that As had the greatest influence on assemblage variance (10.7 %; p < 0.10). Stress-indicating species (primarily centropyxids) characterized the faunas of samples with high As concentrations (median = 121.7 ppm, max > 10000 ppm, min = 16.1 ppm, n = 32),...
This is a repository copy of Sediment accumulation rates in subarctic lakes: Insights into age-de... more This is a repository copy of Sediment accumulation rates in subarctic lakes: Insights into age-depth modeling from 22 dated lake records from the Northwest Territories, Canada.
A multiproxy analysis was carried out on diatom, foraminiferal and macrophyte assemblages across ... more A multiproxy analysis was carried out on diatom, foraminiferal and macrophyte assemblages across the saltmarsh at Zeballos, Vancouver Island, British Columbia. To determine which group, or combination of groups provided the most accurate elevational zonations, 36 stepwise multiple linear regressions (SMLR) were carried out using a variety of data transformations on an elevational training set. Adjusted R 2 values yielded statistically significant results in all analyses as follows: foraminifera (0.658-0.870); diatoms (0.888-0.974); macrophytes (0.671-0.844); foraminifera/diatoms (0.941-0.981); foraminifera/diatoms/macrophytes (0.958-0.993). The most realistic SMLR results were obtained when data transformations comprised of (ln) normalized fractional abundance data was carried out on species present in statistically significant numbers (NrfaEQ). Of the individual proxies assessed, diatoms yielded the most significant adjusted R 2 results, with the low marsh diatom Achnanthes hauckiana being one of the most important predictor variables (pv's). Amongst the foraminifera, the low marsh species Miliammina fusca and high marsh Balticammina pseudomacrescens were determined to be the most significant pv's. For macrophytes, the low marsh species Carex lyngbyei, the high marsh species Juncus balticus, Shannon-Wiener Diversity Index (SDI) and absence of plant cover on the tidal flat were the most important pv's. As SMLR analysis of all individual groups and combinations of groups yielded statistically significant results, the choice of proxies, or combinations of proxies that are suitable for paleo-sea level research is at the discretion of the researcher.
Proxy records derived from ombrotrophic peatlands provide important insights into climate change ... more Proxy records derived from ombrotrophic peatlands provide important insights into climate change over decadal to millennial timescales. We present mid-to late-Holocene humification data and testate amoebae-derived water table records from two peatlands in Northern Ireland. We examine the replication of periodicities in these proxy climate records, which have been precisely linked through tephrochronology. Age-depth models are constructed using a Bayesian piece-wise linear accumulation model and chronological errors are calculated for each profile. A Lomb-Scargle Fourier transform-based spectral analysis is used to test for statistically significant periodicities in the data. Periodicities of c. 130, 180, 260, 540 and 1160 years are present in at least one proxy record at each site. The replication of these periodicities provides persuasive evidence that they are a product of allogenic climate controls, rather than internal peatland dynamics. A technique to estimate the possible level of red-noise in the data is applied and demonstrates that the observed periodicities cannot be explained by a first-order autoregressive model. We review the periodicities in the light of those reported previously from other marine and terrestrial climate proxy archives to consider climate forcing parameters.
Testate amoebae have been used widely as a proxy of hydrological change in ombrotrophic peatlands... more Testate amoebae have been used widely as a proxy of hydrological change in ombrotrophic peatlands, although their response to abiotic controls in other types of mire and fenland palaeo-environments is less well understood. This paper examines the response of testate amoebae to hydroseral and other environmental changes at Mer Bleue Bog, Ontario, Canada, a large ombrotrophic peatland, which evolved from a brackish-water embayment in the early Holocene. Sediments, plant macrofossils and diatoms examined from a 5.99 m core collected from the dome of the bog record six stages of development: i) a quiet, brackish-water riverine phase (prior to ca. 8500 cal BP); ii) a shallow lake (ca. 8500 e8200 cal BP); iii) fen (8200e7600 cal BP); iv) transitional mire (7600e6900 cal BP); v) pioneer raised mire (6900e4450 cal BP); and vi) ombrotrophic bog (4450 cal BP-present). Testate amoebae, notably small (<25 mm diameter) specimens of Centropyxis aculeata type, first appear in low abundances in sediments ascribed to the lacustrine phase. Diatoms from the same horizons record a shallowing in water depth, a decline in salinity and the development of emergent macrophytic vegetation, which may have provided favourable conditions for testate amoeba colonization. The testate amoeba communities of the inferred fen phase are more diverse and include centropyxids, cyclopyxids, Arcellidae and Hyalospheniidae, although the assemblages show some differences to those recently reported in modern European fen environments. The FeneBog Transition (FBT) is also dominated by C. aculeata type. The change in testate amoeba communities around this key transition is apparent in the results of Detrended Correspondence Analysis (DCA), and appears to reflect a latent nutrient gradient and a secondary moisture gradient. DCA analyses of plant macrofossil remains around the FBT show a similar trend, although the sensitivity of the two proxies to the inferred environmental changes differs. Comparisons with other regional mid-Holocene peatland records confirm the important influence of reduced effective precipitation on the testate amoeba communities during the initiation and development of Sphagnum-dominated, raised bog communities.
Arcellacea (testate lobose amoebae) communities were assessed from 73 sediment-water interface sa... more Arcellacea (testate lobose amoebae) communities were assessed from 73 sediment-water interface samples collected from 33 lakes in urban and rural settings within the Greater Toronto Area (GTA), Ontario, Canada, as well as from forested control areas in the Lake Simcoe area, Algonquin Park and eastern Ontario. The results were used to: (1) develop a statistically rigorous arcellacean-based training set for sedimentary phosphorus (Olsen P (OP)) loading; and (2) derive a transfer function to reconstruct OP levels during the post-European settlement era (AD1870s onward) using a chronologically well-constrained core from Haynes Lake on the environmentally sensitive Oak Ridges Moraine, within the GTA. Ordination analysis indicated that OP most influenced arcellacean assemblages, explaining 6.5% (p b 0.005) of total variance. An improved training set where the influence of other important environmental variables (e.g. total organic carbon, total nitrogen, Mg) was reduced, comprised 40 samples from 31 lakes, and was used to construct a transfer function for lacustrine arcellaceans for sedimentary phosphorus (Olsen P) using tolerance downweighted weighted averaging (WA-Tol) with inverse deshrinking (RMSEP jack-77pp; r 2 jack= 0.68). The inferred reconstruction indicates that OP levels remained near presettlement background levels from settlement in the late AD 1970s through to the early AD 1970s. Since OP runoff from both forests and pasture is minimal, early agricultural land use within the lake catchment was as most likely pasture and/or was used to grow perennial crops such as Timothy-grass for hay. A significant increase in inferred OP concentration beginning~AD 1972 may have been related to a change in crops (e.g. corn production) in the catchment resulting in more runoff, and the introduction of chemical fertilizers. A dramatic decline in OP after AD 1985 probably corresponds to a reduction in chemical fertilizer use related to advances in agronomy, which permitted a more precise control over required fertilizer application. Another significant increase in OP levels after~AD 1995 may have been related to the construction of a large golf course upslope and immediately to the north of Haynes Lake in AD 1993, where significant fertilizer use is required to maintain the fairways. These results demonstrate that arcellaceans have great potential for reconstructing lake water geochemistry and will complement other proxies (e.g. diatoms) in paleolimnological research.
Coastal Western Hemlock biogeoclimatic zone Marine palynology Aleutian Low pressure system Sedime... more Coastal Western Hemlock biogeoclimatic zone Marine palynology Aleutian Low pressure system Sediments collected in a 12-m long core (VEC02A04) obtained from Frederick Sound in the Seymour-Belize Inlet Complex of British Columbia were deposited between ca. 4540 cal. yr BP and ca. 1090 cal. yr BP in primarily dysoxic conditions. The sediments are characterized by alternating intervals of fine grained massive and laminated units. Laminated sediments consist of light-coloured diatom-rich layers deposited during summer and dark-coloured mineral-rich layers deposited during winter. Laminated sediments are most common in portions of the core deposited between ca. 2840 cal. yr BP and ca. 1820 cal. yr BP, and correspond to a decline in the relative abundance and pollen accumulation rate of Cupressaceae pollen between ca. 3190 cal. yr BP and ca. 2250 cal. yr BP. The preservation of laminated units and decline of Cupressaceae pollen at this time suggest that a drier and possibly cooler climate punctuated otherwise wet and temperate late Holocene conditions in the Seymour-Belize Inlet Complex. We correlate the occurrence of the mid-late Holocene dry climate interval documented in Frederick Sound to dynamics in the relative position and intensity of the Aleutian Low pressure system and suggest that climate change associated with dynamics of this semi-permanent air mass affected primary productivity and vegetation of the Seymour-Belize Inlet Complex.
Foraminifera and thecamoebian distribution along two marsh transects, in the Waump (WIR 16) and W... more Foraminifera and thecamoebian distribution along two marsh transects, in the Waump (WIR 16) and Wawwat'l (WIR 12) Indian Reserves, in the Seymour-Belize Inlet Complex, north coastal British Columbia were investigated. Based on Q-and R-mode cluster analysis of the faunal distributions three high abundance, low diversity faunal assemblages were identified; the Freshwater, Brackish and High Salt Marsh Assemblages. The Freshwater Assemblage is dominated by the soil thecamoebian species Cyclopyxis kahli, a significant presence of centropyxids and Nebela collaris. The Brackish Assemblage is characterized by abundant centropyxids and less than 10% foraminifera. The High Salt Marsh Assemblage is characterized by the dominance of Balticammina pseudomacrescens. The results of this study show the high potential of combined thecamoebian/foraminifera analyses for paleo-sea level research under lower salinity marsh conditions.
A pollen‐based study from Tiny Lake in the Seymour‐Belize Inlet Complex of central coastal Britis... more A pollen‐based study from Tiny Lake in the Seymour‐Belize Inlet Complex of central coastal British Columbia, Canada, permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change. Open Pinus parklands grew at the site during the early Lateglacial when the climate was cool and dry, but more humid conditions in the later phases of the Lateglacial permitted mesophytic conifers to colonise the region. Early Holocene conditions were warmer than present and a successional mosaic of Tsuga heterophylla and Alnus occurred at Tiny Lake. Climate cooling and moistening at 8740 ± 70 14C a BP initiated the development of closed, late successional T. heterophylla–Cupressaceae forests, which achieved modern character after 6860 ± 50 14C a BP, when a temperate and very wet climate became established. The onset of early Holocene climate cooling and moistening at Tiny Lake may have preceded change at more southern locations, including within the Seymour‐B...
We examine mid-to late Holocene centennial-scale climate variability in Ireland using proxy data ... more We examine mid-to late Holocene centennial-scale climate variability in Ireland using proxy data from peatlands, lakes and a speleothem. A high degree of between-record variability is apparent in the proxy data and significant chronological uncertainties are present. However, tephra layers provide a robust tool for correlation and improve the chronological precision of the records. Although we can find no statistically significant coherence in the dataset as a whole, a selection of high-quality peatland water table reconstructions co-vary more than would be expected by chance alone. A locally weighted regression model with bootstrapping can be used to construct a 'best-estimate' palaeoclimatic reconstruction from these datasets. Visual comparison and cross-wavelet analysis of peatland water table compilations from Ireland and Northern Britain shows that there are some periods of coherence between these records. Some terrestrial palaeoclimatic changes in Ireland appear to coincide with changes in the North Atlantic thermohaline circulation and solar activity. However, these relationships are inconsistent and may be obscured by chronological uncertainties. We conclude by suggesting an agenda for future Holocene climate research in Ireland.
Pollen and plant macrofossils are often well-preserved in coastal sediments, providing a palaeoen... more Pollen and plant macrofossils are often well-preserved in coastal sediments, providing a palaeoenvironmental record of sea-level and landscape change. In this study, we examine the pollen and plant macrofossil assemblages of a well-dated saltmarsh sediment core from southwest Newfoundland, Canada, to establish recent coastal vegetation and land use change, to increase the knowledge of anthropogenic activities in the area and develop pollen chronozones for reconstructing marsh accumulation rates and to examine the representation of plant macrofossil remains in the wetland pollen profile. Grouping the pollen record into upland and wetland assemblages allows local events related to hydrological change to be separated from landscape-scale changes. The wetland pollen and plant macrofossil records indicate a general acceleration in sea-level rise ca.ad1700. The sedge pollen and plant macrofossil records attest to multiple phases of rhizome encroachment during inferred periods of marine re...
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Papers by Helen Roe