South-central Ontario Research Articles

Responses of Benthic Communities to Episodic Acid Disturbances in a Lake Outflow Stream at the Experimental Lakes Area, Ontario

Effects of episodic experimental pH depressions on water chemistry and structure of benthic communities were investigated in northwestern Ontario, a location with low H+ deposition. Acidity levels were increased from background values of pH 6.9 to 5.0, 4.5, and 4.0 to simulate snowmelt and rainstorm events observed in south-central Ontario. Conductivity and concentrations of Ca and Mn increased significantly for all three pH disturbances. Fe and dissolved organic C remained unchanged at pH 4.5 and 4.0 but Fe increased at pH 5.0. Total and inorganic monomeric Al increased at pH 4.5 and 4.0 relative to reference areas. At pH 5.0, density decreases were observed for Baetis, Ectemnia, Simulium, and Prosimulium, at pH 4.5 for Baetis, Lepidostoma, Micropsectra, Simulium, and Prosimulium, and at pH 4.0 for Baetis, Tanytarsus, and Cricotopus. Densities of collector/filterers and clingers decreased at all pH levels, but diversity decreased in the experimental reach at pH 4.0 only. Drift density of the above genera was correlated with H+ concentration. Large reductions in macroinvertebrate densities occurred at higher pH (5.0) and during shorter exposure times compared with previous experiments in areas of higher H+ deposition in south-central Ontario and New Hampshire.

Metal concentrations in chrionomids in relation to peatland geochemistry

Concentrations of Zn, Cu, Al, Fe, and Mn were determined in Chironomidae (Diptera) larvae sampled from three sites within eight peatlands, located in south-central Ontario, Canada. The eight peatlands displayed a range in pH and alkalinity and were classified abiotically (i.e., chemically, hydrologically) and biotically (i.e., dominant vegetation present) as mineral-poor, moderately poor, or as mineral-rich fen. Surface peats of mineral-poor fens were distinct from those of moderately poor and mineral-rich fens; mineral-poor fens contained higher concentrations of organic matter with low concentrations of easily reducible Mn vs. the moderately poor and mineral rich fens. A one-way nested ANOVA indicated that chironomid metal concentrations were peatland dependent (P<0.05). To determine if differences in chironomid metal concentrations among the peatlands could be related to peat geochemistry, an R2 MAX procedure using peat geochemistry as the independent variable and chironomid metal concentrations as the dependent variable was applied. Peat geochemistry was defined as concentrations of peat organic matter, reducible Fe (Fe oxides), reducible Mn (Mn oxides) and easily reducible metal (where metal = Zn, Cu, Al, Mn and Fe), and reducible metal and organically bound metal. Chironomids from mineralrich peatlands, i.e., peatlands low in organic matter with high concentrations of reducible Mn and Fe or easily extractable metal contained greater concentrations of Zn, Mn, and Fe vs. chironomids sampled from mineral poor peatlands, i.e., peatlands with high concentrations of peat organic matter and low concentrations of reducible Mn or easily extractable metal. In contrast, Cu concentrations were greatest in larvae sampled from mineral-poor vs. mineral-rich peatlands. Aluminum larvae concentrations were independent of peat geochemistry. We suggest that bioavailability of metals such as Zn, Fe, and Mn will be greater to invertebrates inhabiting mineral rich vs. mineral poor fens, whereas greater chironomid Cu concentrations will be found in chironomids sampled from mineral poor fens. Differences in metal availability to invertebrates among peatland types has important implications when comparing the impact of contaminant transfer to higher trophic levels among different types of peatlands.

Throughfall and stemflow chemistry under deciduous and coniferous forest canopies in south-central Ontario

By measuring incident precipitation, throughfall, and stemflow chemistry, the roles of coniferous- and deciduous-dominated forest canopies as a source of and sink for ions in precipitation were examined. A regression technique for distinguishing between external (dry deposition) and internal (canopy leaching) sources of ions in the throughfall flux was evaluated. The effect of seasonal changes in the forest canopy on throughfall and stemflow chemistry was also examined. Throughfall comprised 74 and 84%, respectively, of the hydrologic flux at the coniferous and deciduous sites. Sulphate fluxes were highest at the coniferous site during both growing and dormant seasons, suggesting either a higher scavenging efficiency of the needles for atmospheric SO42−, or higher SO42− leaching from the foliage. The deciduous site neutralized acidic inputs, as demonstrated by its net negative H+ flux year round. The buffering capacity of the coniferous forest was exceeded by the higher amount of acid interception by the canopy. Nitrate behaved conservatively and base ions were exported from the canopy. Stemflow contributions of ions, although low, were generally higher than the contribution of stemflow to the hydrologic flux (2–3%). Independent dry deposition measurements for the growing season, when compared with net SO42− flux, overestimated dry deposition collected by the deciduous canopy, but were comparable to the flux at the coniferous site. These data suggest that dry SO2−SO42− deposition may be responsible for all SO42− enrichment seen in throughfall at these sites. A regression technique for separating internal and external ion sources in throughfall yielded inconsistent results, and attributed virtually all ion enrichment to internal sources. Problems with false assumptions and spurious correlations are discussed. We conclude that this method is not satisfactory for separating ion sources. Seasonal patterns in throughfall chemistry are present. During the growing seasons bases exchange for H+ and are exported similarly with SO42−. Hydrogen retention mirrors SO42− export. Base cations (particularly K+) are leached from the canopy primarily during senescence, but from the stem of the tree primarily during the dormant period. This was most evident at the deciduous site. Chloride behaved in a similar manner, while NH4+ and H+ were retained during the senescent period.

Macroforms, large bedforms and rhythmic sedimentary sequences in subglacial eskers, south-central Ontario: implications for esker genesis and meltwater regime

Eskers of south-central Ontario were deposited in closed, subglacial conduits which were continuous (main conduits). This interpretation is supported by: the intimate association of eskers with an anastomosing network of tunnel channels; relatively continuous esker ridges; minimal post-formational disturbance of esker sediments; intercalation of till and stratified sand and gravel; diapiric folding at an esker core; low variability in palaeocurrent direction; and upslope flow paths. Down-esker trends in clast lithology, roundness and sphericity indicate continuous conduits with sediment supply by subglacial deformation of adjacent material into the conduits, melt-out of sediment from the conduit walls, and fluvial resedimentation.Esker ridge morphology is attributed to synchronous erosion, transportation and deposition along the main conduits, such that ridge discontinuities are primarily explained as zones of non-deposition during esker formation. Composite, pseudoanticlinal, and oblique accretion avalanche bed macroforms are identified. Gravel facies within these macroforms were deposited from fluidal flows or hyperconcentrated dispersions. Progradation of macroforms or migration of constituent large bedforms through the main conduits may have temporarily blocked constricted portions of those conduits and acted as possible internal (autogenic) controls on sediment availability and flow resistance. The location of macroforms within conduits was primarily controlled by conduit geometry and sediment availability, and later by feedback between macroform and conduit geometries.Sand and gravel units alternate rhythmically in vertical section. Rhythmicity is interpreted as a response to episodic flood flows, controlled by seasonal changes in water supply, but not necessarily representing annual events. Fans, beads, anabranched reaches and extended, hummocky deposits are intimately associated with the main esker ridges. They are interpreted in terms of subglacial cavities and localized flotation zones, connected to the main conduits during flood events. In-phase wave structures are the products of hydraulic jumps in hyperconcentrated flood flows at flow expansions into swells within the main conduits, into cavities connected to the main conduits, or at a grounding line. Esker ridges record only the most powerful flood events, whereas fans and beads record flow events in finer detail, being primarily depositional reservoirs. Laterally fining deposits record the waning stages of conduit operation.

Tunnel channels and associated landforms, south-central Ontario: their implications for ice-sheet hydrology

The Peterborough–Trenton drumlin field and associated meltwater erosion marks (s-forms) were interpreted as the products of erosion by turbulent separated flows within a catastrophically released subglacial meltwater sheet, the Algonquin event. Recent theoretical modelling of ice-sheet hydrology suggests progressive channelization of meltwater during the collapse of such a sheet. Inductive testing of this hypothesis using observations in south-central Ontario forms the crux of this paper. A geometric model of the interaction of rough ice base and bed surfaces gives inferred meltwater flow patterns. Such a rough interactive geometry is suggested as the bed is drumlinized, and flows responsible for drumlins may be expected to have eroded similar forms into the ice base. Three landforms in south-central Ontario; namely tunnel channels, megachannels, and late-stage sheet-flow scours, are described, and interpreted as evidence of progressive channelization and flow diversion processes, governed by the geometric interactions between the recoupling ice base and its bed and thermodynamic feedbacks within an increasingly discontinuous meltwater sheet. Some fields of transverse ridges within tunnel channels may record meltwater deposition towards the end of the Algonquin event. By contrast, eskers within tunnel channels record a return to seasonally driven meltwater drainage. The Dummer Moraine and the Oak Ridges complex are integrated into a new landform–vent sequence for south-central Ontario which provides a framework for further field testing.

Paleolimnological assessment of damage to fish communities in three acidic, Canadian Shield lakes

Long-term fisheries data from small lakes are often sadly lacking. We employ three classes of sedimentary remains (mandibles of larval Chaoborus, diatom valves and chrysophyte scales) to verify that the fish communities of three small, acidic (pH 5.3–5.6) Canadian Shield lakes in south-central Ontario were richer 20–100 years ago at a time when the lakes were almost certainly less acidic. To do this, we first verify that Chaoborus americanus is never abundant in the presence of fish using data from a new survey of 50 lakes that corrects for methodological flaws of the past. We then examine changes with sediment depth in our three classes of indicators in Lakes Drummer, Little Eastern, and Shoelace. In all cases, appearrances of Chaoborus americanus and changes among algl remains in recent sediments suggest that fish were lost at a time when lake waters were acidifying, particulary because of pH depressions during spring melt. These results contribute to a growing body of literature indicating that the use of multiple sedimentary indicators can provide assessments of past limnological conditions that are of interest to both lake managers and aquatic ecologists. They also suggest that the fish communities of some small, currently acidic lakes in south-central Ontario were almost certainly richer in the past.

The Significance of New Faunal Identifications Attributed to an Early Paleoindian (Gainey Complex) Occupation at the Udora Site, Ontario, Canada

Analysis of calcined bone from the Udora site in south-central Ontario, Canada, indicates that the subsistence of Early Paleoindian (Gainey complex) peoples in the lower Great Lakes region included a mix of both large and small mammals: caribou, hare, and arctic fox. The presence of arctic fox and other paleoecological data indicate that the Paleoindian occupation at Udora occurred in a spruce parkland environment between 10,000 and 10,500 years ago, the minimum age of that habitat, or earlier. Evidence that Paleoindian peoples in northeastern North America also hunted caribou suggests that the concept of a “northern” adaptive zone in the greater Northeast (including the Great Lakes region) has some validity; however, the presence of both parkland and forested environments in this zone and presumed caribou behavioral responses to those environments indicate that Paleoindian adaptations to caribou may have been quite variable.

Chlorinated hydrocarbons and shell thinning in eggs of (Accipiter) hawks in Ontario, 1986-1989.

Eggs of sharp-shinned hawks (Accipiter striatus), Cooper's hawks (A. cooperii), and northern goshawks (A. gentilis) were collected from nests in south-central Ontario from 1986 to 1989. Detectable levels of the chlorinated hydrocarbons DDE, DDT, DDD, mirex, photomirex, cis-nonachlor, trans-nonachlor, oxychlordane, dieldrin, heptachlor expoxide, HCB and PCB were present in all the eggs analyzed. Mean contaminant levels were highest in sharp-shinned hawks, slightly lower in Cooper's hawks, and significantly lower in goshawks; for example, mean DDE values were 7.23, 4.48 and 0.90 mg kg(-1) (wet weight), respectively. Total PCB levels were generally less than 1.5 mg kg(-1), lower than those associated with reproductive effects in field and laboratory studies with other species. Mean shell thicknesses of sharp-shinned and Cooper's hawk eggs were significantly less than mean pre-DDT era thicknesses (-10 and -8%, respectively), reductions that were probably not relevant to reproductive success. Goshawk eggs exhibited no significant reduction in shell thickness. Contaminant levels among the three species probably reflect differing food habits and migratory patterns.

The role of surface and sub-surface runoff processes in controlling cation export from a wetland watershed

Water and cation budgets were calculated for two sub-basins within a small low relief watershed in South-Central Ontario during a period of ephemeral runoff which was initiated by spring snow melt. The hydrology of one (upland) sub-basin was strongly influenced by seasonal fluctuations in the level of regional ground water. Saturated contributing areas formed in low lying regions adjacent to the stream channel where the water table rose to the surface, and stream discharge was a mixture of ground water and saturation overland flow. In the second sub-basin a wetland provided a large and spatially less variable saturated contributing area. Clay soils underlying the wetland resulted in a shallow perched water table, poorly drained and highly organic soils, and greatly reduced inputs of regional ground water. Stream discharge was largely the result of surface runoff from the wetland and adjacent areas of saturated soil.

Fish and Benthic Invertebrates: Community Concordance and Community–Environment Relationships

Fish and benthic invertebrates from 40 lakes in south-central Ontario showed significantly concordant patterns based on community structure. Fish communities were associated significantly with lake morphological characteristics, but were uncorrelated with water chemistry. Large, deep lakes differed from shallow lakes in their fish species, having richer faunas due to the additional cold-water species. Centrarchid species occurred more frequently in small, shallow lakes than in larger lakes. The invertebrate community was not correlated with lake morphology, but showed a significant association with water chemistry, principally lake pH. A strong contrast in the abundance of Chaoborus and Holopedium existed, but it was unclear whether this was due to a predator–prey relationship or to differences in acid tolerance. Although the lakes showed similar patterns in the composition of both communities, each community was associated with a different set of environmental factors. Biotic processes within and between communities explain this paradox in community–environment relationships. Such biotic interactions may involve direct processes such as fish predation on a particular invertebrate taxon or indirect factors, e.g., where fish limit the abundance of invertebrate predators, thereby limiting the impact of these invertebrate predators.

Multivariate analysis of benthic invertebrate communities: the implication of choosing particular data standardizations, measures of association, and ordination methods

Benthic invertebrate data from thirty-nine lakes in south-central Ontario were analyzed to determine the effect of choosing particular data standardizations, resemblance measures, and ordination methods on the resultant multivariate summaries. Logarithmic-transformed, 0–1 scaled, and ranked data were used as standardized variables with resemblance measures of Bray-Curtis, Euclidean distance, cosine distance, correlation, covariance and chi-squared distance. Combinations of these measures and standardizations were used in principal components analysis, principal coordinates analysis, non-metric multidimensional scaling, correspondence analysis, and detrended correspondence analysis. Correspondence analysis and principal components analysis using a correlation coefficient provided the most consistent results irrespective of the choice in data standardization. Other approaches using detrended correspondence analysis, principal components analysis, principal coordinates analysis, and non-metric multidimensional scaling provided less consistent results. These latter three methods produced similar results when the abundance data were replaced with ranks or standardized to a 0–1 range. The log-transformed data produced the least consistent results, whereas ranked data were most consistent. Resemblance measures such as the Bray-Curtis and correlation coefficient provided more consistent solutions than measures such as Euclidean distance or the covariance matrix when different data standardizations were used. The cosine distance based on standardized data provided results comparable to the CA and DCA solutions. Overall, CA proved most robust as it demonstrated high consistency irrespective of the data standardizations. The strong influence of data standardization on the other ordination methods emphasizes the importance of this frequently neglected stage of data analysis.

Effect of pH and Dissolved Organic Carbon on the Toxicity of Copper to Larval Fathead Minnow (Pimephales promelas) in Natural Lake Waters of Low Alkalinity

The impacts of pH and dissolved organic carbon (DOC) on the acute toxicity of Cu to larval fathead minnow (Pimephales promelas) were determined using natural soft water from two Precambrian Shield lakes in south-central Ontario. By artificially manipulating the pH and DOC levels of the water, we demonstrated that both acidification and the removal of DOC increased the toxicity of Cu. The 96-h Cu LC50s were determined over a pH range from 5.4 to 7.3 and a DOC concentration range from 0.2 to 16 mg∙L−1. The LC50s ranged from a low of 2 μg∙L−1(pH 5.6, DOC 0.2 mg∙L−1) to a high of 182 μg∙L−1(pH 6.9, DOC 15.6 mg∙L−1). A multiple regression model (log1096-h Cu LC50 = −0.308 + 0.192 pH + 0.136 (pH∙log10DOC)) was used to describe the relationship between Cu toxicity, pH, and DOC. The model was significant (p &lt; 0.00001) and explained 93% of the variability in the toxicity data. These results suggest that current water quality objectives for Cu, and possibly for other metals, may not be sufficiently protective of aquatic life in soft, moderately acidic water containing low levels of DOC.

Patterns of accumulation of airborne organochlorine contaminants in lichens from the Upper Great Lakes Region of Ontario

Spatial trends and patterns of accumulation of organochlorine (OC) contaminants were determined in lichen samples from 35 locations across Ontario, Canada, between 1985 and 1987. Concentrations of total DDT isomers [0.34-2.6 ng (g of dry wt) -1 ], total chlordane (0.36-1.7 ng g -1 ), and dieldrin (0.17-1.1 ng g -1 ), and dieldrin (0.17-1.1 ng g -1 ) in 1987 were significantly higher in lichen from south-central Ontario locations than samples from northern and northwestern locations, while several of the latter sites had higher levels of hexachlorocyclohexane (HCH) isomers and pentachloroanisole (P 5 -CA).

Seasonal patterns in trap catches of the crayfish Cambarus bartoni and Orconectes virilis in six south-central Ontario lakes

Crayfish were trapped in six south-central Ontario lakes to examine seasonal changes in estimates of relative abundance. Baited-trap catches of Cambarus bartoni and Orconectes virilis correlated with changes in water temperature. Cambarid catches increased in the spring until a midsummer maximum, but dropped suddenly as the water temperature began to fall in August. Ovigerous (i.e., egg-bearing) females and recently moulted males were captured by SCUBA divers in August. Trap catches increased, once breeding and moulting periods concluded, and subsequently decreased as water temperatures continued to drop in the autumn. In contrast, catches of male O. virilis increased in the spring and remained relatively constant throughout the summer until water temperatures fell in September. Catches of female O. virilis peaked somewhat later in the summer and then gradually declined in the early fall. Although the two species and the two sexes differed in the length of the midsummer sampling period when trap catches were relatively constant, similar seasonal trends among lakes suggest that midsummer trap catches can be used to estimate crayfish relative abundance. Other factors, such as the presence of smallmouth bass (Micropterus dolomieui), lake physical and chemical characteristics, and the number of co-occurring crayfish species also correlated with trap catches. Both the presence of bass and the number of co-occurring species of crayfish probably affect crayfish behaviour and activity, thereby reducing catches in baited traps, but not necessarily affecting actual population abundance. Comparisons of relative abundance based on catches from baited traps must control for these seasonal behavioural, and environmental factors.

The Ethics Committee Network of South Central Ontario (Canada).

The Ethics Committee Network of South Central Ontario (Canada).

Late quaternary stratigraphy and geochemistry of the R47 section, Rouge River Basin, south‐central Ontario, Canada: Correlation with Scarborough Bluffs

AbstractQuaternary glacial diamictons in section R47, overlying Ordovician shale in the Rouge River Basin of south‐central Ontario, are considered to be representative of older and younger Wisconsinan glacial diamictons in the field area. Field characteristics, clast composition, mineralogy, particle size and geochemistry permit delineation of two units within the sequence and subdivision of deposits that correlate with Sunnybrook and Halton diamictons of Wisconsinan age. No Wisconsinan interstadial deposits are present in the section; however, outwash sandy gravel capping the Halton diamicton was probably emplaced by a high‐energy stream draining into Lake Iroquois just prior to the incision of the Rouge Valley in the later Wisconsinan (ca. 11 000‐12 000 yr BP). A buried palaeosol, which developed in this sandy gravel and in overlying aeolian sediment, shows partial leaching of carbonates and a slight increase of clay in the palaeosol solum. The main clay‐mineral transformations in the buried palaeosol appear to involve the degradation of illite and illite‐smectite accompanied by the production of vermiculite and minor amounts of chlorite. The ground soil capping the buried palaeosol is formed in colluvium emplaced 200 ± 80 yr BP following a local forest fire; the ground soil Ahk horizon gives an age of 4000 yr in the future, probably as a result of nuclear bomb testing effects on modern radiocarbon. The presence of an A/C profile in the ground soil system, although thin, indicates that surface soils may form rapidly.The geochemistry of the two Wisconsinan diamictons shows similar calcite and SiO2‐corrected mean element concentrations, with slightly elevated levels of Ca, Sr, Hf and Lu in the younger deposit. Both diamictons are geochemically quite different from the shale bedrock in the area, indicating that the bulk of transported sediment came from outside the area.

The inventories of anthropogenic Ph, Zn, As, Cd, and the radionuclides 137Cs and excess 210Pb in lake sediments of the Adirondack region, USA

We determined the inventories of four anthropogenic trace elements, Pb, Zn, As, and Cd, and two radionuclides, 137Cs and excess 210Pb, in sediment cores collected from eight remote lakes in the Adirondack region of the northeastern United States. The inventories of all six substances vary considerably among the sediment cores, although the lakes and their associated catchments must have received similar cumulative per unit area atmospheric inputs of these substances. These variations are highly correlated, indicating that the trace elements and radionuclides are affected in a coherent way by the processes controlling their deposition to the sediments of these lakes. Assuming that the anthropogenic trace element inventories in each sediment core are enhanced or depleted relative to cumulative atmospheric deposition to the extent indicated by the sediment core inventories of either 137Cs or excess 210Pb, we produced estimates of the cumulative atmospheric inputs of the four anthropogenic trace elements to this region. Comparison of the excess 210Pb normalized anthropogenic Pb, Zn, Cd inventories of the Adirondack sediment cores with excess 210Pb normalized inventories of the same substances in a group of South Central Ontario lakes suggests that the Adirondack region has received greater cumulative anthropogenic inputs of Pb, Zn and Cd by a factor of 1.6, 4.5, and 2.9, respectively.

Subsurface Flow in a Shallow Soil Canadian Shield Watershed

Past studies in Canadian Shield headwater catchments have identified the importance of subsurface flow mechanisms in generating storm runoff. Recent work in the Muskoka-Haliburton region of south-central Ontario has suggested that subsurface flow within hillslopes with shallow soils occurs primarily along impermeable bedrock surfaces. Two trenches were dug on the side slope of a small headwater catchment and instrumented to measure flows at different levels in the soil. Results show that flow over the bedrock surface constitutes the largest component of hillslope discharge during fall rain storms. Peak discharge and recession rates for bedrock surface flow hydrographs were synchronous with channel discharge. Calculations show that this component of hillslope flow could account for the majority of peak discharge during storm events.

The distribution of dragonfly nymphs across a pH gradient in south-central Ontario lakes

Exuviae of 37 species of dragonflies were collected from the emergent vegetation of 19 small (&lt;35 ha) lakes across a pH gradient (range 4.9–8.1) in south-central Ontario to assess the effect of low environmental pH on species richness and diversity. The number of species present in a lake was not significantly correlated with lake pH. Two measures of diversity (Keefe and Bergersen's TU and McIntosh's M) indicate an increase in species diversity with decreasing lake pH. Species shifts in the communities were also correlated with lake pH: five species were apparently excluded from lakes with a midsummer epilimnetic pH below 5.8, and seven species were apparently restricted to lakes with a pH of less than 6.2.

Bythotrephes cederstroemi (Schoedler) in Muskoka Lakes: First Records of the European Invader in Inland Lakes in Canada

The large predaceous European zooplankter Bythotrephes cederstroemi is now present in eight large recreational lakes in south-central Ontario, Canada: Lake Muskoka, Lake Joseph, Lake Rosseau, Fairy Lake, Mary Lake, Peninsula Lake, Lake Vernon, and Go Home Lake. These observations represent the first evidence that B. cederstroemi has invaded inland lakes in Canada, and we suggest that close monitoring is now needed to establish whether or not pelagic food webs of the lakes will respond.