Isotopic Variations in Hamilton Harbour Water as an Indicator of Lake Ontario Exchange Flow

In September, 1993, and May, 1994, surface water samples were collected from Hamilton Harbour at the western end of Lake Ontario to determine if hydrogen and oxygen isotopes could be used to estimate the volume of lake water entering the harbor through the Burlington Canal, a shipping canal at the harbor's eastern end. In addition, the survey sought to determine if the isotopic variations were significantly different to allow mapping of the lake water plume present within the harbor. The results of this preliminary survey show a west to east enrichment in stable oxygen and hydrogen ratios. This distribution results from mixing via the Burlington Canal of lake water at the eastern end of the harbor that is enriched in ¹⁸O and ²H, with harbor water that is depleted in ¹⁸O and ²H relative to lake water. The results suggest that variations in the isotopic signature between Lake Ontario and Hamilton Harbour waters differ significantly to allow the use of oxygen and hydrogen isotopes to examine lake water-harbor water mixing relationships. A more detailed sampling will allow the amount of exchange across the Burlington Canal to be calculated, and the extent of the harbor's lake water plume to be determined.     

Volume Visualization of Temperature in Hamilton Harbour,Lake Ontario

The inner structures of lakes can be revealed using volume visualization algorithms since lakes are three-dimensional objects that are explored by taking samples at various stations and at different depths. These algorithms did not exist 20 years ago, they could only be run on supercomputers 10 years ago, on workstations 3 years ago, and now they can be run on personal computers. Using computer graphics it is now possible to combine data, their three-dimensional location, and lake topography to create images of water quality patterns which supersede conventional surface, two-dimensional, graphics. Through solid modeling, temperature data collected on 28 May 1990 and 8 August 1990 in Hamilton Harbour, Lake Ontario, are mapped into voxels and projected onto two-dimensional screens. Various three-dimensional representations of temperature data are displayed including water masses with temperatures of less than 12°C, 13 to 14°C, 16°C to 17°C, and greater than 23°C. The calculation of the 3D representations allows the computation of volumetric properties, e.g., masses, since each voxel has water quality values associated with it and these values can be summed or elaborated numerically as needs arise. For example the harbor has a volume of 254 × 10⁶ m³, and the water mass on 28 May 1990 at 12–13°C had a complex three-dimensional shape with a volume of 61 × 10⁶ m³. A third benefit of visualization is that the data can be viewed interactively from different viewpoints thus increasing the interaction between scientist and the data. These methods should also be able to be used in other limnological applications such as visualization of sediments, algal blooms, and other biological and chemical data.     

Assessing the toxicity of chemically fractionated Hamilton Harbour (Lake Ontario) sediment using selected aquatic organisms

Studies of the sediments of Hamilton Harbour, Lake Ontario, Canada, have shown variable degrees of pollution with a large number of organic and inorganic pollutants. Three areas in the Harbour – Windemere Basin, Cootes Paradise and Randle Reef – exhibited particularly high levels of contaminants, with concomitant impacts on benthic organisms. Sediment samples examined in this study were taken from a site in Randle Reef in Hamilton Harbour and a station (LE 23) in Lake Erie used as a reference sample. The samples were subjected to chemical fractionation to remove organic contaminants, with one fraction being used as total extract, and another aliquot being subjected to silica gel fractionation to give four fractions. Each fraction was chemically analysed and an aliquot used for bioassays following exchange with dimethylsulfoxide. Standard biotests were performed with Daphnia magna, Hyalella azteca, Pimephales promelas (fathead minnows) and Selenastrum capricornutum. Results from direct sediment contact bioassays indicated that sediment from Randle Reef is highly toxic, whereas the Lake Erie sample had no observable impacts. Total extract when added at 1% to the bioassays replicated the solid phase with acute toxicity for Randle Reef, and no effect on Lake Erie. For the silica gel fractionation, Fraction 1 (F1) showed similar toxicity as the total extract, even at low additions, whereas F2–4 gave variable and inconclusive results. F1 eluted with hexane contained the non‐polar fractions, predominantly the polyaromatic hydrocarbons, and these compounds are the most likely causative agents for the highly acute toxicity observed in the sediment of Randle Reef.     

Spatial ecology of reintroduced walleye (Sander vitreus) in Hamilton Harbour of Lake Ontario

Many coastal embayments in the Laurentian Great Lakes have been subjected to extensive human physical modification and pollution that has led to the loss of freshwater biodiversity. For example, Hamilton Harbour is a large coastal embayment situated at the western end of Lake Ontario, with a long history of industrial and urban development that has resulted in the loss and degradation of aquatic habitat and the extirpation of several fish species. To restore the fish community in Hamilton Harbour, several attempts have been made to increase apex predator biodiversity by reintroducing native walleye (Sander vitreus). To assess how reintroduced (i.e., stocked) walleye use Hamilton Harbour, we used acoustic telemetry to characterize the residency of individuals within the boundaries of the harbour as well as their seasonal space use, with a focused interest on the spring spawning period. During the 1?yr tracking period tagged walleye spent an average of 357?days (range 135–365?days) within the harbour. Most individuals (12/15) remained within the harbour during the entire spring spawning period, and over half of the tagged fish departed (n?=?7) at the end of summer and beginning of fall. Core use areas appeared to gradually shift more easterly as the seasons progressed from winter to summer. Results from this study indicate that stocked fish are resident within Hamilton Harbour for most of the year, including the reproductive period, which suggests that stocking efforts to re-establish walleye populations may be an effective restoration strategy if recruitment is successful.     

Organochlorine Contaminant Levels in Waterbird Species from Hamilton Harbour,Lake Ontario: an IJC Area of Concern

The levels of organochlorine (OC) contaminants in eggs and tissues of waterbird species nesting in Hamilton Harbour, Ontario, an International Joint Commission Area of Concern, were monitored between 1981 and 1992. PCBs, DDE, and mirex were present at the highest concentrations of the 29 organochlorines and one trace metal measured. Most contaminants in the various species tested showed a declining temporal pattern during that period. Double-crested cormorant eggs generally had higher concentrations of contaminants than those in herring gull eggs which in turn were higher than those in eggs of black-crowned night-herons, Caspian terns and common terns. The levels of contaminants in the eggs reflect the dietary preferences of the species with the fish-eating birds containing consistently higher accumulations of contaminants when compared to the herbivorous Canada goose for which the levels were consistently much lower for all compounds. The concentrations of contaminants detected are among some of the highest in the Great Lakes but when compared to other sites on Lake Ontario, the levels in Hamilton Harbour are generally equal or lower. Elevated levels of contaminants such as PCBs, mirex, and DDE were also detected in liver and muscle tissues of migrant waterfowl species from the harbor. Despite habitat degradation and continued presence of contaminants, the harbor supports a large number and wide variety of waterbird species. Except for black-crowned night-herons, the nesting populations of colonial waterbirds have increased between 21 and 1061 % since the last survey in 1987.     

Long-term and seasonal nitrate trends illustrate potential prevention of large cyanobacterial biomass by sediment oxidation in Hamilton Harbour,Lake Ontario

Several studies have shown that large, experimental additions of nitrate (NO₃) to eutrophic systems can mitigate large populations of nuisance cyanobacteria and that high NO₃ concentrations can oxidize anoxic sediments. These studies are consistent with observations from numerous aquatic systems across a broad trophic range showing development of reduced surficial sediments precedes the formation of large cyanobacteria populations. We use 50+ years of data to explore whether high NO₃ concentrations may have been instrumental both in the absence of large populations of cyanobacteria in eutrophic Hamilton Harbour, Lake Ontario in the 1970s when total phosphorus (TP) and total nitrogen (TN) concentrations were high, and in delaying large populations until August and September in recent decades despite much lower TP and TN. Our results indicate that large cyanobacteria population events do not occur at the central station in July-September when epilimnetic NO₃ > 2.2 mg N L^?1. The results further suggest that remedial improvements to wastewater treatment plant oxidation capacity may have been inadvertently responsible for high NO₃ concentrations > 2.2 mg N L^?1 and thus for mitigating large cyanobacteria populations. This also implies that large cyanobacteria populations may form earlier in the summer if NO₃ concentrations are lowered.     

Towards the development of an ecosystem model for the Hamilton Harbour,Ontario, Canada

Our main objective is to undertake a synthesis of the Hamilton Harbour ecosystem and to elucidate the relative importance of the underlying trophic relationships using the mass-balance modeling software Ecopath with Ecosim (EwE). We present a conceptual model comprising all the essential food web components of the system, which was parameterized using both local and literature-based information. Among the trophic relationships considered by the Hamilton Harbour ecosystem model, our analysis highlights the central role of round goby demonstrating a wide range of effects on a number of functional groups at both higher and lower trophic levels. Several ecosystem attributes (e.g., primary production/biomass, biomass/total throughput, system omnivory index, amount of recycled throughput, and Finn's cycling index) provide evidence that the Hamilton Harbour is an immature and fairly simple system with linear food chain structure, although the internal redundancy and the system overhead estimates indicate that the Harbour possesses substantial reserves to overcome external perturbations. The aggregation of the ecosystem into discrete trophic levels suggests that most of the trophic flows are concentrated within the first two trophic levels, while flows were practically insignificant at the higher trophic levels of the food web. The fairly low ecotrophic efficiency values for both carnivorous and herbivorous cladocerans are indicative of low zooplanktivory levels in the system. Finally, our study identifies knowledge gaps and critical next steps to rigorously assess the credibility of the model and to consolidate its use for predictive purposes.     

Benthic Community and Sediment Quality Assessment of Port Hope Harbour,Lake Ontario

Sediments in Port Hope Harbour, Lake Ontario, have been heavily contaminated by radionuclides and heavy metals from a radium recovery plant, a uranium refinery, and other industrial activities. Spatial patterns in surficial sediment contamination, benthic community structure, and bioaccumulation of contaminants were assessed to determine possible relationships and potential environmental hazards in the event of dredging. Benthic community differences in species composition and density between inner and outer harbour areas corresponded with both habitat and sediment quality differences. Sediment loss-on-ignition, nitrogen, iron, copper, lead, chromium, zinc, and nickel concentrations in the inner harbour exceeded provincial guidelines for open water disposal of dredged spoils. Only iron exceeded those guidelines in the outer harbour. Tissue levels of radionuclides and heavy metals in benthic invertebrates were greatest at the most heavily contaminated stations in the inner harbour. Reduced benthic densities and maximum sediment contamination occurred near a refinery cooling water discharge.     

Observed Currents and Water Levels in Hamilton Harbour

Measurements of currents, water levels, meteorological inputs and temperatures were made in Hamilton Harbour during 1991. This paper describes the field program and derives features of currents and water level variations. Although the water level measurements clearly showed the fundamental seiche of the harbor itself (period 23 minutes, amplitude 1 mm), the water level in the harbor closely tracks the water level in adjacent Lake Ontario (amplitudes of several cm). A crude estimate of the hypothetical flushing time of the harbor as a result of water level oscillations alone is 3 years. Statistical analysis of both wind and current reveals a looser coupling between winds and currents might be expected, particularly when the water column is homogeneous. This result could be caused by the spatial variation of the wind field or by the bottom topography both as sources of eddying motions. Horizontal eddy diffusivities indicate a subsurface lateral mixing time scale for the entire harbor of 1 year.     

Potential for Fisheries Rehabilitation in the Hamilton Harbour-Cootes Paradise Ecosystem of Lake Ontario

Present and historical information on the status of the Hamilton Harbour-Cootes Paradise ecosystem is synthesized to evaluate the potential for fisheries rehabilitation. Although the Hamilton ecosystem is seriously degraded, it is the largest and most important warmwater fish habitat in western Lake Ontario. Habitat losses, hypolimnetic anoxia, contaminated sediments, nutrients, and sediment inputs are impediments to rehabilitation. Rehabilitation should focus on the warmwater fish assemblage as restoration of the historic coldwater fishery appears unlikely in the foreseeable future. Carroll's Point has the best potential for rehabilitation, the south shore does not have any potential, and the remaining areas fall in between these extremes. Cootes Paradise, which has moderate potential, is adversely affected by sediment inputs from Spencer Creek, nutrients from the Dundas sewage treatment plant, and a large carp population.     

The Incidence of Deformities in Chironomus spp. from Port Hope Harbour,Lake Ontario

Chironomus spp. larvae collected from sediments in the harbour at Port Hope, Ontario, had a greater incidence of mouth part deformities in the more heavily polluted inner harbour area (83%, 33 of 40 individuals) than in the outer harbour (14%, 1 of 7 individuals). Port Hope Harbour, the site of radium and uranium refining operations since 1933, is contaminated by ²³⁸U and (to a lesser extent) ²³²Th decay chain radionuclides and several trace metals. This difference suggests that deformities are related to the areal extent of contamination. An estimated dose rate of 1 mGy/day in chironomids suggests that radiation may be a significant factor in the induction of deformities; however, heavy metals and elevated water temperatures may also be involved.     

Phthalate Esters in Sediments Near a Sewage Treatment Plant Outflow in Hamilton Harbour,Ontario: SFE Extraction and Environmental Distribution

Esters of phthalic acid are ubiquitous environmental contaminants as a result of their use as plasticizers and as constituents in many other commercial products. Although the acute toxicity of phthalates is low, recent concerns over their potential to disrupt the gonadal development of vertebrates has prompted interest in determining the distribution of these compounds in the environment. However, trace analysis of phthalates in environmental samples has been hampered by their presence as ubiquitous laboratory contaminants. In this study, the problem of high background contamination was addressed by developing an analytical method using supercritical fluid extraction (SFE), which was used to extract phthalates from sediment samples collected near the outflow of a sewage treatment plant (STP) in Hamilton Harbour at the western end of Lake Ontario. GC-MS-SIM analysis of sediment samples indicated that di(2-ethylhexyl) phthalate (DEHP)was present at very high concentrations; ranging from a mean of 29.7 μg/g dry weight at a site near the STP outflow to a mean of 6.5 μg/g dry weight at a site 300 m away. Di-n-butyl phthalate (DBP), and benzylbutyl phthalate (BBP) were judged to be present in some sediment samples but at concentrations below the Method Detection Limits (< 0.3 μg/g). Di-isononyl phthalate (DINP) and diethyl phthalate (DEP) were not detected in any of the sediment samples. This study indicates that SFE can be an efficient extraction method for phthalates in sediments, which avoids the extensive use of glassware and organic solvents that may contaminate environmental samples. In addition, STP effluents are sources of phthalates in the aquatic environment; in particular, DEHP.     

Trends in Iron and Phosphorus Loading to Lake Ontario from Waste Water Treatment Plants in Hamilton and Toronto

Resurgences in toxic cyanobacterial blooms, especially Microcystis, have been observed in the lower Great Lakes over the last decade in areas where total phosphorus (TP) levels are below historically high levels. Compliance with regulatory standards for TP in municipal wastewater effluent has likely depended on increased use of iron chloride as a flocculating agent for phosphorus removal in some wastewater treatment plants (WWTP). Since some ecological research suggests that increased supply of biologically available forms of iron may stimulate cyanobacterial growth, TP and iron loadings from WWTPs in the Hamilton Harbour and Toronto areas were examined. TP loadings from the Hamilton and Toronto WWTPs over the last 10–15 years have, in general, not increased. Effluent sampling frequency for iron is much lower than for a regulated parameter such as TP, consequently there is greater uncertainty in loading estimates. Moreover, iron loading estimates are available for only one plant from 1996 and three plants from 1999 so long-term loading trends cannot be established. Iron loading from the Humber WWTP in Toronto increased 5-fold between 2001–2004 while iron loading from the Woodward WWTP in Hamilton is quite high for its size. Iron consumption (i.e., dosing) data are available for three plants from the early 1990s. There was a clear increase in iron consumption by the Burlington-Skyway WWTP beginning in 1997 which was accompanied by a clear decrease in TP loading. However, there were no clear long-term trends in iron consumption in the Toronto plants even when normalized for flow. Increased monitoring and reporting of iron in WWTP effluent by all WWTP operators is recommended along with a review of methods for iron retention.     

Evaluation of stormwater and snowmelt inputs,land use and seasonality on nutrient dynamics in the watersheds of Hamilton Harbour,Ontario, Canada

Between July 2010 and May 2012, 87 24-hour level-weighted composite samples were collected from a variety of catchment states (rain, snowmelt, baseflow) from all four major tributaries to Hamilton Harbour, Ontario, Canada. Samples were analyzed for phosphorus- and nitrogen-based nutrients, and concentrations were examined for trends with catchment state, land use, and seasonality. Total phosphorus (TP) and phosphate concentrations were consistently higher during rain/melt events relative to baseflow. Nitrogen parameters, however, exhibited either concentrating behavior or little change in concentration across a range in flows (chemostasis) depending on the parameter and catchment. Despite differences in land use among the four watersheds, TP concentrations during rain/melt events did not vary among stations; however, spatial variability was observed for other parameters, especially nitrate which was elevated in watersheds on the north shore of the Harbour. Seasonal variability was generally not observed for TP concentrations, mirroring the lack of temporal trends for TSS. In contrast, elevated concentrations of nitrate and phosphate were observed during the fall and/or winter period, except in the primarily agricultural watershed where concentrations were elevated during the summer growing season. Highly elevated concentrations of ammonia and nitrate were observed in some watersheds during the unseasonably cold winter of 2010–2011 but not in the comparatively warm winter of 2011–2012. Implications of the study are discussed including the inferred potential impacts of climate change on nutrient dynamics given the strong contrasts in weather patterns observed between years, and exploration of the feasibility of mitigation measures given the data trends.     

湄公河与洞里萨湖水量交换特征

洞里萨湖是湄公河最大的连通湖泊,湄公河与洞里萨湖水量交换特征一直是国际社会关注的热点问题,但相关研究成果较少。利用4个河湖控制站的长系列水文资料,分析了湄公河与洞里萨湖水量交换特征,结果表明:湄公河与洞里萨湖的水量交换强度大,洞里萨湖对湄公河径流调峰补枯作用明显,每年汛期5—9月份均会发生倒灌,1995—2011年年均倒灌历时122 d,倒灌水量377亿m³,占湄公河干流同期来水的14.4%,倒灌洪峰流量8 402 m³/s,占干流同期来水的20%,其中7—9月份倒灌水量占全年的88.6%;汛后10月份—次年4月份洞里萨湖向湄公河补水,年均补水历时244 d,补水水量711亿m³,是湄公河倒灌入湖水量的1.96倍,占湄公河下游同期来水的29.9%,其中10月份—次年1月份补水量占全年的83.1%。年倒灌历时、水量与洪峰流量,年补水历时、水量与峰值的年际变化较小,变幅分别为76 d、283亿m³、6 095 m³/s和76 d、474 亿m³、4 677 m³/s,变差系数为0.07～0.24。倒灌、补水水量不仅与湄公河和洞里萨湖的来水大小有关,还受到河湖水位差及洞里萨河水位等因素影响。研究成果可为湄公河三角洲和洞里萨湖区治理提供科学依据。     

3D Eutrophication Modeling of Hamilton Harbour: Analysis of Remedial Options

The Water Quality Analysis Simulation Program (WASP) was employed to create a threedimensional eutrophication model for Hamilton Harbour. Calibration of the model was performed using 1991 field data. Four remedial options, namely improvements to the waste water treatment plants (WWTPs), the combined sewer overflows (CSOs), industrial discharges, and removal of WWTP, CSO, and industrial discharges were examined. The model simulated well the response of the harbor under various loading conditions. Improvements in the harbor's water quality were found to range from minor in the case of CSO improvements to significant in the case of WWTP improvements. Specifically, the chlorophyll a, total phosphorus, and ammonia nitrogen concentrations were reduced by as much as 2% in the case of CSO improvements, between 4 and 14% for the industrial loading improvements, and between 24 and 50% for the WWTP improvements case.     

Nepheloid Layer in Lake Ontario

A study was designed to investigate the existence and extent of a nepheloid layer in Lake Ontario. A transmissometer profile of the entire water column was obtained monthly from 94 stations in Lake Ontario during the period of August to December, 1981. The profiles indicated that a turbid layer at the lake bottom existed over the entire lake at water depths greater than 60 meters. The thickness of the layer averaged 22 meters in August and September, but doubled to 45 meters in October. In addition, the average transmission was lowered from 60 percent in August and September to 45 percent in October. A significant increase in soluble reactive phosphorus (SRP) and reactive silica (RSiO₂) in the nepheloid layer was observed. Quartz and calcite were the major mineral constituents of the suspended matter present in the layer. The particles in the nepheloid layer in the western basin of Lake Ontario consisted of many diatoms and some calcite particles and clay minerals. In the central and eastern basins the number of calcite particles significantly increased. Concentrations of Pb and Zn in the suspended matter sampled from the nepheloid layer at the Niagara River mouth were similar to those found in the 1-cm surface sediment at the same station (124 μg g^?1 Pb, 318 μg g^?1 Zn,and139 μg g^?1 Pb and 356 μg g^?l Zn, respectively).     

Winter Circulation in Lake Ontario

Data from a high resolution array of self-recording current meters in a north-south cross section of Lake Ontario are presented. The measurements cover a 140-day period from 4 November 1982 to 23 March 1983. Nearshore current fluctuations are large and generally coherent with wind variations while currents in deep water tend to flow in the opposite direction and are quite uniform in the vertical. Time-averaged currents show a pronounced maximum of eastward flow along the south shore balanced by westward flow in the central part of the cross section, while the net transport near the northern shore tends to vanish. The total transport in the belt of eastward flow is ten times larger than the hydraulic transport associated with the Niagara-St. Lawrence flow, thus suggesting a recirculation of 90% of the river inflow. Corroboration of the south shore current measurements is provided by satellite-tracked drogues.     

Lagrangian Measurements in Lake Ontario

Satellite-tracked trajectories of 19 drifters involving six experiments between 1983 and 1989 in Lake Ontario were analyzed. Three aspects of the observed motions at 3.5 m depth are examined: (1) the spatial structure of the mean and variance velocity fields, (2) the Lagrangian statistics (dispersion and eddy diffusion characteristics) of the variance field based on single-particle analysis, and (3) the Eulerian statistics of the fluctuating velocity field. The spatial structure of the mean velocity field is consistent with that obtained from dynamic height and current meter measurements. The lake circulation is cyclonic. A coastal jet with mean speed in excess of 11 cm/s dominates the mean circulation. The jet is most intense along the southern shore. Two recirculation zones are observed in the western part of the lake. The current variability is strongly anisotropic in the coastal zone. Away from the coastline, the flow is quasi-isotropic.The theory of single-particle diffusion by homogeneous random motion (Taylor 1921) describes the dispersive motions reasonably well. In the western part of the lake, zonal scales greatly exceed the meridional scales while in the eastern part of the lake they are similar. In the western part of the lake, the zonal and meridional integral time and length scales and eddy dijfusivities are, respectively, (T₁₁,T₂₂) = (17.2, 5.5) hr, (L₁₁,L₂₂) = (10.1, 2.1) km and (K₁₁,K₂₂) = (16.5, 2.2) × 10⁶ cm²/s. In the eastern part of the lake, these values are (T₁₁,T₂₂) = (7.9, 14.7) hr, (L₁₁,L₂₂) = (1.7, 2.7) km, and (K₁₁,K₂₂) = (1.1, 1.5) × 10⁶ cm²/s. The presence of inertial oscillations does not affect the diffusivity estimates. The eddy kinetic energy of single-particle motion in the western part of the lake is 189 cm²/s² which is about six times that of the eastern part. The Eulerian decorrelation scales tend to be larger than those of the single-particle estimates. The space scales indicate that the eddy field is quasi-isotropic.