Distribution of Major Elements and Metals in Sediment Cores from the Western Basin of Lake Ontario

An investigation was made of the relationship between the changes in metal concentrations in sediments with the distance from the Niagara River mouth and the chemical and physical characteristics of the sediments. Sediment cores were obtained at nine sampling stations in the western basin of Lake Ontario. In addition, surface sediment was collected at three stations on the Niagara Bar. Minerals present at all stations were silica, feldspars, illite/muscovite, chlorite, kaolinite, and calcite. Dolomite was found at some sampling stations as grains of 2 to 63 μm size. Significantly elevated concentrations of calcite (up to 20%) in the surface sediment (about 0 to 10 cm) at four sampling stations in the western basin and in the entire 25-cm sediment column at the Niagara River mouth indicated increased input of this mineral into Lake Ontario during the past 100 years. Furthermore, sediment concentration profiles of Zn, Pb, Cr, Cu, Ni, and especially Hg at all sampling stations indicated major transport of metals associated with the clay- and silt-size particles from the Niagara River into Lake Ontario (especially north-north-east and east of the river mouth). A significant decrease in Hg loading from the Niagara River during the past 20 years was also observed. Although smaller in magnitude, a similar decrease was found for Pb, Zn, Cr, Ni, and Cu loading. However, elevated Hg concentrations (up to 7 μg g～^l above background values) existed in the surface 10 cm of sediment at eight sampling stations.     

The Influence of the Niagara River on Contaminant Burdens of Lake Ontario Biota

Top predator and forage fish species, netplankton (> 153 μm), zooplankton, and benthic macroinvertebrates from Lake Erie and Lake Ontario were analyzed for whole body levels of trace metals and organic contaminants. Comparison of contaminant concentrations in similar aquatic food chains from both lakes indicated that levels of PCB, DDT, mirex, and mercury are significantly greater (P <0.05) in the biota of Lake Ontario. The Niagara River, the single largest tributary to Lake Ontario, was confirmed as a major source of organic contaminants and trace metals. Organic contaminants are adsorbed to the particulate load of the river and dispersed throughout Lake Ontario by the circulating currents. There was no significant regional difference (P<0.05) in the degree of contaminant accumulation by the pelagic food chain of Lake Ontario. Conversely, both inorganic and organic contaminant levels in the demersal amphipod, Pontoporeia affinis, were significantly different (P<0.05) between the eastern and western basins of Lake Ontario. The uptake and concentration of contaminants at the sediment-water interface is suggested as a possible mechanism to explain this observed difference.     

Measurement of Diporeia respiration rate for Lake Superior

The freshwater amphipod Diporeia is a dominant macroinvertebrate species in Lake Superior’s benthic community and an important prey item for many fish. A capacity to predict growth and production rates of Diporeia using a bioenergetics model requires information on physiological processes of the species. The objective of this study is to quantify oxygen consumption of Lake Superior Diporeia and to determine if respiration rate changes with body length. Diporeia were collected from Lake Superior and kept over natural sediment maintained at 4 °C. Dissolved oxygen levels for groups of immature (2 mm), juvenile (4 mm), and adult (6 mm) Diporeia in 20 ml microcosms were measured using a polarographic microelectrode. Mass-specific respiration rates for Lake Superior Diporeia ranged from 32.0 to 44.7 mg O₂ g DW^− 1 day ⁻¹. A significant relationship between body length and mass-specific respiration rate (p > 0.1) was not found. The estimate of Diporeia respiration presented here is significantly higher (p < 0.05) than previous findings from populations in Lakes Michigan and Ontario. This study provides new data on respiration rates of Lake Superior Diporeia and compares findings to studies for other connecting Great Lakes.     

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.     

Bioaccumulation of PCB Congeners by Diporeia spp.: Kinetics and Factors Affecting Bioavailability

The toxicokinetics of four polychlorinated biphenyl (PCB) congeners were determined for the amphipod Diporeia spp. exposed to selected PCB congeners through both water and sediment to determine the effect of temperature and organism size (mass). For compounds with log K_ow 6 or greater, the water-only uptake coefficient (k_u) was inversely proportional to the size of the organism at all temperatures. For monochlorobiphenyl, k_u was directly proportional to organism mass only at 16°C. Increasing temperature resulted in increasing uptake rate coefficients for all compounds except hexachlorobiphenyl (HCBP) where k_u did not appear to depend on temperature. The hydrophobicity of the contaminants did not contribute significantly to changes in uptake rate from water. The elimination rate constant (k_e) was inversely proportional to organism size but was not significantly affected by temperature. The elimination rate constant declined exponentially with increasing log K_ow. As log K_ow increased, the effect of organism mass on k_e was greatly reduced. The uptake from sediment was affected by temperature and the congener log K_ow. At lower temperatures, the uptake coefficient from sediment (k_s) declined with increasing log K_ow, while at higher temperatures, it exhibited a slight upward trend. Smaller animals had much higher uptake rates from sediment than large or medium size animals. Small animals exhibited very high biota-sediment accumulation factors (5.4 to 20.8) over 4 to 16°C for HCBP (BSAF, concentration in the organism normalized to the lipid content divided by the concentration in the sediment normalized to the organic carbon content). The relationship between BSAF and log K_ow was exponential for both laboratory and field data.     

Geochemical Pathway Studies of Heavy Metals in Lake Sediments from the Sudbury-Temagami Area,Ontario

The concentrations of some heavy metals in lake sediments from the Sudbury-Temagami area were determined by radiochemical neutron activation, atomic absorption, and x-ray fluorescence. Data for dredge samples from 23 lakes indicate that concentration gradients for Pd, As, and Se tend to center about the Sudbury industrial complex and increase toward it. Metal concentration profiles over the top 20 cm of sediment cores from five lakes show pronounced increases in Pd, Ir, Au, As, Se, Cu, Ni, and Pb in the top 5 cm. These data suggest that one of the principal pathways for heavy metal loading of lake sediment in the area is atmospheric fallout of particulate material.     

Some Fungi and Water Molds in Waters of Lake Michigan with Emphasis on Those Associated with the Benthic Amphipod Diporeia spp.

To determine types of fungi in the water and associated with the benthic amphipod Diporeia spp., samples were collected at various depths in Lake Michigan in an area where the Diporeia population was in a severe state of decline. No fungi were found associated with living, freshly-dead, or dried Diporeia cultured separately from Lake Michigan water. When dead Diporeia and other organic substrates (snake skin and hemp seeds) were used to grow fungi in Lake Michigan water, a rich and diverse fungal and water mold community was revealed. A total of 31 species were found, with the most common genera being Achlya, Aphanomyces, Myzocytium, and Pythium. In general, species were homogeneously distributed in the water; that is, few differences were found in species richness between nearshore (10–15 m) and offshore (60–80 m) waters, and between near-surface (1 m) and near-bottom waters (1 m off bottom). Sampling occurred during the unstratified period (April and October) to maximize the number of species collected, which may have contributed to the uniform spatial pattern observed. While conclusions must be placed in context with our methods of detection, we found no evidence that a fungal infestation was associated with Diporeia in this region of the lake.     

Sedimentary Characteristics and Acoustic Detectability of Ship-derived Deposits in Western Lake Ontario

Dual-frequency side-scan sonar surveys (100 and 500 kHz) were conducted in western Lake Ontario to locate and characterize ship-derived deposits. Sedimentary characteristics of these deposits were investigated with the aid of a Remote Operated Vehicle (ROV) and sediment samples. Distinct Acoustic Backscatter Anomalies (ABAs) identified with the sonar, when sampled, were found to be surficial and subsurficial deposits of ship-derived debris including coal, taconite, and cement clinker. These deposits, which are estimated to range in age from less than 10 years to over 100 years, are located in fine-grained lakebed sediment, which has relatively low acoustic attenuation even at high frequency. As a result, the coarse ship-derived debris can be distinguished on side-scan sonar records even though it is buried at depths of up to 15 cm. Calculations suggest that ship-derived debris as deep as 2.5 m should be observable in 100 kHz side-scan sonar records from this environment. Since sediment accumulation rates are less than 0.29 cm/y and shipping has occurred on Lake Ontario for approximately 140 years, most coarse ship-derived debris ever deposited by ships into fine-grained sediments should be detectable with a 100 kHz sonar signal. Layers of granular diagenetic vivianite were identified at about 15 cm depth in several cores. This material may be a good acoustic reflector and may be responsible for some of the broad but diffuse reflective patterns observed in the side-scan sonographs.     

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.     

Additional Link in the Food Web Does Not Biomagnify a Persistent Contaminant in Lake Ontario: The Case of Cercopagis pengoi

Cercopagis pengoi is a new and abundant non-indigenous predator species in the Lake Ontario food web. We explored the impact of this predator on the levels of a chlorinated hydrocarbon in the pelagic food web through assessments of seasonal abundance and mirex concentrations of Cercopagis pengoi (Ostroumov) and the planktivorous alewife (Alosa pseudoharengus). Abundance, stable isotope, and alewife stomach data indicate that Cercopagis pengoi has become an established portion of the Lake Ontario food web. Cercopagis, a predaceous cladoceran, feeds on the lower portion of the trophic web and is clearly fed upon by the planktivorous alewife. Cercopagis is a link in the Lake Ontario food web, in which energy and materials are being passed from one level of the trophic web to another. However, mirex levels of the planktivorous alewife did not increase during the period of highest Cercopagis abundance. The annual load of mirex (mass of Cercopagis times concentration) transferred from one level of the trophic web to the next is low. In the summer, when Cercopagis is abundant, alewives were not feeding on them.     

Sedimentary Records of Spheroidal Carbonaceous Particles from Fossil-Fuel Combustion in Western Lake Ontario

Spheroidal carbonaceous particles (SCPs) were quantified in three sediment cores collected from depositional areas in the western basin of Lake Ontario to examine the impact of fossil-fuel combustion on sediment metal concentrations. SCP profiles were similar for the three cores showing the initiation of the SCP record deep in the core, followed by a rapid increase to a sub-surface maximum, and a subsequent decrease towards the sediment surface. Subsurface maximum SCP concentrations ranged from 1.97 to 5.61 × 10⁵ per gram dry matter/gDM. For ²¹⁰Pb dated cores, dates for the initiation of the SCP record (1850 ± 10 years), the initiation of the rapid rise in SCPs (1880 ± 13 years), and the SCP subsurface maximum (1961 ± 3 years) agree well. The rapid increase in sediment SCPs also agrees well with the US bituminous coal consumption during this same period (1880 to 1980). SCPs in surface sediments decreased between 55 to 83% from the subsurface maximum (1961 to 1996) in these cores while U.S. coal usage continued to increase. SCP decreases were attributed to the increased use and efficiency of particle collection devices by utilities and industry. Lead, Cr, Cu, and Zn showed significant correlations (r² = 0.63 to 0.94) with SCPs within each respective sediment core. Calculations show that although SCPs are not the major source of anthropogenic metals in Lake Ontario sediments, they may account for between 4 to 55% of the Zn, 1 to 12% of the Cu, 2 to 22% of the Pb and 1 to 18% of the Cr in these sediments.     

Compartmental Distribution of Organochlorine Contaminants in the Niagara River and the Western Basin of Lake Ontario

Ten chlorobenzenes, hexachlorobutadiene, and PCBs were measured in Niagara River water and suspended solids, and in western Lake Ontario sediments and benthic fauna. High levels of these contaminants were found on all fractions of the river suspended solids, but the larger particles contained much higher concentrations than the smaller particles. A portion of the CBs, HCBD, and PCBs present in the lake sediments was available to benthic organisms. A trend toward greater bioaccumulation for compounds having higher octanol-water partition coefficients was observed at all trophic levels.     

Mirex in the Sediments of Lake Ontario

Analysis of sediment samples collected in Lake Ontario in 1968 revealed the occurrence of mirex in two anomalous zones related to input from the Niagara and Oswego Rivers. These anomalies were confirmed in a 1976 resampling program. A suspended solids sample taken in the Niagara River confirmed an upstream source (Hooker Chemical) of the compound. Bottom sediment samples in the Oswego River identified an industrial source (Armstrong Cork) 14 km upstream of the river mouth. Known use of mirex by this plant indicated a substantial loss some 15 years ago. This was confirmed by sediment coring in the open lake sediments indicating that mirex deposition commenced 7 to 14 years before present.     

Nearshore Benthic Invertebrates of the Ontario Waters of Lake Ontario

Benthic invertebrates were collected by divers along 25 transects (depths of 2, 5, 10, and 20 m) between the Niagara River and Kingston during July 1981. Total standing stocks, which ranged from 1,600 m⁻² to 314,200 m⁻², were greatest on silt and clay, especially near the mouth of the Humber River, and smallest on rock. Of the 196 taxa which were recognized, Vejdovskyella intermedia, immature Tubificidae, Chaetogaster diaphanus, Potamothrix vejdovskyi, Tanytarsus, Pontoporeia hoyi, and Gammarus fasciatus were the most abundant and most frequently collected. Both inspection of the distributions of common taxa and ordination based on abundances of all taxa found at >5 stations indicated that organic enrichment, depth, and susceptibility to upwelling were the primary factors influencing the composition of invertebrate communities. Exposure to wave action was less important, and type of substratum had little effect. Overall, the nearshore fauna of Lake Ontario was less diverse, but more abundant than that of Lake Huron.     

Diets of the benthic amphipod Diporeia in southern Lake Michigan before and after the dreissenid invasion

Diporeia spp. were a key component of the Great Lakes benthos, converting the pelagic algal rain to secondary production, which is critical for Great Lakes fishes. However, Diporeia declines since the 1980s have been rapid and widespread. While there are temporal relationships between Diporeia declines and spread of zebra and quagga mussels, establishing a mechanistic link has been difficult. Diporeia declines may result from competition for food resources with dreissenid mussels; however, conflicting evidence suggests food limitation may not be the direct link. To test food limitation, we analyzed gut contents of Diporeia collected between the 1980s and 2009 from two deep (>100 m) and one nearshore station (~50 m depth) in southern Lake Michigan. We further analyzed sediment cores from the same stations to resolve relationships among food resources, Diporeia diet, and diet selectivity during pre- and post-dreissenid invasion. In spring, pre-dreissenid Diporeia fed selectively and exclusively on large (Stephanodiscus) and filamentous centric diatoms (Aulacoseira). Diporeia diets showed significant shifts during the 2000s to greater proportions of small centric and araphid diatoms, coincident with Diporeia declines and offshore expansion of quagga mussels. Sediment cores recorded declines in Aulacoseira and large Stephanodiscus from 1960 to 2009 and increases in small centrics after dreissenid introduction. Accounting for high selectivity in springtime Diporeia diets, community changes in sediment records are consistent with changes observed in Diporeia diets and suggest Diporeia declines have been exacerbated by a shift from more nutritious and highly preferred diatom species to less nutritious and negatively selected species.     

Seasonal Food of Juvenile Lake Trout in U.S. Waters of Lake Ontario

Stomach contents of 3,554 lake trout (Salvelinus namaycush), 100 to 449 mm in total length, captured with bottom trawls during April through October 1978–81 along the south shore of Lake Ontario were examined. Invertebrates appeared to be an important food of lake trout less than 200 mm long but were only occasionally eaten by larger fish. For all seasons and size groups of juvenile lake trout combined, the slimy sculpin (Cottus cognatus) was the principal forage fish, making up 42% (by weight) of identifiable fish remains. Young-of-the-year slimy sculpins were a major food of recently stocked yearling lake trout during July through October. Alewives (Alosa pseudoharengus) were the principal forage during April and May, and made up 28% (by weight) of the identifiable fish remains. They were rarely eaten during July and August, however, when lake trout remained in the hypolimnion and alewives were above it. Over 99% of the alewives eaten from April through August were yearlings and over 99% eaten during October were young-of-the-year. Rainbow smelt (Osmerus mordax) were the primary forage during July and August, but contributed only a small part of the diet during other seasons; overall, they made up 25% of identifiable fish remains. Johnny darters (Etheostoma nigrum) made up 4% of identifiable fish remains and were most common in stomachs of small lake trout during October.     

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.     

Evidence for Remote Effects of Dreissenid Mussels on the Amphipod Diporeia: Analysis of Lake Ontario Benthic Surveys, 1972–2003

The status of invasive dreissenid mussels (Dreissena polymorpha and D. bugensis) and native amphipods (Diporeia spp.) in Lake Ontario was assessed in 2003 and compared with historical data. D. polymorpha (zebra mussels) were rarely observed in 2003, having been displaced by D. bugensis (quagga mussels). D. bugensis expanded its depth range from 38 m depth in 1995 to 174 m in 2003 and this dreissenid reached densities averaging 8,000/m² at all sites < 90 m. During the same time period, Diporeia populations almost completely disappeared from 0–90 m depth, continuing a declining trend from 1994–1997 reported in previous studies. The average density of Diporeia in the 30–90 m depth interval decreased from 1,380/m² to 63/m² between 1997 and 2003. Prior to 2003, areas deeper than 90 m represented a refuge for Diporeia, but even these deep populations decreased, with densities declining from 2,181/m2 in 1999 to 545/m2 in 2003. Two common hypotheses for the decline of Diporeia in the Great Lakes are food limitation and a toxin/pathogen associated with dreissenid pseudofeces. The Diporeia decline in deep waters preceded the expansion of D. bugensis to these depths, and suggests that shallow dreissenid populations remotely influence profundal habitats. This pattern of decline is consistent with mechanisms that act from some distance including nearshore dreissenid grazing and downslope transport of pseudofeces.