Surficial Sediment Contamination in Lakes Erie and Ontario: A Comparative Analysis

Sediment surveys were conducted in Lakes Erie and Ontario to characterize spatial trends in contamination, to assist in elucidation of possible sources of contamination, and for identification of areas where contamination exceeded Canadian sediment quality guidelines for protection of aquatic biota. Sediment levels of metals including nickel, lead, zinc, chromium, and copper were compared to pre-colonial concentrations, and sediment enrichment factors, defined as the ratio of surficial concentrations to background concentrations determined from benthos cores, were calculated. Sediments in Lake Ontario exhibited elevated contamination compared to Lake Erie. The average enrichment factor for Lake Ontario (2.6) was comparable to the western basin in Lake Erie but greater than those for the central (1.3) and eastern (1.0) basins. There was a gradient toward decreasing sediment contamination from the western basin to the eastern basin of Lake Erie, and from the southern to the northern area of the central basin. Sediment contamination in Lake Ontario was similarly distributed across the three major depositional basins. The spatial distribution of metals was similar to those of other contaminants including mercury, polychlorinated biphenyls (PCBs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs). Lake-wide averages of sediment mercury, PCBs and PCDDs/PCDFs in Lake Erie were 0.185 μg/g, 96.5 ng/g, and 18.8 pg/g TEQs, respectively. Lake-wide averages of sediment mercury, PCBs and PCDDs/PCDFs in Lake Ontario were 0.586 μg/g, 100 ng/g, and 101 pg/g TEQs, respectively.     

Concentrations of Polychlorinated Biphenyls in the Water Column of the Laurentian Great Lakes: Spring 1993

PCB concentrations were measured in the Laurentian Great Lakes of North America in the Spring of 1993. Quality control criteria were met for 97% of the dissolved phase samples and 90% of the particulate phase samples. Data are reported as total PCBs and as homolog groups for both of the operationally-defined phases at a 0.7 μM cutoff. Detection limit estimates were 21 pg/L for dissolved phase and 23 pg/L for particulate phase total PCBs, based on a sample volume of 190 L. Total PCB concentrations ranged from 100 pg/L in Lake Superior to 1.6 ng/L in the western basin of Lake Erie. Lakes Michigan and Ontario had the highest lakewide average total PCB concentrations, followed by Lake Huron, and then Lake Superior. Lakewide averaging across the three basins of Lake Erie was too variable to be useful.     

Mean Circulation in the Great Lakes

In this paper new maps are presented of mean circulation in the Great Lakes, employing long-term current observations from about 100 Great Lakes moorings during the 1960s to 1980s. Knowledge of the mean circulation in the Great Lakes is important for ecological and management issues because it provides an indication of transport pathways of nutrients and contaminants on longer time scales. Based on the availability of data, summer circulation patterns in all of the Great Lakes, winter circulation patterns in all of the Great Lakes except Lake Superior, and annual circulation patterns in Lakes Erie, Michigan, and Ontario were derived. Winter currents are generally stronger than summer currents, and, therefore, annual circulation closely resembles winter circulation. Circulation patterns tend to be cyclonic (counterclockwise) in the larger lakes (Lake Huron, Lake Michigan, and Lake Superior) with increased cyclonic circulation in winter. In the smaller lakes (Lake Erie and Lake Ontario), winter circulation is characterized by a two-gyre circulation pattern. Summer circulation in the smaller lakes is different; predominantly cyclonic in Lake Ontario and anticyclonic in Lake Erie.     

Contaminant Residues in Tissues of Adult and Prefledged Herring Gulls from the Great Lakes in Relation to Diet in the Early 1990s

In the early 1990s, herring gulls (Larus argentatus) were collected in 15 breeding colonies throughout the Great Lakes basin and in two reference colonies on Lake Winnipeg and the Bay of Fundy. Organochlorine and metal concentrations, and stable isotope ratios (¹⁵N/¹⁴N and ¹³C/¹²C) were measured in their tissues, and we qualitatively assessed their diet. Breast muscle δ¹⁵N suggested that adults fed on planctivorous or insectivorous fish at six colonies, on piscivorous fish at four, and at a lower trophic level at the remaining three. The concentrations of Co, Ni, Al, Cr, Sn, Fe, and Pb in kidneys of adults suggested anthropogenic enrichment in the Great Lakes basin. Concentrations of contaminants were highest most often in tissues of gulls from Lake Ontario and northern Lake Michigan colonies. Concentrations of Pb in adults from Hamilton Harbour and the Detroit River, and of Se in adults from the southern Lake Huron colony, were similar to published toxicity thresholds. Tissue levels of Cd have increased, while those of Pb have decreased markedly since 1983. DDE, dieldrin, mirex, and ΣPCB concentrations in livers collected from nine of these colonies revealed declines of 16 to 87% at most locations since the early 1980s. 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents were highest in adults from the offshore colonies in western Lake Erie and northern Lake Michigan, where gulls feed on piscivorous fish, and were driven by non-ortho PCBs. There was evidence of an unusually high bioavailablity of organochlorines, especially dieldrin, near the northern Lake Michigan colony during the period of chick growth, and of an ongoing loading of mercury to eastern Lake Ontario. Tissues of adult gulls from colonies on Lakes Ontario, Erie, and Michigan best reflect local conditions whereas those from Lake Superior and northern Lake Huron reflect contaminants accumulated from time spent on the lower lakes.     

Significance of toxaphene in Great Lakes fish consumption advisories

Fish consumption advisories have been issued for the Great Lakes generally based on the most restrictive contaminant. For the Canadian waters of the Great Lakes, toxaphene causes minor restrictions only in Lake Superior, i.e., 3% of the total (restrictive + unrestrictive) advisories issued. However, the significance of the hazard posed by toxaphene in fish is not clear since more restrictive advisories due to other priority contaminants may be masking the less restrictive advisories. We simulated fish consumption advisories for the Toxaphene-only scenario by neglecting the presence of contaminants other than toxaphene, and compared with the issued advisories as well as with the published simulated Mercury-only scenario. Restrictive advisories under the Toxaphene-only scenario compared to the issued toxaphene related advisories would increase from 3% to 14%, < 1% to 4%, and 0% to 2% for Lakes Superior, Huron and Ontario, respectively, and remain at 0% for Lake Erie. For Lake Superior, most of the restrictive Toxaphene-only advisories would be for fatty fish. Overall, the Toxaphene-only advisories would be significantly less restrictive compared to the issued advisories, and also generally less restrictive compared to the Mercury-only scenario. These results suggest that toxaphene is less of a concern than PCBs (including dioxin-like PCBs), dioxins–furans and mercury from the perspective of health risk to humans consuming Great Lakes fish; elevated toxaphene is mainly a concern for human consumers of Lake Superior fatty fish. Our results suggest that the routine monitoring of toxaphene in other Canadian waters of the Great Lakes and Lake Superior lean/pan fish could be discontinued.     

Contaminants and Trends in Fall Run Coho Salmon

Fillets of fall run coho salmon from each of the Great Lakes were analyzed for pesticides and industrial compounds. PCBs were the dominant contaminant in all samples ranging from trace concentrations in Lake Superior to 1.74 μg/kg in Lake Ontario. Compounds which have been banned or restricted were detected in most samples. These include PCB, DDT, chlordane, dieldrin, toxaphene, endrin, lindane, and heptachlor-epoxide. The herbicide, dacthal, was detected in samples from Lakes Michigan, Huron, and Erie. Comparison of 1984 coho salmon with those collected in 1980 through 1983 indicates that concentrations of PCB and DDT in coho from Lakes Erie and Michigan have declined, following first order loss kinetics. Dieldrin concentrations in Lake Michigan coho have also declined following first order loss kinetics.     

Trace Element Concentrations in Near-Surface Waters of the Great Lakes and Methods of Collection,Storage, and Analysis

From 1980 through 1985, waters of the Great Lakes were sequentially sampled for dissolved, paniculate, and total trace elements. Major sampling occurred in 1980 for Lake Huron, in 1981 for Lakes Erie and Michigan, in 1983 for Lake Superior, and in 1985 for Lake Ontario. Great care was taken during collection, storage, and analysis to prevent sample contamination and to document any contamination occurring. Trace elements measured by atomic absorption techniques were silver, aluminum, arsenic, boron, barium, beryllium, bismuth, cadmium, cobalt, chromium, copper, iron, mercury, lithium, manganese, molybdenum, nickel, lead, antimony, selenium, tin, strontium, vanadium, and zinc. All results were field and laboratory blank corrected. Excluding aluminum, barium, iron, and strontium, concentrations of trace elements in most of the Great Lakes were a few ppb or less, with many elements being below one ppb. Element concentrations were highest in Lakes Erie and Michigan and lowest in Lakes Huron and Superior. All five Great Lakes had more than 50% of their total iron, aluminum, and manganese associated with paniculate matter.     

Are PCB Levels in Fish from the Canadian Great Lakes Still Declining?

Long- and short-term levels and trends of polychlorinated biphenyls (PCBs) in lake trout (Salvelinus namaycush) and walleye (Sander vitreus) from the Canadian waters of the Great Lakes are examined using the bootstrap resampling method in light of the Great Lakes Strategy 2002 (GLS-2002) objective of decrease in concentrations by 25% during 2000–2007. This objective has been set as an indicator of progress toward the long-term goal of all Great Lakes fish being safe to eat without restriction. Lake Superior lake trout and walleye PCB concentrations were almost unchanged between 1990-2006, and the bootstrap analysis suggests that the probability of achieving the GLS-2002 objective is negligible (< 2%). The PCB levels in Lake Huron lake trout and walleye are decreasing; the declines between 2000–2007 are estimated to be 25–35% and 5–30%, respectively. In contrast, Lake Erie walleye concentrations will likely increase by 25–50% between 2000–2007. For Lake Ontario lake trout, achieving the 25% reduction target seems highly probable with a likely decrease of 45–55%; for Lake Ontario walleye, the probability of achieving such a reduction is only 8% with an expected change of −13 to +15%. Although the targeted reduction may not be achieved for walleye from Lakes Superior, Huron, and Ontario, their best projected 2007 PCB levels are below the unlimited fish consumption guideline of 105 ng/g wet weight used by the Ontario Ministry of the Environment. In contrast, although there are high probabilities of achieving the goal for lake trout from Lakes Huron and Ontario, their best projected 2007 PCB levels (160 and 370 ng/g ww, respectively) will continue to result in consumption restrictions. Lake Superior lake trout concentrations may remain unchanged at the current elevated level of 160 ng/g ww. For Lake Erie fish, the projected 2007 concentrations and the increasing trends are both worrisome. Additional measurements beyond 2007 are necessary to confirm these estimates because of the observed periodic oscillations in the concentrations.     

Chlorinated Contaminants in Surficial Sediments of Lakes Huron,St. Clair,and Erie: Implications Regarding Sources Along the St. Clair and Detroit Rivers

Surficial sediments from southern Lake Huron, Lake St. Clair, and Lake Erie have been analyzed for a broad spectrum of chlorinated organics including PCBs, chlorobenzenes, and several pesticides. The differences between sediment contaminant concentrations in Lake Huron and Lake St. Clair indicated sources of hexachlorobenzene, hexachlorobutadiene, octachlorostyrene, and several other chlorinated benzenes along the St. Clair River. Similar differences between sediment PCB concentrations in Lakes Huron/St. Clair and Lake Erie indicated major PCB sources along the Detroit River. Specific PCB congener analysis revealed that PCBs discharged to the Detroit River contained especially high concentrations of highly chlorinated hexa-, hepta-, and octachloro-biphenyls which are major constituents of the industrial mixture Aroclor 1260. The analysis of individual PCB congeners made it possible to trace PCBs of Detroit River origin to the central and eastern basins of Lake Erie, and to estimate the contribution of the Detroit River to the PCB burden in sediments of these basins.     

Trends in Total Phosphorus in Canadian Near–Shore Waters of the Laurentian Great Lakes: 1976–1999

Beginning as early as 1976 at many locations, total phosphorus concentrations (TP) were measured weekly in samples collected year-round in the intake water of 18 municipal water treatment plants in Canadian (Ontario) waters of the Laurentian Great Lakes. No consistent long-term trends were evident at two north-shore Lake Superior sampling locations, but there were significant long-term declines in TP measured at all three Lake Huron locations; however, concentrations there have remained relatively constant during the past decade. Declines in TP averaging about 1 μg/L/yr during 1976 to 1990 were prevalent at lower Great Lakes sampling locations and by the early 1990s TP had declined to 15–25 μg/L in Lake Erie and 10–20 μg/L in Lake Ontario. Declines generally levelled out in Lake Ontario after 1990, but TP increased substantially at some Lake Erie locations in the late 1990s. Recent (1996 to 1999) total phosphorus concentrations in north-shore Lake Erie locations in the range of 20 to 30 μg/L were 2 to 3 times higher than at Lake Ontario near-shore locations in the 8 to 11 μg/L range. Rates of decline of TP were generally highest for the March–April period (−1.88, −1.61, and −1.34 μg/L/yr in Lakes Ontario, Erie, and Huron, respectively for 1976 to 1990). The March–April Lake Ontario near-shore rate of TP decline was nearly twice as high as that reported previously for off-shore Lake Ontario (attributed to proximity to P loading sources and to lower net sedimentation losses of P in the near-shore environment). There were substantial declines in chlorophyll-to-TP ratios and in the slopes and Y-intercepts of chlorophyll-TP regressions for both Lake Erie and Lake Ontario following the establishment of dreissenid mussels.     

A cross-lake comparison of crustacean zooplankton communities in the Laurentian Great Lakes, 1997–2016

Spring and summer open-water crustacean zooplankton communities were examined across all five Laurentian Great Lakes from 1997 to 2016. Spring communities were dominated by calanoid (lakes Superior, Huron and Michigan) or cyclopoid (lakes Erie and Ontario) copepods. Volumetric biomass of summer communities increased along an assumed trophic gradient (Superior, Huron, Michigan, Ontario; eastern, central and western Erie), as did dominance by cyclopoids and cladocerans. Over the time series of the study, summer communities in lakes Michigan, Huron and Ontario shifted towards greater dominance by calanoids and greater similarity with Lake Superior. Trajectories of changes were different; however, reductions in cladocerans accounted for most of the change in lakes Michigan and Huron while reductions in cyclopoids and increases in Leptodiaptomus sicilis were behind the changes in Lake Ontario. Shifts in the predatory cladoceran community in Lake Ontario from Cercopagis pengoi to occasional dominance by Bythotrephes longimanus, a species much more vulnerable to planktivory, as well as the appearance of Daphnia mendotae in a daphnid community previously consisting almost exclusively of the smaller Daphnia retrocurva, suggest impacts of reduced vertebrate predation. In contrast, strong correlations between cladocerans and chlorophyll in lakes Michigan and Huron point to the possible importance of bottom-up forces in those lakes. Large interannual shifts in cladoceran community structure in the central and eastern basins of Lake Erie suggest intense but variable vertebrate predation pressure. The zooplankton communities of lakes Huron, Michigan and Ontario may be approaching a historic community structure represented by Lake Superior.     

Contaminants Associated with Suspended Sediments in Lakes Erie and Ontario, 1997–2000

Sediment traps were installed at individual index stations in the western basin of Lake Erie and the Mississauga (central) basin of Lake Ontario, and refurbished seasonally during the period 1997–2000. In Lake Ontario, sediment down flux rates and corresponding contaminant down flux rates were highest in winter and increased with depth due to the influence of resuspended bottom sediments. Sediment down flux rates in western Lake Erie (22 to 160 g m⁻² d⁻¹) were far greater than in Lake Ontario (0.19–3.0 g m⁻² d⁻¹). Suspended material in western Lake Erie was characterized as predominately resuspended bottom sediments; down flux rates were roughly 5- to 10-fold higher in spring and fall, compared to summer. Suspended sediment concentrations of PCBs and other organochlorine contaminants, represented by both annual means and individual seasonal values, were higher in Lake Ontario throughout the duration of the study, compared to Lake Erie. The mean annual concentration of PCBs in suspended sediments over the period 1997–2000 was 330 ng/g in western Lake Erie and 530 ng/g in Lake Ontario. Based on a comparison with historical data from Lake Ontario, mean contaminant concentrations over the period 1997–2000 for PCBs, hexachlorobenzene, and mirex corresponded to decreases of 38%, 74%, and 40%, respectively, since the mid-1980s. Corresponding down flux rates for PCBs, hexachlorobenzene, and mirex decreased by approximately 70%, 90%, and 80%, respectively, since the 1980s.     

Metals in the sediments of the Huron-Erie Corridor in North America: Factors regulating metal distribution and mobilization

Sediment samples from the Huron‐Erie Corridor (Great Lakes, North America) were collected to quantify the relative importance of natural and anthropogenic sources of contamination, and to study the spatial metal distribution patterns of metals as a function of the characteristics of the Corridor sediments. A stratified random sampling design was used to measure the spatial patterns of metal inputs, settling and sorting along the length of the Corridor. Factors regulating metal mobilization were assessed by determining metal affinities with the total organic fraction (TOM), the mineral fraction (represented as Al), and the granulometric characteristic (represented as <0.063 mm fraction). The study revealed that anthropogenic factors primarily regulated metal distributions and mobilization throughout the Huron‐Erie Corridor. In the St. Clair and Detroit Rivers, the spatial pattern of metal distributions strongly reflected local industrial sources. In the Walpole Delta and Lake St. Clair, however, inorganic (clays) and organic (TOM) particles dominated the contaminant distribution. Sediment contamination issues throughout the Huron‐Erie Corridor were dominated by mercury, released from sources along the St. Clair and Detroit Rivers. The mean enrichment factor EF_Al for mercury in these sediments has reached 68.3. Other metal pollutants were confined to the sediments in the lower depositional reach of the Corridor.     

PCBs in Great Lakes sediments, determined by positive matrix factorization

Previously determined PCB concentrations in 10 dated sediment cores from Lakes Michigan, Huron, Erie, and Ontario are analyzed by positive matrix factorization in order to find characteristic congener patterns including signs of anaerobic dechlorination. Three or four factors are sufficient to describe the PCB data for each lake. All four lakes are dominated by Aroclors 1248A, 1248G, 1254A, and 1254G. Aroclor 1260 is only a significant factor in Lake Michigan prior to 1975, reflecting in part a usage patterns of heavy chlorinated Aroclors early and less chlorinated Aroclors in the phase-out years in the 1970s. Dated records of factors or sources indicate clear PCB concentration maxima for Lakes Erie (1981) and Ontario(1968), while redistribution of PCBs in the less contaminated Lakes Michigan and Huron has occurred after 1980. Using a single data matrix for all four lakes provides a common basis and possibility to examine low degrees of dechlorination, while individual data matrices for each lake provide more accurate results and better separation of factors. Lakes Ontario, Michigan, and Huron undergo dechlorination via reactions such as 66(24-34) → 25(24-3) and 18(25-2) → 4(2-2) consistent with reactions H' + M, while Lake Erie appears to be dominated by 18(25-2) → 4(2-2) and 53(25-26) → 19(26-2) that are typical for processes M + Q.     

Trends in Mysis diluviana abundance in the Great Lakes, 2006–2016

With the large Diporeia declines in lakes Michigan, Huron, and Ontario, there is concern that a similar decline of Mysis diluviana related to oligotrophication and increased fish predation may occur. Mysis density and biomass were assessed from 2006 to 2016 using samples collected by the Great Lakes National Program Office's biomonitoring program in April and August in all five Great Lakes. Summer densities and biomasses were generally greater than spring values and both increased with bottom depth. There were no significant time trends during these 10–11 years in lakes Ontario, Michigan, or Huron, but there was a significant increase in Lake Superior. Density and biomass were highest in lakes Ontario and Superior, somewhat lower in Lake Michigan, and substantially lower in Lake Huron. A few Mysis were collected in eastern Lake Erie, indicating a small population in the deep basin of that lake. On average, mysids contributed 12–18% (spring-summer, Michigan), 18–14% (spring-summer, Superior), 30–13% (spring-summer, Ontario), and 3% (Huron) of the total open-water crustacean biomass. Size distributions consisted of two peaks, indicating a 2-year life cycle in all four of the deep lakes. Mysis were larger in Lake Ontario than in lakes Michigan, Superior, and Huron. Comparisons with available historic data indicated that mysid densities were higher in the 1960s–1990s (5 times higher in Huron, 2 times higher in Ontario, and around 40% higher in Michigan and Superior) than in 2006–2016.     

Spatial Distributions and Temporal Trends in Sediment Contamination in Lake St. Clair

The sediments of Lake St. Clair were surveyed in 2001 for a range of compound classes including metals (such as total mercury and lead), polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, organochlorine pesticides, polycyclic aromatic hydrocarbons, and short- and medium- chain chlorinated paraffins, in order to evaluate the spatial distribution and temporal trends of contamination. Concentrations of contaminants were generally low compared to the lower Great Lakes (Erie and Ontario), and were typically below the Canadian Sediment Quality Probable Effect Level (PEL) guidelines. The only exceptions were for mercury and DDE, where concentrations exceeded their respective PEL at one of the thirty-four sites sampled. With the exception of mercury, it was difficult to interpret spatial trends in contaminant concentrations due to these low levels, although relatively elevated concentrations of several contaminants were found in L’Anse Creuse Bay and at the outflow of the Thames River. In the case of mercury, historically-contaminated sediments in the St. Clair River associated with chlor-alkali production appeared to contribute to loadings to Lake St. Clair. There have been substantial reductions in sediment contamination in Lake St. Clair over the past three decades, as determined through sediment core profiles as well as through comparison of current data to those from historical surveys conducted in the early 1970s. These results indicate that management actions to reduce contaminant loadings to Lake St. Clair have been generally successful.     

Contaminant Analysis of Fillets from Great Lakes Coho Salmon, 1980

Analyses of coho salmon from each of the Great Lakes by a single laboratory produced residue data on the accumulation of environmental contaminants which have been banned, severely restricted, or are currently permitted in the basin. Coho salmon from Lake Superior contained only trace amounts or low levels of most toxic substances quantified; Lake Erie fish were contaminated with low levels of a number of pesticides and industrial compounds; relatively higher residues were detected in coho from Lake Huron and Lake Michigan; and the highest concentrations for a number of compounds were found in fillets from coho from Lake Ontario. Contaminant concentrations in migratory coho salmon indicate open lake contaminant problems rather than point source or nearshore conditions. Tissue residues were less than USFDA action levels, used by many agencies in assessing the severity of fish contaminant problems. Only mirex concentrations in fish collected from Lake Ontario exceeded a USFDA action level. The data reported in this study generally agree with recent findings from individual state contaminant monitoring programs. Problems with varying analytical and sampling techniques preclude direct comparisons with previously published data of other studies.     

Contaminant Trends in Lake Trout and Walleye From the Laurentian Great Lakes

Trends in PCBs, DDT, and other contaminants have been monitored in Great Lakes lake trout and walleye since the 1970s using composite samples of whole fish. Dramatic declines have been observed in concentrations of PCB, ΣDDT, dieldrin, and oxychlordane, with declines initially following first order loss kinetics. Mean PCB concentrations in Lake Michigan lake trout increased from 13 μg/g in 1972 to 23 μg/g in 1974, then declined to 2.6 μg/g by 1986. Between 1986 and 1992 there was little change in concentration, with 3.5 μg/g observed in 1992. ΣDDT in Lake Michigan trout followed a similar trend, decreasing from 19.2 μg/g in 1970 to 1.1 μg/g in 1986, and 1.2 μg/g in 1992. Similar trends were observed for PCBs and ΣDDT in lake trout from Lakes Superior, Huron and Ontario. Concentrations of both PCB and ΣDDT in Lake Erie walleye declined between 1977 and 1982, after which concentrations were relatively constant through 1990. When originally implemented it was assumed that trends in the mean contaminant concentrations in open-lake fish would serve as cost effective surrogates to trends in the water column. While water column data are still extremely limited it appears that for PCBs in lakes Michigan and Superior, trends in lake trout do reasonably mimic those in the water column over the long term. Hypotheses to explain the trends in contaminant concentrations are briefly reviewed. The original first order loss kinetics used to describe the initial decline do not explain the more recent leveling off of contaminant concentrations. Recent theories have examined the possibilities of multiple contaminant pools. We suggest another hypothesis, that changes in the food web may have resulted in increased bioaccumulation. However, a preliminary exploration of this hypothesis using a change point analysis was inconclusive.     

A New Biological Marker Layer in the Sediments of the Great Lakes: Bythotrephes cederstroemi (Schödler) Spines

The European cladoceran, Bythotrephes cederstroemi (Schödler), recently invaded the Laurentian Great Lakes. Based on recent zooplankton records, it most likely appeared first in 1984 in Lakes Ontario, Erie, and Huron, and in 1985 in Lake Michigan. It has yet to be reported from Lake Superior. This species is a relatively large-bodied predatory form that possesses a long, caudal, latterally barbed spine. B. cederstroemi spines and spine fragments were found in the upper fractions (predominantly 0–4 cm) of 35 sediment cores collected from seven areas of deposition in the eastern basin of Lake Erie. All remains were well preserved and easy to identify. Very few to 0 spines were found in core depths greater than 4 cm suggesting that the invasion of this species has resulted in a new, readily distinguishable time horizon marker.     

Metals and Essential Elements in Herring Gulls from the Great Lakes, 1983

Adult and prefledged herring gulls were collected from one location each in Lakes Ontario, Erie, Huron, and Superior. Composite samples of liver, kidney, and feather were analyzed for 24 elements and composite samples of bone for 22 elements. After consideration of quality assurance results, concentrations of 16 elements (Al, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, P, Pb, Sr, Ti, Zn) in liver, kidney, and feather were accepted for presentation while 6 elements were accepted from bone (Ca, Cd, Hg, P, Pb, Zn). Only lead, cadmium, and mercury values were of toxicological interest. Data on other trace elements are presented as baseline values among locations for each tissue and age class. Concentrations of Cd, Pb, and Hg were higher in adults than in prefledged young. Metal levels varied among different tissues with Cd highest in kidney (2.16 μg/g; Hamilton Harbour, Lake Ontario), Pb highest in bone (30.0 μg/g; Double Island, Lake Huron), and Hg highest in feather (6.11 μg/g; Middle Island, Lake Erie). Lead levels in both age classes were generally higher in tissues from the two upper lakes colonies than in samples from the lower lakes. Cadmium and mercury levels did not vary greatly among locations. Levels found are below those associated with metal toxicoses in laboratory studies with other avian species.