Western Lake Superior Research Articles

An analysis of the late glacial lake levels within the western Lake Superior basin based on digital elevation models

This study establishes a detailed lake-level history for the Lake Superior basin by mapping strandlines from 10-m and 3-m digital elevation models. There are 24 levels above the mid-Holocene Nipissing level, and elevations increase along a direction of 23.1° due to post-glacial rebound. The highest level, the Epi-Duluth, is steeper than subsequent levels and may pre-date the Lake View ice advance into the western Lake Superior basin at the end of the Younger Dryas stade. The most prominent level is the Duluth, ca. 10,800calyrBP. Ice retreat exposed successively lower outlets, routing overflow to the Lake Michigan and Huron basins. By 10,600calyrBP, lake levels in the western Superior basin had dropped almost 200m. This transformative period is complicated by multiple basin-wide events: the influx of glacial Lake Agassiz overflow, the creation of three sub-aqueous moraines, and a red to gray color transition in basin sediments. A later drawdown event has been hypothesized to have initiated the 9300calyrBP cooling event, but this flood was much smaller than estimated previously. If freshwater triggered the 9300calyrBP event, the source of the water must have been Lake Agassiz, not Lake Superior.

Photochemical degradation of dissolved organic matter from streams in the western Lake Superior watershed

The input and fate of dissolved organic matter (DOM) can have important consequences for coastal zone productivity in large lakes and oceans. Chromophoric DOM (CDOM) is often delivered to coastal zones from rivers and streams and affects light penetration in a water column. CDOM can protect biota from damaging ultraviolet (UV) light by acting as sunscreen, resulting in increased ecosystem productivity. Alternatively, CDOM can decrease ecosystem productivity by absorbing light needed for photosynthesis and forming photoreaction products that are harmful to coastal zone biota. Increased urbanization of watersheds and seasonal differences in weather patterns change the delivery pathways, reactivity, input, and energy flow of DOM (and its CDOM component) into aquatic systems. This study investigated the effects of watershed and season on the concentrations and potential photodegradation of stream-derived DOM in Lake Superior tributaries, chosen to be geographically and geologically similar but differing in land use. Organic carbon analysis, UV–Visible spectrophotometry, and terrestrial (land use) analysis were used to investigate differences among samples and sample treatments. The major differences in DOM concentration and photochemical response appeared seasonal rather than site specific, with snow-melt samples showing stronger and more consistent changes in UV–Visible parameters while base-flow samples showed stronger and more consistent losses in DOC.

Repeat surveys of spawning cisco (Coregonus artedi) in western Lake Superior: timing, distribution and composition of spawning stocks

Repeat surveys of spawning cisco (Coregonus artedi) in western Lake Superior: timing, distribution and composition of spawning stocks

Efficient Asset Management Planning: Condition – Criticality Based Assessments of Western Lake Superior Sanitary District Assets

Efficient Asset Management Planning: Condition – Criticality Based Assessments of Western Lake Superior Sanitary District Assets

Seasonally Dynamic Diel Vertical Migrations of Mysis diluviana, Coregonine Fishes, and Siscowet Lake Trout in the Pelagia of Western Lake Superior

AbstractDiel vertical migrations are common among many aquatic species and are often associated with changing light levels. The underlying mechanisms are generally attributed to optimizing foraging efficiency or growth rates and avoiding predation risk (μ). The objectives of this study were to (1) assess seasonal and interannual changes in vertical migration patterns of three trophic levels in the Lake Superior pelagic food web and (2) examine the mechanisms underlying the observed variability by using models of foraging, growth, and μ. Our results suggest that the opossum shrimp Mysis diluviana, kiyi Coregonus kiyi, and siscowet lake trout Salvelinus namaycush migrate concurrently during each season, but spring migrations are less extensive than summer and fall migrations. In comparison with M. diluviana, kiyis, and siscowets, the migrations by ciscoes C. artedi were not as deep in the water column during the day, regardless of season. Foraging potential and μ probably drive the movement patterns of M. diluviana, while our modeling results indicate that movements by kiyis and ciscoes are related to foraging opportunity and growth potential and receive a lesser influence from μ. The siscowet is an abundant apex predator in the pelagia of Lake Superior and probably undertakes vertical migrations in the water column to optimize foraging efficiency and growth. The concurrent vertical movement patterns of most species are likely to facilitate nutrient transport in this exceedingly oligotrophic ecosystem, and they demonstrate strong linkages between predators and prey. Fishery management strategies should use an ecosystem approach and should consider how altering the densities of long‐lived top predators produces cascading effects on the nutrient cycling and energy flow in lower trophic levels.

‘State of Lake Superior’: A review

‘State of Lake Superior’: A review

Estimating mercury concentrations and loads from four western Lake Superior watersheds using continuous in-stream turbidity monitoring

Many streams along the Minnesota coast of Lake Superior have been listed as impaired from either high turbidity or high fish mercury concentrations or both. Both turbidity and total mercury have been shown to be strongly correlated to total suspended sediment in many disturbed watersheds. Turbidity and total mercury concentrations and loads were estimated in four western Lake Superior watersheds from 2005–2006 using automated in-stream turbidity measurements. Regression models were developed relating this near-continuous turbidity data to grab sample measures of mercury during differing flow regimes. Total mercury values ranged from 1 to 28 ng l−1 throughout the open water season and showed a close relationship to total suspended sediment (r2 = 0.85, n = 23; p < 0.001) and a less robust but still significant relationship with turbidity (r2 = 0.40, n = 34; p < 0.001) for all four streams. Mercury loads to Lake Superior were estimated to range from 8 to 97 g yr−1 with watershed yields ranging from 0.5 to 4.3 μg m−2 yr−1. Continuous turbidity monitoring appears to be a reasonable surrogate for both suspended sediment and total mercury concentration, providing information when manual sample collection is cost-prohibitive or logistically difficult, and across a wide range of flows.

“Mr. Burk Is Most Interested in Their Welfare”: J.G. Burk’s Campaign to Help the Anishinabeg of Northwestern Ontario, 1923-53

Although there is a small but growing body of literature on Euro-Canadians who acted "with good intentions" towards the First Nations (Haig-Brown and Nock 2006), precious little has been written about those within the ranks of the Department of Indian Affairs who acted benevolently towards the Aboriginal peoples. James Gerry Burk, Indian agent for the Anishinabeg of the western Lake Superior region for three decades (1923-53), was one such individual. He chose to ignore the department's prevailing racist ideology in favour of nurturing the incipient desire for industry and enterprise that he saw first-hand among the Aboriginal constituents of his agency. In the process, he was compelled to overcome numerous obstacles that Indian Affairs placed in his way. As a result, Burk's career stands as a glowing testament to the indomitable spirit of one departmental official's commitment to assisting the Aboriginal peoples.

Genetic assessment of straying rates of wild and hatchery reared lake sturgeon (Acipenser fulvescens) in Lake Superior tributaries

Natal philopatry in lake sturgeon (Acipenser fulvescens) has been hypothesized to be an important factor that has lead to genetically distinct Great Lakes populations. Due to declining abundance, population extirpation, and restricted distribution, hatchery supplementation is being used to augment natural recruitment and to reestablish populations. If hatchery-reared lake sturgeon are more likely to stray than naturally produced individuals, as documented in other well-studied species, outbreeding could potentially jeopardize beneficial site-specific phenotypic and genotypic adaptations. From 1983 to 1994, lake sturgeon propagated using eggs taken from Lake Winnebago adults (Lake Michigan basin) were released in the St. Louis River estuary in western Lake Superior. Our objective was to determine whether these introduced individuals have strayed into annual spawning runs in the Sturgeon River, Michigan. Additionally, we estimated a natural migration rate between the Sturgeon River and Bad River, Wisconsin populations. Presumed primiparous lake sturgeon sampled during Sturgeon River spawning runs from 2003 to 2008 were genotyped at 12 microsatellite loci. Genotypic baselines established for the Sturgeon River (n=101), Bad River (n=40), and Lake Winnebago river system (n=73) revealed a relatively high level of genetic divergence among populations (mean FST=0.103; mean RST=0.124). Likelihood-based assignment tests indicated no straying of stocked Lake Winnebago strain lake sturgeon from the St. Louis River into the Sturgeon River spawning population. One presumed primiparous Sturgeon River individual likely originated from the Bad River population. Four first-generation migrants were detected in the Sturgeon River baseline, indicating an estimated 3.5% natural migration rate for the system.

Taxonomic Study of the Carex tenera Group (Cyperaceae)

According to previous molecular study, the Carex tenera group sensu lato consists of C. tenera s. l. and C. normalis in one clade and C. festucacea, C. oronensis, and C. tincta in a sister clade. We found that Carex tincta, clarified by thorough review of herbarium materials, has a much narrower geographic range than previously thought, centering on Maine (U. S. A.), adjacent states, and adjacent portions of Canada with rare scattered occurrences to western Lake Superior. Carex tenera has traditionally been thought to consist of two varieties: the transcontinental variety tenera and the upper Midwest (U. S. A.) variety echinodes. In light of ecological and chromosomal differences, AFLP genetic distances, and morphological analysis the latter should be recognized as a distinct species, Carex echinodes comb. et stat. nov. Carex echinodes and narrow-leaved forms of C. normalis can be challenging to differentiate morphologically, but widest leaf width, inflorescence internode length, peduncle diameter, and growth habit separate the two taxa. New chromosome numbers are reported, with those of C. tenera (n = 24 + 2III, 26, 27, 28) having a lower range than either those of C. echinodes (n = 37, 38, 39) or C. normalis (n = 34, 35, 36).

An evaluation of iron bioavailability and speciation in western Lake Superior with the use of combined physical, chemical, and biological assessment

An iron‐dependent cyanobacterial bioreporter (Synechococcus strain KAS101) was used in unison with size‐fractionated iron content (>0.45, <0.45, <0.02 µm), and chemical characterization of iron complexation (C18 resin column) to elucidate the bioavailable forms of iron present in Lake Superior during periods of inverse thermal stratification (May) and strong thermal stratification (September) of the water column. The results provide evidence of organic complexation of iron in Lake Superior waters. Iron in most sampled water was complexed by organic compounds that behaved like fulvic acids, whereas some samples showed evidence for the presence of siderophore‐like compounds. The presence of dissolved organic matter suppressed the cellular luminescence of the bioreporter, indicating an increased iron bioavailability. This effect could result either from the presence of siderophores forming iron complexes that are bioavailable to the bioreporter, or from more indirect effects because of the presence of other organic compounds, such as fulvic acids or polysaccharides. Model ligand additions, iron bioaccumulation, and photo‐oxidation of dissolved organic matter were used to assess the bioavailability of organically complexed iron to the bioreporter. A significant fraction of the iron (40‐100%) was bioavailable to the bioreporter. Iron bioavailability was high enough for the bioreporter not to be iron limited in the water collected from Lake Superior. This measure of bioavailability to picocyanobacteria is relevant because picoplankton accounted for the majority of chlorophyll a in Lake Superior during this study.

Model Calculations of Total Maximum Daily Loads of Mercury for Drainage Lakes1

Abstract: The Watershed Analysis Risk Management Framework watershed model was enhanced to simulate the transport and fate of mercury and to calculate the fish mercury concentrations (FMC) attained by fish through the food web. The model was applied to Western Lake Superior Basin of Minnesota, which has many peat lands and lakes. Topographic, land use, and soil data were used to set up the model. Meteorology and precipitation chemistry data from nearby monitoring stations were compiled to drive the model. Simulated flow and mercury concentrations for several stream stations were comparable to available data. The model was used to perform mercury total maximum daily load calculations for two contrasting drainage lakes (Wild Rice Lake and Whiteface Reservoir). The model results for wet deposition, dry deposition, evasion, watershed yield, and soil sequestration of mercury were comparable with available actual data. The model predicted lake ice cover from November to April and weak stratification in summer, typical of shallow lakes in cold regions. The simulated sulfate decrease and methylmercury increase near the lake bottom in late summer are caused by sulfate reduction and mercury methylation that occur in the surficial sediment. Simulated FMC were within the range of observed values and the R2 of correlation between the simulated and observed FMC was 0.77. Under the 1989‐2004 base condition, the average simulated FMC of four‐year‐old walleye was 0.31 μg/g for Whiteface Reservoir and 0.15 μg/g for Wild Rice Lake. The FMC criterion in Minnesota is 0.2 μg/g. Wild Rice Lake already meets this criterion without any load reduction. The model showed that a 65% reduction in atmospheric mercury deposition will not, by itself, allow Whiteface Reservoir to meet the criterion in 15 years. Additional best management practices will be needed to reduce 50% of the watershed input.

Distribution, Abundance, and Range of the Round Goby, Apollina melanostoma, in the Duluth-Superior Harbor and St. Louis River Estuary, 1998–2004

Round gobies were first discovered in the Duluth-Superior Harbor, Lake Superior, in 1995. Anecdotal sightings by anglers and others suggested that the infestation was growing and expanding; however, direct evidence of the distribution and expansion rate in the harbor was largely unknown. Distribution and range of the round goby, Apollonia melanostoma, (formerly Neogobius melanostomus) was assessed using bottom trawl sampling throughout the Duluth-Superior Harbor, and portions of the lower St. Louis River from 1998 to 2004. Previous to 1998, round gobies only were reported to occupy the harbor between the two shipping entries (river kilometer 1 to 7). By 2004, they expanded throughout the harbor and upstream to river kilometer 13, but remained absent in western Lake Superior. The number of round gobies captured per 5 minutes of trawling (catch per unit effort, CPUE) increased from less than 1 fish in 1998 to an average 5.4 ± 1.2 SE fish in 2004, indicating a large increase in the population. The median yearly fish total length varied from 56.0 to 81.5 mm and wet weight varied from 2.3 to 7.0 g. As nest guarding male round gobies were located in rocky habitats inaccessible to trawling, the initial years were dominated by female round gobies with a 16:1 female to male ratio, but by 2002 the maximum ratio was 2:1. The ratio change may be indicative of the increasing population forcing males from their preferred rocky habitat onto open substrates that were more accessible to trawling.

Recruitment Dynamics of Lake Trout in Western Lake Superior during 1988–1995

AbstractStocks of lake trout Salvelinus namaycush in Lake Superior are recovering from historical collapse. Stocking, control of sea lampreys Petromyzon marinus, and harvest restrictions have aided lake trout recovery, but the contribution of stocked lake trout to contemporary recruitment has not been quantified in western Lake Superior. Using variants of the Ricker stock–recruit model, we evaluated the production of age‐7 lake trout (recruits) by examining age‐8 and older wild and stocked parental lake trout (spawners). We found that density of wild lake trout spawners and recruits increased during 1980–2003, whereas the density of stocked spawners decreased in all management areas. Two competing models best described recruit density of the 1988–2003 year‐classes: (1) wild and stocked parents each contributed to recruitment but stocked parents contributed negatively and (2) only wild parents contributed to recruitment. Recruitment rates declined significantly with increasing spawner density in four of five management areas, which suggests that recruitment is density dependent in much of western Lake Superior. We conclude that stocked lake trout did not contribute significantly to lake trout rehabilitation in western Lake Superior during 1980–1995.

MAGIC method for subnanomolar orthophosphate determination in freshwater

A freshwater magnesium hydroxide coprecipitation method (MAGIC) has been developed to accurately and reproducibly determine low (nanomolar to subnanomolar) soluble reactive phosphorus (SRP) concentrations in freshwater. The method allows investigation of phosphorus distributions and cycling for systems in which SRP is below the detection limits of conventional methods. In natural waters, both inorganic and organic forms of P are coprecipitated; hence the method is essentially a preconcentration rather than a separation technique. Quantification of SRP on dissolved MAGIC precipitates follows a modified version of the standard molybdenum blue colorimetric method, using a spectrophotometer with ~0.1 milliabsorbance (mAbs) noise. Detection limit is 0.15 nM, improving on typical conventional colorimetric methods by a factor of ~50, with precision (RSD of triplicates) of ~10% at the 1 nM SRP level, 10% at ≤0.5 nM, and 4% to 7% at >1 nM. Considerable method development was necessary to eliminate or correct for multiple interferences, including a novel finding of potential interference by colored dissolved organic matter, and to optimize recovery, precision, and detection limit. The method was applied to filtered, frozen samples from western Lake Superior, showing that SRP concentrations are characterized by limited seasonal variability, largely uniform vertical distribution, and near‐bottom enrichment. Concentrations ranged from 0.4 to 10.9 nM SRP, representing ~10% of the total dissolved phosphorus pool. MAGIC is an easily employed analytical method appropriate for measurement of very low SRP in lakes and rivers.

Breeding Bird Communities Across an Upland Disturbance Gradient in the Western Lake Superior Region

Upland breeding bird communities were sampled from 225 points in 15 survey routes in the coastal region of western Lake Superior to examine relationships to human land use. Eighty-four species were detected and 50 were abundant enough to be included in data analysis. Monotonic quadratic regression models were constructed for these 50 species by using species counts as the dependent variable and the proportion of human conversion of the landscape (residential, agriculture, and commercial/industrial land uses) within each study area as the independent variable. Twenty-seven bird species had significant regressions (P < 0.05), 18 of which generally avoided areas developed by humans and 9 of which were attracted to development. Detrended correspondence analysis using counts of these 27 bird species was used to investigate multivariate, community responses to development. The first DCA axis was interpreted as a gradient from urban avoiding to urban exploiting bird species and was strongly correlated with land cover variables related to human development. Our results advance the idea that breeding bird communities can be used as indicators of ecological condition and can diagnose potential causes for changes in these conditions. Further, our study points out the usefulness of bird monitoring data in regional planning efforts that incorporate goals for maintaining native biological diversity.

The Lake Superior varve stratigraphy and implications for eastern Lake Agassiz outflow from 10,700 to 8900 cal ybp (9.5–8.0 14C ka)

Glaciolacustrine rhythmites within sediment cores from Lake Superior record the regional recession of the Laurentide Ice Sheet (LIS) from 10,700 to 8900 cal ybp [ca. 9.5–8.0 14C ka]. LIS retreat from Superior opened eastern Lake Agassiz outlets so that the rhythmites reflect the combined impacts of sediment-laden meltwater and Lake Agassiz discharge. Multiple rhythmite stratigraphies, a time series analysis of the thickness measurements, and high-resolution inorganic carbonate data demonstrate that this is an annual record (varved). The varve thickness records primarily document regional ice margin dynamics; correlative thick varve sequences at 9100 cal ybp [∼ 8.1 14C ka] and 10,400–10,200 cal ybp [∼ 9.2–9.0 14C ka] record two periods of enhanced glaciofluvial discharge, most likely moraine formation (the Nakina and Nipigon). General varve cessation is associated with the circumvention of Lake Agassiz and glacial meltwater into Lake Ojibway at 9040 cal ybp [∼ 8.1 14C ka], although adjacent to the inlets from Lake Nipigon, rhythmic sedimentation persisted for 200 years. Positively identifying Lake Agassiz catastrophic discharge events remains speculative but seems feasible. Following retreat of Marquette ice that had re-advanced to fill the basin, the initial influx of Lake Agassiz water is expected at around 10,600 cal ybp [∼ 9.4 14C ka], but at this time, most of northeastern Lake Superior was covered by ice. Three sets of thick–thin varves in western Lake Superior perhaps record influxes of Lake Agassiz at around 10,630, 10,600, and 10,570 cal ybp [∼ 9.4 14C ka]. Varve formation in Superior coincides with high lake levels in Lake Huron, suggesting that high lake levels in Huron correspond to periods of high Agassiz and/or meltwater flow into Lake Superior.

Factors Affecting Survival Rates of a Recovering Lake Trout Population Estimated by Mark–Recapture in Lake Superior, 1969–1996

AbstractWe used data from a long‐term Wisconsin Department of Natural Resources mark–recapture study to examine the dynamics of survival in a recovering population of lake trout Salvelinus namaycush in western Lake Superior from 1969 to 1996. Survival rates were estimated using the Cormack–Jolly–Seber method, and a series of models were constructed to examine the effect of year, size, sex, and origin (hatchery versus wild) on the survival rates of lake trout captured within the Gull Island Shoal refuge established in 1976. To select among the models, we used Akaike's information criterion corrected for small sample size and overdispersion. Our estimates of survival rates were adjusted using previously published tag loss rates for the three types of tags used since 1969. Survival estimates for wild fish varied widely among years; the lowest survival rates were observed in 1973 and 1974 and again in 1985 and 1986. Survival rates of wild fish were dependent on sex and size: Survival rates for male lake trout were 7% lower on average than those for female fish (means, 0.76 and 0.83), and large‐sized fish tended to have higher survival rates. Survival rates of hatchery‐reared fish could not be estimated for the entire time period owing to sample‐size issues; however, between 1983 and 1996 we found that hatchery fish survival rates were on average about 3% lower than those for wild fish. Survival estimates within the refuge were higher than estimates reported by others for fish outside the refuge and slightly higher than estimates from other Great Lakes studies.

Trace‐element analysis of native copper: The view from Northern Minnesota, USA

AbstractNative copper, both finished artifacts and worked pieces, are relatively common in pre‐Contact sites of northeastern Minnesota. Fifteen artifact samples and seven sources of native copper were submitted for trace‐element analysis as a test of the procedures developed by G. Rapp, Jr. and colleagues (2000). Although the specific sources chosen had high typicality probabilities, very low posterior probabilities preclude confidence that the artifacts were accurately sourced. Potential problems include incomplete characterization of several sources, as well as the limited number of sources in the database. Of more interest than identification of specific sources is the selection of apparent source pairs. Michipicoten (eastern Lake Superior) and Isle Royale (western Lake Superior) are often chosen together; Weyerhauser Mine (Wisconsin) and the Champion Mine (Keewenaw Peninsula) may form another pair. Future research should concentrate on identifying patterns of sources in the region rather than focusing on specific mines. © 2007 Wiley Periodicals, Inc.

Geoarchaeology and late glacial landscapes in the western lake superior region, Central North America

AbstractThe transition from full glacial to interglacial conditions along the southern margin of the Laurentide ice sheet resulted in dramatic changes in landscapes and biotic habitats. Strata and landforms resulting from the Wisconsin Episode of glaciation in the area directly west of Lake Superior indicate a context for late Pleistocene biota (including human populations) connected to ice margins, proglacial lakes, and postglacial drainage systems. Late Glacial landscape features that have the potential for revealing the presence of Paleoindian artifacts include abandoned shorelines of proglacial lakes in the Superior and Agassiz basins and interior drainages on deglaciated terrains. The linkage between Late Pleistocene human populations and Rancholabrean fauna has yet to be demonstrated in the western Lake Superior region, although isolated remains of mammoth ( Mammuthus) have been documented, as well as fluted points assigned to Clovis, Folsom, and Holcombe‐like artifact forms. Agate Basin and Hell Gap (Plano‐type) artifacts also imply the presence of human groups in Late Glacial landscapes associated with the Agassiz and Superior basins. © 2007 Wiley Periodicals, Inc.