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.     

The Great Lakes Cladophora Model: Development,testing, and application to Lake Michigan

A recent review of the Great Lakes Water Quality Agreement has concluded that while controls on phosphorus inputs to Lake Michigan achieved the desired effect in offshore waters, the nearshore region continues to suffer from elevated phosphorus levels. Failure to achieve trophic state goals in the nearshore is manifested in nuisance growth of Cladophora and attendant impacts on property owners, utilities, and the public health and welfare. This study focuses on a site in Lake Michigan near Milwaukee, Wisconsin, where nuisance growth of Cladophora and associated beach fouling occur regularly. A mechanistic model simulating Cladophora growth, suitable for guiding nutrient management in the Great Lakes nearshore, is presented. The model represents an update of the Canale and Auer framework, reflecting current understandings of Cladophora ecology and offering a user-friendly interface making the software more widely available to decision makers. This Great Lakes Cladophora Model (GLCM) is first validated for the Auer/Canale data set collected in 1979 at a site on Lake Huron and then for a data set developed in 2006 for a site on Lake Michigan. Model performance under the strikingly different forcing conditions (depth, light, phosphorus levels) characteristic of these two sites affirms the widespread applicability of the tool. The GLCM is then extended to examine the impacts of ecosystem perturbation (dreissenid colonization) on Cladophora growth and to future approaches to monitoring and management.     

Total gaseous mercury (TGM) concentration over Lake Superior and Lake Michigan

Mercury-contaminated fish are a serious problem in the Great Lakes basin, because mercury is a potent neurotoxin that poses a danger to both humans and wildlife. Lake Superior lake trout and walleye have the highest mercury concentrations of the five Great Lakes. Because the atmosphere is the major source of mercury to the Great Lakes, information on the over-water mercury concentration is essential to model the mercury biogeochemical cycle. For the first time in the peer-reviewed literature, this paper presents total gaseous mercury (TGM) measurements made over Lake Superior and Lake Michigan. The Lake Superior aircraft measurements were made at an altitude of 300 m, and the Lake Michigan aircraft measurements at a variable altitude of 30–300 m. The over-water Lake Superior TGM of 1.02 ± 0.34 ng/m³ is much lower than the TGM from nine stations in the Canadian Atmospheric Mercury Measurement Network (CAMNet) and six stations in the Atmospheric Mercury Network (AMNet). The land-based TGM concentrations average range from 1.25 to 1.75 ng/m³ which are in good agreement with current global average values of 1.3–1.6 ng/m³. The over-water Lake Michigan TGM is 1.65 ± 0.61 ng/m³. We also present Lake Superior over-water measurements of volatile organic compounds (VOC), ozone (O₃), nitrogen oxide (NO_y), and particulate matter. Elemental carbon (EC) is a tracer for mercury because mercury is released during the combustion of coal. EC is significantly correlated with TGM over both Lake Superior and Lake Michigan. TGM over Lake Michigan is also significantly correlated with organic carbon, sulfate, nitrate and ammonium.     

Dreissenid mussels are not a “dead end” in Great Lakes food webs

Dreissenid mussels have been regarded as a “dead end” in Great Lakes food webs because the degree of predation on dreissenid mussels, on a lakewide basis, is believed to be low. Waterfowl predation on dreissenid mussels in the Great Lakes has primarily been confined to bays, and therefore its effects on the dreissenid mussel population have been localized rather than operating on a lakewide level. Based on results from a previous study, annual consumption of dreissenid mussels by the round goby (Neogobius melanostomus) population in central Lake Erie averaged only 6 kilotonnes (kt; 1 kt = one thousand metric tons) during 1995–2002. In contrast, our coupling of lake whitefish (Coregonus clupeaformis) population models with a lake whitefish bioenergetics model revealed that lake whitefish populations in Lakes Michigan and Huron consumed 109 and 820 kt, respectively, of dreissenid mussels each year. Our results indicated that lake whitefish can be an important predator on dreissenid mussels in the Great Lakes, and that dreissenid mussels do not represent a “dead end” in Great Lakes food webs. The Lake Michigan dreissenid mussel population has been estimated to be growing more than three times faster than the Lake Huron dreissenid mussel population during the 2000s. One plausible explanation for the higher population growth rate in Lake Michigan would be the substantially higher predation rate by lake whitefish on dreissenid mussels in Lake Huron.     

Historical changes and current status of crayfish diversity and distribution in the Laurentian Great Lakes

Despite increasing recognition of the importance of invertebrates, and specifically crayfish, to nearshore food webs in the Laurentian Great Lakes, past and present ecological studies in the Great Lakes have predominantly focused on fishes. Using data from many sources, we provide a summary of crayfish diversity and distribution throughout the Great Lakes from 1882 to 2008 for 1456 locations where crayfish have been surveyed. Sampling effort was greatest in Lake Michigan, followed by lakes Huron, Erie, Superior, and Ontario. A total of 13 crayfish species occur in the lakes, with Lake Erie having the greatest diversity (n = 11) and Lake Superior having the least (n = 5). Five crayfish species are non-native to one or more lakes. Because Orconectes rusticus was the most widely distributed non-native species and is associated with known negative impacts, we assessed its spread throughout the Great Lakes. Although O. rusticus has been found for over 100 years in Lake Erie, its spread there has been relatively slow compared to that in lakes Michigan and Huron, where it has spread most rapidly since the 1990s and 2000, respectively. O. rusticus has been found in both lakes Superior and Ontario for 22 and 37 years, respectively, and has expanded little in either lake. Our broad spatial and temporal assessment of crayfish diversity and distribution provides a baseline for future nearshore ecological studies, and for future management efforts to restore native crayfish and limit non-native introductions and their impact on food web interactions.     

High frequency radar and its application to fresh water

High frequency (HF) radar has become an important tool for remotely mapping the spatial distribution and temporal evolution of waves and currents of the nearshore coastal ocean. Its acceptance along ocean coasts has resulted in the development of several commercially available systems and a planned nationwide coastal network to routinely measure coastal currents. Because HF radiation is known to propagate less efficiently over fresh water than seawater, it has been largely overlooked as a viable tool for freshwater application. However, its potential utility in freshwater was clearly demonstrated by a deployment along Lake Michigan as part of the 1999–2001 Episodic Events Great Lakes Experiment. As part of this experiment, the University of Michigan Multi-frequency Coastal Radar consistently produced reliable near surface current measurements to a range of approximately 25 km offshore showing strong correlation with both in-situ measurements and numerical hind-casts. This paper provides background on HF radar technology, a summary of the current state of the art with respect to freshwater and describes the results of a recent experiment to measure the propagation of HF radar signal over freshwater using CODAR Ocean Sensors SeaSondes, operating at 5 and 42 MHz with 21 W and 90 W average radiated powers, respectively. The effective offshore range for these radars was found to be 18 km at 5 MHz and 4–5 km at 42 MHz. These findings are consistent with currently available models for the prediction of propagation loss, verifying that they can reliably be used to estimate ranges in freshwater settings.     

Predicting the potential distribution of the non-native Red Swamp Crayfish Procambarus clarkii in the Laurentian Great Lakes

The ongoing threat of introduction of invasive species, including crayfish, to the Laurentian Great Lakes has motivated the development of predictive models to inform where these invaders are likely to establish. Our study is among the first to apply regional freshwater-specific GIS layers to species occurrence data to predict ecosystem suitability to invasions, specifically for the red swamp crayfish, Procambarus clarkii, in the Great Lakes. We combined a database of crayfish species occurrences with the Great Lakes Aquatic Habitat Framework (GLAHF) GIS layers to model habitats suitable to invasion by P. clarkii using boosted regression trees and physiological information for this species. We developed a model of all suitable crayfish habitat across the Great Lakes, then constrained this habitat to areas anticipated to be suitable for P. clarkii based on known physiological limitations of this species. Specifically, P. clarkii requires a minimum temperature of 15?°C for copulation and oviposition, with peak reproduction occurring at temperatures of 20–23?°C. We identified 2% of the Great Lakes as suitable for P. clarkii establishment and 0.88% as optimal for this crayfish, primarily located on the southern coastlines of lakes Michigan and Erie and shallow bays including Saginaw Bay (Lake Huron), Green Bay (Lake Michigan), and Henderson Bay (Lake Ontario). These predictions of where P. clarkii is likely to establish populations can be used to identify areas where education, outreach, compliance, and law enforcement efforts should seek to prevent new introductions of this crayfish and help prioritize locations for surveillance to detect newly established populations.     

Evidence of a remnant self-sustaining strain of lake trout in the Lake Michigan basin

Managers have long embraced the need to maintain diversity as a requisite condition for population and community sustainability. In the case of Great Lakes lake trout, diversity has been severely compromised. The identification of new gamete sources may be beneficial to lake trout reintroduction efforts, particularly in situations where native stocks have been completely extirpated such as in Lake Michigan. Lake trout from Elk Lake, Michigan, are genetically distinct from domestic hatchery strains and historical forms of lake trout from Lake Michigan. Importantly, Elk Lake fish were genetically distinct from Marquette strain lake trout which were previously stocked into Elk Lake. Elk Lake fish were most similar to Lake Michigan basin-derived Lewis Lake (LLW) and Green Lake (GLW) hatchery strains and to historical Lake Michigan populations from the Charlevoix, Michigan area. While all individuals exhibited characteristics of lean form lake trout, the body shape of lake trout from Elk Lake, stocked lean fish from Lake Michigan and Lake Superior wild lean strains from near Isle Royale differed. Elk Lake fish were more fusiform, elongate, and streamlined with a narrower caudal peduncle compared to hatchery lean strains and wild lean forms from the Isle Royale region of Lake Superior. The lake trout population in Elk Lake is a remnant of a now extirpated native Lake Michigan population that was established either by natural colonization or stocking from historical Lake Michigan populations. Elk Lake lake trout is as genetically diverse as other strains used in Great Lakes reintroduction efforts and likely represent a viable gamete source representing genetic diversity lost from Lake Michigan.     

What do our lakes mean to us? An understanding of Michigan coastline communities’ perceptions of the Great Lakes

Four of the Great Lakes and Lake St. Clair serve as part of the 5261 km coastline of the State of Michigan. Understanding of the relationship between Michigan residents and these Lakes are important for the creation of messages designed to instill the desire to become better stewards of the Michigan coastline. Focus groups totaling 100 Michigan residents were held across the State to learn how residents feel about general issues facing Michigan’s coastline. The two major themes that emerged from the focus groups were issues related to the rising lake waters and the need for education on coastline awareness and stewardship. Other important themes emerged for the focus areas of the research team and its funding organization. There were differences of opinion on some of the issues between residents of the Upper and Lower Peninsulas (for example, public access was not as important an issue in the Upper Peninsula) and also for residents of Lake Michigan versus Lake Huron coastlines in the Lower Peninsula (storms are causing more damage and erosion on the Lake Michigan beaches).     

Temporal Effects of St. Clair River Dredging on Lakes St. Clair and Erie Water Levels and Connecting Channel Flow

A Great Lakes hydrologic response model was used to study the temporal effects of St. Clair River dredging on Lakes St. Clair and Erie water levels and connecting channel flows. The dredging has had a significant effect on Great Lakes water levels since the mid-1980s. Uncompensated dredging permanently lowers the water levels of Lakes Michigan and Huron and causes a transitory rise in the water levels of Lakes St. Clair and Erie. Two hypothetical dredging projects, each equivalent to a 10 cm lowering of Lakes Michigan and Huron, were investigated. This lowering is approximately half the effect of the 7.6 and 8.2 meter dredging projects. In the first case the dredging was assumed to occur over a single year while in the second it was spread over a 2-year period. The dredging resulted in a maximum rise of 6 cm in the downstream levels of Lakes St. Clair and Erie. The corresponding increase in connecting channel flows was about 150 m³s^?1. The effects were found to decrease over a 10-year period with a half-life of approximately 3 years. The maximum effects on Lake Erie lagged Lake St. Clair by about 1 year.     

European Valve Snail Valvata piscinalis (Müller) in the Laurentian Great Lakes Basin

Previously reported from the lower Great Lakes basin and St. Lawrence and Hudson rivers, the nonindigenous gastropod Valvata piscinalis was found for the first time in Superior Bay (Minnesota) of Lake Superior, Lake Michigan (Wisconsin), and Oneida Lake (New York) of the Lake Ontario basin. This snail was not abundant in Lakes Superior and Michigan, whereas in eutrophic Oneida Lake it reached a maximum density of 1,690 individuals/m² (mean density = 216 individuals/m²). Human-mediated disturbances could facilitate the range extension of this snail by providing dispersal opportunities (e.g., canals, shipping traffic) or increasing nutrients (e.g., eutrophication). A native of the Palaearctic region, V. piscinalis has colonized sites across the Great Lakes basin, suggesting that it will likely become common in disturbed Great Lakes areas.     

Range Expansion of the Exotic Zooplankter Cercopagis pengoi (Ostroumov) into Western Lake Erie and Muskegon Lake

Previously reported from Lakes Ontario and Michigan, the nonindigenous zooplankter Cercopagis pengoi was found for the first time in western Lake Erie, the Detroit River, and Muskegon Lake, Michigan, during summer 2001. A native of the Ponto-Caspian region, C. pengoi is currently expanding its range in North America. Analysis of mitochondrial gene ND5 sequences confirmed that the Lake Erie haplotype is identical to that reported previously from Lakes Ontario and Michigan and the Finger Lakes, New York. These findings support the hypothesis that C. pengoi's range expansion in the Great Lakes likely resulted from inter-lake transfer of ballast water, rather than from additional introductions from European locations. Pleasure-craft traffic operating between Lake Michigan and Muskegon Lake is likely responsible for this inland transfer of Cercopagis, a trend that likely will increase due to human activities.     

Distribution of Chlorinated Organic Contaminants in Dreissenid Mussels Along the Southern Shores of the Great Lakes

Samples of dreissenid mussels were collected from 21 sites along the U.S. shores of the southern part of the Great Lakes and their connecting channels. These samples were analyzed for tissue levels of 16 chlorinated organic compounds, mostly pesticides, as well as for lipid levels. Aldrin, endrin, and lindane were found above detection levels at less than one-half of the sites, primarily at sites in Lake Michigan. Mirex was detected at nine sites mostly in Lake Ontario and the Niagara River, but also near Detroit and in Saginaw Bay. Heptachlor was detected at only two sites, both in Lake Erie. Cis-chlordane, dieldrin, hexachlorobenzene, heptachlor, trans-nonachlor, and total DDTs were detected at all or almost all of the sites. Except for hexachlorobenzene, which was highest near Buffalo, these chemicals were found at higher concentrations in Lake Michigan, especially near Milwaukee, than in the other areas studied. A comparison of the concentrations of chlorinated organic compounds to the levels of lipids showed that differences in dreissenid lipid levels among sites were not the major cause of the observed differences in concentrations in the chlorinated organic compounds.At most sampling locations, the category total DDTs was composed primarily of the DDT breakdown products DDD and especially DDE. However, a substantial percentage of the total DDTs detected at sites in eastern Lake Erie and western Lake Ontario was composed of the parent DDT compounds, suggesting the presence of a relatively recent input of this compound in this area.Comparison of the concentrations of chlorinated organic compounds measured in Great Lakes dreis-senids with concentrations of these compounds in marine mussels and oysters found generally similar levels for most of the compounds. Exceptions to this were hexachlorobenzene and mirex which had mean concentrations more than 5 times greater in mussels from the Great Lakes than from marine locations and lindane which had concentrations in mussels from the Great Lakes less than one-tenth of those from marine mussels.     

Introduction and Spread of the Threespine Stickleback (Gasterosteus Aculeatus) in Lakes Huron and Michigan

The threespine stickleback (Gasterosteus aculeatus) was not known to occur in the Great Lakes above Niagara Falls until 1980, when it was collected in South Bay, Manitoulin Island, in the Lake Huron basin. By 1984 this species had been found in tributaries of Lakes Huron and Michigan, and in the open waters of both lakes. All specimens identified were the completely plated morph that is most prevalent in fresh water along the east coast of North America. The status of this species in Lakes Huron and Michigan appears to be “Possibly Established.” If threespine stickleback increase in abundance they may eventually provide additional forage for large salmonids.     

A model for determining satellite-derived primary productivity estimates for Lake Michigan

A new MODIS based satellite algorithm to estimate primary production (PP) has been generated and evaluated for Lake Michigan. The Great Lakes Primary Productivity Model (GLPPM) is based on previous models that required extensive in situ data but it can utilize remotely sensed observations as input for some model variables and therefore allows greater spatial resolution for primary productivity estimates. The Color Producing Agent Algorithm (CPA-A) is utilized to obtain robust chlorophyll a values and the NASA KD2M approach is used to obtain the diffuse attenuation coefficient (K_d). Only incident PAR and carbon fixation rates are additionally needed to generate the primary productivity estimate. Comparisons of the satellite derived PP estimates from single monthly images to average monthly field measurements made by NOAA/GLERL found good agreement between estimates. Satellite derived PP estimates were used to estimate a preliminary Lake Michigan annual primary production of 8.5 Tg C/year. The new algorithm can be easily adapted to work on all the Great Lakes and therefore can be used to generate time series dating back to late 1997 (launch of SeaWiFs). These time series can contribute to improved assessment of Great Lakes primary productivity changes as a result of biological events, such as Dreissenid mussel invasions, climatic change and anthropogenic forcing.     

Predicting the oscillating bi-directional exchange flow in the Straits of Mackinac

The Straits of Mackinac are a unique feature that connects Lake Michigan and Lake Huron into a single hydraulically linked system. With currents of up to 1 m/s and oscillating volumetric transport up to 80,000 m³/s, they play an important role in water quality, contaminant transport, navigation, and ecological processes. We present the first three-dimensional hydrodynamic model of the combined Lake Michigan–Huron, including the Straits of Mackinac at high-resolution, that is able to simulate the three dimensional structure of the oscillating flows at the Straits. In comparison with individual lake models for Michigan and Huron (no connection at the Straits), we are able to isolate the effects of the bi-lake oscillation and have found that although the oscillation (Helmholtz mode) is the dominant forcing mechanism, the flow can be modulated when atmospheric systems are in-phase with water level fluctuations. Furthermore, the area of influence of the Straits is found to extend up to 70 km into each lake, underscoring the need for realistic predictions within the Straits. For the first time, this combined-lake hydrodynamic model provides the capability to investigate and accurately predict flow at the Straits of Mackinac and its effect on Lake Michigan and Huron. This model forms the basis for the next generation of real-time hydrodynamic models being developed for the Great Lakes Coastal Forecasting System, a suite of models designed by the National Oceanic and Atmospheric Administration Great Lakes Environmental Research Laboratory (NOAA/GLERL) that predict hydrodynamic conditions such as currents, temperatures, and water levels in three dimensions.     

Diel Vertical Migration of Round Goby Larvae in the Great Lakes

One hypothesis for the transcontinental and intra-Great Lakes basin transfer of round gobies (Neogobius melanostomus) has been that round gobies were pumped into the ballast water of ships. During June 2005 in Lake Erie, we obtained evidence of a vertical migration of round goby larvae, when we collected 167 round goby larvae in surface ichthyoplankton net tows at night and zero during day. These results complemented similar findings from the Muskegon River estuary of Lake Michigan during 2003 and 2004, documenting diel vertical migration for the first time in larval round gobies. We suggest vertical migration behavior may have allowed larval round gobies to be transported to and within the Great Lakes via ballast water and dispersed in the Great Lakes via advection of 6.5–8.5-mm long larvae at the surface. Based on our results, if ballast water was only taken on near the surface during daylight hours from May through September when larval round gobies were present, it would have mitigated the spread of round gobies throughout the Great Lakes.     

Prevalence and distribution of Renibacterium salmoninarum in non-salmonid fishes from Laurentian Great Lakes and inland habitats

Renibacterium salmoninarum (RS), the causative agent of bacterial kidney disease, has been a serious threat to salmonid health in the Laurentian Great Lakes. Despite its wide spread presence in the Great Lakes basin, little is known about RS ecology and the potential role of non-salmonid species as one of the pathogen’s reservoirs. This information is of paramount importance to fishery managers in order to better understand RS distribution in the different biotic components of the Great Lakes watershed. In this study, non-salmonid species from lakes Michigan and Huron, and from 13 inland waters of the Great Lakes watershed were collected from 1999 to 2008. Out of 380 fish sampled from lakes Michigan and Huron, 42 (11.05%) tested positive for RS as determined by the nested polymerase chain reaction. Prevalence was lower in Lake Huron (5.71%) compared to Michigan (20.74%), but the difference was not statistically significant. Prevalence of RS was not found to be significantly different between species or sites; however, when species were grouped into demersal vs. pelagic categories, significant differences (P < 0.01) in prevalence were observed. Out of 607 fish sampled from inland waters, 111 (18.28%) tested positive for RS as determined by the sandwich enzyme-linked immunosorbent assay. Infection prevalence was highly variable across species and among localities. Our results indicate that many non-salmonid species can harbor this bacterium without progression to disease and may become a reservoir for infection.     

NOTE: First record of natural reproduction by Atlantic salmon (Salmo salar) in the St. Marys River,Michigan

Atlantic salmon (Salmo salar) are native to Lake Ontario; but their populations severely declined by the late 1800s due to human influences. During the early to mid-1900s, Atlantic salmon were stocked throughout the Great Lakes in effort to reestablish them into Lake Ontario and introduce the species into the upper Great Lakes. However, these efforts experienced minimal success. In 1987, Lake Superior State University and the Michigan Department of Natural Resources began stocking Atlantic salmon in the St. Marys River, Michigan, which has resulted in a successful, self-supporting hatchery operation and stable recreational Atlantic salmon fishery. Possibly due to a combination of competition with other salmonid species for spawning habitat, prey selection causing detrimental effects on early life stages and high rates of early mortality syndrome, Atlantic salmon appeared to be severely limited in their ability to naturally reproduce within the upper Great Lakes. In 2012, the first unequivocal documentation of naturally reproduced Atlantic salmon in the St. Marys River was recorded, downstream from the compensation works and parallel to the Soo Locks in Sault Ste. Marie, Michigan.