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.     

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.     

Impacts of the Great Lakes on Regional Climate Conditions

Estimates of lake-induced spatial changes of six climate variables (precipitation, mean minimum and mean maximum temperatures, cloud cover, vapor pressure, and wind speed) were derived for the entire Great Lakes basin. These patterns were estimated by a comparison of maps of each weather variable using: (1) all regional climate data, and (2) regional data when observations within an 80-km zone around the lakes were removed. Results generally confirm expectations and prior findings, but point to inadequacies in data collection that limit a highly precise analysis. Lake effects are most noticeable in precipitation and temperature and vary considerably by season, time of day, and lake size. Greatest lake influences are found near Lake Superior where up to 100% more precipitation falls downwind of the lake in winter compared to that expected without its presence. During summer, all lakes cause a downwind decrease in rainfall of 10% to 20%. Mean minimum temperatures in the basin are higher in all seasons and over all lakes. Lake-induced reductions in mean maximum temperatures in the region are observed during spring and summer. Effects on cloud cover are greatest during winter and show increases of approximately 25% in areas downwind of Lakes Superior and Michigan. Conversely, the cool summertime waters of Lakes Michigan and Huron reduce cloudiness roughly 10%. Variations in vapor pressure are consistent with observed changes in temperature. Amounts in winter are estimated to be 10% to 15% higher across the center of the basin, but decrease by roughly 5% to 10% at many lake shore sites in summer. Seasonal wind speed data were considered to lack an appropriate number of quality long-term climate stations to determine spatial lake effects. Surface elevations, increasing east of the basin, complicated detection of effects due solely to the lakes.     

Contaminated Sediment Management in the Great Lakes Basin Ecosystem

Contaminated sediment remains a pervasive problem to the restoration and delisting in all of the Great Lakes Areas of Concern. Like many other problems, both identification and implementation of ecologically and economically acceptable solutions is complex. Recognizing the scope of this issue and perceiving that limited progress had been achieved, the International Joint Commission (IJC) asked its Great Lakes Water Quality Board to review the magnitude of the problem and what progress had been made in managing contaminated sediment by Canada and the United States. In addition, the Commission also asked for an identification of obstacles to remediation and recommendations for solutions.This paper provides a synopsis of this work and a summary of an IJC workshop held in June of 1997, in Collingwood, Ontario. Six categories of obstacles to sediment remediation are discussed, potential solutions are identified, and a series of recommendations are proposed. A plan of action to further develop approaches to sediment management and to stimulate additional remediation throughout the basin is also presented.     

The Relevance of Seabird Ecology to Great Lakes Management

Seabirds are an integral part of Great Lakes ecosystems. However, most species are of no economic importance to humans and, therefore, they receive little direct management attention. Because many species of seabirds on the Great Lakes rely on fish as their primary food, factors that alter fish availability will also affect seabird populations. This paper examines how management practices may indirectly affect Great Lakes seabirds leading to changes in population sizes, diet composition, and destruction of breeding habitat. Consideration of the impacts of management actions on non-target groups, such as seabirds, will require the application of an ecosystem approach to management. Although the ecosystem approach philosophy has been widely accepted from a theoretical perspective, little tangible evidence exists that it has been routinely applied.     

Ten Ecosystem Approaches to the Planning and Management of the Great Lakes

During the past decade or so, many researchers, planners and managers the world over have propounded some version of “ecosystem approach” for problems and opportunities with the natural environment and renewable resources. Most of these approaches share the following features: a primary focus on ecological phenomena as opposed to engineering, economic, or jurisdictional phenomena; a perception of some self-regulatory capacity on the part of an ecosystem; a recognition of the marked responsiveness of many ecological systems to natural and human activities; and a readiness to strike a pragmatic compromise between detailed reductionistic understanding and more comprehensive, holistic meaning. Great Lakes workers are now trying to implement operational and institutional forms of ecosystem approach. Ten of these initiatives are assessed here, taken from all government levels, directed toward open lake, coastal, and hinterland components of the basin. This comparison illustrates the range of proposals now under consideration in the basin and identifies their common elements. We offer these features as defining criteria of an ecosystem approach with the suggestion that thorough-going synthesis or standardization be avoided. Flexible eclectic pragmatism is, we suggest, the most productive attitude toward Great Lakes environmental problems.     

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.     

Beach science in the Great Lakes

Monitoring beach waters for human health has led to an increase and evolution of science in the Great Lakes, which includes microbiology, limnology, hydrology, meteorology, epidemiology, and metagenomics, among others. In recent years, concerns over the accuracy of water quality standards at protecting human health have led to a significant interest in understanding the risk associated with water contact in both freshwater and marine environments. Historically, surface waters have been monitored for fecal indicator bacteria (fecal coliforms, Escherichia coli, enterococci), but shortcomings of the analytical test (lengthy assay) have resulted in a re-focusing of scientific efforts to improve public health protection. Research has led to the discovery of widespread populations of fecal indicator bacteria present in natural habitats such as soils, beach sand, and stranded algae. Microbial source tracking has been used to identify the source of these bacteria and subsequently assess their impact on human health. As a result of many findings, attempts have been made to improve monitoring efficiency and efficacy with the use of empirical predictive models and molecular rapid tests. All along, beach managers have actively incorporated new findings into their monitoring programs. With the abundance of research conducted and information gained over the last 25 years, “Beach Science” has emerged, and the Great Lakes have been a focal point for much of the ground-breaking work. Here, we review the accumulated research on microbiological water quality of Great Lakes beaches and provide a historic context to the collaborative efforts that have advanced this emerging science.     

Hydrogeomorphic Classification for Great Lakes Coastal Wetlands

A hydrogeomorphic classification scheme for Great Lakes coastal wetlands is presented. The classification is hierarchical and first divides the wetlands into three broad hydrogeomorphic systems, lacustrine, riverine, and barrier-protected, each with unique hydrologic flow characteristics and residence time. These systems are further subdivided into finer geomorphic types based on physical features and shoreline processes. Each hydrogeomorphic wetland type has associated plant and animal communities and specific physical attributes related to sediment type, wave energy, water quality, and hydrology.     

Conceptual Framework for Coordinated Great Lakes Monitoring

The utility of conceptual models is discussed as a basis for effective development of coordinated monitoring efforts on the Great Lakes. The use of conceptual models is illustrated in two ways: (1) the development of a methodology for specifying monitoring objectives of the Great Lakes, based on a conceptual model, and (2) presentation of a comprehensive method for defining resource needs to achieve monitoring objectives.     

Light-absorbing components in the Great Lakes

Features of light absorption are critical in regulating the optical signal available for remote sensing. The magnitudes, spectral characteristics, spatial patterns, and, to a lesser extent, dynamics of light-absorbing components are documented for the Laurentian Great Lakes. This includes the open waters of each of the five lakes, and selected rivers, embayments and near-shore areas. The absorption coefficient, a(m^? 1), is partitioned according to the additive components (a_x) of colored dissolved organic matter (a_CDOM), non-algal particles (a_NAP), phytoplankton (a_φ), and water itself (a_w; known). Dependencies of a_x on various metrics of optically active constituents (OACs), cross-sections, are evaluated. A wide range of magnitudes of a_x and a, and contributions of a_x to a are documented. For example, the magnitude of a at a wavelength of 440 nm was nearly 10-fold greater in the western basin of Lake Erie than in the open waters of Lake Huron. Rivers, embayments, and near-shore areas generally had higher levels than the open waters. The largest a_x throughout the system was a_CDOM, originating mostly from terrestrial sources. Most of a_NAP was associated with clay mineral particles. The distribution of a_φ was highly correlated to chlorophyll concentration. The collected data set is appropriate to support initiatives to develop and preliminarily test mechanistic retrieval algorithms for OACs in the Great Lakes.     

Potential for fisheries-induced evolution in the Laurentian Great Lakes

Fisheries are selective, capturing fish based on their body size, behaviour, life stage, or location. Over time, if harvest pressure is strong enough and variation in traits heritable, evolution can occur that affects key aspects of the ecology of fish stocks. Most compelling examples of rapid evolution in response to harvest have come from marine systems. Here, we review the state of knowledge on fisheries-induced evolution (FIE) in the Laurentian Great Lakes where subsistence, commercial, and recreational fisheries have operated for centuries. We conclude that stocks experienced harvest rates high enough and for long enough to undergo evolution. While historical fisheries exploited more juveniles, some contemporary Great Lakes fisheries target primarily adult size-classes thus reducing current selection for earlier maturation; however, other traits and behaviours could evolve (e.g., growth, timing of spawning, boldness). While commercial harvest previously dominated, recreational fishing is now expected to be a strong contributor to harvest selection in the Great Lakes. Environmental variation, density-dependence, invasive species, and the genetic legacy of population bottlenecks and stocking interact with, and make it more challenging to detect, FIE in the Great Lakes than in marine systems. Case studies are presented for Great Lakes stocks of yellow perch Perca flavescens and lake whitefish Coregonus clupeaformis for which FIE has been investigated. The evidence for FIE in the Great Lakes is currently sparse, potentially because of the low research focus on this topic or because of the interacting influence of environmental variation and anthropogenic stressors.     

Results from the U.S. Great Lakes Fish Monitoring Program and Effects of Lake Processes on Bioaccumulative Contaminant Concentrations

An analysis of composite samples of 820 lake trout, walleye, steelhead, Chinook, and coho from the Laurentian Great Lakes reveals differences in contaminant processing among and between lakes which results in differing concentrations of bioaccumulative contaminants. Generally, contaminants are most concentrated in fish from Lake Michigan and least concentrated in fish from Lake Superior, with the notable exceptions of toxaphene and alpha-HCH. Differences in contamination patterns, however, are apparent not only among the lakes but between sites within a lake or even fish within a site. Lake trout composites from Lake Superior show an increase in the degree of chlorination of PCBs with increasing total PCBs. The PCB congener profile of lake trout from the Sturgeon Bay site of Lake Michigan is substantially different from that of the Saugatuck site of Lake Michigan, possibly due to the influence of contamination from nearby Green Bay. Finally, the ratios of selected PBDE and PCB congeners are much different in Lake Superior fish compared to fishes from all the other lakes. We hypothesize that this is a result of the colder temperatures and associated lower plankton growth rates in Lake Superior allowing PCB and PBDE uptake by phytoplankton to reach near equilibrium, thus enhancing the relative concentrations, in phytoplankton and the food web in general, of congeners that may be kinetically limited in other lakes.     

A simple water clarity-turbidity index for the Great Lakes

There are a multitude of satellite-derived water clarity and turbidity indicators to support the decision making of environmental managers and policy makers. However, water quality dynamic ranges addressed by these indicators can differ significantly, subjecting non-expert users to potential pitfalls. Here we propose a satellite water clarity-turbidity index (CTI) as a simplified way to capture major changes in water clarity/turbidity across all water types in the Great Lakes. The CTI is defined to merge key information from three prerequisite variables derived from Visible Infrared Imaging Radiometer Suite (VIIRS) measurements, namely, the Secchi disk depth, the particulate backscattering coefficient, and the nephelometric turbidity, which are suitable for clear, intermediate, and turbid waters, respectively. Application to the Great Lakes shows that with one parameter, the CTI can illustrate major spatial and temporal patterns that are not entirely visible with each of the three original indicators alone. Using the CTI, we identified significant decrease in water turbidity in Lakes Michigan and Huron from 2000 to 2005, during which daily variability of CTI in August initially spiked and then gradually decreased most likely owing to diminishing whiting events. The CTI is a convenient and holistic assessment tool for water quality management.     

Modelling Effects of Remedial Programs to Aid Great Lakes Environmental Management

Computer simulation of remedial programs was carried out employing a large and diverse information base on both point and nonpoint pollutant sources in the Great Lakes basin to provide a more holistic environmental management perspective. The process utilizes a cascading system of sub-basin unit area pollutant loads (classified by land use and land form), per capita municipal pollutant inputs, river transmission factors, and remedial program effectiveness, in terms of reduced loadings to the lakes and costs. It was employed by PLUARG (Pollution from Land Use Activities Reference Group) to determine scenarios of remedial programs which apparently were practicable and would achieve target lake loads of phosphorus most cost-effectively. The analysis, presented here for Lake Erie, Lake Ontario, and southern Lake Huron, provides a means of evaluating the effectiveness of various remedial program options to fulfill commitments by Canada and the United States to load reductions for these lakes. The methodology can be extended to other pollutants as sufficient data become available to permit a suitable degree of resolution for management decisions.     

Predicted Atrazine Concentrations in the Great Lakes: Implications for Biological Effects

Atrazine is an herbicide used extensively throughout the Midwest corn belt, including the agricultural regions within the Great Lakes basin watershed. Measurements of atrazine concentrations in the Great Lakes are few, however, so knowledge of its current concentrations, persistence, and trends in this ecosystem is limited. A dynamic annual time step model was used to predict atrazine concentrations over time in the Great Lakes based on varied atrazine loading rates to the lakes (“most-likely” and “high” loading conditions). Four degradation scenarios were evaluated: no degradation, and atrazine degradation with half-lives of 2 years, 5 years, and 10 years. Predicted steady-state concentrations for all of the scenarios and all the Great Lakes ranged from 0.0024 to 0.88 μg/L. The number of years until steady-state conditions were achieved ranged from 4 to over 400 years. The most-likely loading rate and two-year half-life scenario had the lowest concentrations (0.0024 to 0.13 μg/L) and the fewest years (4 to 13 years) to achieve steady-state conditions. Available monitored atrazine concentrations in the Great Lakes are very similar to the most-likely loading rate and 2-year half-life scenario predicted values. Monitored and predicted concentrations in the Great Lakes indicate atrazine does not currently pose a toxicological risk to humans or aquatic organisms, and under current and expected lower loading rates should remain well below criteria values.