An appraisal of policy implementation deficits in the Great Lakes

Understanding of the complexities of both public policy implementation and Great Lakes restoration has grown in sophistication since the 1970s. The Great Lakes Water Quality Agreement is the principal policy for reversing environmental decline in the region. Implementation of this and related policies, particularly by the federal governments, suffers from acute and chronic deficits that we summarily document. These policy implementation deficits will continue to frustrate efforts to revitalize the Great Lakes unless significant advances are made to design governance processes within the Great Lakes regime that accommodate the complexity of linked social and ecological systems. The 2010-2011 governmental process to renegotiate the Great Lakes Water Quality Agreement is a potent opportunity to begin to overcome institutional barriers to reducing policy deficits. We argue that the renegotiation must begin a reinvestment in remaking or reimagining Great Lakes institutions in a way that restores capacity, flexibility, and moral authority. Our purpose is to help provide a foundation for that discussion.     

Drivers of revitalization in Great Lakes coastal communities

Sediment remediation and habitat restoration projects have been increasingly employed along the coast of the Great Lakes to improve environmental quality since the designation of 43 highly degraded Areas of Concern (AOCs) by the 1987 Great Lakes Water Quality Agreement between the U.S. and Canada. Improvements in water quality, habitat, and other environmental conditions can also support community wellbeing and revitalization; however, the mechanisms that support these connections are relatively unclear. We address this gap through a case study of three AOCs near Lake Michigan: 1) Grand Calumet River; 2) White Lake, and 3) Muskegon Lake. By analyzing secondary data and planning documents, we found that alongside environmental cleanup, anchor institutions, housing and economic development, and local events drive revitalization. Our research also illustrates that, rather than acting as discrete processes, environmental cleanup and revitalization drivers overlap in time and space. Finally, our research reveals a high level of variation within and across AOCs in terms of diverse socioeconomic contexts, planning capacities, and existing partnerships. Together, our findings point to the need for collaborative and inclusive planning processes that account for the heterogeneity present within and across AOCs to simultaneously support remediation, restoration, and revitalization and to sustain continued revitalization in AOC communities after delisting.     

Contaminant Management Strategies for the Great Lakes: Optimal Solutions Under Uncertain Conditions

Optimization, uncertainty analysis, and mass balance modeling techniques were combined into a framework that can help decision makers identify cost-effective load reduction methods for achieving acceptable contaminant concentrations in the Great Lakes. The utility of the framework is demonstrated by deriving an optimal phosphorus load reduction plan for the Great Lakes. An optimal plan is defined as the least-cost approach that can achieve desired phosphorus concentrations in all Great Lakes basins under realistic, stochastic phosphorus loading and settling rates. The analysis suggests that implementation of phosphorus load reduction measures recommended in the U. S. - Canadian 1978 Great Lakes Water Quality Agreement, its 1983 supplement, and other plans that do not account for environmental uncertainty may by sub-optimal. Compared with the load reduction strategies of the 1978 Water Quality Agreement and its supplement, implementation of the optimized load reduction strategy would lead to substantial annual cost savings and an increased probability of achieving desired phosphorus concentrations. Results emphasize the importance of quantitatively accounting for environmental uncertainty in management models.     

Exploring market-based environmental policy for groundwater management and ecosystem protection for the Great Lakes region: Lessons learned

The Great Lakes–St. Lawrence River Basin Water Resources Compact (the Compact) was created to protect future water supplies and aquatic ecosystems in the Great Lakes. The Compact requires the eight Great Lakes state to regulate, among other things, large withdrawals of groundwater and surface water so that they do not negatively affect stream flows and ecosystems within the Great Lakes Basin. Thus, the Compact raises the possibility of increased restrictions on groundwater withdrawals in many locations throughout the Great Lakes region. However, restricting withdrawals is likely to encounter opposition from water users when such restrictions are viewed as an infringement on existing water use rights and/or as negatively impacting local economic development. Such conflicts could hinder effective implementation of state and regional water policy. This paper explores the application of a market-based environmental management tool called “Conservation Credit Offsets Trading (CCOT)” that could facilitate allocation of groundwater withdrawals, and develops a framework for guiding the implementation of CCOT within the context of a groundwater permitting system. Using a watershed in southwestern Michigan, this study demonstrates how bio-physical information and input from various local stakeholders were combined to aid groundwater policy designed to achieve the objective of no net (adverse) impact on stream ecosystems. By allowing flexibility through trading of conservation credit offsets, this groundwater policy tool appears to be more politically acceptable than traditional, less flexible, regulations. The results and discussion provide useful lessons learned with relevance to other areas in the Great Lakes Basin.     

U.S. EPA Great Lakes National Program Office monitoring of the Laurentian Great Lakes: Insights from 40 years of data collection

The U.S. EPA Great Lakes National Program Office (GLNPO) implements long-term monitoring programs to assess Great Lakes ecosystem status and trends for many interrelated ecosystem components, including offshore water quality as well as offshore phytoplankton, zooplankton and benthos; chemical contaminants in air, sediments, and predator fish; hypoxia in Lake Erie's central basin; and coastal wetland health. These programs are conducted in fulfillment of Clean Water Act mandates and Great Lakes Water Quality Agreement commitments. This special issue presents findings from GLNPO's Great Lakes Biology Monitoring Program, Great Lakes Water Quality Monitoring Program, Lake Erie Dissolved Oxygen Monitoring Program, Integrated Atmospheric Deposition Network, Great Lakes Fish Monitoring and Surveillance Program, and Great Lakes Sediment Surveillance Program. These GLNPO programs have generated temporal and spatial datasets for all five Great Lakes that form the basis for assessment of the state of these lakes, including trends in nutrients, key biological indicators, and contaminants in air, sediments and fish. These datasets are used by researchers and managers across the Great Lakes basin for investigating physical, chemical and biological drivers of ongoing ecosystem changes; some of these analyses are presented in this special issue, along with discussion of new methods and approaches for monitoring.     

Researcher disciplines and the assessment techniques used to evaluate Laurentian Great Lakes coastal ecosystems

The Laurentian Great Lakes of North America have been a focus of environmental and ecosystem research since the Great Lakes Water Quality Agreement in 1972. This study provides a review of scientific literature directed at the assessment of Laurentian Great Lakes coastal ecosystems. Our aim was to understand the methods employed to quantify disturbance and ecosystem quality within Laurentian Great Lakes coastal ecosystems within the last 20 years. We focused specifically on evidence of multidisciplinary articles, in authorship or types of assessment parameters used. We sought to uncover: 1) where Laurentian Great Lakes coastal ecosystems are investigated, 2) how patterns in the disciplines of researchers have shifted over time, 3) how measured parameters differed among disciplines, and 4) which parameters were used most often. Results indicate research was conducted almost evenly across the five Laurentian Great Lakes and that publication of coastal ecosystems studies increased dramatically ten years after the first State of the Great Lakes Ecosystem Conference in 1994. Research authored by environmental scientists and by multiple disciplines (multidisciplinary) have become more prevalent since 2003. This study supports the likelihood that communication and knowledge-sharing is happening between disciplines on some level. Multidisciplinary or environmental science articles were the most inclusive of parameters from different disciplines, but every discipline seemed to include chemical parameters less often than biota, physical, and spatial parameters. There is a need for an increased understanding of minor nutrient, toxin, and heavy metal impacts and use of spatial metrics in Laurentian Great Lakes coastal ecosystems.     

Recent water level changes across Earth's largest lake system and implications for future variability

Water levels on Lake Ontario, the most downstream of the Laurentian Great Lakes, reached a record high in the spring of 2017. This event was accompanied by widespread flooding and displacement of families. Water levels across all of the Great Lakes have risen over the past several years following a period of record low levels. When levels were low, public and expert discussion focused on the possibility that low levels would continue into the future due to climate change, diversions of water from the lakes, and dredging. During the current high water period, variability is being attributed to water management, despite evidence of unusually high precipitation and river flows across the region. Understanding and communicating the drivers behind water level variability, particularly in light of recent extremes, is a fundamental step towards improving regional water resources management and policy.     

Community engagement and the importance of partnerships within the Great Lakes Areas of Concern program: A mixed-methods case study

The Great Lakes Areas of Concern (AOC) program was created through amendments to the Great Lakes Water Quality Agreement (GLWQA) in 1987 to restore contaminated sites using an ecosystem-based approach. This program represents one of the first instances of ecosystem-based management (EBM) in the Great Lakes region with a specific focus on the inclusion of the public and local stakeholders in the process. Despite official language incorporating EBM in the AOC program, implementation of these practices has not been consistent across AOCs given differences in local arrangements of Public Advisory Councils (PACs), approaches to community engagement, and environmental problems. To better understand community engagement in these complex AOCs, this research investigated community, PAC, and state agency perspectives in three AOCs in Michigan: the Kalamazoo River, Saginaw River and Bay, and Rouge River AOCs. We gathered data through interviews, focus groups, and participatory observations with community members, PAC members, and state officials in each AOC. Findings indicate that communities in these areas have minimal connection to the AOC program and PACs. Community members tended to have greater connection to local organizations that provide a variety of opportunities for community members to engage with their environment in ways they value. To better connect the public to the AOC program, PACs may benefit from intentional partnerships with community organizations to increase community engagement. To consistently bolster community engagement in AOCs, we further recommend that state agencies provide additional resources to improve connection to local communities.     

A surrogate regression approach for computing continuous loads for the tributary nutrient and sediment monitoring program on the Great Lakes

Water quality (WQ) in many Great Lake tributaries has been degraded (increased nutrient and sediment concentrations) due to changes in their watersheds, resulting in downstream eutrophication. As part of the Great Lakes Water Quality Agreement, specific goals were established for loading of specific constituents (e.g., phosphorus). In 2010, the Great Lakes Restoration Initiative was launched to identify problem areas, accelerate restoration efforts, and track their progress. In 2011, the U.S. Geological Survey established a monitoring program on 30 tributaries to the lakes, representing ~ 46% of the U.S. draining area and the spectrum of land uses. Discrete measurements of nutrients and suspended sediment, and continuous measurements of flow and WQ surrogates (turbidity, temperature, specific conductance, pH, and dissolved oxygen) are being collected in these tributaries to document their WQ and estimate continuous (5-min) loading. To estimate loadings, two regression models were developed for each constituent for each site: one using continuous flow and a seasonality factor; and one using flow, seasonality, and continuous surrogates. Variables included in the final models for each constituent were chosen from the explanatory variables that worked “best” for all sites. In computing loads, when continuous surrogate data were unavailable for short periods, loads were computed using the flow and seasonality models. Prediction intervals for all loads were calculated using results from both models. These results provide a better understanding of short-term variability and long-term changes in loading affecting the environmental health of the Great Lakes than traditional regression techniques that employ only flow and seasonality parameters.     

Assessing terrestrial wildlife populations in the Toronto and Region Area of Concern

Beneficial use impairments (BUIs) under the Great Lakes Water Quality Agreement identify environmental issues requiring remedial action within the Great Lakes Areas of Concern (AOCs). We conducted this study to support the assessment of the wildlife component of BUI 3: degradation of fish and wildlife populations. We compared bird and amphibian (frogs and toads) data from the Toronto and Region Conservation Authority’s Terrestrial Long-term Monitoring Program in the Toronto and Region AOC to an adjacent, but otherwise similar, reference watershed, Duffins Creek. Twelve of 13 targets were met within the AOC for forest bird, wetland bird, meadow bird and amphibian populations based on averages of mean annual values at sites within the AOC that were within two standard deviations of averages at sites in the Duffins Creek reference watershed between 2008 and 2017. Even though wildlife populations within the AOC were within the normal range of variability expected from a reference watershed, they were often at lower levels than within the Duffins Creek reference watershed. In addition, forest bird and amphibian populations were negatively affected by urbanization within the AOC and meadow bird indices declined. We conclude that while wildlife populations within the AOC currently meet targets for BUI 3, they continue to be negatively impacted by numerous stressors that are primarily related to past and ongoing urbanization. Thus, continued restoration of wildlife habitat and protection of existing habitat within the AOC is highly recommended.     

A brief history of the U.S. EPA Great Lakes National Program Office's water quality survey

The U.S. Environmental Protection Agency Great Lakes National Program Office (GLNPO) water quality survey (WQS) constitutes the longest-running, most extensive monitoring of water quality and the lower trophic level biota of the Laurentian Great Lakes, and has been instrumental in tracking shifts in nutrients and the lower food web over the past several decades. The initial impetus for regular monitoring of the Great Lakes was provided by the 1972 Great Lakes Water Quality Agreement (GLWQA) which asked the parties to develop monitoring and surveillance programs to ensure compliance with the goals of the agreement. The resulting monitoring plan, eventually known as the Great Lakes International Surveillance Plan (GLISP), envisioned a nine-year rotation of intensive surveys of the five lakes. A broadening of the scope of the GLWQA in 1978 and the completion of the first nine-year cycle of sampling, prompted reappraisals of the GLISP. During this pause, and using knowledge gained from GLISP, GLNPO initiated an annual WQS with the narrower focus of tracking water quality changes and plankton communities in the offshore waters of the lakes. Beginning in 1983 with lakes Erie, Huron, and Michigan, the WQS added Lake Ontario in 1986 and Lake Superior in 1992, evolving into its current form in which all five lakes are sampled twice a year. The WQS is unique in that all five lakes are sampled by one agency, using one vessel and one principal laboratory for each parameter group, and represents an invaluable resource for managing and understanding the Great Lakes.     

Renovation and Innovation: It’s Time for the Great Lakes Regime to Respond

This commentary reports on a project to explore and evaluate options for Great Lakes governance renewal in anticipation of the 2006–2007 review of the Canada–US Great Lakes Water Quality Agreement (GLWQA). The research included expert interviews and scholarly analysis of governance regimes in 2006, leading to a Great Lakes St. Lawrence River Governance Expert Workshop held in June 2007 (Krantzberg et al. 2007). The two authors have been participants and at times leaders in the institutions this commentary addresses, Krantzberg with the International Joint Commission and Ontario Ministry of the Environment and Manno with the New York Great Lakes Research Consortium and Great Lakes United. Our familiarity with the topic and many of the people involved was helpful in gaining participation and is in itself a rich source of knowledge and experience. In discussing a topic of contemporary controversy, it also understandably can make readers question the objectivity of our assessment. We are also trained in social science scholarship and have taken precautions against biasing the outcomes. This is not intended to be merely a presentation of data. We believe our experience is a net asset in addressing these questions but we leave it to the interested reader to review the reports referenced herein and judge for themselves whether our findings are fairly presented.     

St. Clair-Detroit River system: Phosphorus mass balance and implications for Lake Erie load reduction,monitoring, and climate change

To support the 2012 Great Lakes Water Quality Agreement on reducing Lake Erie's phosphorus inputs, we integrated US and Canadian data to update and extend total phosphorus (TP) loads into and out of the St. Clair-Detroit River System for 1998–2016. The most significant changes were decreased loads from Lake Huron caused by mussel-induced oligotrophication of the lake, and decreased loads from upgraded Great Lakes Water Authority sewage treatment facilities in Detroit. By comparing Lake St. Clair inputs and outputs, we demonstrated that on average the lake retains 20% of its TP inputs. We also identified for the first time that loads from resuspended Lake Huron sediment were likely not always detected in US and Canadian monitoring programs due to mismatches in sampling and resuspension event frequencies, substantially underestimating the load. This additional load increased over time due to climate-induced decreases in Lake Huron ice cover and increases in winter storm frequencies. Given this more complete load inventory, we estimated that to reach a 40% reduction in the Detroit River TP load to Lake Erie, accounting for the missed load, point and non-point sources other than that coming from Lake Huron and the atmosphere would have to be reduced by at least 50%. We also discuss the implications of discontinuous monitoring efforts.     

Great Lakes total phosphorus revisited: 2. Mass balance modeling

Mass balance models are used to simulate chloride and total phosphorus (TP) trends from 1800 to the present for the North American Great Lakes. The chloride mass balance is employed to estimate turbulent eddy diffusion between model segments. Total phosphorus (TP) concentrations are then simulated based on estimated historical and measured TP loading time series. Up until about 1990, simulation results for all parts of the system generally conform to measured TP concentrations and exhibit significant improvement due primarily to load reductions from the Great Lakes Water Quality Agreement. After 1990, the model simulations diverge from observed data for the offshore waters of all the lakes except Lake Superior with the observations suggesting a greater improvement than predicted by the model. The largest divergence occurs in Lake Ontario where the model predicts that load reductions should bring the lake to oligo-mesotrophic levels, whereas the data indicate that it is solidly oligotrophic and seems to be approaching an ultra-oligotrophic state. Less dramatic divergences also occur in the offshore waters of lakes Michigan, Huron and Erie. In order to simulate these outcomes, the model's apparent settling velocity, which parameterizes the rate that total phosphorus is permanently lost to the lake's deep sediments, must be increased significantly after 1990. This result provides circumstantial support for the hypothesis that Dreissenid mussels have enhanced the Great Lakes phosphorus assimilation capacity. Finally, all interlake mass transfers of TP via connecting channels have dropped since phosphorus control measures were implemented beginning in the mid-1970s.     

Goals,beneficiaries, and indicators of waterfront revitalization in Great Lakes Areas of Concern and coastal communities

Cleanup of Great Lakes Areas of Concern (AOCs) restores environmental benefits to waterfront communities and is an essential condition for revitalization. We define waterfront revitalization as policies or actions in terrestrial waterfront or adjacent aquatic areas that promote improvements in human socioeconomic well-being while protecting or improving the natural capital (the stocks of natural assets, biodiversity) that underlies all environmental, social, and economic benefits. Except for economic measures such as development investments, visitation rates, or commercial activity, evidence of waterfront revitalization in the Great Lakes is mostly anecdotal. We offer a perspective on waterfront revitalization that links indicators and metrics of sustainable revitalization to community goals and human beneficiaries. We compiled environmental, social, economic, and governance indicators and metrics of revitalization, many of which are based on or inspired by Great Lakes AOC case studies and community revitilization or sustainability plans. We highlight the role of indicators in avoiding unintended consequences of revitalization including environmental degradation and social inequity. Revitalization indicators can be used in planning for comparing alternative designs, and to track restoration progress. The relevancy of specific indicators and metrics will always depend on the local context.     

Thirty-five years of restoring Great Lakes Areas of Concern: Gradual progress,hopeful future

In 1985, remedial action plan development was initiated to restore impaired beneficial uses in 42 Great Lakes Areas of Concern (AOCs). A 43rd AOC was designated in 1991. AOC restoration has not been easy as it requires networks focused on gathering stakeholders, coordinating efforts, and ensuring use restoration. As of 2019, seven AOCs were delisted, two were designated as Areas of Concern in Recovery, and 79 of 137 known use impairments in Canadian AOCs and 90 of 255 known use impairments in U.S. AOCs were eliminated. Between 1985 and 2019, a total of $22.78 billion U.S. was spent on restoring all AOCs. Pollution prevention investments should be viewed as spending to avoid future cleanups, and AOC restoration investments should be viewed as spending to help revitalize communities that has over a 3 to 1 return on investment. The pace of U.S. AOC restoration has accelerated under the Great Lakes Legacy Act (GLLA) and Great Lakes Restoration Initiative (GLRI). Sustained funding through U.S. programs like GLRI and GLLA and Canadian programs such as Canada-Ontario Agreement Respecting Great Lakes Water Quality and Ecosystem Health and the Great Lakes Protection Initiative is needed to restore all AOCs. Other major AOC program achievements include use of locally-designed ecosystem approaches, contaminated sediment remediation, habitat rehabilitation, controlling eutrophication, and advancing science. Key lessons learned include: ensure meaningful public participation; engage local leaders; establish a compelling vision; establish measurable targets; practice adaptive management; build partnerships; pursue collaborative financing; build a record of success; quantify benefits; and focus on life after delisting.     

Defining community revitalization in Great Lakes Areas of Concern and investigating how revitalization can be catalyzed through remediation and restoration

An international effort to restore contaminated areas across the Great Lakes has been underway for over 50 years. Although experts have increasingly recognized the inherent connections between ecological conditions and community level benefits, Great Lakes community revitalization continues to be a broad and complex topic, lacking a comprehensive definition. The purpose of this study was to generate a testable “AOC-Revitalization Framework” for linking remediation and restoration success, represented by Beneficial Use Impairment (BUI) removal in U.S. Great Lakes Areas of Concern (AOC), to community revitalization. Using directed content analysis, we conducted a literature review and identified 433 potential revitalization metrics and indicators and grouped them into 15 broader community revitalization attributes to develop the following definition of Great Lakes community revitalization: “locally driven community resurgence resulting in resilient and equitable enhancements to social, economic, and environmental community structures.” We surveyed experts within the Great Lakes AOC program on the likelihood remediation and restoration success, would positively impact revitalization attributes. Focus groups triangulated survey results. Results identified BUI removal was expected to positively affect revitalization, but the type of revitalization outcome was based on the BUI being removed. The AOC-Revitalization Framework is the first to empirically outline these possible linkages, providing a clear testable structure for future research; it can be used to better understand how environmental improvements are or are not leading to community revitalization and more accurately identify components of revitalization impacted, thus supporting more equitable representation, communication, and measurement of the relationship.     

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.     

Phosphorus targets and eutrophication objectives in Saginaw Bay: A 35 year assessment

An aggregated view of total phosphorus and chlorophyll a in Saginaw Bay indicates that concentrations of both constituents declined approximately in concert with declining total phosphorus (P) loads stabilizing by the late 1980s. A more spatially focused view reveals that total phosphorus declines outside of the Saginaw River plume, accompanied by more subtle chlorophyll a decreases. In contrast, soluble reactive phosphorus and ammonia have recently declined throughout the bay, while nitrate has remained relatively stable. Concentration data from nearshore transects do not exhibit large differences from open-water sample sites. The 440 tonne P/year target phosphorus load established in the 1978 amendments to the Great Lakes Water Quality Agreement has almost never been met, and total phosphorus concentrations regularly exceed the 15 μg/L concentration objective proposed in documentation supporting the 1978 amendments. Seasonal patterns in both total phosphorus and chlorophyll a are more pronounced in the most recent data, with peaks occurring in September–October. This apparently evolving seasonal pattern may result from seasonal changes in Saginaw River flow inputs, or seasonal variation in dreissenid mussel feeding and filtration rates. The adaptive management framework stipulated in the 2012 Great Lakes Water Quality Protocol should promote better monitoring of Saginaw Bay water quality into the future, with enhanced opportunities to better understand the factors that have maintained ongoing eutrophication symptoms.     

Development of new indices of Great Lakes water quality based on profundal benthic communities

Benthic invertebrate biomonitoring has long been a tool of choice for assessing the impacts of anthropogenic stress in aquatic systems. The Oligochaete Trophic Index (OTI) is used by the U.S. EPA Great Lakes National Program Office to assess Great Lakes trophic status for State of the Great Lakes reporting under the Great Lakes Water Quality Agreement. OTI scores are based on pollution tolerances of ubiquitous profundal oligochaetes. OTI limitations include the fact that the index is based on a limited number of species belonging to a single oligochaete class, species assignment to trophic groups in the index were determined by best professional judgment and cannot be tested independently, and the index's correlation with lake productivity has not been evaluated. To address these concerns, we developed two new indices of Great Lakes water quality based on the OTI equation by: (1) expanding the number of oligochaete species included in the index and reassigning previous classifications of oligochaete species to trophic groups (improved OTI, or iOTI); and (2) adding non-oligochaete species to the OTI (modified Trophic Index, or mTI). Finally, we tested a modeling approach using Modern Analogue Technique (MAT) transfer functions based on species responses to a surface chlorophyll gradient to derive assessment of site trophic status and an independent assignment of species to trophic categories. We found that both iOTI and mTI had a stronger relationship with surface remote-sensed spring chlorophyll than did OTI, but MAT models had stronger correlations with chlorophyll than did any of the indices.