Great Lakes coastal fish habitat classification and assessment

Basin-scale assessment of fish habitat in Great Lakes coastal ecosystems would increase our ability to prioritize fish habitat management and restoration actions. As a first step in this direction, we identified key habitat factors associated with highest probability of occurrence for several societally and ecologically important coastal fish species as well as community metrics, using data from the Great Lakes Aquatic Habitat Framework (GLAHF), Great Lakes Environmental Indicators (GLEI) and Coastal Wetland Monitoring Program (CWMP). Secondly, we assessed whether species-specific habitat was threatened by watershed-level anthropogenic stressors. In the southern Great Lakes, key habitat factors for determining presence/absence of several species of coastal fish were chlorophyll concentrations, turbidity, and wave height, whereas in the northern ecoprovince temperature was the major habitat driver for most of the species modeled. Habitat factors best explaining fish richness and diversity were bottom slope and chlorophyll a. These models could likely be further improved with addition of high-resolution submerged macrophyte complexity data which are currently unavailable at the basin-wide scale. Proportion of invasive species was correlated primarily with increasing maximum observed inorganic turbidity and chlorophyll a. We also demonstrate that preferred habitat for several coastal species and high-diversity areas overlap with areas of high watershed stress. Great Lakes coastal wetland fish are a large contributor to ecosystem services as well as commercial and recreational fishery harvest, and scalable basin-wide habitat models developed in this study may be useful for informing management actions targeting specific species or overall coastal fish biodiversity.     

Latitudinal gradient of floristic condition among Great Lakes coastal wetlands

Coastal wetland vegetation along the Great Lakes differs strongly with latitude, but most studies of Great Lakes wetland condition have attempted to exclude the effect of latitude to discern anthropogenic effects on condition. We developed an alternative approach that takes advantage of the strong relationship between latitude and coastal wetland floristic condition. Latitude was significantly correlated with 13 of 37 environmental variables tested, including growing degree days, agriculture, atmospheric deposition, nonpoint-source pollution, and soil texture, which suggests that latitude is a good proxy for several environmental drivers of vegetation. Using data from 64 wetlands along the U.S. coast of Lakes Huron, Michigan, Erie, and Ontario, we developed linear regressions between latitude and two measures of floristic condition, the Floristic Quality Index (FQI, adj. r² = 0.437, p < 0.001) and the first axis scores from a non-metric multidimensional scaling of wetland plant cover (MDS1, adj. r² = 0.501, p < 0.001). Departures from the central tendency of these regression models represented wetlands of better or worse condition than expected for their latitude. This approach provides a means to identify wetlands worthy of preservation, to establish vegetation targets for wetland restoration, and to forecast changes in floristic quality associated with future climate change.     

Water depth and lake-wide water level fluctuation influence on α- and β-diversity of coastal wetland fish communities

Coastal wetlands in the Laurentian Great Lakes are critical habitats for supporting fish diversity and abundance within the basin. Insight into the coupling of biodiversity patterns with habitat conditions may elucidate mechanisms shaping diverse communities. Within coastal wetlands, water depth as well as fluctuations in lake-wide water levels over inter-annual timescales, both have the potential to influence fish communities. Water level fluctuation can influence fish habitat structure (e.g., vegetation) in Great Lakes coastal wetlands, but it is unclear how water depth and lake-wide water level fluctuations affect fish community composition and diversity. Using β dissimilarity indices and multivariate ordination techniques, we assessed fish community structure among bulrush (Schoenoplectus acutus)-dominated wetlands in Saginaw Bay, Lake Huron, USA. We examined whether community structure was related to wetland water depth at the time of sampling and whether fish communities were more similar among years with similar Lake Huron water levels. Results suggested relatively high levels of both spatial (among wetlands) and temporal (among year) community dissimilarity that was driven primarily by species turnover. Thus, variability in water depths among wetlands and in Lake Huron water levels among years likely both contribute to regional fish diversity. Further, fish abundance and alpha diversity were positively correlated with wetland water depth at the time of sampling. Both climate change and anthropogenic water level stabilization may alter the magnitude and timing of water level fluctuations in the Great Lakes. Our data suggest that these changes could affect local fish community composition and regional fish diversity.     

Relative importance of macrophyte community versus water quality variables for predicting fish assemblages in coastal wetlands of the Laurentian Great Lakes

Fish have been shown to be sensitive indicators of environmental quality in Great Lakes coastal wetlands. Fish composition also reflects aquatic macrophyte communities, which provide them with critical habitat. Although investigators have shown that the relationship between water quality and fish community structure can be used to indicate wetland health, we speculate that this relationship is a result of the stronger, more direct relationship between water quality and macrophytes, together with the ensuing interconnection between macrophyte and fish assemblages. In this study, we use data collected from 115 Great Lakes coastal marshes to test the hypothesis that plants are better predictors of fish species composition than is water quality. First we use canonical correspondence analysis (CCA) to conduct an ordination of the fish community constrained by water quality parameters. We then use co-correspondence analysis (COCA) to conduct a direct ordination of the fish community with the plant community data. By comparing the statistic ‘percent fit,’ which refers to the cumulative percentage variance of the species data, we show that plants are consistently better predictors of the fish community than are water quality variables in three separate trials: all wetlands in the Great Lakes basin (whole: 21.2% vs 14.0%; n = 60), all wetlands in Lakes Huron and Superior (Upper: 20.3% vs 18.8%; n =  32), and all wetlands in Georgian Bay and the North Channel (Georgian Bay: 18% vs 17%; n =  70). This is the largest study to directly examine plant–fish interactions in wetlands of the Great Lakes basin.     

Influence of lake levels on water extent,interspersion, and marsh birds in Great Lakes coastal wetlands

Coastal wetlands in the Laurentian Great Lakes undergo frequent, sometimes dramatic, physical changes at varying spatial and temporal scales. Changes in lake levels and the juxtaposition of vegetation and open water greatly influence biota that use coastal wetlands. Several regional studies have shown that changes in vegetation and lake levels lead to predictable changes in the composition of coastal wetland bird communities. We report new findings of wetland bird community changes at a broader scale, covering the entire Great Lakes basin. Our results indicate that water extent and interspersion increased in coastal wetlands across the Great Lakes between low (2013) and high (2018) lake-level years, although variation in the magnitude of change occurred within and among lakes. Increases in water extent and interspersion resulted in a general increase in marsh-obligate and marsh-facultative bird species richness. Species like American bittern (Botaurus lentiginosus), common gallinule (Gallinula galeata), American coot (Fulica americana), sora (Porzana carolina), Virginia rail (Rallus limicola), and pied-billed grebe (Podilymbus podiceps) were significantly more abundant during high water years. Lakes Huron and Michigan showed the greatest increase in water extent and interspersion among the five Great Lakes while Lake Michigan showed the greatest increase in marsh-obligate bird species richness. These results reinforce the idea that effective management, restoration, and assessment of wetlands must account for fluctuations in lake levels. Although high lake levels generally provide the most favorable conditions for wetland bird species, variation in lake levels and bird species assemblages create ecosystems that are both spatially and temporally dynamic.     

Fish Habitat Use Within and Across Wetland Classes in Coastal Wetlands of the Five Great Lakes: Development of a Fish-based Index of Biotic Integrity

The relative importance of Great Lake, ecoregion, wetland type, and plant zonation in structuring fish community composition was determined for 61 Great Lakes coastal wetlands sampled in 2002. These wetlands, from all five Great Lakes, spanned nine ecoregions and four wetland types (open lacustrine, protected lacustrine, barrier-beach, and drowned river mouth). Fish were sampled with fyke nets, and physical and chemical parameters were determined for inundated plant zones in each wetland. Land use/cover was calculated for 1- and 20-km buffers from digitized imagery. Fish community composition within and among wetlands was compared using correspondence analyses, detrended correspondence analyses, and non-metric multidimensional scaling. Within-site plant zonation was the single most important variable structuring fish communities regardless of lake, ecoregion, or wetland type. Fish community composition correlated with chemical/physical and land use/cover variables. Fish community composition shifted with nutrients and adjacent agriculture within vegetation zone. Fish community composition was ordinated from Scirpus, Eleocharis, and Zizania, to Nuphar/Nymphaea, and Pontederia/Sagittaria/Peltandra to Spargainium to Typha. Once the underlying driver in fish community composition was determined to be plant zonation, data were stratified by vegetation type and an IBI was developed for coastal wetlands of the entire Great Lakes basin.     

Spatial and temporal trends in invertebrate communities of Great Lakes coastal wetlands,with emphasis on Saginaw Bay of Lake Huron

The shallow-sloping coastal bathymetry of Saginaw Bay (Lake Huron) supports broad fringing wetlands. Because benthic invertebrates form an important forage base for fish, wading birds, and waterfowl that utilize these habitats, understanding the drivers of invertebrate community structure has significant management implications. We used Great Lakes basin-wide data from 2002 to place Saginaw Bay wetland invertebrate communities and their environmental drivers into a basin-wide context. Various aspects of community structure were highly correlated with fetch and watershed agriculture across the basin. Saginaw Bay wetlands had relatively high fetch and watershed agriculture and supported unique invertebrate communities, typified by high abundances of many insect taxa. Wetlands from other regions around the basin tended to have more crustaceans and gastropods than the Saginaw Bay wetlands. A 1997–2012 time series from three representative Saginaw Bay wetlands revealed substantial shifts in community structure throughout the period, especially from 2001 through 2004. These years followed a 1-m decline in Lake Huron water levels that occurred between 1997 and 2000. Major community changes included decreasing insect abundance, especially chironomids, and increasing crustacean abundances, especially Hyalella azteca (Amphipoda). While factors in addition to water levels were likely also important, our time series analysis reveals the marked temporal dynamics of Saginaw Bay wetland invertebrate communities and suggests that water level decline may have influenced these communities substantially. Both the spatial and temporal community patterns that we found should be considered in future bio-assessments utilizing wetland invertebrates.     

Stewardship after delisting: Sustaining long-term progress in Michigan’s Areas of Concern

The Michigan Areas of Concern (AOC) program has made significant progress in recent years following the influx of external funding from the Great Lakes Restoration Initiative and the Great Lakes Legacy Act. However, as more AOCs near delisting, community members from Michigan Public Advisory Councils (PACs) are concerned that the loss of programmatic funding will constrain their ability to sustain key public engagement and long-term restoration progress. In order to understand the local community perspectives surrounding delisting, our study presents findings and recommendations that emerged from interviews with Michigan PAC members. We found that PACs recognize the need to transition away from projects with a short-term focus and instead prioritize longer-term, holistic strategies that could help catalyze effective public engagement and produce transformative community revitalization. This study’s recommendations for the Michigan Department of Environment, Great Lakes, and Energy (EGLE) include: (1) dedicating more time to post-delisting planning, (2) enhancing communication efforts with PACs, and (3) strengthening long-term public engagement efforts and PAC organizational capacity. These recommendations add to the growing literature supporting the value of local community perspectives and social dimensions of environmental restoration and may also provide transferable insights to communities outside of Michigan that are currently engaged in similar complex, multi-stakeholder environmental restoration projects.     

Watershed and lake influences on the energetic base of coastal wetland food webs across the Great Lakes Basin

We examined factors that influence the energy base of Great Lakes coastal wetland food webs across a basin-wide gradient of landscape disturbance. Wetland nutrient concentrations were positively correlated with a principal components-based metric of agricultural practices. Hydraulic residence time influenced the energy base of wetland food webs, with high residence-time systems based mostly on plankton and low residence-time systems based mostly upon benthos. In systems with plankton, the importance of planktonic carbon to the resident fish community generally increased with residence time. A stronger relationship was apparent with an index of nutrient loading that combined residence time and nutrient concentration as the predictor (R² = 0.289, p = 0.026). Shifts toward plankton-based food webs occurred at relatively low levels of loading. In riverine wetlands without plankton, contributions of detrital carbon to fish communities decreased significantly in response to watershed disturbance that reflected nutrient loading. In a third class of wetlands the wetland-resident fish communities were not entirely supported by within-wetland carbon sources and were significantly subsidized by nearshore habitats, which provided 35 (± 22) to 73 (± 9) % of fish community carbon. When lake-run migrant fish were included in the analyses, nearshore subsidies to all 30 wetland food webs ranged from 3 (± 2) to 79 (± 12) %. We obtained similar ranges when examining nearshore contributions to a single wetland species, northern pike. These results illustrate the spatial scale and the degree to which the energetics of coastal wetland food webs are influenced by interactions with their watersheds and Great Lakes.     

Watershed-scale landuse is associated with temporal and spatial compositional variation in Lake Michigan tributary bacterial communities

Populations of stream organisms across trophic levels, including microbial taxa, are adapted to physical and biotic stream features, and are sentinels of geological and hydrological landscape processes and anthropogenic disturbance. Stream bacterial diversity and composition can have profound effects on resident and migratory species in Great Lakes tributaries. Study objectives were to characterize and compare the taxonomic composition and diversity of bacterial communities in 18 rivers of the Lake Michigan basin during April and June 2019 and to quantify associations with stream and watershed physical features and dominant landuse practices. River water was filtered, and genomic DNA was extracted from filtrate using antiseptic techniques. We performed high-throughput amplicon sequencing using the highly variable V4 region of the 16S rRNA gene to characterize microbial community composition and diversity. Effects of landscape-scale landuse, environmental variables and dispersal predictors (e.g., inter-stream distance) on community compositional differences were quantified. Greater than 90% of variation in bacterial relative abundance between rivers and time were attributed to 11 phyla representing 10,800 operational taxonomic units. Inter-stream geographic distance, stream hydrology, and variation in stream properties that were tied to patterns of watershed landuse were significantly associated with differences in bacterial community composition among streams at both sampling time periods. based on Bray-Curtis distances. Understanding how environmental characteristics and watershed-scale landuse influence lower trophic level stream communities such as bacteria will inform managers as biological indicators of ecosystem health, sources of disturbance, and current and future bottom-up trophic changes in coupled tributary-Great Lakes ecosystems.     

Status of the major aquaculture carps of China in the Laurentian Great Lakes Basin

There is concern of economic and environmental damage occuring if any of the four major aquacultured carp species of China, black carp Mylopharyngodon piceus, bighead carp Hypophthalmichthys nobilis, silver carp H. molitrix, or grass carp Ctenopharyngodon idella, were to establish in the Laurentian Great Lakes. All four are reproducing in the Mississippi River Basin. We review the status of these fishes in relation to the Great Lakes and their proximity to pathways into the Great Lakes, based on captures and collections of eggs and larvae. No black carp have been captured in the Great Lakes Basin. One silver carp and one bighead carp were captured within the Chicago Area Waterway System, on the Great Lakes side of electric barriers designed to keep carp from entering the Great Lakes from the greater Mississippi River Basin. Three bighead carp were captured in Lake Erie, none later than the year 2000. By December 2019, at least 650 grass carps had been captured in the Great Lakes Basin, most in western Lake Erie, but none in Lake Superior. Grass carp reproduction has been documented in the Sandusky and Maumee rivers in Ohio, tributaries of Lake Erie. We also discuss environmental DNA (eDNA) results as an early detection and monitoring tool for bighead and silver carps. Detection of eDNA does not necessarily indicate presence of live fish, but bigheaded carp eDNA has been detected on the Great Lakes side of the barriers and in a small proportion of samples from the western basin of Lake Erie.     

Great Lakes coastal wetlands as suitable habitat for invasive mute swans in Michigan

Great Lakes coastal wetlands provide critical habitat and food resources for more species than any other Great Lakes ecosystem. Due to past and current anthropogenic disturbances, coastal wetland area has been reduced by >50% while remaining habitat is frequently degraded. Invasive mute swans have contributed to the degradation of coastal wetlands by removing submergent vegetation and competitively excluding native species from breeding areas and food resources. Despite current control practices, mute swan population estimates in Michigan are ~8000, comparable to population estimates in the entire Atlantic Flyway of North America. We collected local abiotic data and adjacent land cover data at 3 scales from 51 sites during 2010 and 2011 and conducted 2 mute swan detection surveys each year during the summer and fall. We developed a single-species, single-season occupancy-based habitat suitability model to determine current and potential mute swan habitat among Great Lakes coastal wetlands. We found mute swans occupied heterotrophic coastal wetlands adjacent to urban areas, which were high in ammonium and oxidation-reduction potential and low in nitrates, dissolved oxygen, and turbidity. Our model provides managers with a valuable tool for rapidly identifying mute swan habitat areas for control efforts, particularly the need for targeting mute swan populations in or near urbanized areas. Our model will also aid managers in monitoring areas that mute swans may invade and prioritizing coastal wetland areas for restoration efforts.     

Modeling wetland vegetation community response to water-level change at Long Point,Ontario

Three spatially-explicit wetland models were developed in a geographic information system (GIS) to simulate wetland vegetation response to water-level fluctuations at the Long Point, Ontario wetland complex. They included: a rule-based model that used a series of if-then statements related to pre-existing vegetation, water depth and wetland vegetation community tolerance ranges; a vegetation state probability model based on likelihood of certain wetland vegetation communities occurring at specific water depths; and a vegetation transition probability model based on likelihood of wetland communities changing to another community under declining or rising water level conditions. The accuracy of the models was evaluated by comparing area and spatial distribution of the simulated wetland landscape to digital historical wetland vegetation data from air photo interpretation. The accuracy of the models ranged from over 80% of the cells correctly classified by the vegetation transition probability model and rule-based model to about 55% correctly classified by the vegetation state probability model. The vegetation transition probability model was marginally more accurate than the rule-based model when assessed on a cell-by-cell basis, but the rule-based model replicated the spatial distribution of vegetation communities more accurately and may be more broadly applicable. Recommended improvements include: additional environmental factors (wave exposure and substrate) incorporated in the decision rules and more detailed input data for the digital elevation model (DEM). Spatially-explicit modeling such as the rule-based model can explore management issues related to climate change and water-level regulation impacts on wetlands in the Great Lakes basin and elsewhere.     

A pound of prevention,plus a pound of cure: Early detection and eradication of invasive species in the Laurentian Great Lakes

Ballast water regulations implemented in the early 1990s appear not to have slowed the rate of new aquatic invasive species (AIS) establishment in the Great Lakes. With more invasive species on the horizon, we examine the question of whether eradication of AIS is a viable management strategy for the Laurentian Great Lakes, and what a coordinated AIS early detection and eradication program would entail. In-lake monitoring would be conducted to assess the effectiveness of regulations aimed at stopping new AIS, and to maximize the likelihood of early detection of new invaders. Monitoring would be focused on detecting the most probable invaders, the most invasion-prone habitats, and the species most conducive to eradication. When a new non-native species is discovered, an eradication assessment would be conducted and used to guide the management response. In light of high uncertainty, management decisions must be robust to a range of impact and control scenarios. Though prevention should continue to be the cornerstone of management efforts, we believe that a coordinated early detection and eradication program is warranted if the Great Lakes management community and stakeholders are serious about reducing undesired impacts stemming from new AIS in the Great Lakes. Development of such a program is an opportunity for the Laurentian Great Lakes resource management community to demonstrate global leadership in invasive species management.     

An ecological assessment of Great Lakes tributaries in the Michigan Peninsulas

Michigan stream fish and macroinvertebrate community data from multiple sources were combined to conduct a statewide assessment of riverine ecological condition. Using regionally normalized metrics to correct for methodological inconsistencies and natural variation and statistically based scoring criteria, about 50% of all sampled sites were in expected or better ecological condition, 30% were ecologically impaired, and 20% were marginal. Structural Equation Modeling with this regional assessment dataset indicated that land use effects were more important than effects of point-source discharges. Biological metrics appeared to be more sensitive to urban than agricultural land use, and riparian than basin-wide agricultural land use. Invertebrate communities were marginally more sensitive than fish communities to the suite of anthropogenic stressors examined. Using the observed assessment status from sampled sites, Classification and Regression Tree models were used to estimate ecological condition in the state's remaining unsampled river segments. Combining observed and estimated site scores, 25% of the state's river kms were estimated to be impaired, with the Erie and St. Clair basins having the highest degree of impairment (52% and 44% of total channel lengths, respectively) and lakes Superior, Michigan, and Huron basins had the lowest degree of impairment at 4%, 21% and 31%, respectively. We argue that correlations between the state of the Great Lakes and the ecological conditions of their tributary systems reflect both direct impact transmission from watershed to receiving waters, and also non-causal correlation due to shared anthropogenic stressors.     

Diatom and geochemical paleolimnology reveals a history of multiple stressors and recovery on Lake Ontario

Among the Laurentian Great Lakes, Lake Ontario is the farthest downstream and has the longest history of environmental stress from human activities. Two sediment cores, spanning the last 300 years, from Lake Ontario were analyzed for diatom composition and geochemistry and compared with anthropogenic activities in the surrounding watershed. Despite some regional variation a clear, lake-wide record of cultural eutrophication and recovery is presented in three phases: (1) a largely pre-impact phase (1700s through ~ 1920) dominated by oligotrophic/mesotrophic diatoms and more inorganic sediment accumulation; (2) an accelerated eutrophication phase (1920s to 1980s) reflecting human population growth, watershed modifications and rapid industrial expansion as indicated by increases in nutrient-tolerant diatom taxa and sediment contaminants; and (3) a recovery phase (1980s to present) when diatom-inferred nutrient concentrations trended back to pre-impact levels in response to pollution abatement measures and novel stressors such as dreissenid invaders and climate change. Based on our long-term record, Lake Ontario’s ecosystem continues to evolve in response to contemporary stressors.     

Influence of surrounding land cover on marsh-breeding birds: Implications for wetland restoration and conservation planning

Marsh-breeding birds are valuable components of healthy ecosystems and are useful indicators of successful wetland restorations. The occurrence of these species, however, is influenced by the surrounding landscape. To aid decision-makers, we used data from the Great Lakes Marsh Monitoring Program of Birds Canada at 521 sites across four time periods (2000–2001, 2005–2006, 2010–2011, 2015–2016) throughout southern Ontario, Canada, to quantify how initial occupancy and subsequent local extinction or colonization of 13 marsh-breeding bird indicator species (or species groups) was influenced by the composition of, and concurrent changes in, surrounding remotely-sensed land cover within 200–6,400 m. For six species (46 %) initial occupancy was higher or extinction was lower where surrounding wetland/open water land cover was higher. By contrast, initial occupancy was lower, extinction was higher, and/or colonization was lower: 1) where surrounding anthropogenic (predominantly urban) land cover was higher (four species, 31 %), 2) in Great Lakes coastal compared to inland landscapes (five species, 38 %), and 3) where loss of surrounding wetland/open water land cover increased, depending on whether surrounding wetland/open water land cover was initially low or high (seven species, 54 %). We recommend that decision-makers consider the influence of the surrounding landscape during conservation planning and when measuring success of wetland restorations based on marsh-breeding bird indicator species, particularly in Great Lakes coastal landscapes and landscapes with high urban land cover and/or low wetland/open water land cover.     

Stimulating a Great Lakes coastal wetland seed bank using portable cofferdams: implications for habitat rehabilitation

Coastal wetland seed banks exposed by low lake levels or through management actions fuel the reestablishment of emergent plant assemblages (i.e., wetland habitat) critical to Great Lakes aquatic biota. This project explored the effectiveness of using portable, water-filled cofferdams as a management tool to promote the natural growth of emergent vegetation from the seed bank in a Lake Erie coastal wetland. A series of dams stretching approximately 450 m was installed temporarily to isolate hydrologically a 10-ha corner of the Crane Creek wetland complex from Lake Erie. The test area was dewatered in 2004 to mimic a low-water year, and vegetation sampling characterized the wetland seed bank response at low, middle, and high elevations in areas open to and protected from bird and mammal herbivory. The nearly two-month drawdown stimulated a rapid seed-bank-driven response by 45 plant taxa. Herbivory had little effect on plant species richness, regardless of the location along an elevation gradient. Inundation contributed to the replacement of immature emergent plant species with submersed aquatic species after the dams failed and were removed prematurely. This study revealed a number of important issues that must be considered for effective long-term implementation of portable cofferdam technology to stimulate wetland seed banks, including duration of dewatering, product size, source of clean water, replacement of damaged dams, and regular maintenance. This technology is a potentially important tool in the arsenal used by resource managers seeking to rehabilitate the functions and values of Great Lakes coastal wetland habitats.     

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.     

A Tale of Two Waters: the Missouri River,the Great Lakes and Management of Future Water Conflicts

Abstract

This paper analyzes recent developments regarding Missouri River management and water use, and the potential for an emerging inter-basin water dispute involving the Great Lakes. It is suggested that revisions to the U.S. Army Corps of Engineers' master manual for the Missouri River and increasing efforts to put Missouri River water to beneficial use in support of economic growth present the prospect of low water levels in the Mississippi River. With a history of looking to the Chicago diversion as a source for augmenting flows in the Mississippi River, it may yet again prove to be an irresistible temptation. The institutional capacity for managing such a water dispute seems surprisingly weak. The direction suggested is that mechanisms should be installed to ensure that Great Lakes water remains in its basin, consistent with watershed management practices. The recent efforts by the Great Lakes states and provinces represent an important development in this direction. It is further suggested that demand pressures in the Missouri River should be met through a similar commitment, potentially through a water sharing arrangement on the Missouri River, something which could be encouraged in part by ensuring stricter controls on the Chicago diversion.