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.     

Environmental predictors of phytoplankton chlorophyll-a in Great Lakes coastal wetlands

Coastal wetlands of the Laurentian Great Lakes are diverse and productive ecosystems that provide many ecosystem services, but are threatened by anthropogenic factors, including nutrient input, land-use change, invasive species, and climate change. In this study, we examined one component of wetland ecosystem structure – phytoplankton biomass – using the proxy metric of water column chlorophyll-a measured in 514 coastal wetlands across all five Great Lakes as part of the Great Lakes Coastal Wetland Monitoring Program. Mean chlorophyll-a concentrations increased from north-to-south from Lake Superior to Lake Erie, but concentrations varied among sites within lakes. To predict chlorophyll-a concentrations, we developed two random forest models for each lake – one using variables that may directly relate to phytoplankton biomass (“proximate” variables; e.g., dissolved nutrients, temperature, pH) and another using variables with potentially indirect effects on phytoplankton growth (“distal” variables; e.g., land use, fetch). Proximate and distal variable models explained 16–43% and 19–48% of variation in chlorophyll-a, respectively, with models developed for lakes Erie and Michigan having the highest amount of explanatory power and models developed for lakes Ontario, Superior, and Huron having the lowest. Land-use variables were important distal predictors of chlorophyll-a concentrations across all lakes. We found multiple proximate predictors of chlorophyll-a, but there was little consistency among lakes, suggesting that, while chlorophyll-a may be broadly influenced by distal factors such as land use, individual lakes and wetlands have unique characteristics that affect chlorophyll-a concentrations. Our results highlight the importance of responsible land-use planning and watershed-level management for protecting coastal wetlands.     

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.     

Ecological data as a resource for invasive species management in U.S. Great Lakes coastal wetlands

The coordinated use of ecological data is critical to the proper management of invasive species in the coastal wetlands of the Laurentian Great Lakes. Researchers and government programs have been increasingly calling for the use of data in management activities to increase the likelihood of success and add transparency in decision making. Web-enabled databases have the potential to provide managers working in Great Lakes coastal wetlands with relevant data to support management decisions. To assess the potential value of these databases to managers in Laurentian Great Lakes states, we surveyed wetland managers to determine their current data usage as well as their future data interests and catalogued the online databases currently available. Surveys were disseminated via email to managers in 56 different organizations overseeing invasive species management efforts in Great Lakes coastal wetlands; 46 responses were included in this analysis. Of the survey respondents, all reported using raw biotic data for decision making, (i.e. presence of target species) but many indicated that they would prefer to incorporate a greater variety of data, as well as more complex information. Our survey found that managers used web-enabled databases, but most databases that we catalogued only provided presence data for wetland biota. We concluded that databases can provide the types of data sought by invasive species managers but have unmet potential to be integrated into responsive management processes.     

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.     

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.     

The Impact of Changes in Water Level and Human Development on Forage Fish Assemblages in Great Lakes Coastal Marshes

Changes in water levels and development of shorelines are expected to negatively affect coastal marshes. The small-bodied fish assemblage was sampled in the inner marsh vegetation zone in five Les Cheneaux bays with differing levels of development. Observations were made from 1996 to 2004 during which time summer water levels varied from 177.2 m to 176.0 m (chart datum = 176.0 m). Each marsh was sampled for 10 consecutive days in July and August using gangs of five baited commercial minnow traps. Assemblage composition was assayed by species richness, the number of native minnow species, the percentage of selected tolerant fishes (bowfin, Amia calva, mudminnow, Umbra limi, common carp, Cyprinus carpio, and brown bullhead, Ameiurus nebulosus), and catch-per-unit-effort (CPUE). There were no consistent relationships between fish assemblage measures and year, water level, annual change in water level, exposure, and water temperature. Fish assemblage measures except CPUE were impacted by the density of building along the shoreline, a measure of development. Impervious surface area was < 4.5% and was not consistently related to fish assemblage measures.     

Invasive cattail reduces fish diversity and abundance in the emergent marsh of a Great Lakes coastal wetland

Great Lakes coastal wetlands (GLCWs) provide critical fish habitat. The invasion of GLCWs by hybrid and narrow-leaved cattail, Typha × glauca and Typha angustifolia (hereafter Typha), homogenizes wetlands by out-competing native plant species and producing copious litter. However, the effect of this invasion on fish communities is little known. To measure the effect of Typha on fishes, we established plots in Typha invaded and native wetland emergent zones in a northern Lake Michigan coastal wetland, and measured environmental variables, plants, and fishes in each zone over two summers. Dissolved oxygen and water temperature were significantly lower in invaded compared to native plots. Invaded plots were dominated by Typha and its litter; whereas. sedges (Carex spp.) were the most abundant species in native plots. Fish abundance and species richness were significantly lower in Typha compared to native wetland plots. The Typha fish community was dominated by hypoxia tolerant mudminnow whereas other small, schooling, fusiform species such as cyprinids and fundulids were absent. These results illustrate the negative impact of a dominant invasive plant on Great Lakes fishes that is expected to be found in Typha invasions in other GLCWs.     

Enhancing Great Lakes coastal ecosystems research by initiating engagement between scientists and decision-makers

A disconnect between scientific research and environmental management communities can be a detriment to both. In the case of Great Lakes coastal ecosystems, which are inherently complex and subject to uncertain effects of future climatic, environmental, and anthropogenic drivers, greater collaboration could be beneficial to their sustainability. We capture the challenges and opportunities identified by a scientist/decision-maker co-production workshop focused on the future environmental quality of Great Lakes coastal wetlands. We explain our path through the stakeholder workshop process, our challenges in translating meeting outcomes into actionable items, and lessons learned to bridge gaps between scientists and decision-makers. Additionally, we determine topics and directions identified by decision-makers that can be modeled with existing technologies and others that require further research. These topics may be incorporated into future research efforts and could serve as a shortlist of research priorities that were identified by decision-makers working with coastal wetland issues. Based on lessons learned during and after the workshop, we provide suggestions for bridging the gap between researchers and decision-makers, including sustained engagement between these groups and improved interaction through the beginning, duration, and end of research and/or management efforts.     

Relative contributions of nearshore and wetland habitats to coastal food webs in the Great Lakes

Hydrologic linkages among coastal wetland and nearshore areas allow coastal fish to move among the habitats, which has led to a variety of habitat use patterns. We determined nutritional support of coastal fishes from 12 wetland-nearshore habitat pairs using stable isotope analyses, which revealed differences among species and systems in multi-habitat use. Substantial (proportions?>?0.30) nutrition often came from the habitat other than that in which fish were captured. Nearshore subsidies to coastal wetlands indicate wetlands are not exclusively exporters of energy and materials; rather, there is reciprocity in the mutual energetic support of nearshore and wetland food webs. Coastal wetland hydrogeomorphology influenced the amount of multi-habitat use by coastal fishes. Fishes from systems with relatively open interfaces between wetland and nearshore habitats exhibited less nutritional reliance on the habitat in which they were captured, and higher use of resources from the adjacent habitat. Comparisons of stable isotope analyses of nutrition with otolith analyses of occupancy indicated nutritional sources often corresponded with habitat occupancy; however, disparities among place of capture, otolith analyses, and nutritional analyses indicated differences in the types of support those analyses inform. Disparities between occupancy information and nutritional information can stem from movements for support functions other than foraging. Together, occupancy information from otolith microchemistry and nutritional information from stable isotope analyses provide complementary measures of the use of multiple habitats by mobile consumers. This work underscores the importance of protecting or restoring a diversity of coastal habitats and the hydrologic linkages among them.     

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.     

Initial insights into the development and implementation of a citizen-science drone-based coastal change monitoring program in the Great Lakes region

High-resolution spatio-temporal data are needed to improve coastal management programs, particularly along the Great Lakes where lake level fluctuations pose challenges to coastal decision-making and planning. Unfortunately, there is a paucity of coastal change monitoring datasets, particularly those that document event-scale changes over a large spatial scale. This paucity of data is compounded by the large size and range of shore types throughout the region.Unoccupied aerial vehicle (UAV) or drone data collected by citizen scientists are a potential solution to this challenge. However, no citizen science coastal change monitoring program exists in the Great Lakes region, nor does a comprehensive drone-based coastal change monitoring programs exist anywhere in the United States. To inform the development of drone-based citizen science programs, the goal of this paper is to describe the development and implementation of a citizen science coastal change monitoring program along the Great Lakes shores of Michigan. The citizens participating in this project generate imagery in two ways: (1) the submission of photos of coastal changes or hazards via a web app developed for the project called PicShores and (2) drone collection of survey-quality aerial imagery for use in the generation of orthomosaic images and digital elevation models (DEMs). This paper presents the methods utilized to develop the citizen science monitoring program, some initial findings from the citizen science monitoring, and explores some challenges and next steps for the program.     

Edge effects on abiotic conditions,zooplankton, macroinvertebrates,and larval fishes in Great Lakes fringing marshes

Fragmentation and edge creation is common in many freshwater coastal wetlands, though relatively little is known about edge effects on abiotic conditions and faunal communities within these habitats. We investigated edge effects associated with anthropogenic fragmentation in 16 fringing coastal marshes of Lake Michigan and Lake Huron. Environmental data, zooplankton, macroinvertebrates, and larval fish were collected along transects extending into each marsh from reference (i.e., where the wetland naturally interfaced with open water) and anthropogenic edges (i.e., where the wetland interfaced with open water habitats created by vegetation removal). Physical and chemical gradients were apparent from marsh edges toward marsh interiors regardless of edge type. Faunal communities appeared to respond to these gradients. Zooplankton biomass, macroinvertebrate richness and macroinvertebrate Shannon diversity were depressed at edges and increased toward marsh interiors. Larval fish catch per unit effort, taxon richness, and Shannon diversity increased from reference edges toward marsh interiors. Larvae of individual fish species displayed varying patterns across edges. Our results suggest that because of edge effects, fragmentation of coastal marshes causes impacts that exceed the area of marsh habitat that is actually lost. For example, as a marsh's protected inner core area is reduced, the marsh fragment may cease to function as a viable refuge from hydrologic energy and open water predators. Therefore, fragmentation should be viewed as a significant impact to freshwater coastal marsh ecosystems similar to how it is regarded in terrestrial ecosystem management.     

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.     

Methane emissions from riverine and swampy coastal wetlands: influence of open and macrophyte‐infested areas

The atmospheric concentration of methane (CH₄) exerts a strong influence on the global climate. Notably, wetlands are important CH₄ sources, whose emission represents an ecosystem process depending on such wetland characteristics as organic matter, temperature, pH, methanogenesis and CH₄ oxidation, all of which vary on the basis of the type of wetland. Methane fluxes were investigated in a preliminary study in the region, using the chamber method in the open water and macrophyte‐infested wetlands of swampy and riverine types in Kilifi, a coastal district in Kenya, Africa. Despite a lack of significant interactions, the macrophyte‐infested areas emitted the highest quantity of methane of about 21.96 ± 0.04 mg CH₄ m^?2 day^?1, compared with the water areas that emitted about 19.35 ± 0.05 mg CH₄ m^?2 day^?1. The preliminary CH₄ fluxes measured in this study are below the range reported from previous wetland field experiments in the tropics and temperate regions, indicating the need to conduct a series of similar experiments to produce more precise total estimates in the entire region.     

Rapid water level rise drives unprecedented coastal habitat loss along the Great Lakes of North America

Lake Michigan rose to record high water levels in the 2010s; during this time, some coastal sites experienced habitat loss rates an order of magnitude higher than during previous high water periods throughout the 20th century. The high magnitude and rapid rate of rise observed during the 2012–2020 period in combination with a slight increase in the percentage of storm waves likely accelerated habitat loss rates beyond levels that were observed over the past century. Our data suggest that rapid and relatively large changes from low water levels to high water levels are the main driver of large erosional losses, as the coastal system shifts abruptly from one water-level regime to another. One likely impact of climate change on Great Lakes’ water level is an increase in the variability of fluctuations, thus more scenarios of abrupt and rapid water-level rise and associated habitat loss are expected in the future. We propose that the unprecedented habitat loss observed during the 2012–2020 timeframe will become the new normal in the coming century as enhanced variability in water levels facilitates sustained coastal land loss.     

Toward science-informed public policy: A conceptual framework for contributing to and studying Great Lakes coastal shoreland management

Great Lakes coastal shorelands encompass valuable environmental and social resources. Most are privately owned. Governments play an important role in managing the use of those shorelands to ensure adequate conservation of the natural and social benefits they provide. Scientists have demonstrated that imprudent land uses are yielding significant ecological harms and increased risks to coastal shorelands, and yet those uses persist. Public coastal shoreland management appears to be poorly informed by the best available science. In addition to generating good science, scientists are themselves members of the public well-positioned to contribute to improved coastal shoreland management. Two prominent proposals for doing so include calls for scientists, first, to better communicate their knowledge through direct engagement with decision-makers (‘contributing to’) and second, to co-produce the knowledge that decision-makers require by participating in multi-disciplinary, community-engaged research (‘studying’). For either endeavor, scientists need to understand public coastal shoreland management processes to engage effectively with them. Drawing from multiple literatures, this paper presents a conceptual framework to assist scientists working to contextualize and more effectively convey the knowledge they have, or to engage in research designed to co-produce knowledge, in order to better promote science-informed public coastal shoreland management. The framework is set within the institutional arrangements that structure coastal management processes, and it highlights the ways in which key decision-maker attributes—their collective knowledge, capacities, and commitments—influence decision-making actions and outputs. While situated specifically within the context of coastal management, the framework is adaptable to other policy arenas more broadly.     

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.     

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.