Great Lakes Coastal Wetlands Research Articles

Active remote sensing data and dispersal processes improve predictions for an invasive aquatic plant during a climatic extreme in Great Lakes coastal wetlands

Invasive aquatic plants pose a significant threat to coastal wetlands. Predicting suitable habitat for invasive aquatic plants in uninvaded yet vulnerable wetlands remains a critical task to prevent further harm to these ecosystems. The integration of remote sensing and geospatial data into species distribution models (SDMs) can help predict where new invasions are likely to occur by generating spatial outputs of habitat suitability. The objective of this study was to assess the efficacy of utilizing active remote sensing datasets (synthetic aperture radar (SAR) and light detection and ranging (LiDAR) with multispectral imagery and other geospatial data in predicting the potential distribution of an invasive aquatic plant based on its biophysical habitat requirements and dispersal dynamics. We also considered a climatic extreme (lake water levels) during the study period to investigate how these predictions may change between years. We compiled a time series of 1628 field records on the occurrence of Hydrocharis morsus-ranae (European frogbit; EFB) with nine remote sensing and geospatial layers as predictors to train and assess the predictive capacity of random forest models to generate habitat suitability in Great Lakes coastal wetlands in northern Michigan, USA. We found that SAR and LiDAR data were useful as proxies for key biophysical characteristics of EFB habitat (emergent vegetation and water depth), and that a vegetation index calculated from spectral imagery was one of the most important predictors of EFB occurrence. Our SDM using all predictors yielded the highest mean overall accuracy of 88.3% and a true skill statistic of 75.7%. Two of the most important predictors of EFB occurrence were dispersal-related: 1) distance to the nearest known EFB population (m), and 2) distance to nearest public boat launch (m). The area of highly suitable habitat (pixels assigned ≥0.8 probability) was 74% larger during a climatically extreme high water-level year compared to an average year. Our findings demonstrate that active remote sensing can be integrated into SDM workflows as proxies for important drivers of invasive species expansion that are difficult to measure in other ways. Moreover, the importance of a proxy variable for endogenous dispersal (distance to nearest known population) in these SDMs indicates that EFB is currently spreading, and thereby less influenced by within-site dynamics such as interspecific competition. Lastly, we found that extreme climatic conditions can dramatically change this species’ niche, and therefore we recommend that future studies include dynamic climate conditions in SDMs to more accurately forecast the spread during early invasion stages.

Evaluating the Effect of Common Carp Control on Restoration of a Coastal Wetland in the Laurentian Great Lakes

Great Lakes coastal wetlands are under considerable stress from numerous anthropogenic threats, including the introduction of invasive species. Common Carp, an invasive species in North America, has been well documented as an influential wetland stressor. This study documents the impact of Common Carp reintroduction on a restored wetland fish community and abiotic and vegetation variables. Oshawa Second Marsh was restored using an exclusion berm with a fish grate and manual water-level drawdown to re-establish vegetation. Five years into restoration monitoring, Common Carp regained access to the wetland after the fish grate was vandalized. Fish community health was monitored over time using multimetric and multivariate approaches based on abiotic and vegetation variables. Improvements in fish community health were observed during restoration monitoring, but after Common Carp reintroduction, fish community health decreased and the community homogenized. Seven of the ten abiotic and vegetation variables monitored changed significantly after Common Carp reintroduction. This study highlights the impact that Common Carp has on the functional integrity of coastal wetlands and the significance of its management for restoration.

Estimating fish production in wetlands

Fish production integrates changes in biomass from growth, reproduction, and mortality, and is a useful indicator for fisheries management. However, calculation of fish production has been limited by the intensive requirements for data on abundance, biomass, age structure, and vital rates, and so it is uncommon to find estimates of fish production for wetlands. We developed an approach to directly estimate production that is suitable for data-limited systems: a continuous time model of production describing individual growth over short time intervals with continuous time models of abundance and biomass over longer timescales. We applied this model for 18 Great Lakes coastal wetlands (GLCWs) on Lake Ontario, including Big Island Wetland (BIW). In BIW, most species were dominated in abundance and biomass by younger cohorts and, as a result, these young, fast-growing individuals contributed disproportionately to fish production. In total, BIW produced 336.1 kg·ha·year of fish and the other 17 neighbouring ranged between 447.7 and 1119.9 kg·ha·year. These are some of the first estimates of fish production for GLCWs, highlighting their value for managing Great Lakes fisheries.

Relationships Between Muskrat Density and Avian and Anuran Richness in Great Lakes Coastal Wetlands

Relationships Between Muskrat Density and Avian and Anuran Richness in Great Lakes Coastal Wetlands

Increasing marsh bird abundance in coastal wetlands of the Great Lakes, 2011–2021, likely caused by increasing water levels

Abstract Wetlands of the Laurentian Great Lakes of North America (i.e., lakes Superior, Michigan, Huron, Erie, and Ontario) provide critical habitat for marsh birds. We used 11 years (2011–2021) of data collected by the Great Lakes Coastal Wetland Monitoring Program at 1,962 point-count locations in 792 wetlands to quantify the first-ever annual abundance indices and trends of 18 marsh-breeding bird species in coastal wetlands throughout the entire Great Lakes. Nine species (50%) increased by 8–37% per year across all of the Great Lakes combined, whereas none decreased. Twelve species (67%) increased by 5–50% per year in at least 1 of the 5 Great Lakes, whereas only 3 species (17%) decreased by 2–10% per year in at least 1 of the lakes. There were more positive trends among lakes and species (n = 34, 48%) than negative trends (n = 5, 7%). These large increases are welcomed because most of the species are of conservation concern in the Great Lakes. Trends were likely caused by long-term, cyclical fluctuations in Great Lakes water levels. Lake levels increased over most of the study, which inundated vegetation and increased open water-vegetation interspersion and open water extent, all of which are known to positively influence abundance of most of the increasing species and negatively influence abundance of all of the decreasing species. Coastal wetlands may be more important for marsh birds than once thought if they provide high-lake-level-induced population pulses for species of conservation concern. Coastal wetland protection and restoration are of utmost importance to safeguard this process. Future climate projections show increases in lake levels over the coming decades, which will cause “coastal squeeze” of many wetlands if they are unable to migrate landward fast enough to keep pace. If this happens, less habitat will be available to support periodic pulses in marsh bird abundance, which appear to be important for regional population dynamics. Actions that allow landward migration of coastal wetlands during increasing lake levels by removing or preventing barriers to movement, such as shoreline hardening, will be useful for maintaining marsh bird breeding habitat in the Great Lakes.

An Index of biotic condition (IBC) using birds as indicators of coastal wetland quality in North America’s Laurentian Great Lakes

To survive in an area, plant and animal species must confront many interacting environmental stressors at different spatial and temporal scales. Consequently, assemblages of resident species, which have successfully negotiated these stressors, are widely recognized as indicators of environmental quality. Many biotic variables have been employed as indicator metrics, but the simplest is presence/absence of sensitive species in a standardized field sample. We describe a multi-species ecological indicator, the Index of Biotic Condition (IBC), which overcomes key concerns with using indicator species or species assemblages to assess environmental quality. Developing an IBC requires substantial ecological knowledge and preliminary data to identify an appropriate set of species or species groups for the area and habitat(s) of interest and to quantify the sensitivity of these species to an explicit environmental reference gradient. Based on objective biotic response (BR) functions describing the relationship between species occurrences and the environmental gradient, we outline a method for deriving species weights (factors that determine the relative contributions of species / species groups), subsequently used to calculate the simple multispecies index. The IBC is more rigorous than structurally similar metrics like the Floristic Quality Index (FQI) and average Coefficient of Conservatism (C¯) and, at least for some applications, is more parsimonious than comprehensive metrics like the Index of Biotic Integrity (IBI) and our previously described Index of Ecological Condition (IEC). We apply information from standardized basin-wide bird surveys conducted between 2011 and 2022 (particularly a subset of data from 2011 to 2015) to develop an IBC for comparing and interpreting the environmental quality of 794 wetlands in the coastal zone of North America’s Laurentian Great Lakes. Implicit in this formulation is the existence of a high-quality reference assemblage that includes 14 obligate or facultative bird species/species groups characteristic of these wetlands. The index ranges from 0 (worst condition) to 10 (best condition) and is correlated with species richness (r = 0.87), although the IBC provides additional information reflecting the taxon-specific environmental sensitivities. The distribution of IBC values for 4,359 point samples in Great Lakes coastal wetlands between 2011 and 2022 is strongly skewed right, with a median value of 2.31. Only 28 wetland points (<1%) yielded an IBC value of 8.0 or greater, suggesting that relatively complete coastal wetland bird assemblages rarely occur at specific points in today’s Great Lakes coastal wetlands, consistent with the region’s well-documented historical reduction in biological diversity.

Aquatic connectivity treatments increase fish and macroinvertebrate use of Typha‐invaded Great Lakes coastal wetlands

Abstract Coastal wetlands provide critical habitat for aquatic organisms and important ecosystem services for the terrestrial and aquatic landscapes that they bridge, but increasingly common invasive macrophytes disrupt plant communities, food webs, habitat structure and littoral–pelagic linkages. In Laurentian Great Lakes coastal wetlands, invasive cattails (Typha × glauca and T. angustifolia, hereafter Typha) homogenise ecosystem structure and reduce nearshore dissolved oxygen, and plant, fish and macroinvertebrate diversity. We hypothesised that management treatments which reduce Typha and its abundant litter promote structural heterogeneity and mitigate physicochemical and biodiversity impacts. To test this hypothesis, we implemented a large‐scale (2,048 m2 treatment units), multi‐site (four coastal wetlands) experiment in northern Michigan (U.S.A.) to examine how invasive Typha mechanical harvesting treatments (biomass harvest, aquatic connectivity channels, Typha‐dominated control) altered fish, macroinvertebrate, plant, larval amphibian abundance and diversity, and water quality for 2‐year post‐treatment. Both harvest and channel treatments reduced Typha biomass, cover and dominance; harvest increased multi‐taxa species richness, fish diversity and abundance; and channels altered plant, fish, and macroinvertebrate community structures. Dissolved oxygen was greater and litter was reduced by both treatments, indicating likely mechanisms for shifts in fish and macroinvertebrate use. Our results suggest that harvesting invasive macrophytes can ameliorate biodiversity impacts and improve habitat quality, and that adding aquatic connectivity channels can increase community complexity. Typha management that incorporates both harvesting and aquatic connectivity channels appears to provide the greatest benefit to several taxonomic groups, likely by reducing Typha and its litter, increasing dissolved oxygen availability, and increasing the connection between open water and wetland interiors. Increasing habitat complexity and aquatic connectivity of invaded wetlands can promote biodiversity and provides a more realistic management goal than the complete elimination of invasive macrophytes.

Application of habitat association models across regions: Useful explanatory power retained in wetland bird case study

AbstractSpecies often exhibit regionally specific habitat associations, so habitat association models developed in one region might not be accurate or even appropriate for other regions. Three programs to survey wetland‐breeding birds covering (respectively) Great Lakes coastal wetlands, inland Great Lakes wetlands, and the Prairie Pothole Region offer an opportunity to test whether regionally specific models of habitat use by wetland‐obligate breeding birds are transferrable across regions. We first developed independent, regional population density models for four species of wetland‐obligate birds: Pied‐billed Grebe (Podilymbus podiceps), Virginia Rail (Rallus limicola), Sora (Porzana carolina), and American Bittern (Botaurus lentiginosus). We then used adjusted pseudo‐R2 values to compare the amount of variation explained by each model when applied to data collected in each of the three regions. Although certain habitat characteristics, such as emergent vegetation and wetland area, were consistently important across regions, models for each species differed by region—both in variables selected for inclusion and often in the directionality of relationships for common variables—indicating that habitat associations for these species are regionally specific. When we applied a model developed in one region to data collected in another region, we found that explanatory power was reduced in most (71%) models. Therefore, we suggest that ecological analyses should emphasize regionally specific habitat association models whenever possible. Nonetheless, models created from inland Great Lakes wetland data had higher median explanatory power when applied to other regions, and the amount of explanatory power lost by other transferred models was relatively small. Thus, while regionally specific habitat association models are preferable, in the absence of reliable regional data, habitat association models developed in one region may be applied to another region, but the results need to be cautiously interpreted. Additionally, we found that median explanatory power was higher when local‐scale habitat characteristics were included in the models, indicating that regionally specific models should ideally be based on a combination of local‐ and landscape‐scale habitat characteristics. Conservation practitioners can leverage such regionally specific models and associated monitoring data to help prioritize areas for management activities that contribute to regional conservation efforts.

The influence of extreme water levels on coastal wetland extent across the Laurentian Great Lakes

Laurentian Great Lakes coastal wetlands (GLCW) are ecological hotspots and their integrity depends upon dynamic hydrologic regimes of the Great Lakes. GLCW naturally adjust to changes in hydrologic regimes via migration, but Great Lakes water levels may be shifting faster than wetlands can manage: 2000–2015 marked an extended low water level period and was followed by record highs in 2017–2020. Our objective was to quantify how Great Lakes water levels impact GLCW linear extent (from the shoreline to open water). We calculated wetland extent and migration from 2011 to 2019 using data from 1538 vegetation transects at 342 sites across the U.S. shoreline of the Great Lakes. Mediated multiple linear regression with Bayesian hierarchical modeling investigated the relationship between water levels and wetland extent. We employed Bayesian hierarchical modeling because (1) the dataset was spatially nested, with sampling points within wetlands within Great Lakes and (2) Bayesian statistics offer flexibility for environmental modeling, such as the inclusion of mediation in models, where we can assess both direct influences of Great Lake water levels on wetland extent and indirect (i.e., mediated) influences of water levels via the presence of vegetation zones on thus wetland extent. Results showed that, overall, there was a landward migration from 2011 to 2019 (although 38 % of wetlands had lakeward migration of the wetland-upland border). Wetland length and inundation length decreased with increased water levels, as mediated by the presence of certain vegetation zones. This decrease in wetland extent is of concern because it likely relates to a decrease in wetland function and habitat. A better understanding of how GLCW migrate with shifts in water levels enables decision makers to better predict where Great Lakes coastal wetlands are at risk of being lost and thus where to prioritize management efforts.

Environmental drivers of spatial and temporal water quality variability in four coastal wetlands of Lake Ontario

Great Lakes coastal wetlands serve as mediation zones between the land and the lake, regulating the fate of materials received from tributaries prior to discharge to the lake nearshore zone. To improve our understanding of water quality processing and nutrient fate in coastal wetlands, we evaluated within- and across-wetland water quality as a function of environmental drivers over a decade (2009–2018) in three drowned river mouth (Carruthers, Duffin’s, and Rouge) and one barrier lagoon (Frenchman’s Bay) wetlands on the north shore of Lake Ontario. Overall, land-use had a weak relative association with most water quality parameters, reflecting no appreciable changes in land-use across the study years. The barrier lagoon wetland Frenchman’s Bay had a distinctly different water quality pattern from the drowned river mouth wetlands, where water quality followed a high to low concentration gradient from near the tributary confluences (high) to the lake-wetland confluence (low) (permutational analysis of variance p-value < 0.001). Notably, we observed significant differences among celled (i.e., natural ponds in wetlands) and non-celled sites in Duffin’s and Rouge marshes, primarily attributed to strong covariation among phosphorus, phosphate, and organic nitrogen concentrations (permutational analysis of variance p-value < 0.001). This water-quality signature seemed to be driven by solar radiation and lake level variability (i.e., seiche inundation), inferring that wetlands may be important sites for the mobilization of legacy phosphorus in sediments under certain climatic conditions, and following seiche events.

Planning for people and nature: Comparing quality‐of‐life outcomes across environmental systems to inform conservation planning

AbstractConservation programs have been slow to integrate socio‐economic indicators into decision making despite growing recognition that addressing social‐ecological systems improves outcomes for nature and people. Our goal was to identify small, comprehensive sets of socio‐economic indicators for conservation programs designed to (1) improve agricultural soil health and reduce sediment and nutrient loading to freshwater systems, (2) restore Great Lakes coastal wetlands, and (3) implement green stormwater infrastructure in cities. We piloted a structured decision‐making process to select indicators more objectively and transparently. Important elements of our process were (a) using a human quality‐of‐life framework to identify potential indicators and (b) evaluating indicators' relevance to conservation, resonance with communities, and data‐availability. The programs identified 278 potential indicators across seven quality‐of‐life domains, of which 78 were evaluated against six selection criteria. For each program, we developed intended use scenarios, assigned relative weights to selection criteria, and used these weights to calculate a weighted sum of the indicator's criteria scores and rank indicators. Across programs and intended uses, 21 indicators achieved top‐five rankings; indicators for flood risk and damage were common across all three programs. Our collaborative approach provided opportunities to evaluate indicator selections across quality‐of‐life domain, conservation program, and intended uses.

Turbidity and Estimated Phosphorus Retention in a Reconnected Lake Erie Coastal Wetland

Nearly all of the wetlands in the coastal zone of Lake Erie have been degraded or destroyed since the 1860s, and most of those that remain are separated from their watersheds by earthen dikes. Hydrologic isolation of these wetlands disrupts ecosystem benefits typical to Great Lakes coastal wetlands, particularly the ability to trap sediments and retain nutrients when inundated by runoff and lake water. High-frequency measurements of turbidity and discharge were taken in 2013 and 2014 to observe turbidity and water flow dynamics to estimate total phosphorus flux of a hydrologically reconnected diked wetland pool in the Crane Creek-Lake Erie wetland complex. Modeled estimates suggest the reconnected pool retained 8% of the total phosphorus loading in 2013 and 10% in 2014, which included short periods of phosphorus export to Lake Erie. Water flowing out of the wetland generally had lower turbidity than inflowing water, but flux in and out of the pool varied seasonally and was linked to changes in lake-levels, seiche dynamics, and weather conditions. More frequent storms, higher winds, and stronger seiches in the spring and fall created turbidity patterns that suggest more phosphorus retention than in summer or winter. Estimates suggest that phosphorus was released during the summer when higher lake levels and the absence of frequent storms, larger short-term seiche oscillations, and potentially soil oxygen availability were driving flux dynamics. This study demonstrated that reestablishing lake hydrology through reconnection of wetland pools can reduce loading and alter timing of delivery of total phosphorus to Lake Erie.

Influences of seasonality and habitat quality on Great Lakes coastal wetland fish community composition and diets

Influences of seasonality and habitat quality on Great Lakes coastal wetland fish community composition and diets

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.

Sustained‐Flux Global Warming Potential Driven by Nitrogen Inflow and Hydroperiod in a Model of Great Lakes Coastal Wetlands

AbstractWetlands impact global warming by regulating the atmospheric exchange of greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). We investigated GHG emissions in the Great Lakes coastal wetlands across various hydrologic, temperature, and nitrogen (N) inflow regimes using a process‐based simulation model. We found the emission of CH4, N2O, and sequestration of C (i.e., negative net ecosystem exchange, NEE) in our simulations were all positively related to water residence time and N inflow, primarily due to greater plant productivity and N uptake, which facilitated greater C and N cycling rates in the model. Water level scenarios also had an effect on GHG exchanges by moderating the transitions between aerobic and anaerobic conditions. Temperature effects on GHGs were minimal compared with other factors. The net sustained‐flux global warming potential (SGWP; i.e., sum SGWP of CH4, N2O, and NEE) of wetlands on 20‐year and 100‐year time horizons were both primarily driven by CH4 emissions and strongly controlled by the tradeoffs between CH4 emission and CO2 sequestration, with a negligible amount of simulated N2O emissions. Future research could include model enhancements to provide increased process‐level details on the aerobic‐anaerobic transitions or the direct effects of plants on mediating GHG exchanges. Field studies addressing the interaction of N inflows and water residence time at appropriately large scales are needed to test the complex interactions revealed by our modeling study. Our results highlight the previously under‐appreciated role of nitrogen and water residence time in modulating SGWP in coastal wetlands.

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.

Historical surveys reveal a long-term decline in muskrat populations.

The muskrat (Ondatra zibethicus) is an iconic species in Canada, valued for both its fur and its integral role in wetland ecosystems, and widely regarded for its perseverance. However, the resilience of this semiaquatic mammal seems to be in question now as increasing evidence points to widespread population declines. Recent analyses of harvest data across North America suggest a reduction in their numbers, but this has not been widely corroborated by population surveys. In this study we replicated historic muskrat house count surveys at two large Great Lakes coastal wetlands and present confirmation that declines in muskrat harvest correspond to actual declines in muskrat abundance. At the Point Pelee National Park marsh and the Matchedash Bay‐Gray Marsh wetland we found that mean muskrat house counts declined by 93% and 91% respectively between historic surveys 40–50 yrs ago and contemporary surveys over the past 7 yrs. The factors responsible for these dramatic declines remain unclear but there may be a relationship with changes in the habitat quality of these wetlands that have occurred over the same time frame. Not only is the loss of muskrats an issue for the resulting loss of the wetland ecosystem services they provide, but it may be an indication of broader marsh ecosystem degradation. As such, a scarcity of muskrats should be considered a red flag for the state of biodiversity in our wetlands. Continued surveys and ongoing research are needed to shed more light on the current status of muskrat populations and their marsh habitats across their native range.

Classification ofTypha-dominated wetlands using airborne hyperspectral imagery along Lake Ontario, USA

AbstractShoreline wetlands along Lake Ontario are valuable, multi-functional resources that have historically provided large numbers of important ecosystem goods and services. However, alterations to the lake’s natural hydrologic regime have impacted traditional meadow marsh in the wetlands, resulting in competition and colonization by dense and aggressive Typha angustifolia and Typha x glauca (Cattails). The shift to a Typha-dominated landscape resulted in an array of negative impacts, including increased Typha density, substantial decreases in plant species richness and diversity, and altered habitat and changes in associated ecosystem services. Successful long-term adaptive management of these wetland resources requires timely and accurate monitoring. Historically, wetland landscapes have been surveyed and mapped using field-based surveys and/or photointerpretation. However, given their resource- and cost-intensive nature, these methods are often prohibitively time- and labor-consuming or geographically limited. Other remote sensing applications can provide more rapid and efficient assessments when evaluating wetland change trajectories or analyzing direct and indirect impacts across larger spatial and temporal scales. The primary goal of this study was to develop and describe methodology using U.S. Army Corps of Engineers National Coastal Mapping Program hyperspectral imagery, light detection and ranging data, and high-spatial resolution true-color imagery to provide updated wetland classifications for Lake Ontario coastal wetlands. This study used existing field-collected vegetation survey data (Great Lakes Coastal Wetland Monitoring Program), ancillary imagery, and existing classification information as training data for a supervised classification approach. These data were used along with a generalized wetland schema (classes based on physical and biological gradients: elevation, Typha, meadow marsh, mixed emergent, upland vegetation) to generate wetland classification data with Kappa values near 0.85. Ultimately, these data and methods provide helpful knowledge elements that will allow for more efficient inventorying and monitoring of Great Lake resources, forecasting of resource condition and stability, and adaptive management strategies.

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.

Long-term ecosystem change in two highly degraded Lake Ontario (Canada) coastal wetlands

Coastal wetlands are essential to the ecosystem health of the Laurentian Great Lakes (North America) watershed. Multiple anthropogenic stressors have been impacting coastal wetlands since European settlement ca. 1850, and remain a concern for wetland health as watershed development intensifies. We used paleolimnological techniques to explore temporal ecosystem dynamics over the last ~ 100 years in two highly degraded Lake Ontario coastal wetlands located in southern Ontario, Canada, using Cladocera (Branchiopoda, Crustacea) subfossil remains as paleoecological indicators. In Cootes Paradise Marsh (Hamilton, Ontario), cladoceran assemblage changes exhibited a shift in dominance from Chydorus to Bosmina, at the turn of the twentieth century. That shift likely reflected the loss of aquatic macrophytes, and corresponds to the postulated timing of the arrival of invasive carp. Despite recent remediation efforts, including attempts to exclude carp from the wetland, little ecological recovery is evident from the subfossil Cladocera assemblage. No Daphnia remains were observed in our sediment core from Cootes Paradise, in contrast to previous studies on extant zooplankton communities, which reported a large Daphnia population in the west end of the marsh in the 1940s. This could indicate that our sediment core recorded ecological changes solely in the east end of Cootes Paradise Marsh. In Jordan Harbour (Lincoln, Ontario), Bosmina were dominant throughout the sediment record, and increases in littoral cladocerans were observed in the most recent sediments, in particular the appearance of periphytic Pleuroxus taxa after ~ 2008. This suggests that some recovery of aquatic macrophyte communities occurred in response to shoreline remediation efforts. Bosmina size structure exhibited only minimal changes in both wetlands, despite known large changes in historic fish community structure. Overall, our study provides perspectives on the benefits and limitations of paleolimnology for documenting ecological change in the Laurentian Great Lakes coastal wetlands.