Lake Michigan Research Articles

Stable Isotope Analysis of Planktonic Lower Food Webs of Lakes Erie, Huron, Michigan and Superior

Historical plankton samples from the St. Lawrence Great Lakes were subjected to taxon-specific 15N analysis to test the hypothesis that the changes recorded in zooplankton communities during the 21st Century are related to changes in the trophic positions of large-bodied carnivorous copepods. Daphnia mendotae was used as the reference herbivore for trophic-level comparisons. The results were that Limnocalanus macrurus, Diaptomus (Leptodiaptomus) sicilis as well as the cladoceran Bythotrephes cederstroemi show evidence of elevated carnivory compared to data from the 20th Century. The large diaptomid Diaptomus (Leptodiaptomus) sicilis has a stable isotope signature that is significantly more carnivorous in Lake Superior than in Lakes Michigan and Huron by approximately one-half trophic level. Differences were found in 10 cases out of 15 for Limnocalanus (Huron, Michigan Superior), 6 cases out of 15 for Diaptomus (Huron, Michigan) and in 1 out of 1 for Senecella (Superior). We did not find evidence to support the theory that large-bodied calanoid copepods may have improved their representation in the food webs of the upper Great Lakes by shifting their trophic position downward. Instead, large-bodied Calanoida have increased their trophic positions in parallel with their increased relative abundance. More research is thus needed to explain the driving forces for changing food web dynamics in the Great Lakes.

Iron availability regulates carbon accumulation and methane production in a Lake Michigan interdunal wetland

Iron availability regulates carbon accumulation and methane production in a Lake Michigan interdunal wetland

Quantifying Pleistocene loess provenance in midcontinental North America using a mixing model: Implications for glacial lobe evolution along the southern Laurentide ice sheet

Quaternary glaciations have significantly impacted the midcontinental North American landscape, leaving behind a proglacial sediment record of glacial lake deposits, glacio-fluvial sand and gravel, and windblown loess. This paper aims to expand upon a previous study using detrital zircon provenance analysis to investigate midcontinental North American loess provenance in relation to the glacial history of the southern Laurentide ice sheet during the middle to late Pleistocene. The study incorporates previously published detrital zircon data from last glacial tills (representing the Huron-Erie Lobe, Lake Michigan Lobe, Green Bay Lobe, Superior Lobe, Des Moines Lobe, and James Lobe), middle to late Pleistocene loess from several sites along the Illinois and Mississippi River valleys, and suspended sediment load inputs from the Missouri River and Arkansas River. A statistical mixing model (DzMix version 2.2) was used to estimate the relative proportions of glacial and nonglacial sources to Wisconsin Episode, Illinois Episode, and pre–Illinois Episode age loess. We show that mixing models that include the modern suspended sediment loads of the Missouri and Arkansas Rivers significantly improve (up to 23% increase in cross-correlation value) the source characterization of Wisconsin Episode (last glacial) and Illinois Episode (penultimate glacial) loess deposits within the Mississippi River drainage basin. These river sources are dominant inputs for certain loess sites (as much as 51%), but their relative contributions are not static across time and space, which has implications for temporal and spatial differences in relative sediment source estimates and glacial and fluvial sediment transport evolution. Specifically, differences in relative sediment proportion estimates among Wisconsin, Illinois, and pre–Illinois Episode loess support previous evidence for the persistence of a Quebec-Labrador ice dome source through multiple glacial cycles, even with the inclusion of river sources in updated mixing models. Illinois and pre–Illinois Episode loess in the southern portion of our study area received ~20% detrital zircon input from sources similar to the present-day Missouri and Arkansas Rivers, suggesting that these river systems were contributing a significant amount of detritus to the lower Mississippi River valley region during the middle Pleistocene.

An assessment of N, P, Fe, Zn, Ni and Mo limitation on suspended nutrient diffusing substrates in nearshore areas of Lake Michigan and Lake Erie

In large lakes, metal availability sometimes limits the acquisition of nutrients (nitrogen, N and phosphorus, P) in offshore waters that are relatively isolated from tributaries and sediments. We hypothesize that metals may also be important within harmful algal blooms (HABs). HABs occur where nutrient loads are elevated, but bioassays often indicate that phytoplankton in HABs are N or P limited. Nutrient limitation may be exacerbated by corresponding limitations in several metals (i.e. nickel - Ni, molybdenum - Mo, zinc - Zn, and iron - Fe) that facilitate uptake and transformation of oxidized and organic forms of nutrients, such as urea, nitrate and organic phosphorus. The cyanotoxin microcystin has been hypothesized to have a role in metal management, so metal demand may also influence the toxicity of HABs. Here, we used nutrient diffusing substrates to measure how N, P, Ni, Mo, Zn and Fe amendments influenced the growth and toxicity of periphyton. Periphyton was grown suspended in 10 nearshore sites in Lake Michigan and Lake Erie (5 with and 5 without perennial HABs). Outside of blooms, we found no evidence for metal limitation or co-limitation. However, evidence for metal co-limitation was observed in two HABs sites (Zn in Green Bay and Zn, Mo, Ni and Fe in Sandusky Bay). N, P and Zn amendments all stimulated microcystin content in Maumee Bay. These data indicate that nutrient limitation occurs even within blooms, and the availability of metals may have an influence on growth, community composition and toxicity.

Changes in Climatological Variables at Stations around Lake Erie and Lake Michigan

Climatological variables undergo changes over time, and it is important to understand such dynamic changes at global, regional, and local levels. While global and regional studies are common in the study of climate, such studies at a local level are not as common. The aim of this article is to study temporal changes in precipitation, snowfall, and temperature variables at specific stations located on the rims of Lake Erie and Lake Michigan. The identification of changes is carried out by applying change-point analysis to precipitation, snowfall, and temperature data from Buffalo, Erie, and Cleveland stations located on the rim of Lake Erie and at Chicago, Milwaukee, and Green Bay stations located on the rim of Lake Michigan. We adopt mainly the Bayesian information criterion (BIC) method to identify the number and locations of change points, and then we apply the generalized likelihood ratio statistic to test for the statistical significance of the identified change points. We follow this up by finding 95% confidence intervals for those change points that were found to be statistically significant. The results from the analysis show that there are significant changes in precipitation, snowfall, and temperature variables at all six rim stations. Changes in precipitation show consistently significant increases, whereas there is no similar consistency in snowfall increases. Temperature increases are generally quite sharp, and they occur consistently around 1985. Overall, upon combining the amounts of changes from all six stations, the average amount of change in annual average temperature is found to be 0.96 °C, the average percentage of change in precipitation is 16%, and the average percentage of change in snowfall is 17%. The changing local climatic conditions identified in the study are important for local city planners, as well as residents, so that they can be well prepared for changing climatic scenarios.

Egg Size Scales Negatively With System Size in a Periodic Fish Species.

Optimal egg size theory implies that female organisms balance between fecundity and individual offspring investment according to their environment. Past interspecific studies suggest that fishes in large marine systems generally produce smaller eggs than those in small freshwater systems. We tested whether intraspecific egg size variation reflected a similar pattern by comparing egg size among yellow perch (Perca flavescens) populations inhabiting a range of system sizes. In 2018, 2019, and 2023, we collected yellow perch egg samples from 12 locations in systems ranging in surface area from 37 to 5,390,492 ha. First, we found that egg diameter significantly increased with maternal total length in five of eight individually tested populations. After accounting for these maternal effects, we found a significant interaction, where females inhabiting larger lakes, such as the main basins of Lakes Erie and Michigan, produced smaller eggs than those in smaller inland lakes, and the greatest differences were demonstrated among females of greater total length. This egg size variation in the largest females is consistent with interspecific egg size comparisons between marine and freshwater fishes. However, by examining a single species across vastly different environments, we were able to support theoretical expectations that maternal investment in offspring should vary with environmental conditions controlling early-life resource acquisition and competition.

Foredune-ridge development along an urban pocket beach, Montrose dunes natural area, Southwestern Lake Michigan

While foredune geomorphology has been studied along many Great Lakes coastlines, little attention has been given to the development and evolution of foredune ridges along engineered ‘pocket’ beaches, which are common along many urban lakefronts of the region. This paper reports on the recent morphodynamics of Montrose Beach, the largest of Chicago’s engineered coastal embayments, with emphasis on its ‘Dunes Natural Area.’ A post-2020 period of beach recovery occurred after 2013–2020 lake-level rise of >1.5 m, which was accompanied by shoreline recession and overwash-induced backshore accretion. The influx of sand into the urban embayment during this time facilitated post-2020 beach recovery with lake-level fall. This phase of beach expansion was marked by the formation of three distinct, parallel berm lines that have become vegetated and functioned as focal points for eolian accretion. Undisturbed by grooming and other beach-management activities, the Dunes Natural Area continues to be influenced by lake-level changes and storms. Vegetative establishment and eolian sand trapping upon disconnect from active reworking along the shoreline have increased the expression of linear topographic highs. Seasonal ridgelines along natural beach environments, including barrier spits, tend to undergo reworking prior to such stabilization. Insights from Montrose Beach provide coastal managers with up-to-date information on important geomorphic developments at Chicago’s most popular beach destination, whose Dunes Natural Area provides habitat for the endangered Great Lakes piping plover. Understanding its geomorphic trajectory can help inform coastal resiliency planning, here and elsewhere, to protect valuable ecosystems and infrastructure within the urban coastal landscape.

A machine learning approach to nearshore wave modeling in large lakes using land-based wind observations

This study presents a novel machine learning-based (ML) framework that utilizes the ConvLSTM-1D model to simulate wave heights at a nearshore location in Lake Michigan using a nonuniform land-based array of wind observations from a broad geographic region as an input. This approach was applied to Lake Michigan to perform a 70-year ice-free hindcast of waves near Chicago, IL (USA). Because of annual winter gaps in Great Lakes buoy observations, output from the Wave Information System model (WIS) was used for the training, validation, and testing of the ML model. Models with different numbers of wind stations were tested, showing that a single wind station as an input feature produced a reasonably accurate wave height. However, the wave height model accuracy increased as more wind input data was included from around the lake, largely plateauing beyond the inclusion of four stations that spanned Lake Michigan’s southern basin. The optimized model lookback period was found to be 10 h for all models, suggestive of a fetch-limited temporal coupling between the wind observations and nearshore waves. The extended time series showed a statistically significant increase in the interannual standard deviation of the storm wave height and the storm height over the mean wave height while no correlation was found with the annual water level time series. The ML framework offers a promising avenue for utilizing historical wind records to extend wave height time series for nearshore locations, particularly in enclosed and semi-enclosed basins where waves are strongly linked to local winds.

Changing Coasts along Lake Michigan: Shoreline Management Impacts on the Inland Community

Changing Coasts along Lake Michigan: Shoreline Management Impacts on the Inland Community

Revisiting zooplankton as indicators in the Great Lakes: Which indicators detect temporal changes in the zooplankton community composition?

Zooplankton are a vital component of the food web as the major conduit of energy from primary producers to planktivorous fishes. Therefore, changes in the structure of the zooplankton community affect how energy moves through aquatic ecosystems. Changes in the zooplankton community structure are typically documented through detailed community analysis, which can be difficult to interpret and communicate to non-experts. Alternatively, a few key summary indicators of community structure may better disseminate this information to a broader audience. In this study we analyzed zooplankton data from 1997 to 2019 from the US Environmental Protection Agency’s Great Lakes National Program Office to select indicators that summarized changes in the zooplankton community. Two indicators (percent of calanoids by biomass and areal density of herbivorous cladocerans) detected known changes in lakes Huron, Michigan, and Ontario, correlated with the crustacean zooplankton areal biomass above (herbivorous cladocerans) or in the hypolimnion (percent calanoids), and were related to the lake or basin-wide Carlson’s Trophic State Index based on chlorophyll (TSIchl) (percent calanoids by biomass). Our findings suggest that employing one or both selected indicators in addition to TSIchl and total crustacean zooplankton areal biomass, an already reported indicator in the Great Lakes that captures overall food availability for fish, would provide additional key information about zooplankton community structure in simple metrics that could be effectively communicated to stakeholders.

Influences of meteorological conditions, runoff, and bathymetry on summer thermal regime of a Great Lakes estuary

To better understand the primary drivers of the thermal regime in a Great Lakes estuary, and their implications for local biota, water temperature variations in the Milwaukee Estuary of Lake Michigan were studied between July and October of 2019 using a network of 25 sensors at 18 locations. Like Lake Michigan, the estuary was thermally stratified July to October, and historically dredged channels with water depths greater than 6 m allowed for the free movement of cold lake water into the estuary. However, temperatures in the estuary fluctuated rapidly both spatially and temporally, reflecting lake temperature fluctuations driven by changing meteorological conditions. Lake-driven upwelling and downwelling events influenced water temperature more than tributary contributions. Periodic upwelling and downwelling events caused temperature changes by up to 15 °C in less than 24 h. Nearshore upwelling events occasionally allowed cold, hypolimnetic lake water to reach tributary portions of the estuary beyond dredged areas, while downwelling events disrupted thermal stratification and caused the deep, dredged portions of the estuary to exceed 20 °C. Thermal impacts from these events were especially noticeable in transition zones between dredged and not dredged channels less than 2 m deep. The warming effects from downwelling persisted longer inside the estuary – up to two weeks – than cooling effects from upwelling, which typically lasted a few days. The predominantly lake-driven, rapid summer water temperature fluctuations observed in the Milwaukee Estuary serve as an important consideration in habitat restoration activities happening in Great Lakes estuaries.

Declines and shifts in morphological diversity of ciscoes (Coregonus spp.) in lakes Huron and Michigan, 1917–2019

Ciscoes ( Coregonus spp .) were historically abundant and ecologically important in Laurentian Great Lakes ecosystems. Despite well-documented declines in their abundance and taxonomic diversity, declines in morphological diversity remain understudied. This knowledge gap is especially pertinent for lakes Michigan and Huron, which have each lost six of eight historical species. Improved understanding of historical and contemporary morphological diversity of Great Lakes ciscoes can inform ongoing restoration efforts and further elucidate the factors that contributed to declines. Our goal was to characterize shifts in morphological diversity of ciscoes in lakes Michigan and Huron over a century (1917–2019). We analyzed size-corrected morphometric and meristic measurements from three periods: Early (1917–1923), Middle (1950–1972), and Contemporary (2015–2019). We then identified morphologically distinct clusters while remaining agnostic to species identifications. We found that morphological diversity and the number of distinct clusters declined over time. We then leveraged species identifications to highlight key species losses and examine morphological shifts among extant species. Our findings provide insights into the historical and contemporary morphological diversity of ciscoes and will inform restoration efforts.

Evaluation of WRF-Chem air quality forecasts during the AEROMMA and STAQS 2023 field campaigns

ABSTRACT A real-time air quality forecasting system was developed using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to provide support for flight planning activities during the NOAA Atmospheric Emissions and Reactions Observed from Megacities to Marine Areas (AEROMMA) and NASA Synergistic TEMPO Air Quality Science (STAQS) 2023 field campaigns. The forecasting system operated on two separate domains centered on Chicago, IL, and New York City, NY, and provided 72-hour predictions of atmospheric composition, aerosols, and clouds. This study evaluates the Chicago-centered forecasting system’s 1-, 2-, and 3-day ozone (O3) forecast skill for Chiwaukee Prairie, WI, a rural area downwind of Chicago that often experiences high levels of O3 pollution. Comparisons to vertical O3 profiles collected by a Tropospheric Ozone Lidar Network (TOLNet) instrument revealed that forecast skill decreases as forecast lead time increases. When compared to surface measurements, the forecasting system tended to underestimate O3 concentrations on high O3 days and overestimate on low O3 days at Chiwaukee Prairie regardless of forecast lead time. Using July 25, 2023, as a case study, analyses show that the forecasts underestimated peak O3 levels at Chiwaukee Prairie during this regionwide bad air quality day. Wind speed and direction data indicates that this underestimation can partially be attributed to lake breeze simulation errors. Surface fine particulate matter (PM2.5) measurements, Geostationary Operational Environmental Satellite-16 (GOES-16) aerosol optical depth (AOD) data, and back trajectories from the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model show that transported Canadian wildfire smoke impacted the Lake Michigan region on this day. Errors in the forecasted chemical composition and transport of the smoke plumes also contributed to underpredictions of O3 levels at Chiwaukee Prairie on July 25, 2023. The results of this work help identify improvements that can be made for future iterations of the WRF-Chem forecasting system. Implications: Air quality forecasting is an important tool that can be used to inform the public about upcoming high pollution days so that individuals may plan accordingly to limit their exposure to health-damaging air pollutants. Forecasting also helps scientists make decisions about where to make observations during air quality field campaigns. A variety of observational datasets were used to evaluate the accuracy of an air quality forecasting system that was developed for NOAA and NASA field campaigns that occurred in the summer of 2023. These evaluations inform areas of improvement for future development of this air quality forecasting system.

Metals in sediment of the upper Great Lakes: Spatial distribution, temporal trends, anthropogenic enrichment, and risk assessments

Thirteen elements including Al, Ag, As, Co, Cu, Cd, Cr, Fe, Mn, Ni, Se, Zn, and Pb were measured in 107 surface grab sediment samples and 175 segments of eight cores from Lakes Superior, Michigan, and Huron, using inductively coupled plasma mass spectrometry (ICP-MS). Concentrations in Ponar grabs vary considerably among metals and among locations, ranging from the highest median for Fe in Lake Superior (42,000 mg/kg) to the lowest median for Ag in the main Lake Huron (0.05 mg/kg). The inventory at coring sites ranged from 7 × 106 mg/m2 of Fe to 3 mg/m2 of Ag. The background concentrations were estimated from deeper core segments, and enrichment factors (EFs) were calculated with Fe or Al as the reference element. The results show that Al, Fe, Co, Cr, and Mn did not enrich, Ag, Cu, and Ni were present higher than expected from natural sources alone, while Pb, Cd, Se, Zn, and As have been enriched at most sites after European settlement in the region. EFs of most metals are higher for Lake Michigan than the other lakes. However, EF comparison among sampling sites revealed intrinsic problems of this approach for the assessment of human interference. Preliminary risk assessment, conducted by calculating risk quotients, revealed environmental risks of some metals in each lake; however, the results should be interpreted with caution because the approach used is considered to be conservative.

Parasite transmission stage abundance varies in lakes over time and space

AbstractEnvironmentally transmitted parasites produce transmission stages that can remain viable and infective for extended periods of time in the environment where susceptible hosts may encounter them. Although many parasites have this mode of transmission, the abundance and distribution of environmental transmission stages have largely been overlooked, especially in aquatic habitats. Without empirical data to characterize spatial and temporal dynamics of parasite transmission stages in the environment, we might make incorrect assumptions about host–parasite contact rates. For aquatic environments, seasonal habitat structure driven by thermal stratification has been hypothesized to affect the patchiness of transmission stages within the water column, leading to uneven exposure risk to hosts. In this study, we quantified transmission stage concentrations of five common parasites of Daphnia spp. and Ceriodaphnia dubia at every meter of the water column at the deep basin of six lakes in southeastern Michigan every 2 weeks from June to November 2021. We found that transmission stage concentration varied by orders of magnitude over time and with depth. We investigated several possible drivers of these spatial and temporal patterns. For instance, our results suggest that greater mixing depth decreased transmission stage vertical patchiness within the water column of lakes with lower Fee's p values. However, horizontal spore patchiness across a lake was not correlated with the nearshore–offshore gradient of our study lakes. Overall, the results of our study show that parasite transmission stage concentrations have spatial and temporal dynamics that could affect disease dynamics within highly structured aquatic environments.

Chemical speciation, reactivity, and long-term burial of sedimentary phosphorus in Green Bay, a seasonally hypoxia-influenced freshwater estuary

Sediment cores were collected along a trophic gradient in Green Bay, a seasonally hypoxia-influenced freshwater estuary in Lake Michigan, to measure various phosphorus (P) species, including exchangeable-P (Ex-P), iron-bound-P (Fe-P), biogenic-apatite and/or CaCO3-associated-P (CFA-P), organic-P (Org-P) and detrital-apatite-P (Detr-P). Although total phosphorus (TP) decreased with increasing depth, different P species exhibited distinct vertical distribution patterns with different post-depositional behaviors. The Ex-P, Fe-P and CFA-P species were identified as potentially bioavailable-P (BAP). Little variation was observed for Org-P and Detr-P species, especially below the upper-active-layer, both serving as the primary sink for P in sediment. Detr-P% decreased consistently from the near river plume station to the open bay in the north. P accumulation rates were estimated at 25.1 mmol-P/m2/yr (779 mg-P/m2/yr) in the south, 10.9 mmol-P/m2/yr (338 mg-P/m2/yr) in the central region, and 8.1 mmol-P/m2/yr (252 mg-P/m2/yr) in the north of Green Bay, showing a decrease in the depth of the upper active layer for P regeneration along the south-north transect. The overall potential P regeneration back into the water column increased from 2.8 mmol-P/m2/yr (87 mg-P/m2/yr) in the south, and 3.3 mmol-P/m2/yr (101 mg-P/m2/yr) in the central region to 5.6 mmol-P/m2/yr (173 mg-P/m2/yr) in the north of the bay, corresponding to P burial efficiencies of ∼89 %, 70 % and 31 % along the trophic gradient. The recent decrease in Detr-P and thus the increase in BAP over the last 2–3 decades could be related to anthropogenic activities, such as damming and implementation of agricultural conservation practices. Conversely, a recent increase in TOC/TOP ratios may reflect the increased extent of trophic status and seasonal hypoxia in bottom waters and enhanced regeneration and recycling of particulate P in Green Bay since the 1960s. New results from this study provide an improved understanding of the linkage between sources, internal cycling, and long-term burial of P in the basin.

An exopolysaccharide pathway from a freshwater Sphingomonas isolate.

Bacteria produce complex polysaccharides that serve a range of biological functions. These polymers often have properties that make them attractive for industrial applications, but they remain woefully underutilized. In this work, we studied a novel polysaccharide called promonan that is produced by Sphingomonas sp. LM7, a bacterium we isolated from Lake Michigan. We extracted promonan from LM7 cultures and identified which sugars are present in the polymer. We also identified the genes responsible for polysaccharide production. Comparing the promonan genes to those of other bacteria showed that promonan is distinct from previously characterized polysaccharides. We conclude by discussing how the promonan pathway could be used to produce new polysaccharides through genetic engineering.

Long-term geomorphic effects of longitudinal training walls in the Grand River, Michigan (USA)

The Grand River is the longest river in Michigan, flowing from northwest Hillsdale County to Lake Michigan, and draining an area over 14,400 km2. Bathymetric surveys of a ~ 38 km reach of the river from Grand Rapids to the confluence with Bass River, performed in 1906, were uncovered in the Grand Rapids Community Archives and Research Center in 2014. These maps show depth recordings across the channel along cross sections spaced ~90 m apart. The maps also show the location of numerous training walls that were built in the river in the 1890's as an effort to maintain navigation. The 1906 maps were georeferenced, and the bathymetric data were digitized, converted to bed elevation, and interpolated into an elevation model of the channel bed. High-resolution multibeam echo sounding surveys were conducted in June 2019 and 2020 over the same reach and provided a means to assess over 100-years of geomorphic changes. The results from these analyses showed substantial changes to the average channel width and width variability, with some locations narrowing by up to 50 % (~90 m). Volumetric difference maps between 1906 and 2020 revealed a streamwise spatial variation in the net erosion and deposition, with upstream reaches being predominantly erosional and downstream reaches exhibiting net deposition, with the transition occurring close to the extent of backwater influence from Lake Michigan. The presence of the training walls also resulted in the development of many mid-channel islands and narrowing of the channel through floodplain accretion. Findings from this study have implications for river management projects that have been proposed for the Grand River, as well as other rivers where these structures might be implemented.

Study of biological quality of lake waters based on phycocyanin using tree‐based methodologies

AbstractThe provision of drinking water, agricultural, and industrial applications by reservoirs has made lake exploration and monitoring unavoidable. The features of the ecosystem, particularly physical and chemical elements, influence the evaluation of the quality of water resources. Lakes undergo extensive qualitative changes due to their vast amount of water. In general, these bodies of water represent geological conditions as well as water contamination produced by natural and human activities. In the present research, the prediction of the amount of phycocyanin (fPC) in the water of Lake Michigan has been implemented employing four tree‐based machine learning techniques based on seasonality factors. Phycocyanin has significant effects on quality parameters such as turbidity, chlorophyll concentration, algal bloom, and dissolved oxygen in water by affecting the photosynthesis process of algae. Therefore, in this study, the prediction of the amount of phycocyanin dissolved in the lake water using the mentioned variables, along with the temperature of the water, specific conductance, and pH, has been able to interpret the quality of the water and the occurrence of phenomena such as algal blooms. The results of the models in predicting fPCs equal to 0.44 and 0.55 μg/L were consistent with the natural conditions of the lake, and it seems that ensemble tree–based models, along with the biological index of fPC, formed the right combination of input and output parameters in modeling and obtained the lowest prediction error (root‐mean‐square error [RMSE] boosted trees = 0.0140 and RMSE random forests = 0.0141 μg/L).

A decade of data and hundreds of analytes: Legacy and emerging chemicals in North American herring gull plasma

Between 2010 and 2021, 199 herring gull serum samples were collected from Lake Michigan, Lake Huron, and Lake Erie, including two Areas of Concern: Saginaw Bay and the River Raisin. They were analyzed for 21 polybrominated diphenyl ether congeners, 10 non-PBDE flame retardants, 85 polychlorinated biphenyls, 17 legacy organochlorine pesticides, and 36 per- and polyfluoroalkyl substances. Σ36PFAS, Σ85PCB, Σ21PBDE, and Σ17Pesticide concentrations comprised 41–74%, 17–50%, 3–4%, and 5–9% of the total concentration, respectively. Median concentrations of the chemical groups ranged from 81.5 to 129 ng/g ww for PFAS, 26.3–158 ng/g ww for PCBs, 4.26–8.89 ng/g ww for PBDEs, and 8.08–23.0 ng/g ww for pesticides. The regional concentrations of all four classes of compounds are significantly decreasing when sites are combined with halving times of 11.3 ± 4.8, 8.2 ± 4.3, 5.9 ± 3.1, and 8.3 ± 4.2 years for the Penta-BDE mixture, ΣDDTs, Σ85PCBs and Σ36PFAS, respectively. These results suggest that, while PFAS has emerged as the dominant group of chemicals in the plasma, legacy pollutants continue to represent a threat to herring gulls and wildlife in the Great Lakes basin. PCBs were the largest contributors to the chemical load in plasma of birds whose colonies are located near the River Raisin, and continue to pose a threat to herring gulls within the two Areas of Concern.