Journal of Great Lakes Research最新文献

Continued dependence on stocking of hatchery-reared lake trout, Salvelinus namaycush, in the Laurentian Great Lakes indicates recruitment bottlenecks still exist between spawning and the juvenile life stage (age-1). Possible impediments include poor habitat quality and an inability of hatchery-origin adults to select substrates that support successful incubation. Understanding of characteristics of suitable lake trout spawning habitat is limited but has centered on the cobble-contour framework, which identifies sloped reefs with cobble substrate and deep interstices to entrain eggs as spawning habitat. A novel sampling design based on acoustic-telemetry detections was used to evaluate relative importance of cobble-contour habitat characteristics (substrate size, homogeneity, interstitial depth, and slope) for predicting egg presence on two spawning reefs in northern Lake Huron. Fixed effect logistic regression models were used to relate egg presence to all possible combinations of measured physical characteristics. Physical characteristics of sites with naturally spawned eggs present varied, and no single best model predicted egg presence. Model selection and multi-model inference revealed slope to be the only informative predictor. Substrate size, homogeneity, and interstitial depth were not important. Embryo survival-to-hatch was also compared among sampling sites using in situ habitat bioassays seeded with hatchery fertilized embryos. No difference in embryo survival was observed between sites where naturally spawned eggs were present vs. absent. Over half of sites evaluated exceeded 75% survival. Naturally spawned eggs were observed at 25 of 57 sites. We suspect other characteristics such as interstitial flow could be helpful for predicting selection of lake trout spawning habitats.

Tracking the behavior of invasive alien species (IAS) is challenging due to logistical constraints that hinder high frequency surveys. Real-time automated recorders offer a promising solution, but their feasibility needs testing and validation. The acoustic camera is an efficient method to obtain real-time records of the behavior of Hemimysis anomala, a mysid that has invaded a variety of aquatic ecosystems. This approach is also a valuable tool for high-quality video recordings of mysid swarms in shallow habitats. The feasibility of this device to record the continuous behavior, including exit and entry (hereafter referred to as emergence and homing) from a shelter over a diel cycle was validated. Emergence consistently correlated with the onset of civil twilight, while homing displayed more intricate temporal trends. Homing events were longer than emergence events, but both were significantly influenced by light conditions. The termination of emergence was concomitant to the onset of the light preference as already shown by past studies. However, homing showed an earlier onset before light conditions exceeded the preference values, possibly due to inter-individual variability and/or information sharing in swarm behavior. The survey also captured the collapse in the targets number detected by the end of March, underlining the termination of the winter swarm. Furthermore, we demonstrated the importance of high-frequency temporal resolution, with a sampling frequency of at least 10-min, to accurately capture the swarm behavior. Overall, we provide original new insights characterizing H. anomala ecology and encourage the development of real-time automated recorders to track the behavior of IAS.

Invasive species are a key threat to biodiversity in freshwater ecosystems; and, as such, their management can be an important part of ecosystem restoration and conservation. In Hamilton Harbour, an impaired Lake Ontario embayment, invasive species are an important threat. In the early 2000s, an increase in invasive goldfish (Carassius auratus) was identified during monitoring surveys. This population of goldfish was studied via acoustic telemetry to gain knowledge about its biology to support management control options. Hamilton Harbour goldfish exhibited seasonal patterns in site and depth use, and clear preferences for over-wintering and spawning areas. Goldfish were largely resident to Hamilton Harbour with the exception of one individual. To predict when goldfish would move into spawning areas, we examined goldfish presence, abundance, and temperature at a fish-barrier connected to the harbour and developed models to predict goldfish presence based on Cumulative Growing Degree Days (CGDD) and Day of Year (DOY). Goldfish were captured in large numbers (>100 day⁻¹) at the fishway when CGDD > 25.0 and DOY > 100; therefore, we predicted that our tagged fish would move to spawning areas when these thresholds were reached. Both models accurately predicted when tagged fish moved to spawning areas which largely occurred when water temperatures were lower (≥ 9.7 °C) than thresholds previously identified in the literature (i.e., 15.0 °C − 22.0 °C). This suggested that pre-spawn/staging behaviour was detected using telemetry driven by factors including water temperature. Results from this work will inform control strategies for goldfish, including active removal during aggregation prior to spawning.

Municipal water use has been decreasing in the Great Lakes region since the 1970s, though the driving forces behind this decline are not clear. We analyzed this trend by calculating and comparing residential per capita water use across select cities to five socioeconomic factors. Our findings reinforced previous research by indicating that water use, and residential water use in particular, has been decreasing across all five municipalities in our study. We also find the percentage of white residents served by a municipal water supplier to be positively associated with per capita water use, while income inequality is negatively associated with per capita water use. We find per capita water use to be strongly associated with service area population. Water use shifts coincided with abrupt changes in water supply service areas in two of the five cities in our study, underscoring the significance of the rationale for differentiating total water pumped to a distribution system from per capita metered residential use. Our findings have important implications for the economy, the citizens, and the ecosystems of the Great Lakes. They further dovetail with a vision for water use policies guided not just by trends in metered water use, but also by historical and projected changes in the demographics of water users. The relationships observed in our study may help guide water use policies by addressing current and potential future inequities in water distribution and water affordability, and improving understanding of relationships between trends in consumptive use and the regional water balance.

Actions aimed at reducing microplastic pollution need source-specific information to tailor local and global efforts. We applied a source-specific categorization scheme to quantify and characterize microplastics using robust QA/QC methods in 98 nearshore surface waters collected using manta trawls from three Laurentian Great Lakes. The greatest abundances (max. 2.0 x 10⁷ particles/km²) were found adjacent to the Greater Toronto Area, where fragments consistent with commercial and industrial activities contributed up to 58 % ± 21 % of particles on average (0.335 – 4.75 mm size range; near wastewater discharges in Humber Bay, Lake Ontario). Irregularly-shaped polyethylene microbeads were consistently more abundant than spherical microbeads as is typical in personal care products and contributed significantly (up to 44 % ± 21 % on average; Hamilton Harbour, Lake Ontario) in areas dominated by wastewater inputs. Using source-specific microplastic morphology categories may facilitate 1) the development of specific mitigation initiatives for identified and significant sources, and 2) assessing the effectiveness of implemented reduction measures at local levels in marine coastal environments, estuaries, and freshwaters globally.

To minimize the introduction and spread of aquatic nuisance species, the United States Coast Guard (USCG) and the International Maritime Organization (IMO) regulate the allowed microbe, protist, and zooplankton densities present in ballast water discharged from commercial ships. However, the density of eggs and resting stages in ballast discharge are not routinely assessed when determining the effectiveness of ballast water treatment systems. While the density of eggs and resting stages found in residual sediment has been examined by various researchers, the density in ballast water uptake and discharge samples was previously unexamined. Untreated uptake and discharge ballast water samples from 2017, 2022, and 2023, collected on ships within the Laurentian Great Lakes from August through January, were analyzed for eggs and resting stages. The samples contained a total density of 325–140,859 eggs and resting stages per cubic meter. These results demonstrate that uncounted eggs and resting stages are present in ballast water, contributing to the risk of spreading aquatic nuisance species within the Great Lakes.

This paper focuses on the physiography, stratigraphy, and age composition of a migrating strandplain promontory on Lake Michigan, discussing implied changes in alongshore sediment-transport dynamics within context of regional climate data. The Zion Beach-ridge Plain, a mainland-attached system believed to have migrated by >10 km over the past 4.5 kyrs, is partitioned into distinct physiographic zones. Its structural compartmentalization into distinct ridge sets, recognized in LiDAR-based topographic datasets and subsurface reflection geophysical records, reflects a punctuated morphodynamic development that has implications for understanding groundwater-flow patterns, wetland ecology, and coastal morphodynamic evolution. The most recent physiographic boundary within the strand dates to a high-amplitude lake-level rise event (>3 m in magnitude) that coincided with a regional shift in dominant storm-wind direction. The abrupt juxtaposition of young, high-relief dune-ridge terrain against old, low-relief wetland meadow attests to increased rates of littoral sand transport under conditions of heightened wave and current energies. Ongoing work to refine the geochronology of this and similar events is underway and stands to enhance our understanding of late Holocene coastal evolution. Strandplains are studied globally as important coastal paleoclimate archives, yet in the Great Lakes region the emphasis has been on embayed systems. While sheltered environments (e.g., bedrock-confined strandplains) foster high preservation potentials, optimal for paleohydrographic reconstructions from progradational sequences, the complex depositional architectures of strandplain promontories may provide information on open-water processes not contained within the former.

Recurring cyanobacterial blooms have been reported in Lake Nipissing (Ontario, Canada) since at least 2000. However, monitoring data indicate that surface water nutrient concentrations have not increased over the past ∼45 years in this large, shallow, mesotrophic lake. Applying paleolimnological methods, we establish baseline environmental conditions and extend the Lake Nipissing water quality data to pre-industrial times. Lake-wide assessment of changes in nutrient status, algal production, and effects of climate warming are provided by examining: 1) modern and pre-industrial sedimentary diatom assemblages from nine locations; 2) temporal trends in sedimentary photosynthetic pigments over ∼200 years from five locations; and 3) detailed sedimentary profiles of diatom and chironomid assemblage composition from Callander Bay, spanning the past ∼200 years. A pronounced shift in diatom assemblage composition was registered at all sites with pre-industrial sediments dominated by Aulacoseira spp. and modern samples dominated by Discostella stelligera. The detailed diatom analysis for Callander Bay indicated that this shift occurred ca. 1990. Since ca. 1975, cyanobacterial production (spectrally inferred from sediments) exceeded the ∼200-year mean and matches the observed increase in bloom reports. Twentieth century shifts in chironomid assemblages in Callander Bay from Procladius to Chironomus spp. dominance indicate lower hypolimnetic oxygen in recent decades. Collectively, these changes suggest that previously polymictic Lake Nipissing is now experiencing periods of thermal stratification and development of transient anoxia in bottom waters. These conditions are more prevalent and widespread in modern Lake Nipissing, consistent with a response to recent warming, decreased wind speed, and a longer ice-free period.

This study quantified stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes, polychlorinated biphenyl (PCB) concentrations and growth rates among multiple genetic strains of Lake Ontario lake trout (Salvelinus namaycush) to evaluate the potential role of genetics in these parameters. Fish ranging in age from 1 to 31 years (n = 72) and representing nine genetic strains including wild-recruits to hatchery fish derived from Lakes Ontario, Superior and Champlain watersheds, and individuals of unknown hatchery origin. Carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope values averaged −22.2 ‰ and 17.4 ‰, respectively, but did not differ significantly among genetic strains. ΣPCB concentrations ranged from 42 to 1820 ng/g and varied significantly among individuals including those of similar age and genetic strain. For example, Sum PCB (ΣPCB) concentrations among 7-year-old fish (n = 16) ranged from 159 to 607 ng/g, which compares to growth rates of 3.5 – 32.9 %/yr for these same fish. Multivariate analysis of stable isotope and PCB profiles, however, provided considerable resolution among the strains. For example, fish of unknown hatchery origin ordinated most similar to Seneca Lake fish, the predominant strain stocked in Lake Ontario. Wild fish had a unique ordination with only Lake Superior Klondike strain fish overlapping into their ordination space. Lakes Champlain and Superior strain individuals had similar ordinations but did not overlap substantially with wild or Klondike strain fish. Combined, these differences agree with the ecologies described for these strains in their native ecosystems suggesting that insight can be gained from strain specific evaluations of ecological tracers and these pollutants among Great Lakes lake trout.

Among the highest profile invasive species in the Laurentian Great Lakes region are Dreissena polymorpha and D. rostriformis bugensis (collectively dreissenids). Despite their abundance and ecosystem-wide effects, little is known about dreissenid distributions in large connecting channels between lakes. The objectives of this study were to estimate and document dreissenid densities and their habitat characteristics throughout the St. Clair River, to compare dreissenid species demographics, and predict spatial distributions between two connecting waters of the Great Lakes: the St. Clair and Detroit rivers. Two types of species distribution models (SDMs), MaxEnt and classification and regression tree analysis (CART), were created using dreissenid and habitat data collected in both the Detroit and St. Clair rivers. The SDMs were then used to predict presence of dreissenids in the St. Clair River. The St. Clair River had more D. r. bugensis (mean density = 486 ± 152 individuals/m²) than D. polymorpha (mean density = 3 ± 1 individuals/m²). The SDMs created from the Detroit River data reliably predicted presence of dreissenids in the St. Clair River. Depending on the river and species, CART models identified velocity and depth to be important predictor variables, while distance to river inlet/outlet were the most influential variables in the MaxEnt models. Most research on dreissenid distribution modeling is focused on determining areas for potential spread; however, this study presents a unique perspective by modeling dreissenid presence, both D. polymorpha and D. r. bugensis separately and together, where they have been established for more than 30 years.