Great Lakes Drainage Research Articles

Testing the Sensitivity of a WRF-Based Great Lakes Regional Climate Model to Cumulus Parameterization and Spectral Nudging

Abstract The Weather Research and Forecasting (WRF) Model is used to dynamically downscale ERA-Interim global reanalysis data to test its performance as a regional climate model (RCM) for the Great Lakes region (GLR). Four cumulus parameterizations and three spectral nudging techniques applied to moisture are evaluated based on 2-m temperature and precipitation accumulation in the Great Lakes drainage basin (GLDB). Results are compared to a control simulation without spectral nudging, and additional analysis is presented showing the contribution of each nudged variable to temperature, moisture, and precipitation. All but one of the RCM test simulations have a dry precipitation bias in the warm months, and the only simulation with a wet bias also has the least precipitation error. It is found that the inclusion of spectral nudging of temperature dramatically improves a cold-season cold bias, and while the nudging of moisture improves simulated annual and diurnal temperature ranges, its impact on precipitation is complicated. Significance Statement Global climate models are vital to understanding our changing climate. While many include a coarse representation of the Great Lakes, they lack the resolution to represent effects like lake effect precipitation, lake breeze, and surface air temperature modification. Therefore, using a regional climate model to downscale global data is imperative to correctly simulate the land–lake–atmosphere feedbacks that contribute to regional climate. Modeling precipitation is particularly important because it plays a direct role in the Great Lakes’ water cycle. The purpose of this study is to identify the configuration of the Weather Research and Forecasting Model that best simulates precipitation and temperature in the Great Lakes region by testing cumulus parameterizations and methods of nudging the regional model toward the global model.

Survival, healing, and swim performance of juvenile migratory sea lamprey (Petromyzon marinus) implanted with a new acoustic microtransmitter designed for small eel-like fishes

BackgroundLittle is known about the transformer stage of the parasitic lampreys, a brief but critical period that encompasses juvenile out-migration from rivers to lakes or oceans to begin parasitic feeding. Information about this life stage could have significant conservation implications for both imperiled and invasive lampreys. We investigated tag retention, survival, wound healing, and swim performance of newly transformed sea lamprey (Petromyzon marinus) implanted with a new micro-acoustic transmitter, the eel–lamprey acoustic transmitter (ELAT), in a controlled laboratory environment.ResultsThe 61-day survival of our tagged subjects was 71%, within the range reported in similar studies of juvenile lampreys. However, survival was significantly lower in the tagged animals (vs control), with no effect statistically attributable to measures of animal length, mass, condition, or population of origin (Great Lakes vs. Atlantic drainage). Mortality in tagged fish was concentrated in the first four days post-surgery, suggesting injury from the surgical process. An unusually long recovery time from anesthesia may have contributed to the increased mortality. In a simple burst swim assay, tagged animals swam significantly slower (− 22.5%) than untagged animals, but were not significantly different in endurance swim tests. A composite wound healing score at day four was a significant predictor of maximum burst swim speed at day 20, and wound condition was related to animal mass, but not length, at the time of tagging.ConclusionsImpairments to survival and swim performance of juvenile sea lamprey implanted with the ELAT transmitter were within currently reported ranges for telemetry studies with small, difficult to observe fishes. Our results could be improved with more refined anesthesia and surgical techniques. The ability to track migratory movements of imperiled and pest populations of parasitic lampreys will improve our ability to estimate vital rates that underlie recruitment to the adult population (growth, survival) and to investigate the environmental factors that regulate the timing and rates of movement, in wild populations.

RAD-tag and mitochondrial DNA sequencing reveal the genetic structure of a widespread and regionally imperiled freshwater mussel, Obovaria olivaria (Bivalvia: Unionidae).

Obovaria olivaria is a species of freshwater mussel native to the Mississippi River and Laurentian Great Lakes‐St. Lawrence River drainages of North America. This mussel has experienced population declines across large parts of its distribution and is imperiled in many jurisdictions. Obovaria olivaria uses the similarly imperiled Acipenser fulvescens (Lake Sturgeon) as a host for its glochidia. We employed mitochondrial DNA sequencing and restriction site‐associated DNA sequencing (RAD‐seq) to assess patterns of genetic diversity and population structure of O. olivaria from 19 collection locations including the St. Lawrence River drainage, the Great Lakes drainage, the Upper Mississippi River drainage, the Ohioan River drainage, and the Mississippi Embayment. Heterozygosity was highest in Upper Mississippi and Great Lakes populations, followed by a reduction in diversity and relative effective population size in the St. Lawrence populations. Pairwise F ST ranged from 0.00 to 0.20, and analyses of genetic structure revealed two major ancestral populations, one including all St. Lawrence River/Ottawa River sites and the other including remaining sites; however, significant admixture and isolation by river distance across the range were evident. The genetic diversity and structure of O. olivaria is consistent with the existing literature on Acipenser fulvescens and suggests that, although northern and southern O. olivaria populations are genetically distinct, genetic structure in O. olivaria is largely clinal rather than discrete across its range. Conservation and restoration efforts of O. olivaria should prioritize the maintenance and restoration of locations where O. olivaria remain, especially in northern rivers, and to ensure connectivity that will facilitate dispersal of Acipenser fulvescens and movement of encysted glochidia.

Water quality data for Fall Creek, New York, USA: 1972–1995

AbstractThe 33 086 ha mixed land use Fall Creek watershed in upstate New York is part of the Great Lakes drainage system. Results from more than 3500 water samples are available in a data set that compiles flow data and measurements of various water quality analytes collected between 1972 and 1995 in all seasons and under all flow regimes in Fall Creek and its tributaries. Data is freely accessible at https://ecommons.cornell.edu/handle/1813/8148 and includes measurements of suspended solids, pH, alkalinity, calcium, magnesium, potassium, sodium, chloride, nitrate nitrogen (NO3‐N), sulphate sulphur (SO4‐S), phosphorus (P) fractions molybdate reactive P (MRP) and total dissolved P (TDP), percent P in sediment, and ammonium nitrogen (NH4‐N). Methods, sub‐watershed areas, and coordinates for sampling sites are also included. The work represented in this data set has made important scientific contributions to understanding of hydrological and biogeochemical processes that influence loading in mixed use watersheds and that have an impact on algal productivity in receiving water bodies. In addition, the work has been foundational for important regulatory and management decisions in the region.

Absence of genetic structure reflects post-glacial history and present-day host use in Mapleleaf (Quadrula quadrula) mussel from Manitoba, Canada

Our study documents and analyzes the absence of genetic diversity and structure of the Mapleleaf (Quadrula quadrula (Rafinesque, 1820)) (Bivalvia: Unionidae) mussel in the Lake Winnipeg, Assiniboine River, and Red River drainages (Manitoba, Canada). Previous studies have revealed patterns of genetic diversity and structure in the Mississippi and Ohio river drainages, as well as in the Laurentian Great Lakes drainage. Genotypes from six variable microsatellite loci showed that the Q. quadrula population in Manitoba was significantly differentiated from the population in the Great Lakes drainage (Ontario, Canada), supporting the existence of two Designatable Units in Canada. Conversely, there was no evidence of genetic structure within the sampled range of Q. quadrula in Manitoba. The lack of genetic structure in Q. quadrula across its distribution in Manitoba reflected its post-glacial history and use of a vagile host and necessitates that efforts should be made to ensure connectivity and maintain gene flow across the region. Given that the evidence suggests that Manitoba Q. quadrula belong to a single genetic population, movement of hatchery-propagated juvenile Q. quadrula, adult Q. quadrula, or glochidia-carrying host catfish sourced from any location in Manitoba could be used to augment declining populations or at-risk locations in Manitoba.

First record of the Neotropical cladoceran Diaphanosoma fluviatile Hansen, 1899 in the Great Lakes basin

The ctenopod Diaphanosoma fluviatile has been reported primarily from the Neotropical region and occasionally from the southern United States. D. fluviatile was collected in the Great Lakes basin (the Maumee River, Western Lake Erie, and Lake Michigan) in 2015 and 2018, far north from its previously known distribution. The occurrence of this southern species in the Maumee River and Great Lakes may be the result of an anthropogenic introduction, although a natural range expansion cannot be excluded. This report documents the northernmost record of D. fluviatile in the Nearctic region, extending the known distribution of the species to 42°N, which is a notable increase of 11 degrees latitude. Our detection of D. fluviatile is the first record of this southern species from the Laurentian Great Lakes drainage.

The pre-Late Wisconsin stratigraphy of southern Simcoe County, Ontario: implications for ice sheet buildup, decay, and Great Lakes drainage evolution

Recent three-dimensional mapping investigations in southern Simcoe County, Ontario, allow refinement of the existing regional stratigraphic framework. Analysis of 25 continuously cored boreholes has revealed a complex but consistent sediment succession that provides a record of the last two glacial cycles (Marine Isotope Stages 1–6). Five stratigraphic units (SU1–SU5) comprise the pre-Late Wisconsin record. The stratigraphy is floored by a presumed Illinoian glacial complex consisting of a lower, coarse-grained till (SU1), locally overlain by stratified glaciolacustrine and glaciofluvial sediments (SU2), but more commonly capped by a stone-poor, fine-grained till (SU3) of the Georgian Bay lobe. A widespread subaerial unconformity developed on the upper surface of SU3 contains organic-bearing, nonglacial deposits (SU4) ranging between 54 800 ± 3000 years BP (considered beyond the limits of radiocarbon dating) and 37 450 ± 590 14C years BP. SU4 is abruptly overlain by a thick succession of rhythmically laminated lacustrine muds graded upwards into glaciolacustrine silts and clays interrupted by regionally continuous sand bodies (SU5). The succession is capped (and locally truncated) by Late Wisconsin Newmarket Till. The sedimentary record of southern Simcoe County is correlated with other well-studied reference sections in southern Ontario and contains information that informs reconstructions of former ice extents in the lower Great Lakes region following the Illinoian glaciation. Several sediment units host aquifers, but limited thickness and spatial extent, as well as issues with naturally occurring dissolved gases and solids, restrict their use for groundwater supply.

Potential carbon loss associated with post-settlement wetland conversion in southern Ontario, Canada

BackgroundNatural wetlands can mitigate ongoing increases in atmospheric carbon by storing any net balance of organic carbon (peat) between plant production (carbon uptake) and microbial decomposition (carbon release). Efforts are ongoing to quantify peat carbon stored in global wetlands, with considerable focus given to boreal/subarctic peatlands and tropical peat swamps. Many wetlands in temperate latitudes have been transformed to anthropogenic landscapes, making it difficult to investigate their natural/historic carbon balance. The remaining temperate swamps and marshes are often treated as mineral soil wetlands and assumed to not accumulate peat. Southern Ontario in the Laurentian Great Lakes drainage basin was formerly a wetland-rich region that has undergone significant land use change since European settlement.ResultsThis study uses southern Ontario as a case study to assess the degree to which temperate regions could have stored substantial carbon if it had not been for widespread anthropogenic land cover change. Here, we reconstruct the full extent and distribution of natural wetlands using two wetland maps, one for pre-settlement conditions (prior to 1850 CE) and the other for modern-day patterns of land use (2011 CE). We found that the pre-settlement wetland cover decreased by about 56% with the loss most significant for marshes as only 11% of predicted pre-settlement marshland area remains today. We estimate that pre-settlement wetlands held up to ~ 3.3 Pg of carbon relative to ~ 1.3 Pg for present-day (total across all wetland classes).ConclusionsBy not considering the recent carbon loss of temperate wetlands, we may be underestimating the wetland carbon sink in the pre-industrial carbon cycle. Future work is needed to better track the conversion of natural wetlands globally and the associated carbon stock change.

Right practice, right place: A conservation planning toolbox for meeting water quality goals in the Corn Belt

O n August 2, 2014, the residents of Toledo, Ohio, were warned that their drinking water was potentially contaminated with microcystin, an algal-related toxin that can cause various illnesses and liver damage, and unsafe to drink (Bullerjahn et al. 2016). They were the latest victims of a series of water quality crises in the United States, many (including the Toledo event) attributable in large part to nutrients lost from agricultural landscapes. Meanwhile, hypoxia in the Gulf of Mexico continues unabated (USEPA 2015), with the 2017 dead zone being the largest recorded (NOAA 2017). In response to these crises, states in the Mississippi River and Great Lakes drainage basins are undertaking ambitious efforts to achieve 40% to 45% reductions in nutrient losses from agriculture. There is a growing consensus that in-field conservation practices, such as improved nutrient management, conservation tillage, and cover crops, will not, singly or together, achieve the 45% nutrient reduction goals (Schilling and Wolter 2009; Iowa Nutrient Reduction Strategy 2013). Meeting these water quality goals will require combining in-field nutrient management practices with downstream nutrient removal practices, such as bioreactors and filter strips at the edges of fields and wetland creation and floodplain restoration below fields (McLellan et al.

Hierarchical analysis of genetic structure in the habitat-specialist Eastern Sand Darter (Ammocrypta pellucida).

Quantifying spatial genetic structure can reveal the relative influences of contemporary and historic factors underlying localized and regional patterns of genetic diversity and gene flow – important considerations for the development of effective conservation efforts. Using 10 polymorphic microsatellite loci, we characterize genetic variation among populations across the range of the Eastern Sand Darter (Ammocrypta pellucida), a small riverine percid that is highly dependent on sandy substrate microhabitats. We tested for fine scale, regional, and historic patterns of genetic structure. As expected, significant differentiation was detected among rivers within drainages and among drainages. At finer scales, an unexpected lack of within-river genetic structure among fragmented sandy microhabitats suggests that stratified dispersal resulting from unstable sand bar habitat degradation (natural and anthropogenic) may preclude substantial genetic differentiation within rivers. Among-drainage genetic structure indicates that postglacial (14 kya) drainage connectivity continues to influence contemporary genetic structure among Eastern Sand Darter populations in southern Ontario. These results provide an unexpected contrast to other benthic riverine fish in the Great Lakes drainage and suggest that habitat-specific fishes, such as the Eastern Sand Darter, can evolve dispersal strategies that overcome fragmented and temporally unstable habitats.

An Examination of Petromyzontidae in Pennsylvania: Current Distribution and Habitat Preference of Lampreys

Abstract Native populations of lampreys are declining throughout the Great Lakes drainage basin due to habitat loss and degradation, anthropogenic stresses, and stream treatment with lampricides to control the exotic Petromyzon marinus (Sea Lamprey). We surveyed 19 streams across Pennsylvania to determine the presence/absence of six species that were historically found there. In 2011, we found four species—Lamptera aepyptera (Least Brook Lamprey), Lethenteron appendix (American Brook Lamprey), Ichthyomyzon greeleyi (Mountain Brook Lamprey), and Sea Lamprey—in 14 creeks statewide. In 2012, we found three species—Least Brook Lamprey, American Brook Lamprey, and Mountain Brook Lamprey— in 8 creeks in the Allegheny watershed. Lampreys appeared to be extirpated at some sites. Historically, Ichthyomyzon bdellium (Ohio Lamprey) and Ichthyomyzon fossor (Northern Brook Lamprey) were reported, but we did not observe these species during our study. Substrate analysis indicated ammocoetes preferred substrates with a ...

Interactions between invasive round gobies (Neogobius melanostomus) and fantail darters (Etheostoma flabellare) in a tributary of the St. Lawrence River, New York, USA

The initial, rapid expansion of the invasive round goby (Neogobius melanostomus) throughout the Great Lakes drainage was largely confined to lentic systems. We recently observed round gobies ascending two tributaries of the St. Lawrence River. The expansion of gobies into small lotic environments may place ecologically similar species at risk. Fantail darter (Etheostoma flabellare) is one of the several benthic species of the New York Great Lakes drainages that are threatened by round goby invasion. We examined the habitat use and diet composition of fantail darters and round gobies in Mullet Creek, a third-order tributary of the St. Lawrence River, NY, USA. The objectives of this study were to determine the degree of habitat and diet overlap between fantail darters and round gobies in a tributary of the St. Lawrence River. Gobies and darters co-occurred at 22% of capture sites. Of the four habitat variables examined (cover, depth, substrate and velocity), only depth use was significantly different with gobies using deeper habitats than darters. Among the two species and size classes sampled (large vs. small), large darters had the most restricted habitat use requirements. There was variation in round goby and darter diet composition, but only moderate diet overlap occurred between fantail darters and round gobies (Cλ = 0.43). Conditions in Mullet Creek were appropriate for the evaluation of possible spatial and dietary competition between round goby and native darters. Early detection and management of round goby invasions is critical to maintaining ecological integrity of lotic ecosystems in the St. Lawrence Valley.

Glacial cycles as an allopatric speciation pump in north‐easternAmerican freshwater fishes

Allopatric speciation may be the principal mechanism generating new species. Yet, it remains difficult to judge the generality of this process because few studies have provided evidence that geographic isolation has triggered the development of reproductive isolation over multiple species of a regional fauna. Here, we first combine results from new empirical data sets (7 taxa) and published literature (9 taxa) to show that the eastern Great Lakes drainage represents a multispecies suture zone for glacial lineages of freshwater fishes with variable levels of genetic divergence. Second, we performed amplified fragment length polymorphism analyses among four pairs of lineages. Results indicate that lineages with relatively deep levels of mtDNA 5' COI (barcode) sequence divergence (>2%) developed strong reproductive barriers, while lineages with lower levels of divergence show weaker reproductive isolation when found in sympatry. This suggests that a threshold of 2% sequence divergence at mtDNA could be used as a first step to flag cryptic species in North American freshwater fishes. By describing different levels of divergence and reproductive isolation in different co-occurring fishes, we offer strong evidence that allopatric speciation has contributed significantly to the diversification of north-eastern American freshwater fishes and confirm that Pleistocene glacial cycles can be viewed as a 'speciation pump' that played a predominant role in generating biodiversity.

A landscape-based distribution model for fallfish (Semotilus corporalis) in the Great Lakes drainage of New York

Fallfish (Semotilus corporalis) is a large native minnow that can be both an important food source and a predator on juvenile stream fishes, including salmonids. We developed a fallfish abundance-habitat neural network model. The model explained a large fraction of observed fallfish abundance class variation (R2=0.91) and predicted optimal habitat in relatively flat, low elevation, cool to warm streams associated with forested landscapes. The distribution of optimal habitat areas was limited to 9% of the stream network, but one concentration overlapped with the best salmonid production habitat in the Lake Ontario basin. These model results can help managers better understand fallfish distribution and habitat requirements, as well as help them better assess potential interspecific interactions with gamefish in the Lake Ontario–St. Lawrence drainage.

Lake levels in the Erie Basin of the Laurentian Great Lakes

Water levels in the Lake Erie basin are inferred from glacial lake times to present. An era of early to middle Holocene lowstands is defined below outlets by a submerged paleo-beach, and truncated reflectors in glaciolacustrine sediment beneath a mud-covered wave-cut terrace. Also, the glacial clay surface above the paleo-shore level has elevated shear strength because of porewater drainage during subaerial exposure. Below the paleo-shore where exposure did not occur, clay strength remained normal. Sedimentation rates were reduced during the lowstands. The distortion of once-level shore zone indicators by differential glacial rebound was removed by computing original elevations of the indicators using an empirical model of rebound based on observations of upwarped former lake shorelines. Erie water-level history was inferred from a plot of the original elevations of lake-level constraints and outlets versus age. The lake history was validated by reference to ~83 water-level indicators, not used as constraints. During the deglaciation, lake-crossing moraines were likely eroded by fluvial drainage into low-level Lake Ypsilanti and a subsequent unnamed low lake to produce the Lorain Valley and Pennsylvania Channel. Once inflow from the upper Great Lakes basins was directed to Ottawa Valley about 10,400 (12,270 cal BP), Erie water levels descended in a dry, evaporative climate to a closed lowstand during which ostracode δ18O increased ~2‰ above present values. Lake level began to rise 6,000 to 7,000 (6,830 to 7,860 cal) BP in response to increased atmospheric moisture and later, to northern inflow as the Nipissing Transgression returned upper Great Lakes drainage to Lake Erie by about 5,200 (6,000 cal) BP. At that time, the lake overflowed the uplifted Lyell–Johnson Sill north (downstream) of the present Niagara Falls at higher-than-present levels. After recession of the Falls breached this sill about ~3,500 (~3,770 cal) BP, Lake Erie fell 3–4 m to its present Fort Erie–Buffalo Sill. The extended low-water phase with its isolated sub-basins could have restricted migration of aquatic fauna. The early to middle Holocene closed-basin response highlights the sensitivity of Lake Erie to climatic reductions in its water budget.

RESOLUTION ON ECOLOGICAL SEPARATION OF THE GREAT LAKES AND MISSISSIPPI RIVER DRAINAGE BASINS

FisheriesVolume 36, Issue 5 p. 250-250 Miscellany RESOLUTION ON ECOLOGICAL SEPARATION OF THE GREAT LAKES AND MISSISSIPPI RIVER DRAINAGE BASINS First published: 17 May 2011 https://doi.org/10.1080/03632415.2011.583852Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume36, Issue5May 2011Pages 250-250 RelatedInformation

Management of the Lake Sturgeon Acipenser fulvescens population in the lower St Lawrence River (Québec, Canada) from the 1910s to the present

Summary The main objective of this paper is to show that a well-managed lake sturgeon Acipenser fulvescens population can support a high and sustainable commercial catch, even in the Great Lakes drainage where the species has nowadays become rare. In a 350-km long un-fragmented stretch of the lower St Lawrence River located between Montreal and downstream Quebec City, with declared annual catches of 150 tonnes, the lake sturgeon population was considered overexploited by a governmental scientific committee in 1987 on the basis of high annual mortality rates (17–25% for age groups 14–31), unbalanced age structure, deficit of reproductive potential and commercial catch yields well over 1.5 kg ka−1. A first management plan implemented in 1987 failed to reduce the catch and provide more protection to the spawning stock. During the 1990s, the declared catch of the 76 commercial fishermen kept increasing over 200 tonnes. The age at the recruitment of the 20-cm-mesh gill-nets shifted towards older fish, indicating a decrease in the numbers of younger fish. In the population, sub-adult abundance decreased by 60%, as well as the year-class strength and the abundance of the females on the largest known spawning ground. In 2000, a stronger management plan was then enforced in order to adapt the total catch to the potential of the resource. The commercial catch was reduced by 60% in 3 years and an individual code-bar plastic tag and a code-bar weight declaration coupon were established to control its application. The fishing season was also shortened. Ten years later, we are confident in maintaining the actual commercial fishery because the commercial catch is now much lower (80 tonnes) and is more effectively controlled, the abundance of juvenile lake sturgeon increased throughout the St Lawrence River and the regular yearly production of cohorts has been demonstrated. Restrictive management measures, close supervision of landings combined with periodic monitoring of the population are key elements in managing this long-lived species. We also emphasize the importance of preventing any further fragmentation of this portion of 350 km of fluvial habitat as well as to maintain habitat quality to ensure the sustainability of this fishery.

The Younger Dryas and Late Pleistocene peoples of the Great Lakes region

The Late Pleistocene archaeological record of the Great Lakes drainage area shows that there were several, albeit spatially variable, changes in that record in a time period corresponding to the Younger Dryas (YD) climatic reversal at ca. 10,800–10,000 14C BP. Notable here are declines in some areas in the mobility of Paleoindian groups as measured by distance to the main lithic source employed, declines in the overall frequency of sites/findpots, particularly in the western Great Lakes where some northern areas seem to have been largely abandoned, and an increasing association of occupation locales with glacial lake shores or extensive wetlands left by recently drained glacial lakes. Some of the changes, as in range mobility, most likely relate to the colonization of new areas rather than directly to the YD. Specifically, the earliest groups were able to target rich, but widely dispersed, resource locales due to an absence of competing groups. However, the declines in locale frequencies and shifting distributions of those locales may be due to YD influence, notably to an eventual drying out of the area that resulted in less productive environments overall and made the lake shores and wetland areas more attractive environmental niches for human occupation.

Evidence of early Holocene closed-basin conditions in the Huron-Georgian basins from within the North Bay outlet of the upper Great Lakes

Sub-bottom profiling and coring were undertaken at eight sub-basins along the lower French River and at five small lakes near North Bay, Ontario, to collect stratigraphical and chronological evidence to investigate whether lakes occupying the Huron–Georgian basins during the early- to mid-Holocene became hydrologically closed. All of the coring sites are located within the route of the North Bay outlet that carried outflow from the upper Great Lakes during this period. Sand beds containing organic detritus are present within five cores from Muskrat, Crombie and Deep bays that otherwise are composed of glaciolacustrine rhythmites or fine-grained lacustrine deposits. These sand beds are interpreted to represent intervals when water levels within the sub-basins were lower than present, based on chronology, sediment texture, and macrofossil assemblages. It is inferred that the water surface in the Huron–Georgian basins fell below the level of the Dalles Rapids sill isolating the lower French River sub-basins from the large lake. A core from Depensier Lake, North Bay, contains an organic-rich sand interval within a thicker sand unit barren of organic materials. Macrofossils within this organic-rich interval are interpreted to be evidence of substantially diminished flow through the North Bay outlet channel. Radiocarbon dates of terrestrial macrofossils provide correlation of the sand beds between the French River cores as well as with the organic-rich sand in the Depensier Lake core. The possibility that the sand beds in the French River cores represent flood deposits rather than evidence of hydrologically closed conditions is considered, but rejected, based on the occurrence of multiple peaty layers and the record of shallow water conditions inferred from macrofossils within the upper sand bed of core MUS1, Muskrat Bay, in combination with the evidence of quiescent depositional conditions from similarly aged macrofossils in the core from Depensier Lake. Eight radiocarbon dates from the French River cores are incorporated into an elevation-age plot of paleo-indicators of water levels in the Huron–Georgian basins, using additional data from the literature. This plot and stratigraphic evidence from the Muskrat Bay cores indicates that separate closed-basin intervals occurred between 9.0 and 8.4, and 9.5 and 9.3 ka cal BP (~ 8.1 and 7.6, and ~ 8.5 and 8.3 ka BP). The occurrence of these two closed-basin intervals between 9.6 and 8.4 ka cal BP (~ 8.7 and 7.6 ka BP) implies that run-off derived exclusively from precipitation within the non-glaciated portions of the upper Great Lakes drainage basins was likely insufficient at this time to support an open-basin lake hydrology during the contemporary climate, which was colder and drier than present, without being supplemented from glacial Lake Agassiz overflow and/or Laurentide Ice Sheet meltwater.

Alternative Reproductive Behaviors in Lampreys and Their Signifcance

ABSTRACT A typical lamprey mating involves a female attaching to a stone near the upstream end of the nest A male then attaches to the back of the female's head and wraps his body around hers. Both vibrate vigorously as gametes are released. In some cases, a second male, the satellite, circles about the urogenital area of a mating pair at the moment of gamete release in what has been interpreted as an attempt to gain fertilizations. Analysis of videotapes of spawning Lampetra appendix in the North Branch Whitewater River in Minnesota (Mississippi River drainage) and Jambo Creek in eastern Wisconsin (Great Lakes drainage) revealed that at both sites at least 50% of matings in nests with at least three lampreys included a satellite male. Nest associations involving more that one lamprey species in the same nest are known to involve many combinations of species, but especially relevant are cases involving closely related parasitic and nonparasitic species. For example, we have observed nonparasitic Ichthyomyzon gagei and parasitic Ichthyomyzon castaneus spawning in the same nests and have observed a male I. gagei attached to a female I. castaneus. Conventional wisdom is that the size difference between parasitic and nonparasitic lampreys prevents successful mating, but a combination of interspecific nest association and satellite male behavior could conceivably permit gene flow between paired nonparasitic and parasitic forms. This combination is displayed by at least some Lampetra species.