Lasmigona Costata Research Articles

Microparticles in Wild and Caged Biota, Sediments, and Water Relative to Large Municipal Wastewater Treatment Plant Discharges.

Anthropogenically modified microparticles including microplastics are present in municipal wastewater treatment plant (WWTP) effluents; however, it is unclear whether biotic exposures are elevated downstream of these outfalls. In the fall of 2019, the present study examined whether microparticle levels in resident fish, environmental samples, and caged organisms were elevated near the Waterloo and Kitchener WWTP outfalls along the Grand River, Ontario, Canada. Wild rainbow darters (Etheostoma caeruleum) were collected from a total of 10 sites upstream and downstream of both WWTPs, along with surface water and sediment samples to assess spatial patterns over an approximately 70-km river stretch. Amphipods (Hyalella azteca), fluted-shell mussels (Lasmigona costata), and rainbow trout (Oncorhynchus mykiss) were also caged upstream and downstream of one WWTP for 14 or 28 days. Whole amphipods, fish digestive tracts, and mussel tissues (hemolymph, digestive glands, gills) were digested with potassium hydroxide, whereas environmental samples were processed using filtration and density separation. Visual identification, measurement, and chemical confirmation (subset only) of microparticles were completed. Elevated abiotic microparticles were found at several upstream reference sites as well as at one or both wastewater-impacted sites. Microparticles in amphipods, all mussel tissues, and wild fish did not show patterns indicative of increased exposures downstream of effluent discharges. In contrast, elevated microparticle counts were found in trout caged directly downstream of the outfall. Across all samples, cellulose fibers (mainly blue and clear colors) were the most common. Overall, results suggest little influence of WWTP effluents on microparticles in biota but rather a ubiquitous presence across most sites that indicates the importance of other point and nonpoint sources to this system. Environ Toxicol Chem 2024;43:1047-1061. © 2024 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Comparisons of Twelve Freshwater Mussel Bed Assemblages Quantitatively Sampled at a 15-year Interval in the Buffalo National River, Arkansas, USA

Historically, 23 freshwater mussel species have been documented from the Buffalo National River (BNR), a 246 km, free-flowing river in northern Arkansas. The potential threats to BNR include land use/land cover changes, eutrophication, recreation, physical habitat changes, and various climate change-related effects. Twelve quantitative mussel bed sites were established and then sampled using a stratified random sampling protocol to evaluate the long-term changes between 2006 and 2020–2021 in population and assemblage characteristics. We compared (1) overall mussel bed persistence, sampling confidence levels and study-wide relative abundances, and compared species’ size and size-frequency distributions; (2) 10 overall site assemblage variables using paired t-tests; (3) site-level mean density, richness, and diversity indices using pair-wise Mann–Whitney U statistics; and (4) assemblage composition using Non-Metric Multidimensional Scaling. The major findings included the following: (1) sampling efforts based on a targeted 80% confidence level appears relatively robust, (2) BNR mussel assemblage composition and structure were relatively stable (however, small mussel bed persistence is a concern), (3) 7 of 23 sites were outliers based on freshwater mussel composition and habitat characteristics, and (4) assemblage composition changed with three species declining (Actinonaias ligamentina, Lasmigona costata, and Ptychobranchus occidentalis) and four species increasing (Cambarunio hesperus, Cyclonaias tuberculata, Eurynia dilatata, and Venustaconcha pleasii) between monitoring events.

Lethal and Sub-lethal Implications of Sodium Chloride Exposure for Adult Unionid Mussel Species: Eurynia dilatata and Lasmigona costata.

The elevated use of salt as a de-icing agent on roads in Canada is causing an increase in the chloride concentration of freshwater ecosystems. Freshwater Unionid mussels are a group of organisms that are sensitive to increases in chloride levels. Unionids have greater diversity in North America than anywhere else on Earth, but they are also one of the most imperiled groups of organisms. This underscores the importance of understanding the effect that increasing salt exposure has on these threatened species. There are more data on the acute toxicity of chloride to Unionids than on chronic toxicity. This study investigated the effect of chronic sodium chloride exposure on the survival and filtering activity of two Unionid species (Eurynia dilatata, and Lasmigona costata) and assessed the effect on the metabolome in L. costata hemolymph. The concentration causing mortality after 28days of exposure was similar for E. dilatata (1893mg Cl-/L) and L. costata (1903mg Cl-/L). Significant changes in the metabolome of the L. costata hemolymph were observed for mussels exposed to non-lethal concentrations. For example, several phosphatidylethanolamines, several hydroxyeicosatetraenoic acids, pyropheophorbide-a, and alpha-linolenic acid were significantly upregulated in the hemolymph of mussels exposed to 1000mg Cl-/L for 28days. While no mortality occurred in the treatment, elevated metabolites in the hemolymph are an indicator of stress.

Effects of municipal wastewater effluents on the digestive gland microbiome of wild freshwater mussels (Lasmigona costata)

Gut microbial communities are vital for maintaining host health, and are sensitive to diet, environment, and chemical exposures. Wastewater treatment plants (WWTPs) release effluents containing antimicrobials, pharmaceuticals, and other contaminants that may negatively affect the gut microbiome of downstream organisms. This study investigated changes in the diversity and composition of the digestive gland microbiome of flutedshell mussels (Lasmigona costata) from upstream and downstream of two large (service >100,000) WWTPs. Mussel digestive gland microbiome was analyzed following the extraction, PCR amplification, and sequencing of bacterial DNA using the V3-V4 hypervariable regions of the 16 S rRNA gene. Bacterial alpha diversity decreased at sites downstream of the second WWTP and these sites were dissimilar in beta diversity from sites upstream and downstream of the first upstream WWTP. The microbiomes of mussels collected downstream of the first WWTP had increased relative abundances of Actinobacteria, Bacteroidetes, and Firmicutes, with a decrease in Cyanobacteria, compared to upstream mussels. Meanwhile, those collected downstream of the second WWTP increased in Proteobacteria and decreased in Actinobacteria, Bacteroidetes, and Tenericutes. Increased Proteobacteria has been linked to adverse effects in mammals, but their functions in mussels is currently unknown. Finally, effluent-derived bacteria were found in the microbiome of mussels downstream of both WWTPs but not in those from upstream. Overall, results show that the digestive gland microbiome of mussels collected upstream and downstream of WWTPs differed, which has implications for altered host health and the transport of WWTP-derived bacteria through aquatic ecosystems.

Investigation of Microplastics in Freshwater Mussels (Lasmigona costata) From the Grand River Watershed in Ontario, Canada

Microplastics have been identified as a widespread, persistent environmental pollutant. The investigation of microplastics in marine ecosystems has been prevalent in the literature; however, much less consideration has been given to this form of pollution in freshwater ecosystems. Relatively few studies have considered the uptake of microplastics in freshwater mussels. This study investigated the presence of microplastics in fluted-shell mussels (Lasmigona costata) collected from various sites in the Grand River watershed, Southern Ontario’s largest watershed and home to one million people. The soft tissue of adult mussels underwent enzyme digestion, followed by filtration to isolate undigested particles. Particles were removed and analyzed using Raman spectroscopy to determine their composition. Ten different polymers were identified in the sampled mussels, with polypropylene-co-polyethylene being the most prevalent. Microplastic particles were detected in 71% of mussels with the greatest number of particles observed in a single mussel being seven. No significant difference in microplastic particles per mussel was observed among the different sites sampled. A significant positive relationship between particles per mussel and size of upstream catchment was observed, but a relationship between particles per mussel and percentage of urban land use was not observed.

Freshwater mussels in an urban watershed: Impacts of anthropogenic inputs and habitat alterations on populations

The substantial increase in urbanization worldwide has resulted in higher emissions of wastewater to riverine systems near urban centers, which often impairs aquatic populations and communities. This study examined the effect of urbanization on freshwater mussel populations, including Species at Risk in two rivers receiving wastewater. The influence of anthropogenic activities was assessed in a watershed in the Laurentian Great Lakes basin, one that historically supported one of the most diverse mussel faunas in Canada. In the Grand River (ON), four sites along a 60km reach spanning from an upstream reference site to an urban-impacted downstream area were examined. In the Speed River, mussel populations at six sites along a 10km reach, selected to bracket specific anthropogenic inputs and structures were assessed. A semi-quantitative visual search method revealed that catch per unit effort in the Grand River declined by >60% from the upstream reference site to the area downstream of an urban center. The size (length) frequency distribution of the most abundant species, Lasmigona costata, was significantly (p≤0.008) different upstream of the majority of urban inputs (45–130mm) compared to downstream of the cities (85–115mm). In the Speed River, impoundments and wastewater treatment plants (WWTP) reduced both the diversity and catch per effort. Most striking were 84 and 95% changes in the number of mussels found on either side of two impoundments, and a 98% drop in mussels immediately downstream of a WWTP outfall. These population level effects of decreased abundance and underrepresentation of smaller mussels downstream of the urban area correspond to previously documented impacts at the biochemical and whole organism level of biological organization in wild mussels at this location. Our results demonstrate that poor water quality and physical barriers in urban environments continue to impair susceptible populations and communities of aquatic animals.

Phylogeography of the freshwater mussel species Lasmigona costata: testing post-glacial colonization hypotheses

Understanding genetic diversity across large spatial scales helps to reveal patterns of population structure. Mitochondrial DNA sequences and microsatellite loci were used to analyze the phylogeography of a common unionid species (Lasmigona costata) from the Laurentian Great Lakes and historically connected river drainages. Phylogeographic patterns were assessed to determine colonization routes into the Great Lakes following glacial recession. A suite of seven microsatellite loci were genotyped and a fragment of the mitochondrial gene COI was sequenced. Multiple analyses using microsatellite allele frequencies suggest at least two distinct genetic populations for L. costata. A total of seven hypothesized post-glacial dispersal scenarios were compared using isolation by distance to test the various dispersal models. Evidence was strongest for two post-glacial dispersal routes into the Great Lakes: one utilizing a connection between the Wabash and Maumee River watersheds, and one utilizing a connection between the Wisconsin River and Green Bay watersheds. A highly differentiated and monophyletic population of L. costata was identified in the Ozark Highlands, which may constitute a unique taxonomic entity.

Bioaccumulation of pharmaceuticals and personal care products in the unionid mussel Lasmigona costata in a river receiving wastewater effluent.

Freshwater mussels are frequently found in rivers receiving effluent from wastewater treatment plants (WWTP), and there is strong evidence that poor water quality is deleterious to freshwater mussel populations. WWTPs are among the main sources of pharmaceuticals and personal care products (PPCPs) in surface waters. We monitored 145 PPCPs in wild and caged mussels both upstream and downstream of the Kitchener WWTP in the Grand River, Ontario, as well as 118 PPCPs in water samples. Our objectives were to characterize the seasonal changes in PPCP concentrations in water, to calculate bioaccumulation factors (BAFs) of PPCPs in mussels, and to determine the chemical and physical properties of PPCPs driving the bioaccumulation. Seventy PPCPs were detected in water, and concentrations were highest in the summer or early fall, which corresponded to low river flow. Forty-three PPCPs from many pharmaceutical classes were detected in mussel tissues, including stimulants, a contrasting agent, anti-inflammatory drugs, anti-bacterial agents, antibiotics, antidepressants, antihistamines, progestins, and illicit drugs such as cocaine and amphetamines. The BAFs ranged from 0.66 for metformin to 32,022 for sertraline. Using partial least squares to predict BAFs based upon chemical properties, log KOC, Log KOW, and fugacity ratio (sediment) all had similar and positive loadings with BAFs (R(2)X = 0.70; caged mussels). BAFs of PPCPs in mussels were predictable from fugacity models that estimate bioconcentration factors using log KOW. Our study demonstrated that mussels readily bioaccumulate PPCPs, in a manner consistent with expectations based upon BCF models and the chemical characteristics of each compound.

Responses of biomarkers in wild freshwater mussels chronically exposed to complex contaminant mixtures.

Subcellular biochemical biomarkers are valuable early warning indicators of environmental contaminant effects. Thus, the present study evaluated several biomarkers and the relationships among them in wild freshwater mussels (Lasmigona costata) from a gradient of metal exposure and differential levels of other urban-related influences in the Grand River (ON, Canada). The biomarkers examined are related to metal exposure [gill ion and metal concentrations (Na, K, Ca, Mg, Cd, Cu, Ni, Pb and Zn)], oxidative status [reactive oxygen species (ROS), catalase (CAT), superoxide dismutase (SOD), antioxidant capacity (ACAP)], sulfhydryl (SH) metabolism [glutathione (GSH), protein sulfhydryl groups (SH protein), glutathione S-transferase (GST), glutathione reductase (GR)], and lipid peroxidation. Gill metal concentration increased proportionally to waterborne metal concentration and disturbances in osmotic and divalent cations (Ca and Mg) concentrations were observed. This suggests that the observed effects are associated with metal exposure, although simultaneous relationships with other contaminants are also possible. Oxidative status biomarkers (ROS, SOD, CAT and ACAP) were more sensitive to urban-influences than gill metal concentration. In contrast, biomarkers involving SH metabolism (GSH, SH protein, total SH, GR and GST) were more correlated with gill metal concentration. Oxidative damage occurred when both metal and urban-related influences were high. Mechanistically, the way of dealing with oxidative stress changed when mussels were exposed to high levels of contaminants. The reduction in ROS content, SOD and CAT activity, and ACAP accompanying the stimulation of detoxification metabolism via SH (GSH and SH protein contents, GST and GR activities) and their association with gill metal concentration are discussed.

Evidence of oxidative stress in wild freshwater mussels (Lasmigona costata) exposed to urban-derived contaminants

The physiological effect of complex mixtures of anthropogenic contaminants on aquatic organisms is not well understood. This study employed a suite of sub-cellular biomarkers and general health measurements to assess the effect of urban-derived contaminants on wild freshwater mussels. Adult Lasmigona costata were collected from four sites in the Grand River (ON, Canada) that receive incremental amounts of municipal wastewater effluents and road runoff. Biomarkers of metal exposure, oxidative stress, and general health were examined in the gills of wild mussels. Concentrations of nine metals as well as the metal-binding protein, metallothionein (MT), were significantly higher (p<0.05) in mussels living downstream of the urban area. For example the concentrations of Pb, Cr and Zn were five-fold, and Ag more than 20 fold higher in mussels collected downstream of 11 municipal wastewater treatment plants and four cities compared to levels in upstream mussels. Downstream mussels showed evidence of oxidative stress, such that lipid peroxidation (LPO) (as thiobarbiturate reactive substances) was significantly elevated and the antioxidant capacity against peroxyl radicals (ACAP) was significantly decreased (p<0.01) in downstream mussels compared to upstream mussels. Regarding general health indicators, although gill lipid concentrations were similar across sites, protein concentration was significantly (p<0.001) higher in mussels collected from the upstream reference site compared to all downstream sites. The trends observed indicate that there are physiological effects in mussels associated with chronic exposure to complex urban inputs and that some biomarkers respond to municipal wastewater effluent and road runoff exposure in a cumulative manner. The observed oxidative stress response (ACAP) along with the elevation in MT, suggest that even though the defense mechanisms in the chronically exposed mussels have been activated, there is still an excess of reactive oxygen species that result in oxidative damage. The physiological effects of exposure reported in this study correspond with previously reported whole-organism impacts and declines in freshwater mussel populations in the urban-impacted region of this watershed.

The impact of municipal wastewater effluent on field‐deployed freshwater mussels in the Grand River (Ontario, Canada)

To examine effects of municipal wastewater effluent (MWWE) on sentinel organisms, the authors deployed caged freshwater mussels (Lasmigona costata) in the Grand River (ON, Canada) upstream and downstream of an MWWE outfall. Passive sampling devices were deployed alongside caged mussels to confirm exposure. Biomarkers of xenobiotic biotransformation, oxidative stress, estrogenicity, and immunomodulation were investigated. Elevated concentrations of selected pharmaceutical and personal care products (PPCPs) and a natural estrogen (estrone) were found at the downstream sites. Mussels caged downstream of the effluent for 2 wk showed minimal evidence of exposure, while those deployed for 4 wk exhibited significantly higher levels of lipid peroxidation (LPO) and glutathione S-transferase (GST) activity, demonstrating that MWWE-exposed mussels exhibit increased activity in xenobiotic conjugation and oxidative stress. With respect to immune responses, a significant increase in plasma lysozyme activity and hemocyte viability was observed in MWWE-exposed mussels. Vitellogenin (vtg)-like protein in male mussels showed a trend toward induction after 4 wk of deployment at the first downstream site, but mean levels were not significantly different. Discriminant function analysis indicated that mussels deployed for 4 wk upstream and downstream of the MWWE discharge could be discriminated on the basis of LPO, GST, plasma lysozyme, and vtg responses. The physiological stress observed in caged mussels indicates that wild mussels chronically exposed to MWWE in this ecosystem would also be negatively impacted.

Isolation and fractionation of gill cells from freshwater (Lasmigona costata) and seawater (Mesodesma mactroides) bivalves for use in toxicological studies with copper

Gills cells of the freshwater mussel Lasmigona costata and the seawater clam Mesodesma mactroides were isolated (mussel: chemical dissociation; clam: mechanical dissociation) and fractionated (Percoll gradient) into Fractions I and II. Mitochondrial dyes (DASPEI: mussel; MitoTracker(®): clam) and Na(+), K(+)-ATPase activity measurement were used to distinguish between cells of Fractions I and II. For mussel and clam, 80.5±1.5 and 48.3±3.2% of cells were in Fraction II, respectively. For both species, cells of Fraction II had higher fluorescence emission and higher enzyme activity than those of Fraction I, being characterized as 'cells rich in mitochondria'. Cells of Fraction II were kept in saline solutions approximating the ionic composition of hemolymph either under control conditions (no Cu addition) or exposed (3h) to copper (Cu: 5, 9 and 20μg Cu/L). Cell viability and Cu and Na(+) content were measured. For both species, Cu content was higher and Na(+) content was lower in cells exposed to 20μg Cu/L. Furthermore, a strong negative correlation was observed between cell Na(+) and Cu content in the two bivalve species, indicating a possible competition between Cu and Na(+) for ion-transporting mechanisms or binding sites at gill cells of Fraction II. Considering that Cu is an ionoregulatory toxicant in aquatic invertebrates, these preliminary toxicological data support the idea of using isolated gill cells rich in mitochondria to study the mechanisms underlying the acute toxicity of waterborne Cu in freshwater and marine bivalves.

Cumulative impacts of urban runoff and municipal wastewater effluents on wild freshwater mussels (Lasmigona costata)

Aquatic biota living in urban watersheds, are chronically exposed to a complex mixture of contaminants from various sources, including municipal wastewater effluents and road runoff. This study examined the general condition, immune function and contaminant load of wild freshwater mussels collected from a large urbanized river over three consecutive field seasons. Four study sites along the Grand River (ON) were selected to represent an incremental contaminant exposure, such that mussels collected from the final downstream site were exposed to the cumulative inputs from 11 municipal wastewater treatment plants and road runoff from four cities. Wild mussels collected downstream of the urban area had significantly lower (p<0.05) condition factor and did not live as long (significantly reduced mean age) as the mussels collected upstream of the cities. There appears to be a trend of increasing proportions of gravid females at the downstream sites, but whether this trend indicates feminization of the mussel population or is simply an artifact of sampling effort is unclear. An examination of hemocyte phagocytosis revealed a pattern of increasing immune activity at the downstream sites, but only in one of the years sampled. The significant and cumulative increase in Cu, Pb, Zn, Al, Cr, and Ni in the gills of downstream mussels indicates that metals are bioavailable in this ecosystem and that tissue concentrations increase with multiple urban inputs. While the complex nature of the exposure prevents identification of the cause(s) of the observed effects, some contaminants such as ammonia and chloride reach levels known to be toxic to freshwater mussels at the downstream sites. These results indicate that chronic exposure to multiple contaminants negatively impacts mussel health and longevity and corroborates previous assumptions that waterborne contaminants contributed to the decline of the freshwater mussel populations in this watershed.

Evaluating the Mussel Fauna of the Chagrin River, a State-Listed “Scenic” Tributary of Lake Erie

Levels of environmental protection vary among watersheds, and assessing how well conservation efforts protect threatened faunal groups is a critical need for management. Almost the entire 114 km of the Chagrin River is designated as scenic by the state of Ohio, which implies good water quality and community efforts to maintain and improve water resource integrity. We examined mussel diversity and abundance across 30 sites. The mussels present remained largely restricted to the upper reaches. One species, Lampsilis radiata luteola, dominated the assemblage of the upper Chagrin, which now includes only six additional species, none of which are very abundant: Lasmigona costata, Lasmigona compressa, Pyganodon grandis, Strophitus undulatus, Utterbackia imbecillis, and Anodontoides ferussacianus. One additional species, Lampsilis cardium, was the only species found living in the lower Chagrin. Applying the Shannon index of diversity indicated that the Chagrin River has a more depauperate fauna than neighboring watersheds, and therefore, the current passive conservation efforts may be insufficient to protect these small isolated populations of remaining species.

Isolation and characterization of microsatellite loci in the freshwater mussel Lasmigona costata (Bivalvia: Unionoida)

Eleven microsatellite loci for the freshwater mussel Lasmigona costata were isolated and characterized. Genetic screening of individuals from four rivers in southern Ontario confirmed that all loci were highly polymorphic. These loci should prove useful in a range of studies from fine- and coarse-scale population structure and gene flow to reproductive success of individuals.

The Mussels of Muddy Creek on Erie National Wildlife Refuge

A qualitative mussel survey was performed on Muddy Creek, a tributary to French Creek in Crawford County, PA, within the boundaries of the Erie National Wildlife Refuge. Riffle-run-pool sequences were sampled at 20 locations in the study area using visual and tactile timed-search techniques. Live specimens represented by 22 species were encountered at a rate of 54 individuals per person-hour and included the federally-endangered Pleurobema clava (clubshell) and Epioblasma torulosa rangiana (northern riffleshell) as well as four Pennsylvania state-imperiled species. Evidence of recruitment in the clubshell population was found in excavated quadrats and by hand-collecting. Brillouin diversity indices ranged from 0.35–2.88 over the study area, with a mean (SD) of 1.67 (0.59). The three most abundant species were Actinonaias ligamentina, Amblema plicata, and Lasmigona costata, while the three most rare were Anodontoides ferussacianus, E. torulosa rangiana, and Villosa fabalis. The high diversity of mussels along with the presence of federally listed and state-imperiled species warrants a pro-active approach to future protection of the aquatic resources of Muddy Creek.

Diversity of the Unionidae in the Rocky River, Ohio

ABSTRACT We surveyed the freshwater mussels (Mollusca: Bivalvia: Unionidae) of the Rocky River, Ohio, USA, a river surrounded by suburban development. The survey produced 253 live unionid specimens and 572 empty shells. Most occurred in the west branch. Species living in the West Branch Rocky River included Anodontoides ferussacianus, Elliptio dilatata, Lampsilis cardium, Lampsilis radiata luteola, Lasmigona compressa, Lasmigona costata, Pyganodon grandis grandis, Strophitus undulatus undulatus, and Toxolasma parvus. Two additional species (Utterbackia imbecillis and Villosa iris iris) were represented as dead shells. Three species (Potamilis alatus, Quadrula quadrula and Leptodea fragilis) were found only near the mouth of the main stem of the river. No live mussels were found in the east branch. Although mussel diversity changed along the river, the presence of healthy mussel populations downstream of two expanding suburban areas suggests that these developments so far have minimally impacted populations.

An Analysis of Diversity in Freshwater Mussels (Bivalvia: Unionidae) of the Cuyahoga and Rocky River Watersheds (Ohio, USA) Based on the 16S rRNA Gene

The continued loss of freshwater unionid mussel species in the Great Lakes region, and particularly from Lake Erie, raises the question of how much phylogenetic and genetic variation remain in the watershed. The introduction of molecular markers into population biology offers one reproducible technique for assessing this variation. A fragment of the 16S rRNA gene of mitochondrial DNA has previously been used to infer phylogenetic relationships in the family Unionidae. Therefore, we reanalyzed these published molecular data with the addition of 12 species from the Cuyahoga and Rocky rivers in northeast Ohio. Both rivers drain to Lake Erie. The species assessed were Pyganodon grandis, Lasmigona complanata, Lasmigona compressa, Lampsilis radiata luteola, Fusconaia flava, Potamilus alatus, Strophitus undulatus, and Toxolasma parvus, for which published data were unavailable, and northern specimens of four wide ranging species, Lasmigona costata, Leptodea fragilis, Utterbackia imbecillis, and Quadrula quadrula. The resulting phylogenetic tree remained consistent with the accepted major taxonomic divisions in the Unionidae, and it indicates that these rivers still contain a phylogenetically diverse assemblage. However, the most abundant species all are members of the Anodontinae. Intraspecific variation in these unionid species was low, even where results were compared to published sequences on individuals from distant watersheds. One exception was a unique haplotype of Q. quadrula that differed at more base sites than is generally found for many congeneric species.

Post-Extirpation Recovery of the Freshwater Mussel (Bivalvia: Unionidae) Fauna in the Upper Illinois River

ABSTRACT Freshwater mussels are recolonizing the upper Illinois River following their extirpation by pollution in the early part the 20th century. From 1990 to 1999, we collected 332 individuals of 18 species between river miles 232.0 and 271.2. Age structure of the community suggests mussels began recolonizing in the early 1980s, which coincides with improvements in water quality and the upper river fish community. We found four sites with five or more species, which we considered to be recently formed mussel beds. We collected live individuals of six species (Actinonaias ligamentina, Alasmidonta marginata, Lampsilis cardium, Lasmigona costata, Pleurobema sintoxia, and Strophitus undulatus) thought to have been extirpated from the entire Illinois River mainstem, and one species (Anodonta suborbiculata) that has recently expanded its range into the upper river. Upper Illinois River tributaries and lower reaches of the Illinois River harbored source populations for the recolonizing mussels. Although the present community does not approximate the pre-disturbance fauna, these data show that given adequate time and improved conditions, mussel communities may recover from a devastating disturbance.

Relationship between the spatial distribution of freshwater mussels (Bivalvia: Unionidae) and the hydrological variability of rivers

Hydrological variability refers to the differences in the patterns of flow among rivers. Drainage basins in southwestern Ontario and southeastern Michigan were selected a priori using records of flow variability. Hydrological variability was then used as a macrohabitat measure of mussel habitat. The distribution and relative abundance of mussels were determined in drainage basins of two hydrologically different types, three event responsive (i.e., hydrologically flashy) and three stable (i.e., hydrologically stable). Eleven event and 10 stable sites were sampled once each from 18 to 30 August 1993. Fifteen species of unionids were found in the study area (13 in event rivers and 9 in stable rivers), with different relative abundances in each regime. Multivariate analyses revealed that there are distinct mussel communities based on the hydrological variability of the river. Amblema plicata, Pyganodon grandis, and Fusconaia flava characterized event sites and Elliptio dilatata, Lampsilis radiata, and Lasmigona costata characterized stable sites. We propose that some unionids can be associated with river types with specific hydrological features and their distribution can be predicted using flow-related stream attributes.