Mussel Diversity Research Articles

Modeling changes in freshwater mussel diversity in an agriculturally dominated landscape

AbstractFreshwater mussels perform critical ecosystem functions and provide many valuable ecological services. However, anthropogenic effects have severely decreased mussel diversity and abundance at both local and regional scales. Understanding how human disturbances, particularly landuse change, and fish assemblages are related to mussel assemblages is essential for effective conservation and restoration. We used Random Forests (RF) regressions, a data-mining technique, to examine how mussel species richness, total abundance, and abundances of individual species were related to land use at different spatial scales and to fish species richness and abundance in east central Illinois, USA. Mussel richness increased with % wetlands, % open water, % grassland in the riparian zone, and total fish abundance; decreased with % urban land in the riparian zone; but responded poorly to fish species richness and fish Index of Biotic Integrity (IBI) scores. Total mussel abundance mainly increased with total fish abun...

The influence of two differently sized dams on mussel assemblages and growth

Dams have been shown to impact freshwater mussels. We examined how mussels respond to differently sized dams (18 vs. 4 m) on the St. Croix River and its tributary, the Sunrise River. We hypothesized that: mussel density and growth rate would be greater downstream of the smaller dam due to the relatively greater food subsidies and temperature effects of the reservoir above it; and the effects of the small dam would moderate downstream as the localized impacts of the dam were reduced. We quantitatively sampled mussels upstream and downstream of the dams. For a common species, Actinonaias ligamentina, we ascertained growth rates by measuring successive growth rings. The highest mussel richness and diversity were upstream and downstream of the large dam. Higher mussel density was found immediately below the small dam but declined downstream. A. ligamentina downstream of the small dam grew faster and were larger than individuals in other reaches. Food availability and temperature appeared to influence mussel density and growth rate for A. ligamentina downstream of the small dam. This study provides information that may help managers decide whether to remove small dams or to maintain them because of the unique mussel habitats below these structures.

Historical vs. Current Biological Assemblages in the Little Choctawhatchee Watershed, Southeastern AL

The Little Choctawhatchee River watershed is currently affected by effluents from wastewater treatment plants and may be subject to impoundment as a water supply reservoir. We used historical data from the literature and the results of recent surveys (2006–2008) to assess past and current patterns of the diversity of mussels, crayfishes, and fishes throughout the river basin in order to gain information about the past and potential future effects of degraded water and habitat quality to the fauna of this region. Our results suggest that mussel assemblages have declined dramatically from historical levels, with only three of the eleven historically recorded species found. Several statelisted mussel species and candidates for federal protection formerly present are now believed extirpated from the watershed. Fish and crayfish collections during 2006–2008 were more diverse (52 and 6 species) than historical records indicated (39 and 3 species). This increased diversity was probably due to a more concentrated sampling effort in the current study than in the past. Future impoundment may cause further and possibly drastic changes to the remaining freshwater faunal diversity.

Biodiversity on the brink: an assessment of conservation strategies for North American freshwater mussels

The North America freshwater mussel fauna has suffered an inordinately high recent extinc- tion rate, and the small size and isolation of many remaining populations portends a continued diminish- ment of this fauna. Causes of extinction and imperil- ment are varied but revolve around massive habitat loss, deterioration, and fragmentation. The National Strategy for the Conservation of Native Mussels, published in 1997, has guided efforts to address this crisis. Considerable progress has been made toward several of the Strategies' goals, particularly increasing our knowledge of mussel biology, promoting mussel conservation, and development of techniques for captive mussel propagation. However, mussel conser- vation should focus more directly on reducing frag- mentation through bold and aggressive habitat restoration. In addition to dam removal, improvement in dam tailwater flows, and restoration of channelized streams, identification of factors that eliminated mussels from many otherwise intact streams is critical. Translocation and captive propagation will be key elements in reestablishing mussel assemblages in restored habitats, but these techniques should be used with caution and primarily to increase the occurrence of a species throughout its historical range. Conserving mussel diversity in an ever-changing world is depen- dent on promoting the natural, long-term sustainability and evolutionary potential of mussel populations.

Multifactorial model of habitat, host fish, and landscape effects on Louisiana freshwater mussels

Unionoids are important in aquatic ecosystems, but despite their continued decline in diversity, few multifactorial studies have been done to identify determinants of their distribution and diversity. We studied the effects of multiple environmental factors on species richness and abundance at 65 sites in 6 major watersheds in the Pine Hills region, Louisiana. We surveyed in-stream habitat variables, land use/cover, and the co-occurring fish assemblages in 2nd- through 6th-order streams. A structural equation model suggested that 2 major latent variables were important: 1) reduced habitat disturbance, influenced by lower current velocity, substratum composed mostly of fine sediments, and increasing stream order, and 2) agricultural land use in riparian corridors and associated reduced water quality. These 2 latent variables explained 84% of mussel species richness and 48% of total mussel abundance. Mussel, but not host-fish species richness and abundance increased with stream order. Sites in the lower river basins had increased amounts of fine sediments and lower current velocities. We suggest that the lower river basins have extensive riparian wetlands that ameliorate the effects of frequent floods, thus mediating hydrologic disturbance and increasing mussel diversity.

The role of fecundity and reproductive effort in defining life‐history strategies of North American freshwater mussels

Selection is expected to optimize reproductive investment resulting in characteristic trade-offs among traits such as brood size, offspring size, somatic maintenance, and lifespan; relative patterns of energy allocation to these functions are important in defining life-history strategies. Freshwater mussels are a diverse and imperiled component of aquatic ecosystems, but little is known about their life-history strategies, particularly patterns of fecundity and reproductive effort. Because mussels have an unusual life cycle in which larvae (glochidia) are obligate parasites on fishes, differences in host relationships are expected to influence patterns of reproductive output among species. I investigated fecundity and reproductive effort (RE) and their relationships to other life-history traits for a taxonomically broad cross section of North American mussel diversity. Annual fecundity of North American mussel species spans nearly four orders of magnitude, ranging from < 2000 to 10 million, but most species have considerably lower fecundity than previous generalizations, which portrayed the group as having uniformly high fecundity (e.g. > 200000). Estimates of RE also were highly variable, ranging among species from 0.06 to 25.4%. Median fecundity and RE differed among phylogenetic groups, but patterns for these two traits differed in several ways. For example, the tribe Anodontini had relatively low median fecundity but had the highest RE of any group. Within and among species, body size was a strong predictor of fecundity and explained a high percentage of variation in fecundity among species. Fecundity showed little relationship to other life-history traits including glochidial size, lifespan, brooding strategies, or host strategies. The only apparent trade-off evident among these traits was the extraordinarily high fecundity of Leptodea, Margaritifera, and Truncilla, which may come at a cost of greatly reduced glochidial size; there was no relationship between fecundity and glochidial size for the remaining 61 species in the dataset. In contrast to fecundity, RE showed evidence of a strong trade-off with lifespan, which was negatively related to RE. The raw number of glochidia produced may be determined primarily by physical and energetic constraints rather than selection for optimal output based on differences in host strategies or other traits. By integrating traits such as body size, glochidial size, and fecundity, RE appears more useful in defining mussel life-history strategies. Combined with trade-offs between other traits such as growth, lifespan, and age at maturity, differences in RE among species depict a broad continuum of divergent strategies ranging from strongly r-selected species (e.g. tribe Anodontini and some Lampsilini) to K-selected species (e.g. tribes Pleurobemini and Quadrulini; family Margaritiferidae). Future studies of reproductive effort in an environmental and life-history context will be useful for understanding the explosive radiation of this group of animals in North America and will aid in the development of effective conservation strategies.

Spatial and Temporal Trends of Freshwater Mussel Assemblages in the Meramec River Basin, Missouri, USA

Abstract The Meramec River basin in eastcentral Missouri has one of the most diverse unionoid mussel faunas in the central United States with 40 species identified. Data were analyzed from historical surveys to test whether diversity and abundance of mussels in the Meramec River basin Big, Bourbeuse, and Meramec rivers, representing 400 river miles decreased between 1978 and 1997. We found that over 20y, species richness and diversity decreased significantly in the Bourbeuse and Meramec rivers but not in the Big River. Most species were found at fewer sites and in lower numbers in 1997 than in 1978. Federally endangered species and Missouri Species of Conservation Concern with the most severe temporal declines were Alasmidonta viridis, Arcidens confragosus, Elliptio crassidens, Epioblasma triquetra, Fusconaia ebena, Lampsilis abrupta, Lampsilis brittsi, and Simpsonaias ambigua. Averaged across all species, mussels were generally being extirpated from historical sampling sites more rapidly than colonization was occurring. An exception was one reach of the Meramec River between river miles 28.4 and 59.5, where mussel abundance and diversity were greater than in other reaches and where colonization of Margaritiferidae, Lampsilini, and Quadrulini exceeded extirpation. The exact reasons mussel diversity and abundance have remained robust in this 30mile reach is uncertain, but the reach is associated with increased gradients, few long pools, and vertical rock faces, all of which are preferable for mussels. Complete loss of mussel communities at eight sites 16 with relatively diverse historical assemblages was attributed to physical habitat changes including bank erosion, unstable substrate, and sedimentation. Mussel conservation efforts, including restoring and protecting riparian habitats, limiting the effects of instream sand and gravel mining, monitoring and controlling invasive species, and protecting water quality, may be warranted in the Meramec River basin.

Pearl mussels (Bivalvia, Margaritiferidae, Dahurinaia) from the Amur River basin

Until recently it was considered that in the Amur basin there are four species of pearl mussels of the genus Dahurinaia (Bogatov et al., 2003) differing in the curvature of the “frontal” (or more precisely max� imum convex) section of the valves: D. prozorovae Bog. et Star. in: Bogatov et al., 2003; D. dahurica (Midd., 1850); D. ussuriensis Bog., Proz. et Star., 2003; and D. tiunovae Bog. et Star., 1988 (the order of the mentioned species corresponds to the increase in valve convexity). Recently, Klishko in the journal Zoological Herald (2008) published a paper on pearl mussels collected in the upper part of the Amur basin (Ingoda, Omon, Argul, Budumkan, Ilya, and Unda rivers) and in the closed Arei Lake that in the Pleistocene was connected with the Amur basin. The author of the paper discov� ered in this region six species of pearl mussels, among which, besides those listed above, she mentioned D. sujfunensis Moskv., 1973, previously known only from the basin of the Razdolnaya River (south of Pri� morskii krai) and a species new to science D. transba� icalica Klishko, 2008 found in Arei Lake and the Ingoda and Onon rivers. The study by Klishko of the shell morphology, hinge apparatus, and soft body of Amur pearl mussels demonstrated allegedly reliable features of similarity in this species of the genus Dahu� rinaia with species of the European genus Marga� ritifera. In addition, the recorded high modern taxo� nomic diversity of pearl mussels (6 species) and known findings of fossil forms of this group of mollusks enabled Klishko to speak about Transbaikalia as “a possible center of their origin and evolutionary devel� opment” (p. 299).

The Evolutionary Allure of Mussels

Genetic studies have revealed that mussel diversity in North America is even higher than past studies suggested, meaning species that were once thought to be widely distributed could in fact be imperiled.

Nearly Buried, Mussels Get a Helping Hand

North America is home to a record diversity of freshwater mussels with dazzling reproductive strategies and key ecological roles. But can they withstand the hard knocks of a modern world?

Science Podcast

The show includes biomaterials, preserving mussel diversity, early hunting technology, and more.

Freshwater Mussels of the Powell River, Virginia and Tennessee: Abundance and Distribution in a Biodiversity Hotspot

The Powell River, located in southwestern Virginia and northeastern Tennessee, is a tributary of the Clinch River in the headwaters of the Tennessee River system. Historically, the Powell River had a diverse freshwater mussel fauna of 46 species. Various surveys conducted over the past century have recorded a decline in mussel densities and diversity throughout much of the river, due to historical and on-going anthropogenic impacts. In 2008 and 2009, random timed-search, systematic search, and quadrat sampling of 21 sites were completed to document species richness, relative abundance, density, and size-class structure of resident mussel populations. During the random timed search (10 sites) and systematic search (10 additional sites) portions of the survey (n=1,399 person-h), surveyors collected 15,084 mussels of 29 species. Catch-per-unit-effort ranged from 0.33 to 22.12 mussels/person-h. We observed living individuals (n = 412) of 9 of the 17 federally endangered species previously reported in the river (Dromus dromas, Epioblasma brevidens, E. triquetra, Fusconaia cor, Lemiox rimosus, Plethobasus cyphyus, Quadrula cylindrica strigillata, Q. intermedia, and Q. sparsa) and two candidate species for federal protection (Pleuronaia dolabelloides and Ptychobranchus subtentum). We recorded 19 species from 18 sites, including 5 endangered species during quadrat sampling efforts. Mean densities ranged from 0.00 to 2.25 mussels/m2 among sites sampled. Relatively recent recruitment was also evident for 16 of 29 species; including 4 endangered species (D. dromas, E. brevidens, Q. intermedia, and Q. sparsa). The mussel fauna of the lower Powell River continues to represent one of the most diverse in the United States. Outside of the Powell River, only 2 or 3 populations remain for most of the listed species extant in the river. Given these qualities, the Powell River deserves recognition as a location for focused conservation efforts to protect its diverse mussel assemblage.

A Qualitative Freshwater Mussel (Bivalvia: Unionidae) Survey of the Lamine and Blackwater River Basins, Missouri

From 2003 to 2006 freshwater mussels (Bivalvia: Unionidae) were qualitatively surveyed in the Lamine River basin, a Missouri River tributary in west central Missouri. Timed searches (average time/site = 1.9 hr) were conducted to ascertain the distribution, diversity and abundance of unionids in the basin. A total of 45 sites were sampled and 5287 individuals from 27 species were observed, including Ligumia recta, a Missouri Species of Conservation Concern. The invasive Corbicula fluminea was observed live at nearly all sampling locations throughout the basin. Overall average Catch per Unit Effort (CPUE, live individuals/person hr) was 54.7 and ranged from 0 to 417.6. Amblema plicata was the most abundant species, with 2989 individuals recovered at 34 sites, representing 56.5% of the live mussels collected. Leptodea fragilis and Potamilus alatus were the most widely distributed species, each occurring at 36 sites. The Lamine basin unionid fauna (30 historic, 27 extant species) is more diverse than that of prairie streams in the Missouri River system and is similar to Ozark rivers. Given the anthropogenic impacts occurring in the basin, the Lamine River basin has a diverse freshwater mussel fauna. A number of species rich mussel assemblages were observed in the mainstem Lamine River. Continuing with management objectives to maintain water quality, improve aquatic habitat, and work with private landowners to stabilize streambanks and improve riparian zones will be necessary to maintain the diversity of freshwater mussels in the Lamine River basin.

Annotated synonymy of the recent freshwater mussel taxa of the families Margaritiferidae and Unionidae described from Florida and drainages contiguous with Alabama and Georgia

Freshwater habitats of the southeastern U.S. support a high diversity of mussels in the families Margaritiferidae and Unionidae, order Unionoida. River systems of Florida and drainages contiguous with Alabama and Georgia are known to be inhabited by 65 mussel species, representing about 20% of the North American fauna north of Mexico. This diversity led early naturalists to describe a large number of species which were based primarily on shell characters. There are 149 nominal taxa described from the study area, 72 (48%) in Florida, 68 (46%) in Georgia, and nine (6%) in Alabama. Most of the Florida taxa were descibed from the St. Johns River drainage. In Georgia, the majority of taxa were described from the Chattahoochee and Flint River drainages. Type localities were restricted herein for several taxa with vague specimen collection information reported in the original description. Of the 149 taxa described from the study area, it was determined that 41 (28%) are valid species. This represents 64% of the recognized mussel fauna that occur in the study area. The remaining 23 (35%) recognized species in the study area were described from outside drainages, and one (1%) species is undescribed. There are 40 described and one undescribed species endemic to the study area.

Assessing sampling adequacy of mussel diversity surveys in wadeable Illinois streams

Freshwater mussels are one of the most imperiled groups of animals in North America. Effective resource management and conservation efforts require reliable estimates of species diversity and their distributions. However, sampling protocols for qualitative mussel surveys have not been well established and tested. Furthermore, the sampling effort required for a given data-quality goal (90% of species captured) often varies substantially among sites, and application of a standard effort probably would introduce bias into assemblage comparisons. We tested the sampling adequacy of time-based hand searches. We conducted 16-man-hour (mh) searches at each of 18 wadeable stream sites in Illinois that differed widely in environmental factors and historical species diversity and collected 27 to 942 individuals and 5 to 18 species per site. We accounted for imperfect species detectability by using the Chao-1 richness estimator and measured sampling adequacy as the % of the estimated number of species sampled. Four-mh searches, a frequently used effort, captured 15 to 100% of all species with an average of 61%, and yielded estimates of richness that were not significantly correlated with the estimated total richness (Pearson’s r = 0.39, p > 0.05). Ten-mh searches captured >70% of all species at >70% of sites and resulted in a significant correlation between observed and estimated richness (Pearson’s r ≥ 0.78, p < 0.01). A Random Forests (RF) model based on watershed and habitat characteristics (e.g., stream size and dominant substrate types) accounted for 45% of the variance in sampling adequacy of 4-mh searches. Sampling adequacy decreased with increasing stream size and substrate size but increased with % forest in the riparian zone and logs in the stream. A 2nd RF model was developed to predict the number of man-hours required to capture 70 ± 3% of all species, and it accounted for 37% of the variance. Our findings should serve as a guide for setting standard sampling efforts for mussel surveys in Illinois and probably other midwestern states and should provide a baseline for setting site-specific efforts. Our modeling approach is of general applicability for addressing sampling-adequacy issues in studies of any assemblage.

Species traits and environmental conditions govern the relationship between biodiversity effects across trophic levels

Changing environments can have divergent effects on biodiversity-ecosystem function relationships at alternating trophic levels. Freshwater mussels fertilize stream foodwebs through nutrient excretion, and mussel species-specific excretion rates depend on environmental conditions. We asked how differences in mussel diversity in varying environments influence the dynamics between primary producers and consumers. We conducted field experiments manipulating mussel richness under summer (low flow, high temperature) and fall (moderate flow and temperature) conditions, measured nutrient limitation, algal biomass and grazing chironomid abundance, and analyzed the data with non-transgressive overyielding and tripartite biodiversity partitioning analyses. Algal biomass and chironomid abundance were best explained by trait-independent complementarity among mussel species, but the relationship between biodiversity effects across trophic levels (algae and grazers) depended on seasonal differences in mussel species' trait expression (nutrient excretion and activity level). Both species identity and overall diversity effects were related to the magnitude of nutrient limitation. Our results demonstrate that biodiversity of a resource-provisioning (nutrients and habitat) group of species influences foodweb dynamics and that understanding species traits and environmental context are important for interpreting biodiversity experiments.

A DNA-barcoding approach to identifying juvenile freshwater mussels (Bivalvia:Unionidae) recovered from naturally infested fishes

AbstractWe developed a multilocus deoxyribonucleic acid (DNA)-barcoding approach to identify newly transformed juvenile mussels collected from naturally infested fishes in a federally protected waterway that is home to a diverse mussel community, the St Croix River (Minnesota/Wisconsin, USA). We used new and publicly available data downloaded from GenBank to build reference databases for identified adult mussels. We assessed the efficacy of the mitochondrial loci cytochrome oxidase c subunit I (COI) and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (ND1) for DNA barcoding. We concluded that the barcoding gap between average intra- and interspecific genetic distances is wider for ND1 than for COI, but both loci perform well for species identification in character-based phylogenetic analyses. Almost every species formed a monospecific clade with high bootstrap and posterior-probability support. We obtained newly transformed juvenile mussels by collecting individuals of 3 different fish species t...

The importance of land use/land cover data in fish and mussel conservation planning

Freshwater fish and mussel diversity is declining at an alarming rate across North America. Human land uses and disturbances within watersheds have been implicated as the primary cause of declines. In this paper, we demonstrate the utility of land use/land cover (LULC) variables in species distribution modeling and conservation planning using a straightforward multiscale approach for prioritizing freshwater fish and mussel conservation areas in the upper Green River catchment (Ohio River basin, USA). We developed distribution and species richness models for 10 uncommon fishes and 14 rare mussels using multiscale landscape data and boosted regression tree (BRT) analyses based on LULC composition and pattern, geology composition, and soil composition data. We then used probability of occurrence, endemicity, prevalence, trend and range of individual species to estimate the conservation value of each stream reach. Conservation areas were defined for three spatial scales nested within the catchment management zone (focal areas, riparian management buffer and subcatchment management zone) using a simple optimization technique. Priority conservation areas were located primarily in the eastern (upper Green River) and southern (upper Barren River) portions of the catchment. We found that focal species richness is explained most by soil composition in the subcatchment. However, nested within the subcatchment scale focal species richness responded positively to percent forest and negatively to patch density of developed/exposed land in the reach buffer. For both the reach and riparian buffers, retaining forested tracts of land and limiting the level of development and fragmentation would benefit the focal species.

Freshwater Mussel (Bivalvia: Unionidae) Distributions and Habitat Relationships in the Navigational Pools of the Allegheny River, Pennsylvania

The main-stem Allegheny River is nationally recognized for its freshwater mussel (Unionidae: Bivalvia) diversity; however, habitat disturbance and degradation may have triggered the decline and loss of mussel communities in the lower river, where lock and dam structures restrict the free flow of water and sand and gravel removal threaten limited habitat. We examined mussel diversity and abundance across 75 transects throughout navigational pools and recorded 21 live native mussel species, including federally endangered Pleurobema clava (Clubshell) and Epioblasma torulosa rangiana (Northern Riffleshell) and several species with state endangered or threatened status. Riverine species richness and counts were significantly higher in the most-upstream portions of the upper pools, indicating that areas with consistent flows and suitable substrate just downstream of the dams may provide refugia for riverine freshwater mussel species. Sand, gravel, cobble, boulder, and organic debris had significant positive effects on riverine and facultative counts, while clay, bedrock, and woody debris had significant negative effects. Silt and woody debris had significant negative effects on riverine species richness, and sand and gravel had significant positive effects. These data will help identify sensitive areas for future protection and provide baseline data for monitoring future trends. The protection of relatively shallow areas with suitable substrates not yet impacted by dredging operations will be important to sustain remaining freshwater mussel populations in these pools.

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.