Mussel Diversity Research Articles

Application of OEPA-Produced Biotic Indices and Physical Stream Measurements to Assess Freshwater Mussel (Unionidae) Habitat in the Upper Mahoning River, Ohio

Freshwater mussels continue to experience declines in population numbers in response to changing environments. Identifying aspects of the environment associated with the presence and abundance of mussels in small streams is challenging where past records are minimal. Thus, we sought to produce models of habitat favoring mussel species richness and abundance in the upper Mahoning River using data collected in 2 ways: (1) surveying sites deemed as suitable habitat via observation and (2) surveying existing Ohio Environmental Protection Agency (OEPA) sites used to evaluate water quality and aquatic life through biotic indices. Detailed physical measurements were added at each survey site. Surveys identified 963 freshwater mussels of 11 species. The more-forested Eagle Creek contained an abundant mussel assemblage compared to the rest of the Upper Mahoning River, yet this stream was still dominated by just 1 common species, Lampsilis siliquoidea (Fatmucket). Drainage area alone correlated with mussel richness and abundance, but a complex model of multiple characteristics provided equivalent predictive power to assess how variation in environmental components may enhance the likelihood of mussel presence. The OEPA composite qualitative habitat evaluation index, which encompasses substrate, instream cover, channel morphology, riparian zone, pool quality, and map gradient, also was indicative of greater mussel diversity.

Prehistoric Molluscan Faunas of the Yazoo River, Mississippi, USA: Archaeological Perspectives for Modern Conservation

ABSTRACTArchaeological faunal assemblages can provide data valuable to modern conservation ecology. For example, while freshwater mussels (Bivalvia: Unionidae, Margaritiferidae) are common constituents in the archaeological record of North America, today they are one of the world’s most imperiled faunal groups. Efforts to aid habitat restoration, population growth, and species reintroduction can be informed by studies of prehistoric mussel assemblages. These data can provide a historical perspective, cataloging communities as they existed prior to extensive modern impacts, thus representing an ecological baseline to be compared with modern populations. This study focuses on two late prehistoric (ca. 300–600 AD) sites on the Yazoo River, where nearly 24,000 freshwater mussel valves were recovered. Though modern data are extremely limited for the river, analysis revealed it once supported a diverse mussel community containing numerous species currently considered rare, endangered, or extinct in Mississippi. In total, the combined shell assemblages yielded 23 new river records for the Yazoo River. One species in particular, Quadrula fragosa, represents the second such occurrence in Mississippi, and bolsters its candidate status as a new state record, as argued in a recent report from a neighbouring river in the Yazoo Basin.

Diversity, biogeography and conservation of freshwater mussels (Bivalvia: Unionida) in East and Southeast Asia

Recent research efforts have significantly advanced our knowledge on Asian freshwater mussel (Bivalvia: Unionida) diversity and distribution. Here we provide a modern consensus of the diversity, biogeography and conservation of Unionida in the region comprising East and Southeast Asia (excluding Wallacea) and Asian Russia. A data review confirmed the presence of 228 native and 3 non-native Unionida (98% Unionidae, 2% Margaritiferidae), rendering the region a global hotspot of freshwater mussel diversity. Species richness was highest in China (particularly Yangtze basin) in absolute numbers and Cambodia when correcting for country area, and decreased gradually towards the south and steeply towards the north and east. Six of the seven unionid subfamilies are native to the region, with species richness peaking in Southeast Asia for Rectidentinae, Gonideinae, Parreysiinae and Modellnaiinae, China for Anodontinae and Unioninae, and Asian Russia for Margaritiferidae. Conservation status and data collected after 1980 were not available for 61 and 24% of species, respectively. Dams, deforestation and pollution are likely the major threats to mussels in the region, though data in this respect are scarce. The Philippines, Laos, Indonesia, Myanmar and Malaysia are among the countries with the poorest data availability and urgently require research.

Tracking the Recovery of Freshwater Mussel Diversity in Ontario Rivers: Evaluation of a Quadrat-Based Monitoring Protocol

Watershed inventories and population monitoring are essential components of efforts to conserve and recover freshwater mussel diversity in Canada. We used two datasets to assess the efficacy of a quadrat-based sampling protocol for: (1) detecting mussel species at risk; (2) characterizing species composition; (3) providing accurate estimates of abundance; and (4) detecting changes in density. The protocol is based on a systematic design (with random starts) that samples 20% of monitoring sites with visual-tactile surface searches and excavation of 1 m2 quadrats. The first dataset included 40 sampling sites in five Ontario rivers, and the second dataset consisted of complete census sampling at two 375 m2 sites that represented contrasting mussel assemblages. Our results show that the protocol can be expected to detect the majority of species present at a site and provide accurate and precise estimates of total mussel density. Excavation was essential for detection of small individuals and to accurately estimate abundance. However, the protocol was of limited usefulness for reliable detection of most species at risk. Furthermore, imprecise density estimates precluded detection of all but the most extreme changes in density of most individual species. Meeting monitoring objectives will require either substantially greater sampling effort under the current protocol, or a fundamental revision of the sampling approach.

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.

Factors driving changes in freshwater mussel (Bivalvia, Unionida) diversity and distribution in Peninsular Malaysia

Freshwater mussels (Bivalvia, Unionida) fulfil important ecosystem functions and are one of the most threatened freshwater taxa globally. Knowledge of freshwater mussel diversity, distribution and ecology in Peninsular Malaysia is extremely poor, and the conservation status of half of the species presumed to occur in the region has yet to be assessed. We conducted the first comprehensive assessment of Peninsular Malaysia's freshwater mussels based on species presence/absence and environmental data collected from 155 sites spanning all major river catchments and diverse habitat types. Through an integrative morphological-molecular approach we recognised nine native and one widespread non-native species, i.e. Sinanodonta woodiana. Two species, i.e. Pilsbryoconcha compressa and Pseudodon cambodjensis, had not been previously recorded from Malaysia, which is likely a result of morphological misidentifications of historical records. Due to their restriction to single river catchments and declining distributions, Hyriopsis bialata, possibly endemic to Peninsular Malaysia, Ensidens ingallsianus, possibly already extinct in the peninsula, and Rectidens sumatrensis, particularly require conservation attention. Equally, the Pahang, the Perak and the north-western river catchments are of particular conservation value due to the presence of a globally unique freshwater mussel fauna. Statistical relationships of 15 water quality parameters and mussel presence/absence identified acidification and nutrient pollution (eutrophication) as the most important anthropogenic factors threatening freshwater mussel diversity in Peninsular Malaysia. These factors can be linked to atmospheric pollution, deforestation, oil-palm plantations and a lack of functioning waste water treatment, and could be mitigated by establishing riparian buffers and improving waste water treatment for rivers running through agricultural and residential land.

Conservation status of freshwater mussels in Europe: state of the art and future challenges.

Freshwater mussels of the Order Unionida provide important ecosystem functions and services, yet many of their populations are in decline. We comprehensively review the status of the 16 currently recognized species in Europe, collating for the first time their life-history traits, distribution, conservation status, habitat preferences, and main threats in order to suggest future management actions. In northern, central, and eastern Europe, a relatively homogeneous species composition is found in most basins. In southern Europe, despite the lower species richness, spatially restricted species make these basins a high conservation priority. Information on freshwater mussels in Europe is unevenly distributed with considerable differences in data quality and quantity among countries and species. To make conservation more effective in the future, we suggest greater international cooperation using standardized protocols and methods to monitor and manage European freshwater mussel diversity. Such an approach will not only help conserve this vulnerable group but also, through the protection of these important organisms, will offer wider benefits to freshwater ecosystems.

Search effort and imperfect detection: Influence on timed-search mussel (Bivalvia: Unionidae) surveys in Canadian rivers

Inventories and population monitoring are essential activities supporting the conservation of freshwater mussel diversity in Canadian rivers. Despite widespread use of timed-search methods to survey river mussels, the relationship between species detection and search effort has received limited study. In this study, repeat-sampling data from 54 Ontario river sites were used to estimate: (1) species detection probabilities; (2) the number of sampling events required to confidently detect species; and, (3) the power of timed-search surveys to detect future distribution declines. Mussels were collected using visual and tactile methods, and collection data were recorded separately for each 1.5 h of search time (up to 4.5 h). Thirteen species were collected; including two endangered species (Rainbow Villosa iris and Eastern Pondmussel Ligumia nasuta ). In all cases, species detection was imperfect. However, detection probabilities (p ) for most species were high (>0.69). Two repeat 4.5 h surveys are required to confidently assess whether most (83%) species are present at a site. Search effort had a positive effect on estimates of species richness, detection probability and site occupancy, and the power to detect future distribution declines. At all levels of sampling effort, detection probability and site occupancy estimates were positively correlated to mussel abundance.

Remnant Freshwater Mussel Diversity in Rondeau Bay, Lake Erie

In 2014 and 2015, 27 sites in Rondeau Bay, Ontario, Canada, were surveyed for freshwater mussels. Rondeau Bay is a large coastal wetland on the north shore of Lake Erie. Twenty-three species were identified from 120 live mussels, 15 fresh whole shells, 329 weathered whole shells, and 1121 weathered valves. Live individuals of the following species were collected: Eastern Pondmussel (Ligumia nasuta; endangered in Canada), Giant Floater (Pyganodon grandis), Round Pigtoe (Pleurobema sintoxia;endangered in Canada), and Three-ridge (Amblema plicata). Fresh whole shells of the Mapleleaf (Quadrula quadrula; threatenedin canada) were also found. Most species (78%), including 7 species at risk, were collected only as weathered shells. These results indicate a substantial decline in freshwater mussel diversity since the Zebra Mussel (Dreissena polymorpha) invasion of Lake Erie. Evidence shows that a viable population of only Giant Floater remains.

Effects of environmentally relevant mixtures of major ions on a freshwater mussel

The Clinch and Powell Rivers (Virginia, USA) support diverse mussel assemblages. Extensive coal mining occurs in both watersheds. In large reaches of both rivers, major ion concentrations are elevated and mussels have been extirpated or are declining. We conducted a laboratory study to assess major ion effects on growth and survival of juvenile Villosa iris. Mussels were exposed to pond water and diluted pond water with environmentally relevant major ion mixtures for 55 days. Two treatments were tested to mimic low-flow concentrations of Ca2+, Mg2+, SO42−, HCO3+, K+ and Cl− in the Clinch and Powell Rivers, total ion concentrations of 419 mg/L and 942 mg/L, respectively. Mussel survival (>90%) and growth in the two treatments showed little variation, and were not significantly different than in diluted pond water (control). Results suggest that major ion chronic toxicity is not the primary cause for mussel declines in the Clinch and Powell Rivers.

Dispatches

Dispatches

Modelling and mapping the distribution, diversity and abundance of freshwater mussels (Family Unionidae) in wadeable streams of Illinois, U.S.A.

Summary Freshwater mussels are one of the most imperilled animal groups in the world. Their effective conservation and restoration require a better understanding of their spatial distributions at a relevant scale and of their relationships with natural environmental factors and human disturbances. In this study, we sampled over 900 sites on wadeable streams throughout Illinois, U.S.A., and compiled environmental data for a wide range of natural and anthropogenic factors related to climate, geology, land use, and connections to large rivers, dams and ponds. Using random forest classification and regression, we modelled the presence–absence of mussels as a group (87% accuracy), the abundances of 29 individual mussel species (R2 = 0.2–0.51), species richness (R2 = 0.52) and total mussel abundance in a standard sample (R2 = 0.41). The abundances of most species increased with stream size, the proportion of agricultural land in the catchment and the distance to the nearest dam or pond, but decreased with increasing catchment or channel slope and the proportion of forest in the catchment. Species varied in their relationships with climate variables, suggesting that they respond differently to climate change. Geology, particularly bedrock depth, was important for many species. Species richness and total mussel abundance responded positively to stream size and negatively to the slope of streams or catchments. The models were applied to unsampled wadeable stream reaches to generate mussel distribution maps at the reach scale, useful tools for resource managers to effectively protect and restore mussel biodiversity. The models also improve our understanding of how mussel populations and assemblages are structured by natural factors and human disturbances at a broad scale.

Developing environmental flow recommendations for freshwater mussels using the biological traits of species guilds

Summary North American freshwater mussels (Unionidae) are a diverse and imperilled fauna that are very sensitive to flow alterations. Previous attempts to develop environmental flows for mussels have struggled to accommodate their varied habitat requirements and complex life histories. We review what is known about the habitat requirements of mussels, how they can vary among species within a community, and how this variation influences the effectiveness of different environmental flow methodologies. We propose a trait‐based environmental flow method that addresses the needs of mussel guilds differentiated by their thermal tolerances and reproductive strategies. Used previously for fish, plants and macroinvertebrates, the guild approach groups species by traits and identifies flow requirements of guilds as opposed to entire communities. We apply the guild approach to the mussel fauna of the Kiamichi and Little Rivers in south‐eastern Oklahoma, U.S.A., and illustrate how changes in the hydrograph can be made to better meet the seasonal flow needs of differing mussel guilds and their host fish. The guild environmental flow method can provide flow recommendations that cater to the life history and habitat requirements represented within diverse mussel communities. In addition, the method can be adapted among regions where trait data are available or combined with rating models that estimate trait data for understudied species.

Transcriptomic analysis of the mussel Elliptio complanata identifies candidate stress-response genes and an abundance of novel or noncoding transcripts.

Mussels are useful indicator species of environmental stress and degradation, and the global decline in freshwater mussel diversity and abundance is of conservation concern. Elliptio complanata is a common freshwater mussel of eastern North America that can serve both as an indicator and as an experimental model for understanding mussel physiology and genetics. To support genetic components of these research goals, we assembled transcriptome contigs from Illumina paired-end reads. Despite efforts to collapse similar contigs, the final assembly was in excess of 136,000 contigs with an N50 of 982 bp. Even so, comparisons to the CEGMA database of conserved eukaryotic genes indicated that ∼20% of genes remain unrepresented. However, numerous candidate stress-response genes were present, and we identified lineage-specific patterns of diversification among molluscs for cytochrome P450 detoxification genes and two saccharide-modifying enzymes: 1,3 beta-galactosyltransferase and fucosyltransferase. Less than a quarter of contigs had protein-level similarity based on modest BLAST and Hmmer3 statistical thresholds. These results add comparative genomic resources for molluscs and suggest a wealth of novel proteins and noncoding transcripts.

Freshwater Mussels (Bivalvia: Margaritiferidae and Unionidae) of the Buffalo River Drainage, Tennessee

The Buffalo River in Tennessee historically contained a rich diversity of freshwater mussels. Sampling efforts in the 1980s documented declines in most of the main channel. Recent collection data indicated recovery in the upper and lower reaches of the river. The objective of this study was to update the current status, distribution, and species composition of the mussel fauna in the main channel and major tributaries through qualitative sampling, and document community structure using quantitative sampling at the most diverse location in the main channel for use in future monitoring efforts. In the qualitative sampling portion of this study, timed searches established catch-per-unit effort (CPUE) at intervals of ∼5 river miles in the main channel and tributaries. We recorded a total of 36 species at 62 sites, including 3 federally protected species: Margaritifera monodonta (Spectaclecase), Pleuronaia dolabelloides (Slabside Pearlymussel), and Theliderma cylindrica (Rabbitsfoot). An additional 3 species being considered for the federal endangered species list were also found extant in the main channel: Obovaria subrotunda (Round Hickorynut), Pleuronaia barnesiana (Tennessee Pigtoe), and Toxolasma lividum (Purple Lilliput). Multiple sites in the upper and lower main-stem were suitable for reintroduction of species. These findings should be considered in future management and conservation efforts.

Clinch River Freshwater Mussels Upstream of Norris Reservoir, Tennessee and Virginia: A Quantitative Assessment from 2004 to 2009

AbstractThe Clinch River is located in northeastern Tennessee (TN) and southwestern Virginia (VA) of the United States, and contains a diverse mussel assemblage of 46 extant species, including 20 species listed as federally endangered. To facilitate quantitative monitoring of the fauna, quadrat data were collected from 2004 to 2009 at 18 sites in the river, including 12 sites in TN and 6 sites in VA. Thirty‐eight mussel species were collected alive in total from quadrat samples taken annually at sites in the TN section of the river. Over the five‐year study period, mussel density averaged 25.5 m−2 at all sites sampled in TN. In contrast, mussel density averaged only 3.1 m−2 at sites sampled in VA. The best historical site in VA was Pendleton Island in Scott County, where mussel density was estimated as high as 25 m−2 in 1979, comparable to current densities recorded in TN. Mussel densities are now <1 m−2, indicating a collapse of the fauna. A severe reduction in mussel abundance has occurred in a 68‐km section of the river from St. Paul, VA, downstream to approximately Clinchport, VA (river kilometers 411.5‐343.3). While the environmental factors responsible for the faunal decline are largely unknown, they must have been severe and sustained to reduce such large populations to their current low levels. Long‐term water and habitat quality monitoring is needed to determine whether environmental degradation is still occurring in the river.

Freshwater Mussels (Unionidae) in the Paint Rock River (Jackson, Madison, and Marshall Counties), Alabama

The Paint Rock River (PRR) drainage in northern Alabama and southern Tennessee historically supported 58 freshwater mussel species. This study semi-quantitatively examined the mussel assemblage at 42 sites in the Paint Rock mainstem and 5 sites in Estill Fork, a headwater tributary. A total of 1825 live mussels were collected over 78.9 person-hours, with an overall catch per unit effort (CPUE) of 23.1 mussels/person-hour. Forty-one species were collected live and/or fresh dead, including federally protected Epioblasma triquetra (Snuffbox), Fusconaia cor (Shiny Pigtoe), Lampsilis abrupta (Pink Mucket), Lampsilis virescens (Alabama Lampmussel), Pleuronaia dolabelloides (Tennessee Pigtoe), Quadrula cylindrica cylindrica (Rabbitsfoot), and Toxolasma cylindrellus (Pale Lilliput). The river system continues to support a high diversity of mussels (48 species collected in the past 25 years). The survey also identified several sites in the basin suitable for the reintroduction of extirpated species.

A Comparison of Two Timed Search Methods for Collecting Freshwater Mussels in Great Lakes Coastal Wetlands

Given the catastrophic losses of freshwater mussel diversity across the Laurentian Great Lakes, the identification and protection of remnant assemblages are priority conservation actions. In contrast to riverine mussels, there has been little evaluation of different sampling gear and strategies to support the design of coastal wetland inventory or monitoring programs. We compared timed-search (qualitative) collections from 21 Lake Ontario coastal wetlands using clam rake and visual/tactile methods. Live mussels were collected with visual/tactile searches from 90% of wetlands sampled, and from 71% with the clam-rake. A total of 756 live mussels (representing nine species) were collected. Collections included three mussel species at risk: Ligumia nasuta, Quadrula quadrula, and Toxolasma parvum. Compared to clam-raking, visual/tactile searches collected more than twice as many live individuals and fresh shells, a broader range of sizes and significantly more species (and at a faster rate). Estimates of live mussel abundance and species number associated with each method were imprecise (CV > 0.35). The concordance of variation in mussel assemblage structure among wetlands (as described by each method) was not consistent or in strong agreement. Based on our findings, we recommend visual/tactile searches for future coastal wetland sampling efforts.

Use of Occupancy Modeling to Assess the Status and Habitat Relationships of Freshwater Mussels in the Lower Flint River, Georgia, USA

The Flint River in southwestern Georgia is known for its historically diverse mussel fauna, but the current status of the fauna is poorly known. The rediscovery of two presumed extirpated and extinct species in 2006 and 2008 exemplifies the need for a large-scale survey of the river. We used an occupancy modeling approach to estimate the presence of mussel species at 39 locations along a 119 km reach of the lower Flint River between Lake Seminole and Albany Dam. Twenty species were collected and evidence of recent reproduction was documented for 8 species. Elliptio crassidens, E. fumata/pullata, and E. nigella were the most abundant species and accounted for 43%, 40%, and 8% of the total mussels collected, respectively. Among species, mean detection probabilities averaged 0.25 and ranged from 0.01 to 0.69, whereas occupancy averaged 0.56 and ranged from 0.03 to 1. We fitted models relating site-level and sample-level habitat characteristics and site location to detection and occupancy for nine species. Detection probabilities varied among species, substrate, searcher experience, and distance from Albany Dam. Estimated occupancy varied by species and substrate composition indicating different substrate use by different species. Our modeling approach indicated that our sampling design was efficient for detecting most species with the exception of rare species. The Lower Flint River continues to harbor a widely distributed and diverse assemblage of freshwater mussels. The occupancy modeling approach used in our study was a useful and efficient method to assess the status, distribution, and habitat use of freshwater mussels in the Flint River while also providing a measure of sampling efficiency. Similar model-based study designs may be effective in other streams, particularly when sampling resources are limited.

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...