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3.6 Freshwater Mussels Freshwater bivalve molluscs, or mussels, are filter-feeders with a diet that varies across habitats and among species but primarily consists of microscopic particular matter such as phytoplankton, zooplankton, bacteria, and organic detritus (Vaughn and Hakenkamp2001; Haag 2012). North America has the richest mussel fauna with more than 300 species distributed among approximately 50 genera that are members of the family Unionidae (Haag 2012). Mussels live most of their lives burrowed in the bottom of a stream or lake and depending on species and season they may be closer to the substrate surface (warm seasons) or burrow more deeply during colder seasons (Amyot and Downing 1991, 1997; Watters et al. 2001; Schwalb and Pusch2007; Haag 2012). When population density is high mussels can be the dominant biomass and exert control over the structure of an aquatic community (Vaughn and Hakenkamp 2001) as demonstrated in locations which have large populations of the non-native Asian Clam. Most mussel species have a complex life history that includes a reproductive process dependent on an obligate larva parasite on fish called a glochidium, which has important ramifications for many aspects of mussel ecology and conservation (Layzer and Scott 2006). Recolonization success is dependent on the successful parasitizing of a host fish and subsequent movement of the infected host fish into water that provides suitable habitat for the mussel (Layzer and Scott 2006). Many freshwater mussels have undergone drastic declines and many are predicted to go extinct in the next few decades (Eckblad and Lehtinen1991; Bogan 1993; Neves 1993; Shannon et al. 1993; Wilson et al. 1995; Neveset al. 1997; Vaughn and Taylor 1999; Vaughn and Brook Floater (Brena Jones NCWRC) Hakenkamp 2001). A list of freshwater mussels considered Species of Greatest Conservation Need (SGCN) is provided in Table 3.6.1 and the Taxa Team evaluation results can be found in Appendix#. River basin and habitat associations for these species can be found in Appendix#. Table 3.6.1 Conservation Concern SGCN priority freshwater mussel species. Family Unionidae Unionidae Unionidae Scientific Name Alasmidonta heterodon Alasmidonta raveneliana Alasmidonta sp. 2 Common Name Dwarf Wedgemussel Appalachian Elktoe A freshwater bivalve Federal/ State Listing* E/E E/E Family Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Unionidae Scientific Name Alasmidonta undulata Alasmidonta varicosa Alasmidonta viridis Anodonta couperiana Anodonta implicata Cyclonaias tuberculata Elliptio dilatata Elliptio lanceolata Elliptio marsupiobesa Elliptio steinstansana Elliptio waccamawensis Fusconaia masoni Fusconaia subrotunda Lampsilis cariosa Lampsilis fullerkati Lampsilis sp. 2 Lasmigona decorata Lasmigona subviridis Pegias fabula Pleurobema collina Pleurobema oviforme Pleuronaia barnesiana Toxolasma pullus Villosa constricta Villosa delumbis Villosa iris Villosa modioliformis Villosa vaughaniana Common Name Triangle Floater Brook Floater Slippershell Mussel Barrel Floater Alewife Floater Purple Wartyback Spike Yellow Lance Cape Fear Spike Tar River Spinymussel Waccamaw Spike Atlantic Pigtoe Longsolid Yellow Lampmussel Waccamaw Fatmucket Chameleon Lampmussel Carolina Heelsplitter Green Floater Littlewing Pearlymussel James Spinymussel Tennessee Clubshell Tennessee Pigtoe Savannah Lilliput Notched Rainbow Eastern Creekshell Rainbow Eastern Rainbow Carolina Creekshell Federal/ State Listing* - /T - /E - /E - /E - /T - /E - /SC - /E - /SC E/E - /T - /E - /E - /T E/E - /E E/E E/E - /E - /E - /E - /SC - /SC - /E *Federal Listing Status: E – Endangered; a taxon which is in danger of extinction throughout all or a significant portion of its range. T – Threatened; a taxon which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. C – Candidate; taxa for which the [Fish and Wildlife] Service has on file enough substantial information on biological vulnerability and threat(s) to support proposals to list them as endangered or threatened. FSC – Federal Species of Concern; an informal term not defined in the federal Endangered Species Act. Defined as those species that appear to be in decline or otherwise in need of conservation and are under consideration for listing or for which there is insufficient information to support listing at this time. State Listing Status: E – Endangered; any native or once-native species of wild animal whose continued existence as a viable component of the State’s fauna is determined to be in jeopardy or listed as a federal endangered species. T – Threatened; any native or once-native species of wild animal which is likely to become an endangered species Family Scientific Name Common Name Federal/ State Listing* within the foreseeable future throughout all or a significant portion of its range or listed as a federal threatened species. SC – Special Concern; any species of wild animal native or once-native to North Carolina which is determined to require monitoring but which may be taken under regulations adopted under State laws. 3.6.1 Comparison of 2005 - 2015 Priority Species The 2015 evaluation identified 31 species as SGCN; 27 species as knowledge gap priorities; and 30 species as management concern or need priorities. Some species may be considered a priority in more than one of the evaluation categories. The 2005 WAP listed 43 freshwater mussel species as SGCN priority species but did not provide separate evaluation categories to identify knowledge gap or management concern priorities. Table 3.6.2 provides a list of species included on the 2005 priority list that were not ranked by the Taxa Team as a priority for conservation concern and are therefore not included on the 2015 SGCN priority list. Table 3.6.2 2005 priority species that are not included on the 2015 SGCN priority list. Scientific Name Common Name Alasmidonta robusta Elliptio cistellaeformis Carolina Elktoe Box Spike Fusconaia barnesiana Lampsilis radiata conspicua Lasmigona holstonia Villosa trabalis Villosa vanuxemensis Tennessee Pigtoe Carolina Fatmucket Tennessee Heelsplitter Cumberland Bean Mountain Creekshell 3.6.2 Conservation Concern Haag (2012) notes that because the conservation status of many species remains poorly known, high conservation concern stems from expecting the potential for future imperilment will exceed current imperilment. Freshwater mussels are among the most globally imperiled freshwater organisms, with about 75% of those historically found in the Southeastern U.S. thought to now be extinct or at risk of extinction (Williams et al. 1993; Bogan, 1996; Neves et al. 1997; Gangloff et al. 2009). The synergistic effects of numerous point and nonpoint source impacts that affect water and habitat quality are likely causes of these declines, with changes to the physical and chemical variables in a stream believed to be principle factors for this decline (Neves et al. 1997; Brim-Box and Williams 2000; Gillies et al. 2003; Lydeard et al. 2004; Gangleoff et al. 2009). 3.6.3 Knowledge Gaps Progress toward species recovery depends on knowledge about species distribution patterns as well as a clear understanding of habitat and life history requirements of species (Flebbe and Herrig 2000). Compared to other taxa, we have limited knowledge levels and data regarding freshwater mussels. Accurate distribution information is still lacking for many species, as is work related to fish host identification, ecology (both of individual species and among communities of organisms), and basic systematics (genetics, taxonomy, and morphology). Extensive monitoring of populations is generally lacking. There are endemism concerns associated with many species, both throughout the Tennessee River Basin tributaries, as well as concerns about the distribution of some species with rather restricted ranges within South Atlantic river systems. Taxonomic difficulties have yet to be resolved for several genera, most notably Elliptio. There is an extreme knowledge deficit regarding the pea clams; attaining information on their distributions should be pursued whenever possible. A rigorous phylogenetic study based on quantifiable, heritable attributes such as DNA sequence data for scientifically defensible estimates of North American mussel diversity is needed (Lydeard and Roe 1998). Such efforts have already yielded surprising departures from traditional classifications. Because mussel dispersal occurs primarily by transport of glochidia on fish hosts, cryptic variation may be high for mussels (Haag 2012). Molecular studies have uncovered a high degree of cryptic variation not reflected by shell morphology. These studies show that several currently recognized species include multiple evolutionary units (Mulvey et al. 1997; Roe andLydeard1998; King et al. 1999; Jones et al. 2006; Serb 2006), suggesting that diversity of North American mussels has been underestimated. Protecting a rich fauna of mussels (about 50 species of mussels in North Carolina) from environmental contamination requires an understanding of mussel sensitivity to diverse toxicants. The vast majority of mussel species remain untested for most toxicants, and estimating safe environmental concentrations is a critical need, especially for the protection of rare, threatened, or endangered species. Freshwater mussel toxicology still lacks full identification of pollutants that may limit mussel survival, recruitment and recovery. Few of the compounds that mussels encounter in the wild have been evaluated in the lab. Also, toxicity tests seldom address mussel reproduction, and tests are still short relative to mussel lifespans. In particular, there is a need to test previously unevaluated contaminants of emerging concern, using long-term exposures which more closely mimic natural conditions, and to evaluate more ecologically relevant endpoints such as mussel health and recruitment. Several publication over the last decade have noted the absence or under-protectiveness of national water quality criteria for particular pollutants to which mussels are known to be sensitive (Augspurger et al. 2003, Wang et al. 2010, Stokstad 2012, Haag 2012). To facilitate habitat evaluation, work is needed to better characterize chemical and contaminated sediment exposure and provide benchmarks to define acceptable pollutant concentrations. Researchers at N.C. State University, University of Georgia, and U.S. Geological Survey have started work on testing additional classes of chemicals (Bringolf et al. 2010, Hazelton et al. 2012, 2013, Wang et al. 2012), and the U.S. Environmental Protection Agency has been an active participant in design and funding these studies but more are needed. Publication of recommended benchmarks for pollutants of concern (e.g., metals, major ions) will be useful in developing water quality regulations. In the wild, almost all mussels require a fish host for the transformation of the larval glochidia stage into the free-living juvenile stage. Transformation on a host fish is referred to as in vivo transformation. In the lab, artificial growth media has been used to transform glochidia to juveniles in vitro with increasing success (as measured by % transformation) as mussel nutritional needs are better understood and with improvements in artificial media (Lima et al. 2012). There is a need to better define the relative health of in vivo and in vitro transformed juveniles by other measures such as reproductive fitness and tolerance to environmental stressors, including pollutants (Augspurger pers.comm.). There are 27 species identified as research priorities because there are knowledge gaps, of which 15 are also considered SGCN (see Table 3.6.1). Table 3.8.3 represents only those species considered a knowledge gap priority. Table 3.6.3 Knowledge Gap priority freshwater mussel species. Scientific Name Corbicula fluminea Strophitus undulatus Pyganodon cataracta Lampsilis radiata Ligumia nasuta Uniomerus carolinianus Pyganodon grandis Taxolasma parvum (parvus) Elliptio fisheriana Utterbackia imbecillis Elliptio roanokensis Elliptio icterina Common Name (Population) Asian Clam Creeper Eastern Floater Eastern Lampmussel Eastern Pondmussel Florida Pondhorn Giant Floater Lilliput Northern lance Paper Pondshell Roanoke Slabshell Variable Spike Federal/ State Listing Status* - /T - /T - /T - /T 3.6.4 Management Needs Restoring mussels into areas where they have been extirpated but the habitat is now suitable is a high priority. Propagation and release of mussels to augment existing populations will help reduce risk of extinction and may increase genetic diversity of small populations. Removing barriers and other impediments to host fish movement will allow natural recolonization of suitable habitats and facilitate gene flow between populations. Waters important for mussels must be monitored for water quality use support ratings. Rating of water quality (poor to excellent) by the N.C. Division of Water Resources (NCDWR) Environmental Sciences Section informs several other aspects of state water quality programs. For example, some waters with excellent quality can be petitioned for additional protection, and waters rated as poor may be listed as impaired thereby making them subject to restoration planning. Not all waters are monitored, so having important mussel habitat included in a longterm monitoring program is an important step in having access to other water quality management tools. Waters rated as Excellent and which have outstanding resources values (defined in water quality statutes) can be petitioned for Outstanding Resource Waters (ORW) or High Quality Waters (HQW) designations. Those designations afford additional protections to ensure that water quality and associated resources are maintained. The process is not automatic and starts when NCDWR is petitioned to provide the additional designation and associated protections. Resource agencies should identify the waters important for mussel conservation which are eligible for ORW or HQW designations and petition for those protections. Cooperation between NCDWR and others is needed to develop site-specific water quality restoration plans under N.C. Administrative Code (see 15A NCAC 02B 0.0110) which outlines rules for considerations for federally-listed threatened or endangered aquatic species. Through collaborative efforts, NCWRC along with NCNHP, USFWS, and NCDWR developed the technical basis for a site-specific water quality management plan for Goose Creek (Yadkin – Pee Dee River Basin), and there are other waters with federally-listed aquatic species and water quality concerns in need of additional site-specific restoration plans. 3.6.5 Threats and Problems Invasive and non-native species can create competitive pressures on food resources and their burrowing activity can uproot native mussels in sandy sediments (Vaughn and Hakenkamp 2001; Bogan et al. 2011). The first location in the state of the non-native Lilliput was first discovered in 2007 at Falls Lake in Wake County and was confirmed through DNA analysis (Bogan et al. 2011). Asian Clam can be found throughout the state, often in such large quantities they create high levels of ammonia in streams that can negatively affect native mussels. Contaminants and water pollution are a significant threat to all aquatic species and especially to mussels. Point source discharges from municipal wastewater that contains monochloroamine and unionized ammonia compounds are acutely toxic to freshwater mussels and may be responsible for glochidial mortality that results in local extirpation of mussels (Goudreau et al. 1993; Gangloff et al. 2009). However, given the transient nature of flowing systems (e.g., a water continuum) and potential for dilution at any point along the system it is especially difficult to detect not only origination points but also concentration levels in the water column (Fleming et al. 1995). A dieoff event affecting Tar River Spinymussel populations was detected in the Swift Creek watershed (Nash County) as it occurred and was attributed to anticholinesterase poisoning related to organophosphorus and carbamate pesticides used in agricultural applications (Hill and Fleming 1982; Fleming et al. Tar River Spinymussel (NCWRC) 1995). Since the publication of Kolpin et al. (2002) on the extent and diversity of chemicals present in the nation’s waters, there has been increased concern about the biological relevance of the mix of chemicals to which mussels and other aquatic organisms are exposed, including pharmaceuticals, personal care products, and agrochemicals. Many pollutants detected in streams have never been evaluated for their impacts to mussels (Augspurger pers.comm.). Given their burrowing nature and consumption of detritus and particulate matter mussels may be more susceptible to trace metal exposure and uptake of contaminants than other aquatic animals (Wilson 2008; Jarvis 2011). Sediments from upstream locales, especially hydroelectric impoundments, can be a source of sediments laden with trace metals (Jarvis 2011). A decline in Appalachian Elktoe populations in the Upper Little Tennessee River watershed may be related to trace metals concentrations, especially copper and zinc, found in stream sediments (Jarvis 2011). In urbanized areas, a lack of riparian vegetation and increased impervious areas contributes to higher sediment loads from erosion that carry fertilizers, pesticides, herbicides, and many other chemical compounds (Gangloff et al. 2009). Lab studies indicate freshwater mussels are more sensitive than most other aquatic animals to toxicity from sodium chloride and potassium chloride (Gillis 2011, Wang et al. 2012). As sea levels rise and salt water moves upstream into freshwater habitats, it could be predicted that mussels would be particularly vulnerable. Field conformation of the estimated limits of tolerance predicted by the lab tests is important in determining the significance of this threat and in design of ameliorative measures (Augspurger pers.comm.). Climate change, mining, hydraulic fracturing, and other energy development will bring additional stressors that need to be evaluated for mussels. In addition to specific pollutants that may be introduced into the aquatic environment, the interactions of pollutants and temperature (from climate change), salinity (related to sea level rise), and lower dilution (from altered flows) will need to be considered (Augspurger pers.comm.). Impervious areas in urbanized watersheds contribute to high water levels, even during short rainfall events, which can result in flash flooding. These high or flashy flow events contribute to increased sediment loads, turbidity throughout the water column, and stream bed movement that stress mussel populations (Gangloff et al. 2009). 3.6.6 Additional Information The Southern Appalachian Man and the Biosphere program, in partnership with several federal and state agencies, conducted the Southern Appalachian Assessment which was designed to be a regional assessment of all resources in 132 counties in mountain areas of North and South Carolina, Georgia, Alabama, Tennessee, and Virginia (Flebbe et al. 1996). 3.6.7 Recommendations In general, protection and restoration of natural community composition and function and protection of surrounding natural areas under current conditions are the best ways to ensure suitable habitats are available for this species. Measures that protect a large and diverse pool of populations are the best way to ensure that species are able to survive future stresses and adapt to changing climate conditions. Distributional and status surveys. Priorities for conducting distributional and status surveys need to focus on species believed to be declining or mainly dependent on at-risk natural communities. Continue species distribution surveys for all SGCN and priority species. Monitoring. Long-term monitoring is critical to assessing species and ecosystem health and in gauging resiliency of organisms to a changing climate. These efforts will inform future decisions on how to manage species and their habitats. Long-term monitoring is needed to identify population trends and to assess performance of conservation actions. Monitoring plans should be coordinated with other existing monitoring programs where feasible. We will Conduct long-term monitoring to identify population trends for SGCN and priority species. Research. Research to facilitate appropriate conservation actions includes habitat use/preferences, spawning location and timing, fecundity, population dynamics, population genetics, feeding, competition, and predation. Research must also be conducted to determine vulnerability of SGCN and other priority species to specific threats and studies should provide recommendations for mitigation and restoration. Specific research needs are to Support taxonomic resolution with completion of species descriptions for undescribed taxa and resolution of species complexes using DNA research. Conduct research to facilitate appropriate conservation actions. Research should focus on life history studies of priority species. Specific questions to be addressed include: habitat use/preferences, spawning location and timing, fecundity, population dynamics, mortality and other demographic parameters, feeding, competition, predation. Pea clam species are a research priority because there is little knowledge about them in North Carolina. Determine appropriate areas of suitable habitat for augmentation or restoration activities. Develop propagation techniques and protocols. Investigate host fish relationships for all SGCN and priority species. Research into the impact of chemicals, especially pharmaceuticals, personal care products and agrochemicals and their interaction, to all mussel life stages. Test chemical selection should be guided by chemical occurrence and class (representative compounds from various classes of pharmaceuticals, for example) (Augspurger pers.comm). Histological and toxicological assessments to help understand health of mussel cellular and tissue fitness will improve ability to investigate mussel die-off events (Augspurger pers.comm). Field conformation of the estimated limits of tolerance for sodium chloride and potassium chloride concentrations (Augspurger pers.comm). The influence of suspended sediment and its associated contaminants, especially metals, on mussels needs to be evaluated. Development and application of a standard test method for evaluating the quality of sediment on mussel survival, growth and reproduction is needed (Augspurger pers.comm). The interactions of pollutants and temperature (climate change), salinity (sea level rise), and lower dilution (altered flows) need to be investigated (Augspurger pers.comm.). Management Practices and Conservation Programs. Management practices that reduce impacts and work synergistically with other conservation actions are needed to enhance the resilience of natural resources. Particular needs include preserving biodiversity, protecting native populations and their habitats, and improving degraded habitats. Conduct population augmentations and restorations using hatchery reared and translocated mussels. Promote best management practices on Commission-owned game lands and other state lands (parks, forests, preserves). Cooperative Efforts and Partnerships. Conservation programs and incentives and partnerships should be utilized to the extent possible to preserve high quality resources and protect important natural communities. Protection measures that utilize existing regulatory frameworks to protect habitats and species should be incorporated where applicable. Land conservation or preservation can serve numerous purposes in the face of anticipated climate change but overall, promotes ecosystem resilience. Continue to work with partners such as N.C. State University and propagation facilities from other states to facilitate a robust production and augmentation program. Riparian buffers are recognized as important in maintaining suitable instream physical and chemical habitat quality. Not all waters of the state have buffer rules, so voluntary approaches or local, regional, state land use ordinances which encourage riparian buffers should be pursued. References will be cited at the end of the chapter Amyot, J. P. and Downing, J. A. 1991. Endo-and epibenthic distribution of the unionid mollusk Elliptio complanata. Journal of the North American Benthological Society, 280-285. Augspurger pers.comm. Personal communication June 2015 with Tom Augspurger, USFWS regarding freshwater mussels, water quality, research, and management needs. Bogan AE, Smith JM, and Raley ME. 2011. The Lilliput (Toxolasma parvum) (Mollusca: Bivalvia: Unionidae) introduced into North Carolina. Journal of the North Carolina Academy of Science 127(2): 192-193. Bogan AE. 1996. Decline and decimation: the extirpation of the unionid bivalves in North America. Journal of Shellfish Research 15: 484. Brim-Box J and Williams JD. 2000. 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Thesis, Western Carolina University, Department of Geosciences and Natural Resources. 88 pp. Layzer JB and Scott EM. 2006. Restoration and colonization of freshwater mussels and fish in a southeastern United States tailwater. River Research and Applications 22: 476-491. Moore, J. 2006. An introduction to the invertebrates. Cambridge University Press. Pp. 120-134. Neves RJ, Bogan AE, Williams JD, Ahlstedt SA and Hartfield PW. 1997. Status of the aquatic mollusks in the southeastern United States: a downward spiral of diversity. In: Aquatic Fauna in Peril: the Southeastern Perspective. Eds. G.W. Benz & D.E. Collins, pp. 43-86. Special Publication 1, Southeast Aquatic Research Institute. Decatur, GA. 554 pp. Neves RJ. 1993. A state-of-the-unionids address. In: Conservation and Management of Freshwater Mussels, Proceedings of a UMRC Symposium, 12±14. October, 1992, St Louis, MO. Eds. K.W. Cummings, A.C. Buchanan and L.M. Koch, pp. 1-10. Upper Mississippi River Conservation Committee. Rock Island, IL. [NCAC] North Carolina Administrative Code 15A Subchapter 2B Surface Water and Wetland Standards. Section .0100 Procedures for Assignment of Water Quality Standards. http://ncrules.state.nc.us/ncac/title%2015a%20%20environment%20and%20natural%20resources/chapter%2002%20%20environmental%20management/subchapter%20b/subchapter%20b%20rules.pdf Shannon L., Biggins R.G. and Hylton R.E. 1993. Freshwater mussels in peril: perspectives of the U.S. Fish and Wildlife Service. In: Conservation and Management of Freshwater Mussels. Eds. K.S. Cummings, A.C. Buchanan and L.M. Koch, pp. 66-68. Proceedings of a UMRCC symposium, 12-14 October, 1992, St Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, IL, USA, pp. 117-122. Vaughn C.C. and Taylor C.M. 1999. Impoundments and the decline of freshwater mussels: a case study of an extinction gradient. Conservation Biology (13): 912-920. Vaughn CC and Hakenkamp CC. 2001. The functional role of burrowing bivalves in freshwater ecosystems. Freshwater Biology 46: 1431–1446. Vaughn CC. 2010. Biodiversity losses and ecosystem function in freshwaters: emerging conclusions and research directions. BioScience 60(1): 25-35. Vaughn CC. and Hakenkamp, C. C. 2001. The functional role of burrowing bivalves in freshwater ecosystems. Freshwater Biology 46: 1431-1446. Williams JD, Warren Jr. ML, Cummings KS, Harris JL, and Neves RL, 1993.Conservation status of freshwater mussels of the United States and Canada. Fisheries 18: 6–22. Wilson DM, Naimo TJ, Wiener JG, Anderson RV, Sandheinrich MB and Sparks RE. 1995. Declining populations of the fingernail clam Musculium transversum in the upper Mississippi River. Hydrobiologia (34): 209-220. Wilson WAS. 2008. Bioaccumulation of Trace Elements by Bivalves in the Altamaha River System. Dissertation at the University of Georgia. Athens, GA.