SFS Annual Meeting

6/06/2024  |   15:30 - 15:45   |  Salon 3/4

USING LONG-TERM ASSEMBLAGE COMPOSITION AND FUNCTIONAL TRAITS TO GUIDE MUSSEL CONSERVATION IN THE LOWER FLINT RIVER BASIN, GEORGIA The lower Flint River Basin (LFRB) in southwestern Georgia is one of the most productive agricultural regions in the United States and presently has five federally listed mussel species. Water withdrawals for irrigation provide critical support for the agricultural economy but intensify low stream flow during drought. Three multi-year droughts occurring between 1999 and 2012 caused significant mussel declines in the basin. A Habitat Conservation Plan for the LFRB is under development to balance water withdrawals for irrigation with adequate flows to support listed mussels and other aquatic life. Historical surveys were conducted in 1999 and 2001 to assess drought effects on mussels. We revisited 23 sites in 2023 to collect current population data and determine the distribution of listed species. Additionally, we used a previous in situ study to classify drought tolerance for 12 of the 25 species we found to determine changes in functional composition over time. We observed increased total abundance (>45%) at seven of the 12 sites that showed significant declines during the 2001 drought. However, seven sites where mussels survived the 2001 drought showed substantial declines in total abundance by 2023. Since 1999, the percentage of known drought sensitive mussels at our sites has decreased from 23.1% to 9.8%. We are using mixed linear models to assess the effects of climate, hydrology, and land use on mussel abundance and richness. Our results show the utility of functional traits in conservation and are being used to inform the Habitat Conservation Plan for the LFRB.

Caitlin Sweeney (Primary Presenter/Author), The Jones Center at Ichauway, caitlin.sweeney@jonesctr.org;

Natalie Horn (Co-Presenter/Co-Author), Florida State University, n.horn@fsu.edu;

Emma Greenberg (Co-Presenter/Co-Author), The Jones Center at Ichauway, emma.greenberg@jonesctr.org;

Brian Clayton (Co-Presenter/Co-Author), The Jones Center at Ichauway, brian.clayton@jonesctr.org;

Stephen Golladay (Co-Presenter/Co-Author), Georgia Water Planning and Policy Center at ASU, steve.golladay@jonesctr.org;

Kristin Rowles (Co-Presenter/Co-Author), Georgia Water Planning and Policy Center at Albany State University, krowles@h2opolicycenter.org;

Mark Masters (Co-Presenter/Co-Author), Georgia Water Planning and Policy Center at Albany State University, mmasters@h2opolicycenter.org;

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6/06/2024  |   15:45 - 16:00   |  Salon 3/4

THE EFFECT OF DROUGHT ON DEPAUPERATE MUSSEL COMMUNITIES IN THE COLORADO RIVER BASIN, TEXAS AND DIFFERENCES IN GROWTH AND SURVIVAL BETWEEN RIVER SEGMENTS A major threat to unionid mussels in the southwestern US is the increasing intensity and frequency of droughts due to climate change, exacerbated by increased human water use. Mussel communities of the Colorado River basin in Texas are depauperate with patchy distributions, which can, at least in part, be attributed to previous exceptional droughts, e.g., in 2011. The objectives of this study were (1) to examine how exceptional droughts in 2022 and 2023 affected the remaining mussels in the Colorado River basin by comparing site occupancy, species richness, abundance, and community composition in 2023 with data previously collected in 2021 at 30 sites in 4 tributaries and the mainstem of the upper Colorado River, Texas. (2) To use a mark-recapture study to compare growth and survival of mussels at two sites each in the upper and the lower segments of the San Saba River. At two sites that were dry in 2023, no live mussels were found, but mussels had been present in 2021. Similarly, mortality of tagged mussels was highest at the mark-recapture site that dried in 2023. However, no significant differences in abundance, species richness, and community composition were found between 2021 and 2023 at wet sites. Preliminary results also showed growth rates were higher in the lower than the upper segment in the San Saba River, which may be associated with higher food availability (chlorophyll). Our results suggest that remaining mussel populations occur in drought refuges, but growth and survival can vary spatially.

Eleanor Krellenstein (Primary Presenter/Author), Texas State University, eek16@txstate.edu;

Astrid Schwalb (Co-Presenter/Co-Author), Texas State University, schwalb@txstate.edu;

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6/06/2024  |   16:00 - 16:15   |  Salon 3/4

DAM FAILURES AS AN OPPORTUNITY TO CONSIDER LOTIC TO LENTIC TRANSITIONAL ZONE FRESHWATER MUSSEL ASSEMBLAGES Dams throughout the world have created reservoirs that often link riverine systems therefore modifying the habitat of aquatic organisms. Classic theories such as River Continuum (Vannote et al. 1980) and Serial Discontinuity concepts (Ward and Stanford 1983) have provided a framework for upstream to downstream gradients of abiotic and biotic parameters. In 2020, dams failed on a series of four lakes in mid-Michigan. Post-dam failure, in 2021 and 2022, we surveyed freshwater mussels (Unionidae) and quantified abiotic habitat parameters in all four influenced reservoirs and determined there were likely unquantified transitions in lotic (riverine) to lentic (reservoir) habitats. In 2023, we surveyed 19 sites in the lotic to lentic transitional zone using a standardized excavation of random quadrat survey method. We hypothesized that we would observe a transitional zone in unionid density, unionid diversity, and habitats upstream of the reservoir (e.g., Serial Discontinuity Concept) from the lotic to lentic sites. This study found that rather than a gradient-like transition of abiotic and biotic parameters between the lotic and lentic zones there was an abrupt change in many parameters. We will present these data, including endangered and listed unionid species data, and fine-scale additions to the Serial Discontinuity Concept based in our results and the supporting analyses. We suggest that attention should be paid to the transitional zones upstream of reservoirs when considering management of dam-fragmented habitats and these data will aid in unionid mussel conservation.

Daelyn A. Woolnough (Primary Presenter/Author), Central Michigan University, wooln1d@cmich.edu;

Nicole Vellequette (Co-Presenter/Co-Author), Central Michigan University, velle1n@cmich.edu;

David T. Zanatta (Co-Presenter/Co-Author), Central Michigan University, zanat1d@cmich.edu;

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6/06/2024  |   16:15 - 16:30   |  Salon 3/4

REDUCED GROWTH OF NATIVE JUVENILE MUSSELS WITH INCREASING INVASIVE BIVALVE DENSITY AND LOW FOOD RESOURCE AVAILABILITY Biological invasions cause ecological and economic impacts worldwide. Freshwater ecosystems are vulnerable to species introductions and extinctions because of their high degree of isolation and endemism. The southeastern United States is a global hotspot for freshwater mussel biodiversity, but Corbicula fluminea is an invasive species that may compete with native mussels given their similar trophic and habitat niches as filter-feeding bivalves. Here, we tested if interactions with C. fluminea influenced the growth of juvenile mussels (Lampsilis fasciola) and determined if filtration rates differed between the two species. We hypothesized mussel growth would be negatively related to increased C. fluminea abundances and would be exacerbated under low food availability. We also hypothesized C. fluminea would have higher filtration rates than native L. fasciola due to their more rapid growth rates and ability to capture a broader range of particulate sizes. We examined L. fasciola growth in response to both varying C. fluminea densities (0-1197 individuals m-2) and resource availability (high and low algal concentrations) in a 12-week mesocosm experiment. In a complimentary microcosm experiment, we compared filtration rates between C. fluminea and L. fasciola under high and low resource availability. L. fasciola growth rates declined with greater C. fluminea densities in low resource availability treatments. Notably, an increase in C. fluminea densities corresponded to a decrease in %P for L. fasciola tissue. However, filtration rates did not differ between the species. Our results suggest native mussel communities in more nutrient poor environments may be most at risk from C. fluminea invasions.

Taylor Kelley (Primary Presenter/Author), The University of Alabama, Department of Biological Sciences, Tekelley@crimson.ua.edu;

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6/06/2024  |   16:30 - 16:45   |  Salon 3/4

Beyond the Brine: Unveiling the Impact of Elevated Sodium Chloride on Freshwater Ecosystems and Unionid Mussel Dynamics. Secondary salinization from fertilizer application, mining, urbanization, and de-icing salts like sodium chloride (NaCl), is elevating chloride (Cl) and sodium (Na) in streams. While Cl effects on streams are well-studied, Na effects are less known. Elevated Cl levels in the environment can surpass physiological thresholds for some aquatic organisms, affecting nutrient cycling in ecosystems. A global review showed salinization negatively impacted freshwater animals in 78% of non-arthropod invertebrates, 68% of zooplankton, 62% of amphibians and insects, 56% of mollusks and crustaceans, and 51% of fishes. However, the diverse study designs and ionic concentrations hindered generalizable comparisons across taxa. Our first objective was to expand the existing review by calculating population-level effect sizes for crustaceans, zooplankton, and mollusks. Despite the initial prediction that mollusks would exhibit the strongest negative response due to their low internal salt concentration, our findings indicated zooplankton were the most sensitive, followed by mollusks, while crustaceans exhibited more positive effects. The limited representation of unionid mussel population responses in the literature precluded their inclusion in our analysis, although studies have noted that elevated NaCl can influence mussel filtering behavior, potentially impacting other ecosystem processes. Our second objective is to examine how unionid mussels' filtering behavior, retention, excretion, and C, N and P biodeposition change with elevated NaCl. We anticipate reduced filtering rates, attributed to avoidance behavior (i.e. clamming-up), leading to decreased ammonium excretion and biodeposition, thereby altering nutrient cycling. Examining these effects is vital for understanding the ecosystem services provided by mussels amid increasing secondary salinization.

Donya Mohamed (Primary Presenter/Author), Virginia Tech, donyamohamed63@gmail.com;

Jess Jones (Co-Presenter/Co-Author), U.S. Fish and Wildlife Service, Jess_Jones@fws.gov;

Chester Zarnoch (Co-Presenter/Co-Author), Baruch College, City University of New York, Chester.Zarnoch@baruch.cuny.edu;

Timothy Hoellein (Co-Presenter/Co-Author), Loyola University Chicago, thoellein@luc.edu;

Denise Bruesewitz (Co-Presenter/Co-Author), Colby College, dabruese@colby.edu;

Richard Walker (Co-Presenter/Co-Author), Upper Iowa University, walkerr03@uiu.edu;

Sally Entrekin (Co-Presenter/Co-Author), Virginia Tech, sallye@vt.edu;

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6/06/2024  |   16:45 - 17:00   |  Salon 3/4

DETECTING VARIABLE PATTERNS OF UNIONID ASSEMBLAGES AND CONTAMINANTS OF EMERGING CONCERN IN UNIONID TISSUE, WATER, AND SEDIMENTS IN A MIDWESTERN RIVER Contaminants of emerging concern (CECs) including pesticides, pharmaceuticals and personal care products (PPCP), hormones, plasticizers, and per- and polyfluoroalkyl substances. CECs have been increasingly detected in natural systems and are of interest due to their potential influence on aquatic organisms. Native freshwater mussels (unionids) are benthic aquatic organisms exposed to CECs and are relatively sedentary in nature. Possible impacts of CECs on unionids are important since unionids can be used as environmental monitors for contaminants, provide many ecosystem services, and can comprise >50% of benthic biomass. We examined sites along a 26km reach of the Chippewa River passing through a mid-Michigan city surrounded by agriculture. This study considers how CECs detected in water and sediment differ from upstream to downstream and whether CECs in unionid tissues and unionid assemblages exhibit similar trends. This study found that the number of PPCPs increased at downstream sites compared to upstream sites in water, sediment, and unionid tissue, however there was no difference in unionid density along the gradient. Fifteen unionid species were found alive across all sites, with three species common to all sites, 3 species unique to the most downstream site, and 2 species unique to a middle site. This study has identified unique CECs and concentration values to each media and highlights the relationship between CECs and unionid assemblages that may be influenced by land use. CEC trends in this study will increase the understanding of CECs in rivers and help guide future priorities on how CECs may influence aquatic organisms.

Marta Springer (Primary Presenter/Author), Central Michigan University, sprin2mj@cmich.edu;

Hunter J. Carrick (Co-Presenter/Co-Author), Central Michigan University, carri1h@cmich.edu;

Daelyn A. Woolnough (Co-Presenter/Co-Author), Central Michigan University, wooln1d@cmich.edu;

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