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SFS Annual Meeting

Thursday, June 6, 2024
15:30 - 17:00

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S05 Contaminant and Trace Element Biogeochemical Cycling in Aquatic Ecosystems

15:30 - 15:45 | Freedom Ballroom F | STOICHIOMETRY AND GROWTH RESPONSE OF STREAM BIOFILM AND MACROINVERTEBRATE GRAZER TO LIMITING METAL AND MACRONUTRIENT ENRICHMENT.

6/06/2024  |   15:30 - 15:45   |  Freedom Ballroom F

STOICHIOMETRY AND GROWTH RESPONSE OF STREAM BIOFILM AND MACROINVERTEBRATE GRAZER TO LIMITING METAL AND MACRONUTRIENT ENRICHMENT. Macronutrients (N, P) in limiting conditions have been hypothesized to influence food quality, constrain energy, and alter the nutrient balance in basal resources and consumers. However, the extent to which trace nutrients like metals influence energy transfer and stoichiometry in the freshwater food web is not fully understood. Studying the stoichiometry and growth of algal food and grazers under varying metal and macronutrient conditions can help us understand the role of essential metals on resource-consumer relationships. We used a river-fed flow-through artificial stream system, comprised of 32 circular mesocosm streams (ExStream), which were treated with iron, phosphate, and nitrate in a fully crossed experimental design. Unglazed tiles were placed in each stream for biofilm colonization and Heptageniidae mayflies were added as consumers. After 24 days, biofilm and mayfly samples were collected, measured for growth, and digested for C, N, P, trace metals, and elemental ratios analyses. Biofilm C:N ratios were slightly higher than Redfield in control streams (>23) but were lower in all streams receiving nitrate and iron (<23). Heptageniid mayfly growth was greater in streams receiving Fe and N, but P did not increase growth rates. However, mayfly C:N was not affected by any nutrient treatments and these organisms remained homeostatic across treatments. These results suggest that iron can be co-limiting with macronutrients and may modify the nutrient quality of food for grazers. Future work should focus on the mechanisms by which iron can influence microbial and animal nutrition and species interactions.

Olufemi Akinnifesi (Primary Presenter/Author), Kent State University, oakinnif@kent.edu;

Renn Schipper (Co-Presenter/Co-Author), Kent State University, rschipp1@kent.edu;

Talia Pope (Co-Presenter/Co-Author), Kent State University, tpope8@kent.edu;

Claire Ebner (Co-Presenter/Co-Author), Kent State University, cebner3@kent.edu;

David Costello (Co-Presenter/Co-Author), Kent State University, dcostel3@kent.edu;

15:45 - 16:00 | Freedom Ballroom F | METAL DYNAMICS IN THE UPPER CLARK FORK RIVER: ALGAL BIOFILMS DRIVE METAL ACCUMULATION AND CYCLING DURING A FILAMENTOUS GREEN ALGAL BLOOM.

6/06/2024  |   15:45 - 16:00   |  Freedom Ballroom F

Metal dynamics in the Upper Clark Fork River: Algal biofilms drive metal accumulation and cycling during a filamentous green algal bloom. The Upper Clark Fork River (UCFR) in northwestern Montana, USA, faces compounding threats due to historical metal contamination and nutrient pollution. During the growing season, nutrient pollution causes enhanced productivity, dominated by the filamentous green alga, Cladophora glomerata, which then becomes colonized by epiphytic algal biofilms and senesces. Although it is well-known that algae can accumulate metals and mediate metal transfer to primary consumers, how these contaminants accumulate during different stages of algal blooms remains poorly understood. Our study examined the accumulation of metals by algae during the 2021 growing season along the UCFR. We measured water metal concentrations, algal standing stocks, and tissue metal content in filamentous algae, epiphytic algal biofilms, and epilithic algae. We used metabolism data to estimate biomass turnover rates for filamentous algae and algal biofilms. We found that biofilm metal concentrations more closely tracked water metal concentrations than filamentous algae, which displayed lower metal concentrations across elements. Biomass turnover rates in biofilms surpassed those in filamentous algae by up to 2.5-fold. Our findings imply that despite lower biomass, algal biofilms may play a disproportionate role in the trophic transfer of metals to consumers. For instance, in the most intense bloom location (98┬▒14g dry mass*m-2), biofilms comprised 12% of the total standing crop but accounted for 77%, 78%, and 70% of the total Cd, Cu, and Pb turnover, respectively. However, filamentous algae exert both direct and indirect effects on overall metal accumulation in this system by acting as a substrate for epiphyte growth.

Rafael Feij├│ de Lima (Primary Presenter/Author), University of Montana, rfeijod@clemson.edu;

Dylan T. White (Co-Presenter/Co-Author), University of Montana, dylan1.white@umconnect.umt.edu ;

Alice M. Carter (Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, alicecarter05@gmail.com;

H. Maurice Valett (Co-Presenter/Co-Author), University of Montana, Division of Biological Sciences, maury.valett@umontana.edu;

Robert O. Hall (Co-Presenter/Co-Author), Flathead Lake Biological Station, University of Montana, bob.hall@flbs.umt.edu;

Michael DeGrandpre (Co-Presenter/Co-Author), University of Montana, michael.degrandpre@umontana.edu;

Benjamin Colman (Co-Presenter/Co-Author), University of Montana, ben.colman@umontana.edu;

16:00 - 16:15 | Freedom Ballroom F | PFAS IMPACTS ON LEAF LITTER DECOMPOSITION IN A STREAM ECOSYSTEM

6/06/2024  |   16:00 - 16:15   |  Freedom Ballroom F

PFAS Impacts on Leaf Litter Decomposition in a Stream Ecosystem The processing of organic matter in streams is a fundamental ecosystem function and critical to the biogeochemical cycling of both carbon and nutrients. Organic matter processing in stream ecosystems can be strongly influenced by anthropogenic impacts, including chemical contamination. Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment and highly resistant to degradation, yet little information exists regarding the influence of PFAS on organic matter processing in streams. Here, we investigated leaf decomposition and microbial respiration rates upstream and downstream of a known PFAS point source in a third-order agricultural stream. We deployed 12 pre-weighed leaf packs constructed from senescent maple leaves (Acer saccharum) at locations upstream and downstream of the PFAS point source. At two weeks and four weeks, three packs were retrieved from each reach for a final mass measurement to determine litter decomposition and three packs were analyzed for PFAS. We also performed light and dark incubations of leaf disks to quantify microbial respiration. We observed lower decomposition and microbial respiration rates for leaf litter deployed downstream of the outfall. However, a follow-up laboratory study where we exposed maple leaves to PFOS (perfluorooctanoic sulfonic acid) could not reproduce observed field results. Next steps include dosing leaves with 6:2 FTS (fluorotelomer sulfonate), which was a prevalent PFAS compound below the outfall and returning to the field site now that the PFAS source is removed to determine if legacy effects exist from past PFAS discharges or if the stream ecosystem has recovered.

Alison Zachritz (Primary Presenter/Author), University of Notre Dame, Department of Biological Sciences, azachrit@nd.edu;

Abagael Pruitt (Co-Presenter/Co-Author), University of Notre Dame, apruitt2@nd.edu;

Therese Reisch (Co-Presenter/Co-Author), University of Notre Dame, treisch@nd.edu;

Laura Hubbard (Co-Presenter/Co-Author), United States Geological Survey , lhubbard@usgs.gov;

Daniele Miranda (Co-Presenter/Co-Author), University of Notre Dame, ddealmei@nd.edu;

Brittany Perrotta (Co-Presenter/Co-Author), United States Geological Survey, bperrotta@usgs.gov;

Christopher Kotalik (Co-Presenter/Co-Author), United States Geological Survey, ckotalik@usgs.gov;

Dana Kolpin (Co-Presenter/Co-Author), United States Geological Survey, dwkolpin@usgs.gov;

David Walters (Co-Presenter/Co-Author), United States Geological Survey, waltersd@usgs.gov;

Jennifer L. Tank (Co-Presenter/Co-Author), University of Notre Dame, jtank@nd.edu;

Gary Lamberti (Co-Presenter/Co-Author), University of Notre Dame, glambert@nd.edu;

16:15 - 16:30 | Freedom Ballroom F | FRESHWATER INESECT-MEDIATED POLYCHLORINATED BIPHENYL TRANSFER FROM FRESHWATER AND TERRESTRIAL ECOSYSTEMS

6/06/2024  |   16:15 - 16:30   |  Freedom Ballroom F

FRESHWATER INESECT-MEDIATED POLYCHLORINATED BIPHENYL TRANSFER FROM FRESHWATER AND TERRESTRIAL ECOSYSTEMS Discharged coolant water in streams and military activity have left a legacy of polychlorinated biphenyl (PCB) contamination near Tullahoma, Tennessee. Affected streams drain into a reservoir, creating a mosaic of PCB-contaminated sediment through the military installation, home to rare and endangered consumers that utilize freshwater insects as a food source. Emergent adult freshwater insects can transport bioaccumulated PCBs to insectivorous terrestrial consumers, such as endangered gray bats present on the base. The transport of PCBs to terrestrial food webs is likely influenced by the route of bioaccumulation in immature insects, PCB flux from bodies of water, and possibly by insect stoichiometry. A better understanding of factors that control PCB transport could provide better management of species toxicity exposure, and better focus limited resources. To assess the movement of PCBs within and between aquatic and terrestrial systems, we examined bioaccumulation pathways within stream food webs using stable isotopes, insect-derived PCB flux using floating emergence traps, and nutrient stoichiometry on regulating PCB transfer through the aquatic food web and into terrestrial consumers. We predict differences in insect-derived PCB flux between stream and reservoir sites, a positive correlation between higher insect trophic level and PCB concentration, and an inverse correlation between insect carbon:phosphorus ratio and PCB concentrations. This research will provide information on how PCBs move into aquatic organisms and across ecosystem boundaries and how species diversity and nutrient availability may influence transport rates across trophic levels.

Peter Blum (Primary Presenter/Author), Tennessee Technological University, pwblum@gmail.com;

Justin Murdock (Co-Presenter/Co-Author), Tennessee Technological University, jnmurdock@tntech.edu;

16:30 - 16:45 | Freedom Ballroom F | MICROPLASTICS AS HOTSPOTS FOR INTERACTIONS OF PHARMACEUTICALS AND MICROBES

6/06/2024  |   16:30 - 16:45   |  Freedom Ballroom F

Microplastics as Hotspots for Interactions of Pharmaceuticals and Microbes Microplastics and pharmaceuticals are anthropogenic contaminants that can co-occur in wastewater and human-impacted surface waters. Due to their high surface area and hydrophobicity, some microplastics can adsorb other contaminants, including pharmaceuticals, resulting in high localized concentrations of these contaminants on microplastic surfaces. Microbial biofilms, which can include bacteria and algae, also attach to microplastic surfaces in aquatic ecosystems, potentially enhancing interactions between these microorganisms and pharmaceuticals. These interactions could affect microbial community composition and potentially select for strains that are resistant to antimicrobial pharmaceuticals, including antibiotics. We assessed interactions between pharmaceuticals and microbial communities on microplastic surfaces with laboratory experiments. In one study, exposure of microplastic fibers to the antimicrobial compound triclosan resulted in high triclosan adsorption on polyester and acrylic fibers and low adsorption on nylon fibers. Incubation of these fibers with river water in laboratory-scale microcosms showed that the bacterial and algal communities that colonized triclosan-exposed fibers were significantly different in composition from those on non-exposed fibers. In another study, addition of polyester fibers and a cocktail of eight common pharmaceuticals to stream mesocosms resulted in adsorption of all eight pharmaceuticals to microplastics and development of significantly different bacterial communities on the pharmaceutical-adsorbed microplastics compared to controls. These results confirm our hypothesis that microplastic surfaces can be hot spots for microbial interactions with pharmaceuticals. Ongoing work is exploring the prevalence of antimicrobial and antibiotic resistance within these microbial communities.

John Kelly (Primary Presenter/Author), Loyola University Chicago, Jkelly7@luc.edu;