SFS Annual Meeting

6/04/2024  |   15:30 - 15:45   |  Freedom Ballroom F

Elevated Greenhouse Gas Emissions in Freshwater Microcosms following Glyphosate and 2,4-D Herbicide Exposure Wetlands play an important role in the global greenhouse gas (GHG) budget through biogeochemical processes. The use of agrochemicals may impact GHG production in freshwater ecosystems with increased herbicide contamination indirectly leading to a potential rise in GHG emissions. Glyphosate and 2,4-Dichlorophenoxyacetic acid (2,4-D) are among the mostly widely used herbicides in agriculture and are frequently combined in pesticide mixtures to combat noxious weed tolerance. While the individual effects of glyphosate and 2,4-D on aquatic ecosystems are well-documented, affecting various non-target organisms, including microorganisms, there exists a gap in the literature concerning their combined effects on microbial communities, which are challenging to understand due to complex ecosystem interactions. Microbial processes drive biogeochemical cycling, influencing subsequent GHG emissions from wetlands. To investigate the independent and synergistic effects of glyphosate and 2,4-D herbicides on wetland microbial processes, we conducted a microcosm experiment using low, medium, and high individual concentrations of these herbicides, and in combination, measuring methane, carbon dioxide, and nitrous oxide fluxes as well as porewater concentrations. Our results indicate that elevated herbicide concentrations significantly increase carbon dioxide fluxes. In particular, high glyphosate when combined with 2,4-D had a synergistic effect on carbon dioxide emissions. These findings highlight glyphosate and 2,4-D contamination to wetlands may result in changes to biogeochemical cycling, which may have substantial implications for climate change. Our research underscores the importance of implementing management strategies aimed at reducing agrochemical use to mitigate GHG emissions from wetlands.

Christine Cornish (Primary Presenter/Author), North Dakota State University, christine.cornish@ndsu.edu;

Olivia Schloegel (Co-Presenter/Co-Author), Kent State University, ojohns16@kent.edu;

Jacob Meier (Co-Presenter/Co-Author), Northern Prairie Wildlife Research Center, jmeier@usgs.gov;

Ted Harris (Co-Presenter/Co-Author), Kansas Biological Survey and Center for Ecological Research, ted.daniel.harris@gmail.com;

Sheel Bansal (Co-Presenter/Co-Author), Northern Prairie Wildlife Research Center, sbansal@usgs.gov;

Jon Sweetman (Co-Presenter/Co-Author), The Pennsylvania State University, jfs6745@psu.edu;

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6/04/2024  |   15:45 - 16:00   |  Freedom Ballroom F

SALTY OR SWEET: A COMPARATIVE ANALYSIS OF TRADITIONAL ROAD SALTS AND BEET-BASED ALTERNATIVES ON ORGANIC MATTER DECOMPOSITION IN STREAMS Freshwater salinization threatens water quality in freshwater ecosystems, particularly in urban areas where road salt is applied to maintain safe driving conditions. To minimize salinization, some municipalities have turned to ‘eco-friendly’ alternatives, such as a mixture of beet molasses and salt brine, for winter road maintenance. While the reduction in chloride application has earned beet-brine products an ‘eco-friendly’ reputation, few studies have verified these claims. Our study compared the effects of beet-brine versus traditional chloride salts on leaf litter decomposition utilizing recirculating stream mesocosms. We quantified microbial respiration, leaf toughness, and decomposition (as mass loss) over a two-week period for a labile (Acer saccharum) and recalcitrant leaf species (Quercus stellata) under five treatments: control, low-beet, high-beet, low-salt, and high-salt. We hypothesized the carbon content of beet-brine would alter decomposition rates, while traditional road salts would alter decomposition via changes in osmotic pressure. We further predicted both treatments would exhibit a stronger impact on the labile species. Preliminary results indicate our high-beet treatment increased microbial respiration on both species, while high-salt, low-salt, and low-beet treatments had no effect. This may be driven by inputs of excess carbon associated with the high-beet treatment. We did not observe changes in toughness or decomposition during the study. Our results indicate beet-brine should be further tested prior to widespread use, as it may impact key ecosystem functions.

Caroline Anscombe (Primary Presenter/Author), University of Arkansas, anscombe@uark.edu;

Shannon Speir (Co-Presenter/Co-Author), University of Arkansas, slspeir@uark.edu;

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

Kathleen Cutting (Co-Presenter/Co-Author), University of Arkansas, kjcuttin@uark.edu;

Alana Strauss (Co-Presenter/Co-Author), University of Arkansas, alanas@uark.edu;

Jennifer L. Tank (Co-Presenter/Co-Author), University of Notre Dame, tank.1@nd.edu;

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6/04/2024  |   16:00 - 16:15   |  Freedom Ballroom F

THE EFFECT OF LEAF LITTER DECOMPOSITION ON TRANSPORT OF ANTIMICROBIAL RESISTANCE GENES (ARGs) IN STREAMS The widespread use of antibiotics in animal agriculture, combined with manure application on farm fields as a soil amendment, contributes to the runoff of antimicrobial resistance genes (ARGs) to adjacent waterways. Leaf litter decomposition is a key feature of temperate streams in autumn, and may influence ARG fate and transport. We conducted replicated short-term, steady-state additions of cow manure slurries over 21 days of leaf decomposition during autumn 2023 using four experimental streams (Q=2L s-1, width=67cm , depth=5cm). We compared water column removal rates (k in m-1) for two clinically relevant ARGs found in manure (tetracycline-resistant tetQ and tetW) and compared them between two control (no leaves) and two treatment streams (150g DM m-2 of sugar maple leaves). The two treatment streams exhibited similar leaf decomposition rates (k=0.004 and 0.009 d-1; ANCOVA, p=0.25). For ARGs, water column removal was 56% higher in the treatment streams for tetQ (control=0.010 m-1; treatment=0.016 m-1) and 62% higher for tetW (control=0.012 m-1; treatment=0.019 m-1), but there was no significant difference in removal between tetQ and tetW (t-test, p=0.48). We did not see a clear temporal trend in ARG removal over the 21-day colonization period, but leaves influenced removal rates more prior to day 7, suggesting that physical complexity and increased surface area, rather than leaf biofilm, drives removal. Understanding how decomposing leaves alter fate and transport will improve our ability to predict ARG behavior, ultimately informing strategies to mitigate the dissemination of antimicrobial resistance via streams.

Mitchell Liddick (Primary Presenter/Author), University of Notre Dame, mliddick@nd.edu;

Jennifer L. Tank (Co-Presenter/Co-Author), University of Notre Dame, tank.1@nd.edu;

Emma M. Thrift-Cahall (Co-Presenter/Co-Author), University of Notre Dame, ethrift@nd.edu;

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

Elise Snyder (Co-Presenter/Co-Author), University of Notre Dame, esnyder4@nd.edu;

Anna Vincent (Co-Presenter/Co-Author), University of Notre Dame, avincen5@nd.edu;

Ursula H. Mahl (Co-Presenter/Co-Author), University of Notre Dame, umahl@nd.edu;

Diogo Bolster (Co-Presenter/Co-Author), University of Notre Dame, diogo.bolster.5@nd.edu;

Kyle Bibby (Co-Presenter/Co-Author), University of Notre Dame, kbibby@nd.edu;

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6/04/2024  |   16:15 - 16:30   |  Freedom Ballroom F

THE IMPACT OF MANURE MANAGEMENT ON TRANSPORT DYNAMICS OF ANTIMICROBIAL RESISTANCE GENES (ARGs) IN STREAMS The use of antibiotics in animal husbandry has contributed to the spread of antimicrobial resistance (AR) in agricultural watersheds via the spread of treated manure to fields as a soil amendment. While acquiring an AR infection can pose significant threats to human health, we lack a comprehensive understanding of drivers that influence the fate and transport of antimicrobial resistance genes (ARGs) in agricultural landscapes and adjacent waterways. We used experimental streams, and short-term, steady-state additions of manure slurry, sourced from different stages of management, to examine water column ARG removal paired with biofilm accumulation of two medically-significant ARGs (tetracycline-resistant tetW and tetQ). We collected three manure types: before microbial digestion, from an active digester, and post-digestion from a holding lagoon and screened them for various ARGs and the fecal indicator bacR. There was a reduction in ARG and bacR concentrations across some manure management steps (Dunn’s test, p<0.05) but no reduction in tetW (p>0.05). In experimental streams, water column removal rates of tetQ and tetQ did not differ across manure types (GLM; emtrends, p>0.05). With water column removal, ARGs accumulated in stream biofilms, however their declines with distance did not differ across manure types (emtrends, p<0.05). Finally, removal rates for tetW and tetQ estimated using biofilms mirrored water column ARG removal rates (t-test; p>0.05). While the impact of manure management on ARG transport needs further study, the similarity of water column and biofilm removal rates suggests that physical deposition onto biofilm is an important driver of ARG removal in streams.

Emma M. Thrift-Cahall (Primary Presenter/Author), University of Notre Dame, ethrift@nd.edu;

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

Olivia Ginn (Co-Presenter/Co-Author), University of Georgia, oliviaginn@uga.edu;

Mitchell Liddick (Co-Presenter/Co-Author), University of Notre Dame, mliddick@nd.edu;

Ursula Mahl (Co-Presenter/Co-Author), University of Notre Dame, Ursula.H.Mahl.1@nd.edu;

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

Diogo Bolster (Co-Presenter/Co-Author), University of Notre Dame, diogo.bolster.5@nd.edu;

Kyle Bibby (Co-Presenter/Co-Author), University of Notre Dame, kbibby@nd.edu;

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6/04/2024  |   16:30 - 16:45   |  Freedom Ballroom F

Unravelling the Bio-Ecological Traits Mediating Macroinvertebrate Colonisation of Macroplastic Substrates in Selected Afrotropical Rivers In Africa, macroplastic threatens riverine bio-physical and hydro-geomorphological processes. Recent studies reported that macroplastics alter benthic habitat diversity and variably supports diverse macroinvertebrate assemblages. However, using a trait-based approach to gain a mechanistic understanding of the response of macroinvertebrates to riverine macroplastic remains a constraint. We examined the bio-ecological traits of macroinvertebrates colonising macroplastic substrates for six months. Macroplastic substrates (100% natural substrates; NS > 50% natural + plastic substrate; NP >100% plastic-dominated substrate; PD), representing an increasing gradient of plastic substrates, were deployed in three hydraulic biotopes from four headwater streams of Eastern Cape, South Africa. The trait analysis revealed differential spatiotemporal distribution of macroinvertebrate traits. The early colonisers (days 30 – 60) were dominated by a group of taxa characterised by medium (>10 – 20 mm) and large (20 > 40) body sizes, flat bodies, collector-gatherers, free-living, and predators. In contrast, taxa with a preference for high flow velocity (0.3 - 0.6 m/s), permanent attachment, and filter-feeding mode showed predominance on days 150 – 180. Traits such as oval and flat body shape, medium body size (>10 - 20 mm), skating and clinging/climbing mobility, temporal attachment, shredders, predators, prey, and plastron and spiracle respiration showed a positive correlation with the 100% macroplastic substrates. Filter feeding, crawling, permanent attachment, a preference for fast velocity (0.3-0.6 m/s), and coarse particle organic matter were positively correlated with the 50% macroplastic substrates. Hence, we encourage using a trait-based approach to continually unravel the response of macroinvertebrate communities to plastic-impacted habitats in rivers.

ANDREW ABAGAI ALI (Primary Presenter/Author), Institute for Water research, Rhodes University, aliandy598@gmail.com;

Frank Akamagwuna (Co-Presenter/Co-Author), University of Alabama, fcakamagwuna@ua.edu;

Chika Nnadozie (Co-Presenter/Co-Author), Institute for Water research, Rhodes University, c.nnadozie@ru.ac.za;

Nelson Odume (Co-Presenter/Co-Author), Institute for Water Research, Rhodes University, Grahamstown, n.odume@ru.ac.za;

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6/04/2024  |   16:45 - 17:00   |  Freedom Ballroom F

TOLERANT BENTHIC COMMUNITIES IMPEDE RECOLONIZATION BY SENSITIVE SPECIES FOLLOWING REMEDIATION OF A HISTORICALLY METAL-POLLUTED STREAM Novel communities resulting from long-term exposure to contaminants and other anthropogenic disturbances may persist for many years after the initial stressors have been eliminated. However, the mechanisms responsible for state shifts in freshwater benthic communities are not well understood. We use results of a 35-year observational study conducted in the Arkansas River (Colorado) and a series of mesocosm experiments to test the hypothesis that the presence of novel macroinvertebrate communities in a previously metal-contaminated stream impeded recolonization and recovery of sensitive species. Results of long-term monitoring of benthic communities demonstrated that abundance and species richness quickly recovered following improvements in water quality; however, community composition and trophic structure has remained altered compared to upstream reference sites for over 20 years after remediation was completed. Mesocosm experiments conducted with reference and downstream communities demonstrated that downstream communities retained their tolerance to metals, but were significantly more susceptible to other anthropogenic stressors, including acidification, UVB radiation and diesel fuel. Additional experiments were conducted to determine if the presence of metal-tolerant species inhibited recolonization by upstream reference communities. Results showed that while metal-tolerant communities could readily colonize reference communities, the reverse was not true. In other words the presence of metal-tolerant communities located immediately downstream from metal-sensitive communities in stream mesocosms significantly reduced recolonization. We suggest that the failure of downstream communities to completely recover in the Arkansas River following improvements in water quality and habitat likely resulted from the presence of novel communities that inhibited recolonization by metal-sensitive species.

William Clements (Primary Presenter/Author), Colorado State University, william.clements@colostate.edu;

McKenzie Moore (Co-Presenter/Co-Author), Colorado State University, Mckz.Moore@colostate.edu;

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