SFS Annual Meeting

Fernando Carvallo (Co-Presenter/Co-Author)
Texas A&M University–Corpus Christi, fcarvallo@islander.tamucc.edu ;

James Hogan (Co-Presenter/Co-Author)
Texas A&M University – Corpus Christi, james.hogan@tamucc.edu;

Christopher Patrick (Co-Presenter/Co-Author)
Virginia Institute of Marine Science (VIMS), cpatrick@vims.edu;

Alexander Solis (Primary Presenter/Author)
VIMS, alexander.tr.solis@gmail.com;

Abstract: Water control structures such as dams are significant obstacles for the freshwater prawn, Macrobrachium, on their migration to estuaries to complete their amphidromous life cycle and prevent juveniles from returning to higher reaches of rivers and streams to live out their adult life stage. Four species of Macrobrachium, once found throughout Texas waterways, have been extirpated from much of their former range and have been relegated to coastal plains in the last 30 years. Using comprehensive historical sampling events of Macrobrachium throughout Texas, and pulling data from the US Army Corps of Engineers’ National Inventory of Dams data set, we determined the impact of the dams and their key attributes on the probability of Macrobrachium being present upstream of these dams using mixed effect logistic regression models. We found that dams have had a significant impact on the Macrobrachium range since 1987, reducing their presence upstream of most dams. Due to morphological differences between species in Macrobrachium, dam attributes that influenced whether Macrobrachium would be present upstream of the dam varied for each species. Other tested anthropogenic factors were not as explanatory of Macrobrachium range loss as dams.

Amanda Subalusky (Co-Presenter/Co-Author)
University of Florida, asubalusky@ufl.edu;

Christopher Dutton (Co-Presenter/Co-Author)
University of Florida, duttonc@ufl.edu;

Laban Njoroge (Co-Presenter/Co-Author)
National Museums of Kenya, nnlaban@yahoo.com;

Joshua Benjamin (Co-Presenter/Co-Author)
University of Florida, joshuaben3@gmail.com;

Emma Rosi (Co-Presenter/Co-Author)
Cary Institute of Ecosystem Studies, rosie@caryinstitute.org;

David Post (Co-Presenter/Co-Author)
Yale University, david.post@yale.edu;

Therese Frauendorf (Primary Presenter/Author)
Yale University, therese.frauendorf@yale.edu;

Abstract: Animal subsidies have important effects on aquatic food webs, yet we know little about how these effects vary with the magnitude of subsidies. The Mara River in Kenya has over 4000 hippopotamuses who forage on savanna grasslands during the night and rest in the river during the day. We selected six sites along the hippo abundance gradient (from 0 to 4300 hippos) in the Mara River and measured invertebrate biomass and diversity at each site. Hippo dung increased from 0 to 70 g of dry mass/m², which resulted in a > 10-fold growth in invertebrate biomass. Total biomass of scrapers like Tricorythid mayflies increased exponentially, while other functional feeding groups increased to a lesser extent. The number of invertebrate species doubled at sites with hippo dung, but they did not change with the magnitude of the subsidy. Lastly, the density of invertebrates within hippo dung itself did not vary across the gradient, although invertebrate density in hippo dung did increase during high discharge periods. These patterns indicate that it is not just the occurrence, but the magnitude of animal subsidies that play an important role in structuring freshwater macroinvertebrate communities.

Jennifer Howeth (Primary Presenter/Author)
University of Alabama, jghoweth@ua.edu;

Thomas Olinger (Co-Presenter/Co-Author)
University of Alabama, ctolinger@crimson.ua.edu;

Justin Hart (Co-Presenter/Co-Author)
University of Alabama, hart013@ua.edu;

Abstract: Metacommunity theory predicts that the relative importance of regional and local processes structuring communities will change over succession. To test theoretical predictions of the increasing importance of local processes over succession, we evaluated fish species and trait diversity in three pond metacommunities undergoing secondary succession from beaver (Castor canadensis) disturbance. Taxonomic and trait diversity were contrasted across pond communities of different ages and in reference streams. Counter to predictions, the local environment became less important in structuring communities over succession but did exert a stronger effect on trait sorting. Beta diversity and trait richness declined over succession while there was no influence on species richness or trait dispersion. The trait filtering in older habitats was likely driven by the larger and deeper ponds of late succession. In contrast, the environment primarily structured species and trait diversity in streams. Analyses of the relative importance of regional and local processes in structuring fish assemblages within each pond metacommunity suggests that habitat age and connectivity were more important than the environment. Together, these findings highlight that regional and local processes can differentially influence taxonomic and trait diversity in successional metacommunity mosaics.

Stephen Blake (Co-Presenter/Co-Author)
Saint Louis University, stephen.blake@slu.edu;

David Post (Co-Presenter/Co-Author)
Yale University, david.post@yale.edu;

Amanda Subalusky (Primary Presenter/Author)
University of Florida, asubalusky@ufl.edu;

Diego Ellis Soto (Co-Presenter/Co-Author)
Yale University, diego.ellissoto@yale.edu;

Abstract: In Santa Cruz Island, many adult Galapagos giant tortoises (Chelonoidis porteri) undertake seasonal altitudinal migrations driven by rainfall. During the dry season, they spend a large portion of their time resting in small, freshwater ponds, using both natural ponds and ponds maintained to attract tortoises for tourist viewing. We have documented up to 50 tortoises using a single pond at a given time. GPS movement data of a focal individual showed the tortoise re-visited a single pond over 60 times in a given year and spent 1-5 hours in the pond during each visit. Tortoises transfer a large quantity of carbon and nutrients into the pond through excretion and egestion, leading to high conductivity and low dissolved oxygen levels. Tortoises also transfer a large quantity of sediment out of ponds on their carapace, up to 1 kg of mud (dry weight) per tortoise per visit, and this bioturbation may play an important role in maintaining open water habitats. Tortoise movements play a large role in shaping the physical and biogeochemical structure of both natural and human maintained freshwater habitats on the Galapagos Islands.

Marco Scarasso (Co-Presenter/Co-Author)
The Ohio State University, scarasso.2@buckeyemail.osu.edu;

Alexander Reisinger (Co-Presenter/Co-Author)
University of Florida, reisingera@ufl.edu;

Lauren M. Pintor (Co-Presenter/Co-Author)
The Ohio State University, pintor.6@osu.edu;

Lindsey Reisinger (Co-Presenter/Co-Author)
University of Florida, lreisinger1@ufl.edu;

Bana Kabalan (Primary Presenter/Author)
University of Florida, bana.kabalan@ufl.edu;

Abstract: Although intraspecific trait variation is increasingly recognized as having strong effects on ecosystem processes, few studies have examined the ecological significance of among-population variation in behavioral traits in natural ecosystems. In freshwater ecosystems, crayfish play a key role in the benthic-water column link and may affect ecosystem function by translocating benthic nutrients and organic matter to the water column. Here, we test whether population-level crayfish behavioral traits (boldness, activity, and foraging voracity) are stronger predictors of stream metabolism and leaf litter decomposition than environmental drivers (land use, light, and water temperature). To test this, we hand-collected Faxonius rusticus and Faxonius virilis from 21 streams across the midwestern USA, measured ecosystem function in the field, and quantified crayfish behavioral traits using laboratory assays. Our results suggest that crayfish behavioral traits often had a greater role in structuring rates of water column metabolism and leaf litter decomposition than environmental variables. However, intraspecific behavior-ecosystem links only occurred in F. rusticus, which is invasive throughout most of our study range. Thus, examining among-population trait variation in animals, especially invasive species, may be central to understanding the mechanisms shaping ecosystem functions.

FRANK MASESE (Primary Presenter/Author)
UNIVERSITY OF ELDORET, f.masese@gmail.com;

Thomas Fuss (Co-Presenter/Co-Author)
Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany, fuss@igb-berlin.de ;

Lukas Bistarelli (Co-Presenter/Co-Author)
Department of Ecology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria, lukas.thuile-bistarelli@uibk.ac.at;

Caroline Buchen-Tschiskale (Co-Presenter/Co-Author)
Thünen Institute of Climate-Smart Agriculture, Bundesallee 65, 38116 Braunschweig, Germany, caroline.buchen@thuenen.de ;

Gabriel Singer (Co-Presenter/Co-Author)
University of Innsbruck, gabriel.singer@uibk.ac.at;

Abstract: In this study, we challenge existing theoretical concepts on energy sources and flow in riverine food webs in the Mara River, which is an African montane-savanna river known to receive large subsidy fluxes of terrestrial carbon and nutrients mediated by large mammalian herbivores (LMH). Using stable carbon (?13C) and nitrogen (?15N) isotopes, we identified spatial patterns of the relative importance of allochthonous carbon from C3 and C4 plants (woody vegetation and grasses, respectively) and autochthonous carbon from periphyton for macroinvertebrates in the river. Sites were selected in different stream sizes (orders 1 to 7) in various catchment land uses and receiving different loading rates of organic matter and nutrients by LMH (livestock and hippopotamus). The importance of different sources of carbon along the river did not follow predictions of RCC or RPM models. Notably, C4 carbon was important for macroinvertebrates in rivers inhabited by hippos, while autochthonous carbon was a major source of energy for macroinvertebrates, even in low order forested streams. Our results show that replacing wildlife (hippos) with livestock shifts river systems towards autochthony as opposed to reliance on allochthonous inputs of C4 carbon through a detrital pathway.

Jacob Iteba (Primary Presenter/Author)
University of Eldoret, Kenya, mesmerisejsmith@gmail.com;

Abstract: Populations of large wildlife have declined in many landscapes around the world, and have been replaced or displaced by livestock. Consequences of these changes on transfer of organic matter (OM) and nutrients from terrestrial to aquatic ecosystems are not well understood. We used behavioural data, excretion and egestion rates and C: N: P stoichiometry of dung and urine of zebu cattle, to develop a metabolism-based estimate of loading rates of OM (dung), C, N and P into the Mara River, Kenya. We also directly measured deposition of OM and urine by cattle into the river during watering. Per head, zebu cattle excrete and/or egest 22.3 g DM (86.6 g wet mass; metabolism) - 24.6 g DM (direct input) of OM, 13.8-22.2 g C, 5.1-10.6 g N, and 0.26-0.50 g P per day into the river. In order to replace loading rates OM of an individual hippopotamus by cattle, 100 individuals will be needed, but much less for different elements. Changing these patterns of OM and nutrients transport and cycling will have significant effects on structure and functioning of both terrestrial and aquatic ecosystems.

Garrett Hopper (Primary Presenter/Author)
Department of Biological Sciences, University of Alabama, gwhopper@ua.edu;

Gabriella Dickinson (Co-Presenter/Co-Author)
Department of Biological Sciences, University of Alabama, gabikdickinson@gmail.com;

Carla L. Atkinson (Co-Presenter/Co-Author)
The University of Alabama, carla.l.atkinson@ua.edu;

Abstract: Knowledge of species elemental composition empowers predictions regarding animal legacy effects in ecosystems. Ionomics characterizes elemental composition of organisms beyond C, N, and P (i.e., the ionome). Considering novel suites of elements as phenotypes increases the probability of linking elements in species’ biomass and ecosystem functions. Freshwater mussel (family: Unionidae) shells can remain in riverscapes across geological time, providing accessible and ecologically relevant morphological features to study animal legacy impacts on aspects of elemental cycles. Whether interspecific differences in life history traits and morphology influence shell elemental composition is not well understood. We quantified 11 elements and constructed nutrient balances for seven mussel species comprising diverse morphologies, life histories, and two reproductive strategies to test whether biological factors influence elemental relationships. Ionomes, traditional stoichiometry, and novel nutrient balances varied taxonomically and with conventional species traits. Shell P composition was negatively related to growth rates, while [C|P] and [C, Ca |P] were positively related to growth rates, suggesting P allocation is prioritized to soft tissue growth which mediates shell biomineralization. Overall, we uncovered intra-guild functional diversity and relationships among elements mediating traits influencing animal legacies via storage of understudied elements.

Katherine Handler (Primary Presenter/Author)
Yale University, katherine.handler@yale.edu;

Abstract: Animal mortality can leave a legacy in aquatic ecosystems through the decomposition and assimilation of carcasses. The magnitude of the mortality event can influence the spatial and temporal availability of carcasses in the ecosystem and the scavengers that use them. We used photographic time series, river?side surveys, and telemetry data to investigate scavenger use and succession of wildebeest carcasses after mass drownings in the Mara River, Kenya. Carcass material was present three weeks after drownings, and bones remained even longer. Avian scavenger density per carcass was almost two orders of magnitude lower than has been documented for single terrestrial carcasses. Temporal resource partitioning by scavenger species was observed on a diel scale and throughout the period of decomposition. Telemetry data indicated approximately half of the tagged vultures used mass drowning events but only spent a small proportion of their time there. This suggests that competition still plays a role in scavenger dynamics at mass mortality events, and rewards of abundant resources may be offset by the risk of the river. Further research is needed to better understand the role of scavengers in processing animal carcass legacies in aquatic ecosystems.

Adam Siders (Primary Presenter/Author)
University of Florida, asiders@ufl.edu;

Alexander Reisinger (Co-Presenter/Co-Author)
University of Florida, reisingera@ufl.edu;

Matt Whiles (Co-Presenter/Co-Author)
University of Florida, mwhiles@ufl.edu;

Abstract: Once restricted to south Florida due to water temperatures, Florida manatees have expanded their range northward as anthropogenic temperature changes (e.g., climate change, power plant discharges) expand suitable habitat. Manatees primarily inhabit marine ecosystems, feeding on sea grasses, but seek thermal refuge near power plant discharges or spring-fed freshwater ecosystems when coastal temperatures drop in the winter. When manatees aggregate in freshwater habitats, they graze entire beds of macrophytes, recycle nutrients via excretion and egestion, and bioturbate sediments, which increases suspended solids and decreases light availability. We seek to understand how migrating manatees affect nutrient cycling and food webs in Kings Bay, FL, a complex of 41 inland springs that form the headwaters of the Crystal River flowing 11 km into the Gulf of Mexico. Nutrient diffusing substrata indicate that biofilms are autotrophic when manatees are absent, but switch to heterotrophy when manatees are present, likely due to sedimentation and reduced light availability. Urea-N can reduce biofilm nutrient limitation, but manatee-induced bioturbation effects likely limit biofilm production more than nutrients. Our studies suggest that manatees are ecosystem engineers that have significant impacts on Florida springs.

Eugenia Zandona (Primary Presenter/Author)
Universidade do Estado do Rio de Janeiro, eugenia.zandona@gmail.com;

Priscila Cunha (Co-Presenter/Co-Author)
Universidade do Estado do Rio de Janeiro, priscilacunhaoli@gmail.com;

Vinicius Neres-Lima (Co-Presenter/Co-Author)
Universidade do Estado do Rio de Janeiro, vinicius.lima.eco@gmail.com;

Maira Moraes (Co-Presenter/Co-Author)
Universidade Veiga de Almeida, maira.eco@gmail.com;

Alexander Flecker (Co-Presenter/Co-Author)
Cornell University, Ithaca, NY, USA, asf3@cornell.edu;

Luisa Manna (Co-Presenter/Co-Author)
Universidade do Estado do Rio de Janeiro , luisamanna@gmail.com;

Rosana Mazzoni (Co-Presenter/Co-Author)
Universidade do Estado do Rio de Janeiro, romazzoni.uerj@gmail.com;

Abstract: In the highly diverse Rio Ubatiba in Brazil, in the last 25 years, fish abundance has been declining and invasive species have substituted native ones. Changes in fish abundance and identity can affect stream nutrient dynamics, as different species have different excretion rates, due to their differences in size, diet, and demand. We measured excretion rates of all fish species and estimated the total areal excretion over 25 years based on the changes in population density. We also focused on the effect of the substitution of one native armored catfish species with an invasive one. Overall, we found that fish-driven nutrient recycling decreased through the years, due to the general decrease in fish abundance. After the introduction of the invasive, smaller-sized catfish, areal nutrient excretion dropped, due to the sharp decrease in overall catfish biomass. This lack of functional replacement was mostly due to the lower biomass of the invasive catfish after the invasion compared to the native species before the invasion. The loss of fish species, introduction of invasive species, and reduction in fish biomass can strongly affect nutrient dynamics and other ecosystem processes in fast-changing human-impacted tropical streams

Hannah Talbert (Co-Presenter/Co-Author)
Georgia Gwinnett College, htalbert@ggc.edu;

Alanna James (Co-Presenter/Co-Author)
Georgia Gwinnett College, ajames13@ggc.edu;

Paul Hebert (Co-Presenter/Co-Author)
Georgia Gwinnett College, phebert@ggc.edu;

Elizabeth Sudduth (Primary Presenter/Author)
Georgia Gwinnett College, esudduth@ggc.edu;

Abstract: Beaver populations are rebounding throughout the US and seem well adapted to living in urban streams. By retaining stormwater and sediment, increasing microbial processing, and returning stream channels towards pre-colonial geomorphology, beaver dams could improve water quality and habitat in impacted urban streams. Beaver dam analogs (BDAs) are a process-based restoration technique used in locations not currently colonized by beavers, potentially more effective and less expensive than traditional form-based restoration. In Atlanta, GA, USA, we sampled stream macroinvertebrates in 2018 and 2021 upstream and downstream of urban beaver dams and BDAs, which were installed in 2020. We also sampled stream water chemistry monthly 2017-2021 upstream and downstream at the same sites and additional beaver sites. We found some positive changes in the macroinvertebrate community following the BDA installation, but the beaver dam site had declined in both abundance and diversity. The water quality trends at all sites were complicated, with some indications of improved downstream water quality, in particular nitrogen retention, but these trends were also affected by hydrology, in particular large, dam-removing storm events, a common occurrence for urban beavers that decreases the benefits seen in less impacted systems.

Lauren Kinsman-Costello (Co-Presenter/Co-Author)
Kent State University, lkinsman@kent.edu;

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

Taylor Michael (Primary Presenter/Author)
Kent State University, tmichae9@kent.edu;

Abstract: Freshwater aquatic sediments are teeming with thousands of invertebrates per m2, yet we lack an understanding of how invertebrates contribute to nutrient recycling and burial. Bioturbating invertebrates burrow/rework sediment which introduces oxygenated water to anoxic sediments and alters the rate and directionality of nutrient fluxes. Roles that bioturbators play in ecosystem functioning likely differ under changing environmental conditions. Using an intact core flow-through experiment with sediments from Sandusky Bay, Ohio, we measured how chironomid larvae bioturbation and excretion alter nutrient fluxes using ambient and elevated bioturbator densities under periods of oxic, hypoxic, and alternating water oxygen conditions. Preliminary results suggest that nitrate is removed from surface water under all oxygen conditions, likely via different mechanisms. Elevated bioturbator densities appear to facilitate greater fluxes of nitrate compared to ambient invertebrate densities in oxic and alternating oxygen conditions. Sulfate is released in oxic and alternating treatments, indicating oxygen’s role in facilitating sulfate release. Phosphate flux was dominated by physical processes under oxic and alternating oxygen but phosphate release under hypoxic conditions was exacerbated by bioturbation activity. Shifting oxygen conditions appear to shape how bioturbators contribute to internal loading within shallow water ecosystems.

Nicole Yetke (Primary Presenter/Author)
University of Florida, nyetke@ufl.edu;

Abstract: Many animal species across both terrestrial and aquatic ecosystems modify their environments in ways that benefit other species. Burrows created by animals can influence environmental characteristics and provide microhabitats relied upon by commensal species. American alligators (Alligator mississippiensis) dig burrows in geographically isolated wetlands (GIWs), which may provide important habitat in these highly seasonal environments. We plan to study the ecological role of alligator burrows and how this role changes with environmental context at the Jones Center at Ichauway. We will 1) quantify alligator and commensal species use of burrows, 2) document the abundance and location of burrows within and across GIWs, and 3) characterize the temperature, humidity, and inundation profiles of burrows. Thus far, we have documented alligator burrows in at least 16 of nearly 100 GIWs on the site. We have analyzed time-lapse video recordings of burrow entrances when they provided the only standing water in the GIW and documented at least 5 different vertebrate species using the burrows for foraging and shelter. Our research suggests that alligator burrows provide an important microhabitat and refugia for an array of aquatic and terrestrial species, such as snakes and birds.