SFS Annual Meeting

6/06/2024  |   15:30 - 15:45   |  Independence Ballroom B

TAXON-SPECIFIC RESPONSES DRIVE ENHANCED MACROINVERTEBRATE PRODUCTION IN AN EXPERIMENTALLY WARMED FOREST STREAM In a rapidly changing climate, it is increasingly important to understand the effects of elevated temperatures on ecosystem productivity, including in ecosystems dependent on detrital subsidies for secondary production (P). Assuming constant resource supply from such subsidies, the metabolic theory of ecology predicts decreases in consumer biomass (B) and increases in consumer biomass turnover (P:B) at higher temperatures, which results in temperature-invariant secondary production. To test the response of consumer productivity to higher temperatures, we warmed a forested headwater stream by 1.8°C for two years, comparing macroinvertebrate production to a year of pre-warming and a reference stream. Macroinvertebrate production, biomass, and P:B increased in the treatment stream during the warming period. Taxon-specific production, biomass, and growth rates varied significantly across streams and years. Relative to other taxa, the production of Isoperla larvae exhibited the most pronounced negative response, the biomass of Diplectrona larvae decreased the most, and Copepods exhibited the most significant increases in production and biomass. Compared to other taxa, Leuctra larvae exhibited the greatest decrease in growth rates, whereas Corynoptera larvae increased the most in response to warming. We found no significant relationships between changes in production and functional feeding group or body size. Resource (leaf litter) standing stock did not change with warming. These results suggest that even subtle increases in temperatures may enhance secondary production and biomass turnover in ecosystems, with taxon-specific changes driving these shifts. Understanding the role of these changes in consumer productivity is crucial for comprehending ecosystem responses to warming.

Phoenix Rogers (Primary Presenter/Author), The University of Alabama, parogers@crimson.ua.edu;

Jonathan P. Benstead (Co-Presenter/Co-Author), The University of Alabama, jbenstead@ua.edu;

Amy D. Rosemond (Co-Presenter/Co-Author), University of Georgia, rosemond@uga.edu;

Seth Wenger (Co-Presenter/Co-Author), University of Georgia, sethwenger@fastmail.fm;

Ashley Helton (Co-Presenter/Co-Author), University of Connecticut, ashley.helton@uconn.edu;

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6/06/2024  |   15:45 - 16:00   |  Independence Ballroom B

INCREASED DISCHARGE SUPPORTS MORE AQUATIC ANIMAL BIOMASS IN A WETLAND Water movement and variation in discharge are important structuring features for aquatic communities. Everglades restoration includes increasing flow rates (1-3 cm/s) in a large wetland landscape, but the net effects of discharge variation for the food web have not been examined. We experimentally created a gradient of discharge along a 2.5-km transect of interconnected sloughs by discharging low-nutrient water (TP < 10 ppb) during the wet season and monitored the response of aquatic communities. Twenty-three sloughs were sampled across the flowing transect and two parallel non-flowing/reference transects. We used 1-m2 throw traps to quantify small fish and macroinvertebrate biomass and electrofishing to quantify large fish (SL > 8 cm) biomass. All sites were sampled seven times over four years and biomass variation was modelled linearly with both experimental discharge (180-days prior to sampling) and TP concentrations in the flocculent detritus. Responses varied by group, but discharge generally had positive impacts on biomass. Discharge interacted with floc TP to explain variation in small fish and macroinvertebrate biomass (P < 0.05) that could not be explained by their additive effects. These groups had the strongest positive response with discharge under low floc TP conditions. Moreover, large fish biomass increased with discharge at all levels of floc TP (P <0.05). The results indicate that bottom-up effects of low discharge pulses can support higher consumer biomass in wetlands, but the response depended on consumer group and local TP.

Marco Fernandez (Primary Presenter/Author), Florida International University, mfern532@fiu.edu;

Nathan Dorn (Co-Presenter/Co-Author), Florida International University, ndorn@fiu.edu;

Joel Trexler (Co-Presenter/Co-Author), Florida State University, jtrexler@fsu.edu;

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6/06/2024  |   16:00 - 16:15   |  Independence Ballroom B

Zooplankton Communities in Stormwater Management Ponds, Ontario, Canada We collected zooplankton and associated water quality and other environmental data from 50 permanent stormwater management (SWM) ponds in Brampton, Canada during summer 2022 to investigate species composition patterns and their drivers. The SWM ponds are engineered systems designed to temporarily store surface runoff before it enters urban streams and rivers, as well as improve water quality by allowing pollutants (e.g. suspended solids and associated heavy metals and phosphorus) to settle to the pond bottom. Given their recent colonization by aquatic organisms (e.g., zooplankton and fish), the ponds provide an excellent opportunity to study the mechanisms underlying population dynamics and community assembly in novel habitats. We determine the relative importance of different suites of factors, such as water chemistry parameters (e.g., chloride and dissolved oxygen), pond morphology (pond size, depth), pond age, and the presence of fish, in explaining variation in zooplankton composition (primarily Crustacea). We also consider the influence of land cover surrounding each site, which can play a critical role in determining local water chemistry conditions and likelihood of fish introduction. Relationships between environmental parameters, fish presence, and zooplankton species composition offer insight into how pond communities are assembled in urban landscapes, as well as how SWM ponds design and management may influence the ecological functioning of these important aquatic habitats.

Xiaozhuo Tang (Primary Presenter/Author), University of Toronto, xiaozhuo.tang@mail.utoronto.ca;

Charlie Loewen (Co-Presenter/Co-Author), Iowa State University, cloewen@IASTATE.EDU;

Donald Jackson (Co-Presenter/Co-Author), University of Toronto, don.jackson@utoronto.ca;

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6/06/2024  |   16:15 - 16:30   |  Independence Ballroom B

Whole-stream nitrogen and phosphorus additions interact with temperature to influence stream macroinvertebrate communities A key challenge in predicting how freshwater ecosystems respond to global change lies in quantifying interactions and non-linearities that emerge from multiple coinciding stressors. In particular, there is large uncertainty about how temperature and nutrients combine or interact to influence the structure and production of aquatic communities. We conducted experimental whole-stream enrichments of nitrogen (N) and phosphorus (P) in four Icelandic streams that lie along a 5°C gradient of ambient temperatures. During three summers (year 1: ambient nutrient concentrations, year 2: +200 µg P/L, year 3: +200 µg N/L), we quantified responses of macroinvertebrate abundance, biomass, community structure, and production to nutrient enrichment across the thermal gradient. Consistent with previous studies, temperature had a strong influence on community structure, with higher temperatures leading to lower abundances of cold-adapted taxa (e.g., Diamesa spp., Eukiefferiella minor) and increased abundances of warm-tolerant taxa (e.g., gastropods, oligochaetes). Community structure also responded strongly to N – but not P – addition, and N enrichment interacted with temperature to influence total invertebrate biomass (g m-2) and production (g m-2 d-1). At moderate temperatures, biomass and production were positively influenced by N enrichment, whereas warmer temperatures led to declines in biomass and production. We suggest that predicting stream ecosystem responses to climate warming will require a deeper understanding of how temperature interacts with nutrient supply to influence community structure.

Wyatt Cross (Primary Presenter/Author), Montana State University, wyatt.cross@montana.edu ;

Jonathan P. Benstead (Co-Presenter/Co-Author), The University of Alabama, jbenstead@ua.edu;

James Hood (Co-Presenter/Co-Author), The Ohio State University, hood.211@osu.edu;

Alexander D. Huryn (Co-Presenter/Co-Author), The University of Alabama, huryn@ua.edu;

Jill Welter (Co-Presenter/Co-Author), St. Catherine University, jill.welter@gmail.com;

Jon Olafsson (Co-Presenter/Co-Author), Iceland Marine and Freshwater Research Institute, jon.s.olafsson@hafogvatn.is;

Gisli Mar Gislason (Co-Presenter/Co-Author), University of Iceland, gmg@hi.is;

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6/06/2024  |   16:30 - 16:45   |  Independence Ballroom B

FINE-SCALE MACROINVERTEBRATE METACOMMUNITY DYNAMICS WITHIN A FRAGMENTED HEADWATER STREAM NETWORK: IMPLICATIONS FOR BIOASSESSMENT AND RESTORATION Small streams provide receiving waterbodies with vital ecosystem services but typically go unmonitored by government agencies where bioassessment tools are not calibrated to evaluate them. Headwaters are vulnerable to human pressures given their low dilution capacity and proximity to upland disturbance and while biomonitoring and restoration efforts aim to safeguard this valuable resource, there is a need to describe the underlying mechanisms of community assembly. To gain insights into macroinvertebrate dynamics in small unmonitored streams, we seasonally investigated fine-scale alpha and beta diversity with abiotic factors in 15 reaches (4–38 ha catchment area) grouped as within-network (5 mainstem and 5 tributary) and 5 outside-network mainstem streams; these sites had variable connectedness and fragmentation. We also evaluated seasonal and group-wise differences in trait-based dispersal tendencies, functional feeding group composition, and regional bioassessment indices. Beta diversity partitioning showed high taxa turnover related to abiotic factors across sites but low nestedness. Season and location were clustered in ordination space, but dispersion was higher across out-of-network sites than network sites. Catchment area and environmental heterogeneity contributed to beta diversity; within the network, beta diversity was also related to physical proximities. Across group locations, we observed few differences among dispersal traits, but seasons structured these and functional feeding group composition. Despite that study streams were much smaller than experiences of regional bioassessment indices, we found comparable scores with existing state tools and that indices were resilient to high turnover. The opinions are those of the authors and do not represent policies of the U.S. Government.

Gregory Pond (Primary Presenter/Author), USEPA, Region 3, Laboratory Services and Applied Science Division, pond.greg@epa.gov;

Kelly Krock (Co-Presenter/Co-Author), U.S. EPA, Region 3, Laboratory Services and Applied Science Division, krock.kelly@epa.gov;

Frank Borsuk (Co-Presenter/Co-Author), U.S. EPA, Region 3, Laboratory Services and Applied Science Division, borsuk.frank@epa.gov;

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6/06/2024  |   16:45 - 17:00   |  Independence Ballroom B

IMPACTS OF SHORT-TERM FLOW CHANGES ON MACROINVERTEBRATE COMMUNITIES IN STREAMS DRAINING AGRICULTURAL AND UNCLEARED CATCHMENTS Freshwater macroinvertebrate communities are altered by the press disturbance of upstream conversion to agriculture as well as pulse disturbances by temporary changes to flow. The diversity and redundancy of response traits should be key to understanding how chronic disturbances affect the capacity of communities to respond to pulses of changed flow. We experimentally tested how the ecosystem changes resulting from agricultural conversion affected the short-term responses of macroinvertebrate communities to flow changes using temporary weirs in each of eight streams in Tasmania spanning a range of catchment conversion using a before-after control-impact study design. As well as documenting changes in community structure, we also measured decomposition (using both leaves and cotton strips) and accumulation of algal biomass during and after flow change as proxies of the major ecosystem functions in these streams to provide a comprehensive picture of the different aspects of ecosystem recovery.

Bridget White (Primary Presenter/Author), University of Tasmania, bridget.white@utas.edu.au;

Sean Atkinson (Co-Presenter/Co-Author), Murdoch University, sean.atkinson@murdoch.edu.au;

Belinda J. Robson (Co-Presenter/Co-Author), Murdoch University, b.robson@murdoch.edu.au;

Russell Death (Co-Presenter/Co-Author), Pohangina Environmental Consulting, Ashhurst, New Zealand, r.g.death@massey.ac.nz;

Leon A. Barmuta (Co-Presenter/Co-Author), University of Tasmania, Leon.Barmuta@utas.edu.au;

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