SFS Annual Meeting

6/06/2024  |   10:30 - 10:45   |  Freedom Ballroom E

SPATIAL PATTERNS IN NUTRIENT STOICHIOMETRY TRENDS IN NORTHERN PRAIRIE RIVERS Anthropogenic activities are changing the supply of nitrogen (N) and phosphorus (P) to northern Prairie rivers. Differential loadings of N and P have the potential to shift riverine N:P over time, impacting nutrient cycling and primary production. However, little is known about long-term N:P trends in Prairie rivers. Our goal was to evaluate long-term (25-year) trends in total and dissolved N:P ratios at 11 sites situated on five rivers across the Red and Assiniboine River Basins in Canada. Total N:P changed at all but two sites across the basin, with stationary trends reflective of special circumstances at the local watershed level. Of the sites that recorded shifts in total N:P, those in the Red River basin all declined over the 25-year period. In contrast, trends were not consistent across the Assiniboine River basin, with total ratios increasing and decreasing in a half and a third of the sites, respectively. Across both basins, dissolved nutrient ratio trends were concordant with total N:P trends at five of the 11 sites, suggesting dissolved nutrient fractions are an inconsistent driver of total stoichiometry. Positive relationships between total and dissolved N:P appeared unrelated to broad patterns of land use. Analysis is underway to investigate the roles of nutrient concentrations and hydrology as drivers of stoichiometric trends. Our initial findings show that nutrient stoichiometry is changing in Prairie rivers, but the causes are unclear and will require further analysis.

Amy White (Primary Presenter/Author), University of Waterloo, a33white@uwaterloo.ca;

Robert Brua (Co-Presenter/Co-Author), Environment Canada, bob.brua@ec.gc.ca;

Arthur Friesen (Co-Presenter/Co-Author), Environment and Climate Change Canada, arthur.friesen@ec.gc.ca;

Helen Jarvie (Co-Presenter/Co-Author), University of Waterloo, helen.jarvie@uwaterloo.ca;

Adam Yates (Co-Presenter/Co-Author), University of Waterloo, adam.yates@uwaterloo.ca;

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6/06/2024  |   10:45 - 11:00   |  Freedom Ballroom E

Influence of water stargrass on water quality in the lower Yakima River, WA In the lower Yakima River, WA, macrophyte beds of native water stargrass are prolific and can extend bank to bank altering local water quality conditions. In this study, we collected continuous water quality data over 2.5 years and estimated water stargrass biomass monthly through the growing season at 3 sites during water years 2018 to 2020. The objective of this study was to document water quality conditions and to analyze what relationships there were between the amount of water stargrass and daily cycles of water quality. During summer, frequent exceedances of established water quality criteria were observed. Maximum daily temperatures exceeded 21oC, minimum dissolved oxygen (DO) fell below 8 mg/L, and maximum pH was greater than 8.5 almost every day from June through August. Water stargrass biomass during summer months showed increases from June through September and a ‘reset’ prior to the next summer likely from high winter and spring river flows. Water quality metrics were computed for 7-day and 28- day time periods prior to each water stargrass sample to examine correlations between the plant biomass and water quality metrics. These metrics included daily maximum temperature, maximum DO and daily range, pH maximum and daily range, and stream metabolism. Relationships between plant biomass and water quality were inconclusive; however, there seems to be strong inverse relationship between spring flows and late summer biomass in these reaches. This indicates that spring flows may be controlling late summer biomass and changes in flow management may help reduce summer water quality issues.

Rich Sheibley (Primary Presenter/Author), USGS Washington Water Science Center, Sheibley@usgs.gov;

James Foreman (Co-Presenter/Co-Author), USGS Washington Water Science Center, jforeman@usgs.gov;

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6/06/2024  |   11:00 - 11:15   |  Freedom Ballroom E

ECOSYSTEM METABOLISM AS A TOOL TO ASSESS AN ECOLOGICAL DISASTER: THE RIVER ODER Anthropogenic impacts on freshwater ecosystems range from nutrient and contaminant inputs to flow regulation and climate change, the effects of which may act antagonistically, additively, or synergistically to affect ecosystem biota and function. Extremes of multiple stressors can lead to ecological disasters, such as occurred in August 2022 in the River Oder, when prolonged low flows combined with high temperatures created low oxygen concentrations which were compacted with high salt inputs and a toxic algal bloom. These combined stressors resulted in a large fish kill of an estimated 1000 tons dead. The evaluation of ecosystem resistance and resilience after such an event is limited by a lack of ecological information before the event as they are rare and unexpected. Long-term water quality monitoring stations could provide tools to evaluate such ecological disasters, especially if ecological functional metrics, such as ecosystem metabolism, can be estimated long-term (>25y time series available). Daily average temperatures in the first week of August were 2–4°C higher at 23–25°C and oxygen concentrations 2–3mg/L lower at 6–7mg/L compared to the previous year, while chlorophyll concentration increased with a delay of approximately one week, potentially explaining why low oxygen concentrations recovered by mid-August. Estimation of metabolism, as gross primary production and ecosystem respiration, has the potential to determine whether the high chlorophyll concentrations equaled high production and whether the increase in dead organic matter due to the fish kill increased respiration. The long-term metabolic patterns will also reveal whether such metabolic events happened before and under what conditions.

Janine Ruegg (Primary Presenter/Author), Brandenburg University of Technology, jrueegg@GMAIL.COM;

Flavia Tromboni (Co-Presenter/Co-Author), Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, flavia.tromboni@rptu.de;

Dominik Martin-Creuzburg (Co-Presenter/Co-Author), Brandenburg University of Technology, dominik.martin-creuzburg@b-tu.de;

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6/06/2024  |   11:15 - 11:30   |  Freedom Ballroom E

Aquatic insect emergence in dynamic floodplain habitats of a large river ecosystem Aquatic insect emergence provides nutrient subsidies to aquatic and terrestrial ecosystems. However, the timing and location of emergence events are highly variable making it difficult to quantify their importance as a subsidy, especially in large river ecosystems characterized by habitat heterogeneity and dynamic hydrologic conditions. In this study, we quantified temporal and spatial variability of aquatic insect emergence for four years (2020-2023) in floodplain habitats of the Upper Mississippi River near La Crosse, WI, USA. Insects were collected each summer (June-August) using emergence traps at 27 sites ranging in their distance from the main river channel and historic duration of water inundation. We predicted distance from the main channel and historic inundation duration would affect taxonomic richness and biomass of insect emergence by influencing dispersal and life-history characteristics (e.g., desiccation-resistance) of the aquatic insect community. We found high temporal and spatial variability in insect emergence from floodplain habitats. Contrary to our prediction, distance from the main channel and historic inundation duration did not affect insect emergence. However, both insect richness and biomass were positively correlated with above normal spring runoff events. These results suggest insect communities in this large river floodplain are not dispersal limited and that recent hydrological events, rather than historical events, may drive the richness and biomass of insect emergence. The predicted increase in the frequency and intensity of spring floods associated with climate change could cause an increase in floodplain insect productivity.

Ross Vander Vorste (Primary Presenter/Author), University of Wisconsin - La Crosse, rvandervorste@uwlax.edu;

Brad Morris (Co-Presenter/Co-Author), University of Wisconsin-La Crosse, brad.e.c.morris@gmail.com;

Skylar Voigt (Co-Presenter/Co-Author), University of Wisconsin-La Crosse, voigt0503@uwlax.edu;

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6/06/2024  |   11:30 - 11:45   |  Freedom Ballroom E

CHANGES IN MACROINVERTEBRATE COMMUNITY COMPOSITION AND DIVERSITY ACROSS SIDE CHANNELS OF A LARGE RIVER SYSTEM Large rivers are inherently diverse in habitat types and the biological communities they support. Adjacent to the main channel in large rivers, side channels may provide more favorable and heterogeneous habitats for organisms such as macroinvertebrates. However, few studies have quantified their biological communities and explored differences among side channels, particularly across large geographical scales, leaving their biodiversity value and function unknown. Our objective was to quantify aquatic macroinvertebrate community composition within side channels (n = 23) of six reaches in the Upper Mississippi River System along a 2000 river km longitudinal gradient. We tested for longitudinal patterns in taxonomic and functional diversity and community composition. Macroinvertebrates were collected using rock baskets and Hester-Dendy samplers following a 30-day colonization period (n = 134 samples) and were counted and identified to genus. Macroinvertebrate abundance ranged from 50 – 38,400 individuals/m^2 across side channels but there were no longitudinal trends in abundance among reaches. We found longitudinal trends for both taxonomic richness and composition, in which richness decreased and percentage of Ephemeroptera, Plecoptera and Trichoptera increased from upstream to downstream. Our results suggest that side channels may be more important habitat for certain taxa, such as EPT, in downstream reaches of large rivers where off-main channel habitats are less abundant. Throughout this large river system, side channels appear to support diverse macroinvertebrate communities suggesting this habitat type contributes importantly to overall macroinvertebrate biodiversity.

Cheyana Bassham (Primary Presenter/Author), University of Wisconsin - La Crosse, bassham0884@uwlax.edu;

Kristen Bouska (Co-Presenter/Co-Author), U.S. Geological Survey, kbouska@usgs.gov;

Molly Sobotka (Co-Presenter/Co-Author), Missouri Department of Conservation - Big Rivers and Wetlands Field Station, molly.sobotka@mdc.mo.gov;

Ross Vander Vorste (Co-Presenter/Co-Author), University of Wisconsin - La Crosse, rvandervorste@uwlax.edu;

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6/06/2024  |   11:45 - 12:00   |  Freedom Ballroom E

Fish 'n' Floods: The Impact of the Flood Pulse on Catch in the Amazon River Floodplain Fish catch in floodplain ecosystems is crucial to the livelihoods of millions of people worldwide. The catch is regulated by seasonal fluctuations in water levels, known as "flood pulses," which determine the ecosystem's structure and function. However, the key aspects of the flood pulse that control fish catch are not well understood, even though changes in fish biomass due to interannual variability in flood pulses have a significant impact on fish catch. To identify these aspects, we conducted a study on the Amazon Basin, analyzing 13 years of fish catch and river hydrology data using a generalized additive mixed model (GAMM). We looked at daily fishing trips and river water levels over the Amazon River mainstem to calculate hydrological metrics and fishing efforts. We then modeled the total catch response to hydrological indices based on fish effort and gear type over each fishing trip for each fishery boat. Preliminary results showed that total catch is associated with two previous flooded years, where the rate of change and magnitude of the flood season are the key hydrological aspects of the flood pulse. Long, high flood waters and predictable years led to increased catch in subsequent years, especially for fish taxa that depend on the flood to reproduce and recruit. These research results will provide vital information on the effects of the flood pulse on fish catch, allowing for the development of management strategies to help fishers better adapt to hydrological alterations induced by climate change.

Gabriel Borba (Primary Presenter/Author), Virginia Tech , gabrielcostaborba@gmail.com;

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