SFS Annual Meeting

Michael Gooseff (Co-Presenter/Co-Author)
University of Colorado, michael.gooseff@colorado.edu;

Diane McKnight (Co-Presenter/Co-Author)
University of Colorado, diane.mcknight@colorado.edu;

Christa L. Torrens (Primary Presenter/Author)
University of Colorado at Boulder, christa.torrens@flbs.umt.edu;

Abstract: In the McMurdo Dry Valleys [MDV], Antarctica, little is known about concentration-discharge (C-q) relationships for biological solutes like DOC. Because MDV streams are low in organic carbon and experience large diel fluctuations in discharge(q), we expected that the MDV DOC-q relationship would be dilution-based and limited by the DOC generation rate, not the fluid transit time. To evaluate the DOC-q relationship in these glacial-meltwater streams, we fit the long-term DOC-q data to two models: a power law and an advection-reaction model. We then used model outputs and other common metrics to quantify the DOC-q relationship. Surprisingly, our results demonstrate this relationship is chemostatic; however, they do not provide a clear explanation why. After examining and eliminating various potential DOC-q drivers, we propose a conceptual model where hyporheic carbon storage, hyporheic exchange rates, and net DOC generation rates are key interacting components that enable chemostatic DOC-q behavior in MDV streams. This model clarifies the role of autochthonous carbon stores in maintaining DOC-q chemostasis and may be useful for examining these relationships in temperate systems, where the role of autochthonous carbon is masked by a far larger allochthonous signal.

Nicolas Lamouroux (Co-Presenter/Co-Author)
INRAE, nicolas.lamouroux@irstea.fr;

Thomas Condom (Co-Presenter/Co-Author)
IRD, thomas.condom@ird.fr;

Isabelle Gouttevin (Co-Presenter/Co-Author)
INRAE, isabelle.gouttevin@inrae.fr;

Maxence Forcellini (Co-Presenter/Co-Author)
INRAE, maxence.forcellini@inrae.fr;

Bertrand Launay (Co-Presenter/Co-Author)
INRAE, bertrand.launay@inrae.fr;

Sophie Cauvy-Fraunié (Co-Presenter/Co-Author)
INRAE, sophie.cauvy-fraunie@inrae.fr;

Juliette Becquet (Primary Presenter/Author)
INRAE, juliette.becquet@inrae.fr;

Abstract: Alpine catchments display particularly complex hydrographic networks, characterized by high environmental and hydrological heterogeneities, as they include streams from different water sources. This mosaic of stream habitats generates high spatial variability in aquatic communities within catchments. Combined effects of climate change and anthropogenic pressures on water resources induce rapid environmental changes in alpine catchments. To maintain the sustainability of alpine streams, it is urgent to quantify the relative effects of hydrological and environmental drivers on aquatic communities. To date, relationships between stream habitats and macroinvertebrate communities have not been compared among multiple alpine catchments. In this study, we measured physico-chemical and hydraulic conditions, estimated hydrological conditions (simulation), and sampled benthic macroinvertebrates in 66 stream reaches located in three catchments in the French Alps. Based on Co-Inertia analyses and Negative Binomial Generalized Linear Mixed models, we quantified, respectively, the responses of macroinvertebrate at both community and taxa level to stream habitat characteristics, and we tested the transferability of invertebrate responses across different catchments.

Landon Falke (Primary Presenter/Author)
Colorado State University, landonfalke@gmail.com;

Daniel Preston (Co-Presenter/Co-Author)
Colorado State University, Dan.Preston@colostate.edu;

Abstract: In lotic ecosystems, the River Continuum Concept (RCC) provides a framework for understanding changes in environmental factors and free-living communities, yet how parasite populations shift along river continua remains less clear. We quantified infections by a pathogenic trematode parasite (Nanophyetus salmincola) in >14,000 host snails across 130 stream reaches in the Willamette River Basin in western Oregon, USA. Environmental factors – including flow volume, temperature, benthic algae, and land cover – changed predictably with stream order, consistent with the RCC. From first- to eighth-order reaches, infection prevalence decreased by ~42-fold and infected snail density, a measure of disease risk to fish hosts, decreased ~3-fold. Infected snail density, but not prevalence, was positively associated with snail biomass density, and individual infection probability increased strongly with host size. Shifts in snail population characteristics across stream orders, however, did not explain the observed changes in N. salmincola populations, suggesting that environmental variables and corresponding changes in non-snail hosts explain the downstream decrease in infections. Our findings show predictable spatial variation in disease risk to vertebrate hosts from N. salmincola and indicate the RCC can help explain shifts in parasite populations in lotic ecosystems.

Erika Tatiana Cifuentes Vargas (Primary Presenter/Author)
Universidad Pedagógica y Tecnológica de Colombia, erika.cifuentes01@uptc.edu.co;

Nelson Javier Aranguren Riaño (Co-Presenter/Co-Author)
Universidad Pedagógica y Tecnológica de Colombia, nelson.aranguren@uptc.edu.co;

Luz Nidia Gil Padilla (Co-Presenter/Co-Author)
Universidad Pedagógica y Tecnológica de Colombia, luznidia.gil@uptc.edu.co;

Abstract: In Colombia, intermittent rivers are gaining importance because some of what we considered perennial rivers are becoming temporary. We do not know how the structure and function of macroinvertebrates communities are altered and, how they respond to these water intermittent events. Therefore, this study evaluated the expression of functional traits of resistance and resilience in response to intermittent events in the Salitre stream in Boyacá-Colombia. A total of 4550 taxa were recorded, with 50 taxas, highlighting the richness of the order Trichoptera (61%) and genus Grumichella. The substrate with the highest abundance of organisms was the rock (62%). The PCA was arranged depending on the hydroclimatic season, where temperature, alkalinity, and salinity increased during the dry season and the concentration of dissolved oxygen decreased. The resistance mechanism most frequent were presented collector-collector organisms, respiration by gills, the body size of 5 to 10 mm, cylindrical body which was associated with rainy season. The resilience they were similar during sampling as crawlers, life cycle duration ? 1 year. The functional traits did not present temporal differences, but there is a pattern in the expression of the traits for this system.

Christopher Whitney (Primary Presenter/Author)
University of New Hampshire, chris.whitney@unh.edu;

Wilfred M. Wollheim (Co-Presenter/Co-Author)
University of New Hampshire, wil.wollheim@unh.edu;

Michael Palace (Co-Presenter/Co-Author)
University of New Hampshire, palace@guero.sr.unh.edu;

Christina Herrick (Co-Presenter/Co-Author)
University of New Hampshire, christina.herrick@unh.edu;

Abstract: While human activities have led to substantial environmental change, they are not the only organism causing change to the landscape. North American beaver (Castor canadensis) are ecosystem engineers and were once ubiquitous across North America before being trapped to near extinction across the continent by the beginning of the 20th century. Conservation efforts, changes to trapping laws, and abundant suitable habitat has spurred a resurgence in beaver populations in much of their previous range, particularly in New England. This beaver activity has led to additional landscape modification, causing alterations to hydrological and biogeochemical regimes. While evidence of their expansion is evident, comprehensive watershed-scale estimates of their abundance and distribution are lacking in many states such as Massachusetts. We mapped the areal expansion of beaver habitat in two watersheds in northeastern Massachusetts through classification of high-resolution aerial imagery. We found that in one study watershed, wetland area has increased by about 15% since the beginning of the beaver expansion, primarily at the expense of forested land. With such maps, we gain a better understanding of beaver propagation through these watersheds and how it relates to modified biogeochemical exports from river networks.

Ikechukwu Onwuka (Primary Presenter/Author)
Florida International University, ionwu002@fiu.edu;

Abstract: Concentration–discharge (C-Q) relationships were applied to the manmade and regulated canals of the Greater Everglades Ecosystem, to understand phosphorus (P) export dynamics. Twenty-five years of discharge and P data were obtained from three canal monitoring stations (S5a, S39 and S9) that respectively drain agricultural, wetland and urban basins. C-Q relationship for P shows slight positive relationships with discharge for the three canals. Piecewise regressions reveal the presence of threshold behaviors (inflections in C-Q slopes) at S5a and S9, which indicate different P dynamics at low and high flows. During low flows, there are no significant relationships (chemostasis) between concentration and discharge. This means non-hydrologic factors (e.g. biogeochemical processes) dominate the export of P. However, at high flows, there are positive slopes which suggest that higher discharges cause enrichment in P concentrations. An explanation is that higher discharges can mobilize and transport P through entrainment of particulate P from canal bed sediments, desorption of P from suspended particles, and release of pore water P. The ability to determine discharge thresholds above which there can be an increase in P export makes C-Q relationships a crucial management tool for Everglades restoration.

Lauren Giggy (Primary Presenter/Author)
University of California, Santa Cruz, lgiggy@ucsc.edu;

Margaret Zimmer (Co-Presenter/Co-Author)
University of California, Santa Cruz, margaret.zimmer@ucsc.edu;

Abstract: Drying and rewetting patterns in intermittent and ephemeral streams significantly impact biogeochemical processing and the movement of sediment, solutes, and other materials through stream networks. Despite non-perennial streams comprising the majority of stream lengths globally, the controls on these wet up and dry down dynamics are not well understood. We used 40 sensors to map the spatiotemporal presence and absence of surface flow across a 0.23 km2 catchment located in the Mediterranean climate of central coastal California. We observed large variability in wet up and dry down rates across the stream network with active surface drainage densities ranging from 0 to 25.5 km/km2. Analysis of watershed characteristics shows a complex relationship between slope, curvature, and upslope accumulated area, where the importance of each variable varies across adjacent tributaries. Further, stable water isotopes, major ions, and nutrients suggest a shift in dominant stream water sources across the wet to dry season transition. Understanding the physical controls and stream water sources that drive observed variations in flow persistence has significant implications for the ecological and biogeochemical function of non-perennial streams and managing water resources in the face of global change.

Chris Robinson (Primary Presenter/Author)
Eawag, robinson@eawag.ch;

Christa Jolidon (Co-Presenter/Co-Author)
Eawag, jolidon@eawag.ch;

Simon Bloem (Co-Presenter/Co-Author)
Eawag, bloem@eawag.ch;

Christian Ebi (Co-Presenter/Co-Author)
Swiss Federal Institute of Aquatic Science and Technology, EAWAG, Urban Water Management dpt., christian.ebi@eawag.ch ;

Abstract: Macun lakes is an alpine (>2600 m asl) cirque landscape in the Swiss National Park comprising 26 small lakes with interconnecting streams. The drainage network consists of a North and South basin influenced by rock glaciers overlying an ortho-gneiss, meta-granitoid bedrock. Physico-chemistry of surface waters have been monitored annually in mid-summer since 2001, including an Exosonde employed since 2016 at the lowest lake. Results showed clear physico-chemical differences between the two basins that reflect rock glacier inputs in the South basin. Nitrogen values were two-fold higher and particulate phosphorus values two-fold lower in the South than North basin. Physico-chemistry in the two basins became more homogeneous over time with reduced rock glacial inputs in the South basin and a general decrease in nitrogen. North basin streams were ca. 3°C warmer than South basin streams, but with high inter-annual variation reflecting annual differences in climate and no evidence of a general temporal trend (increase or decrease). Exosonde data revealed strong seasonality and diel variability in measured parameters (dissolved oxygen, temperature, chlorophyll-a); the latter being most pronounced in summer. Results highlight the importance of long-term monitoring towards understanding changes in alpine freshwaters.