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SFS Annual Meeting

Monday, June 3, 2024
10:30 - 12:00

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S06 The Ecology of Aquatic Plants (Macroalgae Bryophytes, and Macrophytes) in Streams, Rivers, Wetlands, and Lakes

10:30 - 10:45 | Salon 5/6 | INTRODUCTION TO THE ECOLOGY OF AQUATIC PLANTS

6/03/2024  |   10:30 - 10:45   |  Salon 5/6

Introduction to the Ecology of Aquatic Plants An introduction to the Ecology of Aquatic Plants, the unifying theme for the session.

James Wood (Primary Presenter/Author), West Liberty University, James.Wood@westliberty.edu;

10:45 - 11:00 | Salon 5/6 | AQUATIC PLANT REMOVAL CAN INCREASE NIGHTTIME DISSOLVED OXYGEN CONCENTRATION IN A LOWLAND RIVER

6/03/2024  |   10:45 - 11:00   |  Salon 5/6

AQUATIC PLANT REMOVAL CAN INCREASE NIGHTTIME DISSOLVED OXYGEN CONCENTRATION IN A LOWLAND RIVER In streams and rivers where aquatic plants are confined to the margins, the primary drivers of dissolved oxygen (DO) concentrations are often algal metabolism and organic matter decomposition. However, when plants are abundant throughout the channel, their metabolism can be a major control over ecosystem metabolism and resultant DO concentrations. In the lower Yakima River (Washington State, USA), preliminary evidence suggests that water stargrass (Heteranthera dubia) respiration depletes nighttime DO to concentrations that are insufficient for migrating salmonids (Oncorhynchus spp.). The effect of plant respiration is magnified by lower flows, which are becoming more common as the climate changes. Current plant-free areas are too small to be effective refugia from low DO conditions, so we investigated medium-scale (~ 20,000 m²) plant removal as an adaptation strategy. We deployed DO sensors upstream and downstream of the removal site and calculated the removal effect by comparing the difference between minimum DO at the downstream and upstream sites before and after removal. Post-removal, there was a 0.6 mg/L average increase in minimum DO concentration at the downstream relative to the upstream site. Pre-removal, mean minimum DO at the most downstream site was 0.82 mg/L lower (range: 0.56–1.28 mg/L) than at the upstream site, while in the three weeks immediately following removal, it was 0.22 mg/L lower (range: 0.39–0.55 mg/L). The small post-removal increase in DO minima suggests larger-scale plant removal could be effective at improving salmonid habitat in rivers with abundant plant life.

Aaron Pelly (Primary Presenter/Author), Washington State University, aaron.pelly@wsu.edu;

Marcella Appel (Co-Presenter/Co-Author), Benton Conservation District, marcella-appel@bentoncd.org;

Sarah Roley (Co-Presenter/Co-Author), Washington State University, sarah.roley@wsu.edu ;

11:00 - 11:15 | Salon 5/6 | MACROPHYTES AS ECOSYSTEM ENGINEERS: ROLE OF JUSTICIA AMERICANA IN DISTURBANCE-PRONE OZARK STREAMS

6/03/2024  |   11:00 - 11:15   |  Salon 5/6

MACROPHYTES AS ECOSYSTEM ENGINEERS: ROLE OF JUSTICIA AMERICANA IN DISTURBANCE-PRONE OZARK STREAMS Streams are highly biodiverse despite being disturbance-prone systems. Aquatic macrophytes provide vital ecosystem services within the active channel and may act as ecosystem engineers by creating stable habitat in flashy streams. We asked if water willow (Justicia americana) affects streambed sediment size distribution and macroinvertebrate assemblages in bedrock-lined and gravel-bedded stream reaches in the Ozark Highlands ecoregion (USA). In each reach, we collected data from two habitat types: within and outside of J. americana patches. To quantify sediment size distribution in each habitat, we collected all particles from six replicate cores driven approximately 20cm in the streambed. We then dried and sorted particles into five size classes: silt, fine sand, medium sand, coarse sand, and gravel. We characterized size distributions according to the dry mass of each size class. We also collected six replicate macroinvertebrate samples in each habitat using a modified Hess sampler. Fine sediments represented greater proportions of particles and increased overall heterogeneity of sediment sizes within J. americana patches in both reaches. Macroinvertebrate richness and abundance were greater within macrophyte patches in the bedrock reach, including a few terrestrial taxa. In the gravel reach, richness and abundance were greater outside macrophyte patches, despite terrestrial insects accounting for 25% of total abundance within patches. This might be explained by the rich hyporheic assemblages occupying the interstitial space of gravel-dominated Ozark streams. Overall, our results support conclusions of studies in other regions that J. americana modifies stream habitat and could provide stable refuge for organisms during extreme floods.

Alexis Reifsteck (Primary Presenter/Author), Missouri State University, reifsteckalexis@gmail.com;

Michelle Bowe (Co-Presenter/Co-Author), Missouri State University, mbowe@missouristate.edu;

La Toya Kissoon-Charles (Co-Presenter/Co-Author), Missouri State University, lkissoon@missouristate.edu;

Debra Finn (Co-Presenter/Co-Author), Missouri State University, dfinn@missouristate.edu;

11:15 - 11:30 | Salon 5/6 | HYDROECOLOGY OF MARSHALLIA PULCHRA, A RIVERSCOUR ENDEMIC FORB OF HIGH GRADIENT RIVERS IN THE EASTERN UNITED STATES

6/03/2024  |   11:15 - 11:30   |  Salon 5/6

HYDROECOLOGY OF MARSHALLIA PULCHRA, A RIVERSCOUR ENDEMIC FORB OF HIGH GRADIENT RIVERS IN THE EASTERN UNITED STATES Marshallia pulchra is a globally rare forb endemic to riverscour ecosystems within high-gradient rivers in the Appalachian Plateau of eastern North America. Given the high conservation priority and limited ecological understanding of M. pulchra, we sought to establish knowledge pertaining to the hydrologic conditions of sites supporting this species. We assessed flow records for ten rivers to determine if climate change is modifying flood frequency, magnitude, or duration of M. pulchra-supporting rivers. Records in the Youghiogheny River were also linked to cameras trained on individual plants to quantify the flood frequency and duration sustained annually. Finally, we used a century of M. pulchra presence/absence data from the Youghiogheny River to assess long-term persistence. Discharge records indicate that floods in smaller, free-flowing rivers are becoming more frequent at a rate of up to one flood per year. However, we detected no trends suggesting that floods are becoming more intense. M. pulchra individuals in the Youghiogheny are inundated a median of 17 times annually, mostly during winter and spring, and usually for periods less than two days. Results suggest that the long-term viability of M. pulchra in the Youghiogheny may be diminishing, as individuals were absent in nearly 40% of previously occupied sites during the most recent surveys. Given the signs of population decline in the Youghiogheny, additional investigations exploring the hydroecology of M. pulchra are urgently needed, especially those that consider the role of invasive species in changes to riverscour ecosystem dynamics.

Ryan Utz (Primary Presenter/Author), Chatham University, rutz@chatham.edu;

Nick Leo (Co-Presenter/Co-Author), CESO, Inc., lankatron99@gmail.com;

Christopher Tracey (Co-Presenter/Co-Author), christopher_tracey@natureserve.org, NatureServe;

Ephraim Zimmerman (Co-Presenter/Co-Author), Pennsylvania Natural Heritage Program, ezimmerman@paconserve.org;

Steve Grund (Co-Presenter/Co-Author), Pennsylvania Natural Heritage Program, sgrund@paconserve.org;

11:30 - 11:45 | Salon 5/6 | UNDERSTANDING FLOODPLAIN WETLAND VEGETATION OUTCOMES FROM ENVIRONMENTAL FLOWS AT LARGE SCALES

6/03/2024  |   11:30 - 11:45   |  Salon 5/6

Understanding floodplain wetland vegetation outcomes from environmental flows at large scales The vegetation that occurs along floodplains and wetlands is highly valued for the ecological and cultural benefits it provides. A combination of land use changes and flow modification has had a detrimental effect on the condition of vegetation across many of the world’s large river systems. Environmental flows are being increasingly used to improve the condition and diversity of floodplain and wetland vegetation. Outcomes are typically reported at the scale of individual species or single sites. We lack examples of learning across multiple sites or at regional scales. However, evaluation at large scales is difficult where species vary spatially and temporally, and data are limited. Here we use vegetation monitoring data from across the Murray-Darling Basin to describe the structural and functional vegetation assemblages associated with groups of sites that have experienced similar inundation regimes over the past 8 years. The resulting associations between the inundation group and the vegetation are then used to predict the vegetation assemblage that would occur in the absence of environmental water. We show that 72 monitored sites display three distinct inundation regimes that have correspondingly distinct functional and structural assemblages of vegetation. A modelled counterfactual inundation regime shows that in the absence of environmental water, all sites would have experienced a similar, drier inundation regime and we predict that the corresponding vegetation assemblage would have very few submerged, amphibious and damp-loving species. This highlights the role of environmental water in maintaining a diversity of species across the Murray-Darling Basin.

Fiona Dyer (Primary Presenter/Author), Centre for Applied Water Science, University of Canberra, fiona.dyer@canberra.edu.au;

Will Higgisson (Co-Presenter/Co-Author), Centre for Applied Water Science, University of Canberra, will.higgisson@canberra.edu.au;

Cherie Campbell (Co-Presenter/Co-Author), Centre for Applied Water Science, University of Canberra, cherie.campbell@canberra.edu.au;

Alica Tschierschke (Co-Presenter/Co-Author), Centre for Applied Water Science, University of Canberra, alica.tschierschke@canberra.edu.au;

Tanya Doody (Co-Presenter/Co-Author), CSIRO, Tanya.Doody@csiro.au;

11:45 - 12:00 | Salon 5/6 | CONSEQUENCES OF CHANGES IN FLOW FLUCTUATIONS AND DAM OPERATION ON THE COLORADO RIVER BELOW GLEN CANYON DAM

6/03/2024  |   11:45 - 12:00   |  Salon 5/6

CONSEQUENCES OF CHANGES IN FLOW FLUCTUATIONS AND DAM OPERATION ON THE COLORADO RIVER BELOW GLEN CANYON DAM For decades, epiphytic diatoms have been recognized as the primary food-base for aquatic consumers in the Colorado River downstream from Glen Canyon Dam. Multiple studies from 1980-1998 consistently reported a near-dominant growth of Cladophora glomerata year-round, which served as the primary host for epiphytic diatoms that were consumed by invertebrate consumers, mainly chironomid larvae and Gammarus. Beginning in 1991 the extent and variation in daily flow fluctuations and other dam operation policies in the Colorado below Glen Canyon Dam were modified to reduce fluvial sandbar erosion, and improve habitat quality, and recreational experiences. These hydrographic changes, combined with record drought affecting recent reservoir storage, warming river water, and altered nutrient availability, have profoundly altered the ecosystem. In 2020 our study of the 24-km tailwaters reach documented a major change to macrophyte community structure: a seasonally dynamic assemblage of Fontinalis hypnoides, Chara vulgaris, Potamogeton pectinatus, Zannichellia palustris, and several filamentous algae, including Cladophora. We observed a substantial increase in epiphytic taxa richness and shifts in major diatom taxa and guilds, with 15 diatom taxa comprising 80% of the epiphytic flora, of which the majority (75%) were upright forms, compared with just 4 taxa in the 1980s. We also recorded significant differences in diatom composition among macrophyte hosts. In addition, the system experienced gelatinous blooms of Didymosphenia geminata and Cymbella mexicana, conditions not observed in prior decades. We also found evidence of differential consumption of specific diatoms by new, non-native invertebrates that recently invaded the tailwaters ecosystem.

John Wehr (Primary Presenter/Author), Louis Calder Center - Fordham University, wehr@fordham.edu;