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SFS Annual Meeting

2021 Detailed Schedule

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Benthic and pelagic inorganic nutrient processing rates at the interface between a river and lake [Oral Presentation]

James Larson (Primary Presenter/Author)
U.S. Geological Survey, jhlarson@usgs.gov;

Mary Anne Evans (Co-Presenter/Co-Author)
U.S. Geological Survey, maevans@usgs.gov;

Faith Fitzpatrick (Co-Presenter/Co-Author)
U.S. Geological Society, fafitzpa@usgs.gov1;

Paul C Frost (Co-Presenter/Co-Author)
Trent University, paulfrost@trentu.ca1;

Marguerite A. Xenopoulos (Co-Presenter/Co-Author)
Trent University, mxenopoulos@trentu.ca1;

William James (Co-Presenter/Co-Author)
UW-Stout, jamesw@uwstout.edu;

Paul Reneau (Co-Presenter/Co-Author)
US Geological Survey, pcreneau@usgs.gov;

Abstract: The interface between lotic and lentic ecosystems is often a zone of intense metabolic activity, as primary production in streams and rivers can be light limited whereas nutrients often limit primary production in lake ecosystems. Here we developed a simple model to describe the combined effects of water column processing and sediment flux on nutrient dynamics of river water as it passes through a rivermouth. We then used measured rates of nutrient processing to estimate the role of the Fox rivermouth in altering riverine loads of nutrients prior to the river water entering Lake Michigan. Within the range of conditions that likely occur in the Fox rivermouth, discharge, water residence time and overall concentration of nutrients in river water strongly drive variation in the rivermouth effect in both absolute and relative terms. Applying the model to conditions within the Fox rivermouth suggests this ecosystem is often a net sink for SRP and source for ammonia (NH4). These results demonstrate that the interface zone between lotic and lentic systems has the potential to substantially alter the load and character of nutrients as river waters pass through rivermouths to adjacent nearshore areas.

COMMUNITIES IN FLUX: THE INFLUENCE OF HYDROPERIOD ON THE ASSEMBLY AND DISASSEMBLY OF TEMPORARY POND INVERTEBRATE COMMUNITIES [Oral Presentation]

William Gerth (Co-Presenter/Co-Author)
Oregon State University, william.gerth@oregonstate.edu;

Dave Lytle (Co-Presenter/Co-Author)
Oregon State University, lytleda@oregonstate.edu;

Christi Kruse (Primary Presenter/Author)
Oregon State University, krusech@oregonstate.edu;

Abstract: Aquatic invertebrate community assemblages in temporary ponds are in a constant state of change, with colonization as ponds fill and dispersal and dormancy (disassembly) as ponds dry. Within a given landscape, the hydroperiod of temporary ponds can differ so that assembly and disassembly occur over various lengths of time. Our research aims to understand how hydroperiod length influences the community structure of aquatic invertebrates in temporary ponds during the filling and drying transition periods. We studied nine temporary ponds and one permanent pond in the Willamette Valley, OR with hydroperiods ranging from four to eight months. We sampled macroinvertebrate and zooplankton communities in each pond one month after ponds began to fill and within one month of when ponds dried. We identified 57 unique insect taxa and 17 unique non-insect taxa from temporary ponds and 4 additional taxa that only occurred in the perennial pond. Non metric multidimensional scaling ordinations indicate that community turnover occurred in a characteristic manner in most temporary ponds and hydroperiod was a significant variable associated with pond community structure. Our results suggest that hydroperiod has a stronger correlation with community structure as ponds dry.

Crayfish Trophic Niches in Lotic, Lentic, and Terrestrial Ecosystems [Oral Presentation]

Zanethia Barnett (Primary Presenter/Author)
USDA Forest Service, zanethia.c.barnett@usda.gov;

Abstract: Understanding the trophic ecology of a species gives insight into food webs, functional roles of a species, and the flow of energy throughout the system. This benefits our understanding of both species-specific natural histories, community-level interactions, as well as provides invaluable information for conservation planning. Crayfishes can have significant impacts on their environment and have been reported to be both ecosystem engineers and potential keystone species due to their ability to modify microbenthic and macrophyte community compositions. However, the trophic ecology of crayfishes is greatly lacking, with very little species-specific data. We are assessing the trophic position of sympatric crayfishes (four lotic, three lentic, and two terrestrial crayfish species) within the Sumter National Forest through stable isotope analyses. To obtain data on the trophic position, we collected tissue from the chela of crayfishes and representative food groups. Our work highlights the similarities and differences between the trophic positions of sympatric crayfishes and ecologically different crayfishes (e.g., terrestrial, lentic, lotic).

CROSSING ECOSYSTEM BOUNDARIES TO BETTER UNDERSTAND MACROSCALE FISH DIVERSITY IN LAKES AND STREAMS [Oral Presentation]

Tyler Wagner (Co-Presenter/Co-Author)
U.S. Geological Survey, Pennsylvania Cooperative Fish and Wildlife Research Unit, Pennsylvania State University, txw19@psu.edu;

Mary Tate Bremigan (Co-Presenter/Co-Author)
Michigan State University, bremigan@msu.edu;

Dana Infante (Co-Presenter/Co-Author)
Department of Fisheries and Wildlife, Michigan State University, infanted@msu.edu;

Kendra Cheruvelil (Co-Presenter/Co-Author)
Michigan State University, ksc@msu.edu;

Katelyn King (Primary Presenter/Author)
Michigan State University , kingka21@msu.edu;

Abstract: Stream and lake fishes are important economic and recreational resources and serve as indicators of ecological stressors on aquatic ecosystems. Research suggests that fish species diversity is largely influenced by surface water connectivity and fragmentation. For example, lake and stream connections support fish movement among ecosystems and provide access to refugia, food, and spawning sites. Unfortunately, connections can also distribute contaminants and invasive species and contribute to homogenization of fish communities. Interestingly, few studies consider freshwater connections and their effect on both lake and stream fish communities across broad spatial extents. Therefore, this talk examines 1) the relationship between connectivity and fish species diversity for lakes versus streams and 2) how these relationships change in response to regional anthropogenic drivers. Using fish data from 559 lakes and 854 streams from the midwestern/northeastern U.S. and Bayesian hierarchical modeling, we found that connectivity was associated with higher species richness, but that connectivity has different effects on richness depending on regional-scale land use. By studying lakes and streams together and incorporating multi-scale drivers into models, our results inform scientific understanding of what drives variation in fish species diversity at broad spatial scales.

DOES DENITRIFICATION DRIVE NITROGEN REMOVAL ACROSS RESTORED FLOODPLAIN WETLANDS? [Oral Presentation]

Robert Brown (Primary Presenter/Author)
Tennessee Technological University, brownrs1991@gmail.com;

Abstract: Wetland restoration projects commonly seek to promote denitrification, which permanently removes NO3 from ecosystems by stepwise conversion to N2 gas. Anammox (N2 production from NH4 and NO2) and dissimilatory nitrate reduction to ammonium (NH4 production from NO3) are assumed to be less common than denitrification in freshwater systems. However, the relative importance of these processes may not be consistent across wetlands subject to different vegetation and hydrologic restoration practices. We measured NO3, NH4, NO2, and N2 flux in 18 restored floodplain wetlands across west Tennessee and Kentucky, USA, in summer 2019 and 2020 using flow-through soil core incubations (n > 500). We predict N2 production will be positively correlated with NO3 uptake and sediment oxygen demand if denitrification is the dominant N removal process across our sites. A weak relationship between N2 production and NO3 uptake would indicate that other N cycling processes contribute significantly to NO3 uptake or N2 production. We will use mixed effects models to explore potentially dominant N cycling pathways while accounting for effects of restoration practices. Results will inform future isotopic labeling experiments designed to trace sources and fates of excess N in restored floodplains.

LONG-TERM WINTER CHLOROPHYLL DYNAMICS ARE ASYNCHRONOUS AMONG REACHES AND LENTIC-LOTIC AREAS OF A LARGE RIVER [Oral Presentation]

KathiJo Jankowski (Primary Presenter/Author)
U.S. Geological Survey, Upper Midwest Environmental Sciences Center, kjankowski@usgs.gov ;

Jeffrey Houser (Co-Presenter/Co-Author)
USGS Upper Midwest Environmental Sciences Center, jhouser@usgs.gov;

Mark Scheuerell (Co-Presenter/Co-Author)
University of Washington , scheuerl@uw.edu;

Adrianne Smits (Co-Presenter/Co-Author)
University of California, Davis, asmits@ucdavis.edu;

Abstract: Winters are changing rapidly but the implications for aquatic productivity and food webs are not well understood. In addition, the degree to which winter dynamics respond to climate versus ecosystem-level factors is unclear but important for managing potential changes. We used a unique dataset from the Upper Mississippi River System (UMRS) to explore spatiotemporal patterns in chlorophyll (CHL) and associated environmental covariates across 25 years and ~1,900 river km. To assess the role of regional climate vs site-specific drivers of winter CHL, we evaluated whether there were synchronous long-term dynamics from north to south and across lotic-lentic areas and estimated the degree to which they were associated with climate variability, winter severity, discharge, or site-specific environmental variables. CHL increased from north to south and was typically highest in lentic areas. Temporal dynamics differed among river reaches and lotic-lentic areas within the same reach. Inter-annual variation was most responsive to winter temperatures, with CHL consistently higher in years with warmer winters. This indicates that changing winters have the potential to affect aquatic productivity but accounting for the spatial complexity in ecosystem dynamics will be important in understanding and managing ongoing change.

MISSED OPPORTUNITIES: DECOUPLING OF WETLANDS FROM NUTRIENT SOURCE AREAS LIMITS DENITRIFICATION POTENTIAL IN THE UNITED STATES [Oral Presentation]

Frederick Cheng (Primary Presenter/Author)
University of Waterloo, frederick.cheng@uwaterloo.ca;

Kimberly Van Meter (Co-Presenter/Co-Author)
University of Illinois at Chicago, kvanmete@uic.edu;

Danyka Byrnes (Co-Presenter/Co-Author)
University of Waterloo, danyka.byrnes@uwaterloo.ca;

Nandita Basu (Co-Presenter/Co-Author)
University of Waterloo, nandita.basu@uwaterloo.ca;

Abstract: Growing populations and agricultural intensification have led to elevated riverine nitrogen (N) loads, coastal hypoxia and occurrences of algal blooms. Although recent work has suggested that wetlands are critical ecosystems that can protect downstream waters and improve water quality by intercepting N loads, restoration and protection of wetlands are often conducted in an ad-hoc manner, with a focus on maximizing total restored area rather than other spatial attributes of the wetland network. Here, we use National Wetland Inventory data and 5km2 estimates of N inputs and outputs across the entire contiguous US to demonstrate that current N removal by US wetlands (~860 kilotonnes N/year) is severely limited by a spatial disconnect between high-density wetland areas and N hotspots. We further show that additional restoration efforts of 10% wetland area using a spatially targeted approach across the US can double current wetland N removal. This increased removal would provide an estimated 54% decrease in N loading to the Mississippi River network. Our results suggest that wetland protection and restoration policies need to reduce the spatial disconnect between N sources and wetlands to have significant improvements to downstream water quality.

ORGANIC MATTER QUANTITY AND QUALITY FROM LOTIC TO LENTIC ALONG A RESERVOIR CONTINUUM [Oral Presentation]

Alexandria Hounshell (Primary Presenter/Author)
Virginia Tech, alexgh@vt.edu;

Whitney Woelmer (Co-Presenter/Co-Author)
Virginia Tech, wwoelmer@vt.edu ;

Heather Wander (Co-Presenter/Co-Author)
Virginia Tech, hwander@vt.edu ;

Durelle Scott (Co-Presenter/Co-Author)
Virginia Tech, dscott@vt.edu;

Cayelan Carey (Co-Presenter/Co-Author)
Virginia Tech, cayelan@vt.edu;

Abstract: While there is increasing recognition of the role reservoirs play in altering biogeochemical cycling along the river continuum, there is still uncertainty around how organic matter processing changes from stream inflows to reservoir outflows. To address this, we measured organic matter quantity and quality along a reservoir continuum from stream inflow to reservoir outflow throughout a summer season. We measured organic matter quantity via dissolved organic carbon concentrations ([DOC]) and dissolved organic matter (DOM) quality using absorbance and fluorescence based-metrics from March to November 2019 at seven sites in a small eutrophic, drinking water reservoir located in southwest Virginia, USA. We observed similar [DOC] and humic, allochthonous-like DOM quality at all sites in spring and early summer followed by increasing [DOC] at the in-reservoir sites and increasing autochthonous, microbial-like DOM. This was accompanied by increasing chlorophyll-a concentrations, indicative of phytoplankton production throughout the reservoir. Clear differences in lotic versus lentic sites demonstrate notable changes in DOM quantity and quality along the reservoir continuum. Results have important implications for our understanding of carbon cycling across aquatic ecosystems and highlights the important role of reservoirs in carbon processing along the river continuum.

PATTERNS OF STREAM AND LAKE CARBON FLUX IN SIMULATED AQUATIC NETWORKS [Oral Presentation]

Ryan Sponseller (Co-Presenter/Co-Author)
Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden, ryan.sponseller@emg.umu.se;

Jan Karlsson (Co-Presenter/Co-Author)
Umeå University, jan.p.karlsson@emg.umu.se;

Dominic Vachon (Primary Presenter/Author)
Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden, domvachon@gmail.com;

Abstract: Significant amounts of terrestrial carbon (C) are transferred to inland waters. Whether this C is emitted or exported is generally investigated separately for streams versus lakes. As these systems are connected within networks, maintaining this divide may impede our regional scale understanding of C fluxes. Here we investigate C fluxes in simulated networks of connected streams and lakes. C inputs to networks in gaseous form were essentially entirely emitted within the network boundary. C inputs in organic form, however, have to first be mineralized before being able to be emitted. The proportion of this C mineralized at the network scale was driven by the travel time and the combination of hydrological regime and network configuration. For a similar residence time, networks with higher runoff but with more lakes were able to mineralize more C than those with lower runoff and fewer lakes. Hydrological regimes further affected the relative contribution of streams and lakes to the whole network total organic C mineralization. Our simulations suggest emergent behaviors in C processing when lakes and streams are integrated into networks, and provide a framework to understand regional scale C fluxes.

Re-examining connections between terrestrial and aquatic carbon cycling in boreal arctic systems [Oral Presentation]

David Butman (Primary Presenter/Author)
University of Washington, dbutman@uw.edu;

Fenix Garcia-Tigreros (Co-Presenter/Co-Author)
University of Washington, fenixg@uw.edu;

Catherine Kuhn (Co-Presenter/Co-Author)
University of Washington, ckuhn@uw.edu;

Matthew Bogard (Co-Presenter/Co-Author)
University of Lethbridge, matthew.bogard@uleth.ca ;

Robert Striegl (Co-Presenter/Co-Author)
USGS, rstriegl@usgs.gov;

Robert Spencer (Co-Presenter/Co-Author)
Florida State University, rgspencer@fsu.edu;

Kimberly Wickland (Co-Presenter/Co-Author)
U.S. Geological Survey, kpwick@usgs.gov;

Mark Dornblaser (Co-Presenter/Co-Author)
USGS, mmdornbl@usgs.gov;

Sarah Ellen Johnston (Co-Presenter/Co-Author)
University of Lethbridge, sarah.johnston3@uleth.ca ;

Abstract: Lakes as a proportion of the landscape are greatest within the boreal and arctic regions. Their spatial extent is dynamic, increasing and decreasing within a season and shifting in location due to changes in the landscape. The current consensus is that lake ecosystems function as both ‘sentinels’ of altered climate and as ‘hots spots’ for the processing and remineralization of carbon received from terrestrial ecosystems. Predicting the impact of a changing north on lotic environments involves understanding the presence, persistence, and dynamics of surface and subsurface hydrology, as well as the impact of non-uniform change in climate. Using both chemical traces and remote sensing techniques, we present evidence that large regions of the boreal arctic do not show strong connections between terrestrial and lotic ecosystems in the context of carbon cycling. Using remote sensing, we suggest that the spatial variability of landscapes, precipitation and temperature require significant further investment in field-based research to accurately understand terrestrial-aquatic linkages in the context of atmospheric emissions.

SEASONAL MIGRATION OF WATER BOATMEN (HEMIPTERA: CORIXIDAE) AS A WETLAND-RIVER LINKAGE AND DIETARY SUBSIDY TO RIVERINE FISH [Oral Presentation]

Tim Jardine (Co-Presenter/Co-Author)
University of Saskatchewan, tim.jardine@usask.ca;

Iain Phillips (Co-Presenter/Co-Author)
Troutreach Saskatchewan/ Water Security Agency of Saskatchewan, iain.phillips@wsask.ca;

Doug Chivers (Co-Presenter/Co-Author)
University of Saskatchewan, doug.chivers@usask.ca;

Stephen Srayko (Primary Presenter/Author)
University of Saskatchewan, shs176@mail.usask.ca;

Abstract: Migratory organisms can link aquatic ecosystems by subsidizing recipient food webs. We investigated a food web subsidy in the form of corixids that fly from wetlands into large rivers in the prairies of North America every fall. Within the North and South Saskatchewan Rivers in the province of Saskatchewan, this migration led to drastically increased corixid densities as high as >3,000 individuals/m2 in areas of standing or slow-moving water, and shifted the species composition to one of a wetland assemblage. During fall migrations, we estimate that ~40,000 corixids entered every square meter of water along the banks of these rivers, which may have represented the movement of ~2,000 metric tons of biomass. Fish species such as goldeye (Hiodon alosoides), mooneye (Hiodon tergisus), longnose sucker (Catostomus catostomus) and white sucker (Catostomus commersoni) foraged heavily on this resource, with corixids occurring in 97% to 100% of individuals and accounting for 38% to 97% of stomach contents during the corixid migration period in fall. This transfer of insect material between wetlands and rivers links the food webs of these two ecosystems, highlighting a need for conservation to ensure that this connection is maintained.

The decoupling of contaminant pulses by recipient food webs in a major U.S. river [Oral Presentation]

James J. Roberts (Co-Presenter/Co-Author)
U.S. Geological Survey, Ann Arbor, MI 48105, jroberts@usgs.gov;

Craig A. Stricker (Co-Presenter/Co-Author)
USGS, cstricker@usgs.gov;

Holly Rogers (Co-Presenter/Co-Author)
U.S. EPA, hrogers290@gmail.com;

Patricia Nease (Co-Presenter/Co-Author)
Purdue University, neasep@purdue.edu;

Travis S. Schmidt (Co-Presenter/Co-Author)
U.S. Geological Survey, Helena, MT 59601, tschmidt@usgs.gov;

Jessica E. Brandt (Primary Presenter/Author)
University of Connecticut, jessica.brandt@uconn.edu;

Abstract: Hydrologic regimes in rivers mobilize contaminants to aquatic ecosystems and pulsed flows often account for substantial proportions of annual contaminant loading and export from catchments. Though it is commonly assumed that contaminant uptake by recipient food webs is lower in lotic than lentic systems, the timing of contaminant trophodynamics is understudied in rivers. We investigated temporal patterns in selenium mobilization, partitioning, and trophic transfer in the Lower Gunnison River Basin (Colorado, USA), a selenium-impaired ecosystem influenced by the underlying Mancos Shale and irrigation practices. Using analyses of selenium concentrations in ~1,000 surface water, particulate, macroinvertebrate, and fish samples collected between June 2015-October 2016, we show that: (1) temporal patterns in Se partitioning and trophic transfer were independent of surface water concentrations, (2) primary producers can quickly accumulate pulsed contaminants, and (3) that macroinvertebrates may sustain elevated Se concentrations from earlier periods of high Se mobilization. Evidence that periods of high-flow selenium mobilization can have a greater influence on the selenium status of recipient food webs than periods characterized by both longer residence times and higher loading challenges the assumption that contaminant bioaccumulation potential is reduced in lotic systems.

THE POSSIBILITY OF FRESHWATER ESTUARIES AS HOTSPOTS IN LITTORAL BENTHIC COMMUNITIES [Oral Presentation]

Janine Rüegg (Primary Presenter/Author)
University of Lausanne, janine.ruegg@unil.ch;

Marie-Elodie Perga (Co-Presenter/Co-Author)
University of Lausanne, marie-elodie.perga@unil.ch;

Stuart Lane (Co-Presenter/Co-Author)
University of Lausanne, stuart.lane@unil.ch;

Abstract: Freshwater ecosystems are often linked, such as streams flowing into lakes or wetlands, but lotic-lentic transitions are rarely studied. The ecotone between tributary stream and lake may function as a freshwater estuary. We hypothesized that the littoral influenced by the tributary will be a hotspot (e.g., higher macroinvertebrate diversity/biomass, higher metabolism). We measured macroinvertebrate diversity and biomass and benthic metabolism of nine littoral locations along the 50 cm depth line parallel to shore in each of the two inlets of Lake Derborence (Switzerland). Sample locations spanned littoral from beyond to through and, again, beyond the influence of the inflowing stream water, with sampling occurring monthly from July through October. Macroinvertebrate communities differed between stream and lake and varied greatly in abundance and diversity among inlets and months. Metabolic rates were similar among the two inlets but highest in September when temperatures were highest. In general, variation in macroinvertebrates and metabolism was high at small scales (within an inlet and month), but differences were not explained by proximity to the mixing zone. Transition zones of Lake Derborence did not reveal expected biological hotspots but rather a highly heterogeneous lake littoral.

THE STREAM-LAKE INTERFACE: PRODUCTIVITY AND THE CONSEQUENCES OF FOREST HARVEST [Oral Presentation]

Mariella Becu (Primary Presenter/Author)
The University of British Columbia, mariella.becu@ubc.ca;

Abstract: Forest harvesting (FH) can adversely affect lake and stream biota by altering sediment and nutrient inputs, and food availability. Small lakes are productive ecosystems, and they connect the terrestrial and aquatic by way of lake-inflow streams. However, downstream contributions, especially to lakes, are rarely measured or considered within FH management. Our research investigated stream-inflow contributions and the effects on lake productivity from FH along inflow streams within British Columbia. We compared communities along lake shorelines fed by streams that have been recently harvested, or undisturbed, and shoreline areas without stream inflows nearby. We tested the hypothesis that biotic communities within lakes are altered from changes in biotic and abiotic inputs induced by upstream harvesting activities. Consistent with our predictions, we found higher relative invertebrate abundance and algal biomass in stream inflow areas compared to shoreline areas. Our results also demonstrate higher relative invertebrate abundance and algal chlorophyll-a measures in undisturbed compared to disturbed stream-inflow sites. There was no statistical difference in algal biomass between undisturbed and disturbed stream-inflow sites. These results advance our understanding of FH disturbance in relation to stream-lake connectivity.

Timing is everything, but are we using the right clock? Temperature sensors measure precise inundation timing of temporary ponds [Oral Presentation]

Kerry Gendreau (Co-Presenter/Co-Author)
Virginia Tech, kerryg@vt.edu;

Valerie Buxton (Co-Presenter/Co-Author)
Virginia Tech, valbux@gmail.com;

Chloe Moore (Co-Presenter/Co-Author)
Virginia Tech, chloe9mo@vt.edu;

Meryl C. Mims (Primary Presenter/Author)
Virginia Tech, mims@vt.edu;

Abstract: Regime-based approaches have long aided our understanding of streamflow dynamics, a well-known environmental filter of aquatic organisms. The timing of streamflow events is a key determinant of the ways in which flow regimes structure communities and populations of lotic biota. A regime-based approach may aid in our understanding of temporary lentic systems as well, where the hydroperiod, or the amount of time a pond holds water, plays a critical role in population and community dynamics. Yet, fine-scale temporal dynamics of hydroperiod – particularly the intra and inter-annual variability in pond inundation date, duration, and frequency of inundation – is often poorly understood. We present results from an inundation timing monitoring effort for a network of temporary ponds (N=16) in southern Arizona, USA. Using daily temperature variance collected from temperature loggers and analyzed using Hidden Markov Models, we identified clear wet and dry states of ponds and were able to identify inundation dates with high precision. Our results support the use of temperature sensors in collecting fine-scale inundation timing data and aiding in regime-based classification of temporary ponds.

ATMOSPHERIC AND WATER QUALITY CORRELATES TO CYANOBACTERIAL DENSITY IN A SOUTHERN NEW JERSEY RESERVOIR [Poster Presentation]

Aaron Krivchenia (Co-Presenter/Co-Author)
Rowan University, krivchena9@students.rowan.edu;

Sara Iuliucci (Co-Presenter/Co-Author)
Rowan University, iuliuc98@students.rowan.edu;

Michael Grove (Co-Presenter/Co-Author)
Rowan University, Grove@rowan.edu;

Courtney Richmond (Co-Presenter/Co-Author)
Rowan University, Richmond@rowan.edu;

Nathan Ruhl (Co-Presenter/Co-Author)
Rowan University, Ruhl@rowan.edu;

Matthew Pierce (Primary Presenter/Author)
Rowan University, pierce92@students.rowan.edu;

Abstract: Cyanobacterial Harmful Algal Blooms (cHABs) are increasing in frequency and severity because of anthropogenic activities and climate change. When cHABs occur, they can alter ecosystem function and release toxins that are dangerous to humans, pets, and livestock. We studied Elmer Lake, a shallow polymictic impoundment on Muddy Run in southern New Jersey during the summer of 2019, during which time a cHAB occurred. A variety of water quality variables were significantly correlated with cyanobacterial density at both the dam and the headwaters of the reservoir. Significant correlations with atmospheric variables were observed at the headwater site, but not the site near the dam. These results suggest that bloom dynamics are different across locations within Elmer Lake despite its small size, shallow depth, and low shoreline development index. Future investigations of the relationship between atmospheric variables, water quality, and cyanobacterial density across lakes within the same watershed is critical for a comprehensive understanding of cHAB dynamics.

DIVE DURATION AND FREQUENCY DIFFER WITH GROUP SIZE AMONG COMMON LOONS (GAVIA IMMER) OVERWINTERING ON A FRESHWATER LAKE IN SOUTH CAROLINA [Poster Presentation]

Devon Jackson (Primary Presenter/Author)
Ohio Northern University, Department of Biological & Allied Health Sciences, d-jackson.5@onu.edu;

Sarah Armstrong (Co-Presenter/Co-Author)
Ohio Northern University, s-armstrong.1@onu.edu;

Nakiah Dague (Co-Presenter/Co-Author)
Ohio Northern University, n-dague@onu.edu;

James Paruk (Co-Presenter/Co-Author)
St. Joseph's College, jparuk@sjcme.edu;

Wade Brooks (Co-Presenter/Co-Author)
Jocassee Outdoor Education, brooks@jocasseewild.org;

Sherry Abts (Co-Presenter/Co-Author)
Jocassee Outdoor Education, birdingabts@gmail.com;

John Mager (Co-Presenter/Co-Author)
Ohio Northern University, j-mager@onu.edu;

Abstract: More Common Loons (Gavia immer) are likely overwintering on freshwater lakes in southeastern North America. Some individuals exhibit a degree of sociality that is not commonly seen in marine environments. From 1-hour time-activity budgets of focal individuals (N=93), we examined differences in the foraging behavior associated with group size among loons overwintering on Lake Jocassee in 2019 and 2020. Common Loons spent an average of 48.6+3.8% of their time with conspecific groups (mean group size=4, range=1-13 individuals). We found individuals spent more time foraging when alone in comparison to living in a group (ANOVA F7, 318=2.23, P =0.03), but did not observe a change in foraging time with increasing group size. However, we did find individuals had higher dive rates (ANOVA F7,241=4.07, P =0.0003) and shorter dive durations (ANOVA F7,260=16.20, P <0.0001) with increasing group size. These differences may reflect tradeoffs associated with benefits and costs of group foraging for smaller, schooling fishes and larger, solitary fishes.

FLIPPING THE FLOW REGIME: EXAMINING HOW WINTER LAKE DRAWDOWNS IMPACT DOWNSTREAM FLOWS AND TEMPERATURE [Poster Presentation]

Alec Baker (Primary Presenter/Author)
University of Massachusetts Amherst, ambaker@umass.edu;

Abstract: Winter lake drawdowns are a common management tool for recreational lakes in the northeastern USA, whereby lake surface levels are lowered during the winter to expose shoreline and destroy nuisance aquatic vegetation. Effects of various types of flow alterations on downstream hydrology, temperature, and stream ecology have been widely documented; however, downstream responses to drawdowns are limited. This study quantifies downstream changes in hydrology and temperature in response to lake drawdowns in Massachusetts. We installed non-vented pressure transducers at 9 drawdown and 3 non-drawdown control sites to obtain continuous (15 min) stream discharge and temperature. Preliminary results show dam releases during the fall lake drawdown period led to increased flow magnitude, decreased flow variation, and increased temperatures compared to non-drawdown systems; however, responses differed based on drawdown magnitude. We predict decreased releases during the spring lake refill period will lead to reduced flow magnitudes and flow variation, which is atypical for spring hydrographs in this region, as well as an increase in temperature compared to non-drawdown systems. This study will advance understanding of impacts of drawdown on downstream hydrology and temperature and inform guidelines minimizing impacts to stream ecosystems.

IMPACT OF WILDFIRE ON STREAM CARBON DYNAMICS: LINKING TERRESTRIAL AND AQUATIC CARBON CYCLING IN MONTANE WATERSHEDS USING ISOTOPIC ANALYSIS [Poster Presentation]

Carly Bonwell (Co-Presenter/Co-Author)
Colorado College, c_bonwell@coloradocollege.edu;

Amelia Nelson (Co-Presenter/Co-Author)
Colorado State Univeristy, Amelia.Nelson@colostate.edu;

Mike Wilkins (Co-Presenter/Co-Author)
Colorado State University, Mike.Wilkins@ColoState.edu;

Cheristy Jones (Primary Presenter/Author)
Colorado College, cheristy.jones@gmail.com;

Michelle Wolford (Co-Presenter/Co-Author)
Colorado College, m_wolford@coloradocollege.edu;

Rebecca Barnes (Co-Presenter/Co-Author)
Colorado College, rbarnes@coloradocollege.edu;

Abstract: Understanding how fire shifts carbon (C) stocks and processing is critical as climate warms, increasing severe fire frequency. Characterization of hillslope soils, stream C pools, and their respective microbiomes across five montane watersheds with varying fire history illustrates the lasting legacy of fire on watershed C dynamics. Seventeen years post-fire, soil organic matter (SOM) appears to have a shorter residence time, as it is more bioavailable and more likely to be laterally exported to streams as compared to SOM within unburned watersheds. These differences are likely due to shifts in SOM quality, microbial community composition and function, and hydrology. Stable isotope analyses indicate that terrestrial sources dominate the dissolved inorganic carbon (DIC) flux in all streams. However, DIC pools in streams unaffected by fire more closely reflect the ?13C of dissolved organic carbon pools as summer progresses, suggesting differences in in-situ sources and/or processing between systems. Shifts in vegetation and microbiome structure post-fire help explain greater terrestrial and aquatic OM degradability in burned watersheds. Results demonstrate that fire can increase lateral C flux to aquatic systems and alter the fate of ecosystem C stocks for decades.

SEASONAL AND SPATIAL VARIATION IN TEMPERATURE AND DISSOLVED OXYGEN REGIMES IN HIGH ELEVATION PONDS IN THE SIERRA NEVADA, CALIFORNIA [Poster Presentation]

Steve Sadro (Co-Presenter/Co-Author)
University of California, Davis, ssadro@ucdavis.edu;

Adrianne Smits (Co-Presenter/Co-Author)
University of California, Davis, asmits@ucdavis.edu;

Mary Farruggia (Primary Presenter/Author)
University of California Davis, mjfarruggia@ucdavis.edu;

Abstract: Ponds are globally abundant and often regionally outnumber lakes, yet we lack an understanding of their relative importance in a landscape context despite emerging evidence that they are hotspots of carbon cycling and subsidize terrestrial food webs. The Sierra Nevada mountains of California contain thousands of ponds, yet their physical and chemical dynamics remain undocumented, despite their potential sensitivity to observed climatic changes at high elevations. We characterized stratification dynamics, thermal regimes, and ecosystem metabolism in ponds at the within-basin and among-basin scale, and investigated seasonal variation in a subset of these ponds. We measured 24-hour high frequency temperature and dissolved oxygen and collected water chemistry, pCO2, and oxygen isotope samples in 10 sub-alpine and alpine ponds along an elevational gradient throughout the Sierra Nevada in 2019. We compared these measurements with nearby lakes and found that ponds generally have higher diel temperature variation and CO2 saturation. In 2020, we measured high frequency temperature and dissolved oxygen in 10 ponds in a single basin continuously throughout the summer. Ponds stratified daily and mixed nightly throughout the season, with deeper ponds showing stronger thermal stratification than shallower ponds.