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SFS Annual Meeting

Thursday, May 23, 2019
11:00 - 12:30

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11:00 - 11:15: / 251 DE NET-SPINNING CADDISFLIES REDUCE STREAMBED HYDRAULIC CONDUCTIVITY

5/23/2019  |   11:00 - 11:15   |  251 DE

NET-SPINNING CADDISFLIES REDUCE STREAMBED HYDRAULIC CONDUCTIVITY The streambed is an ecotone between surface waters and underlying hyporheic systems. Identifying the controls that modulate advective flow through this ecotone is critical to understanding the movement of energy and matter in streams. Hydropsychids (net-spinning caddisflies) are aquatic ecosystem engineers that influence streambed cohesion, yet evidence of direct influence on hydrologic processes is lacking. Through a novel permeameter experiment, we demonstrate how net-spinning caddisfly colonization of the streambed interstitia at moderate densities (2000 m-2) can reduce the saturated vertical hydraulic conductivity (Kv) by up to 60% in course sand and gravels (1.4mm – 22mm). Permeameter cores incubated in stream water occupied by caddisflies showed reduced Kv relative to those similarly incubated without caddisflies. Our research shows that the ubiquitous and numerous net-spinning caddisflies are likely to modulate the exchange of channel and hyporheic water by constructing nets in open pore spaces, increasing flow resistance and decreasing flow velocities. These results suggest that caddisfly induced reductions in pore flow may increase the contact time between water and sediments and therefore alter biogeochemical processes in the hyporheic zone.

Michael MacDonald (Primary Presenter/Author), Montana State University, macdonald.mik@gmail.com;


Geoffrey Poole (Co-Presenter/Co-Author), Montana State University, Montana Institute on Ecosystems, gpoole@montana.edu ;


Lindsey Albertson (Co-Presenter/Co-Author), Montana State University , lindsey.albertson@montana.edu;


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11:15 - 11:30: / 251 DE FACILITATION BY ECOSYSTEM ENGINEERS DIFFERENTIALLY INFLUENCES INVERTEBRATE SIZE STRUCTURE ACROSS A STRESS GRADIENT

5/23/2019  |   11:15 - 11:30   |  251 DE

FACILITATION BY ECOSYSTEM ENGINEERS DIFFERENTIALLY INFLUENCES INVERTEBRATE SIZE STRUCTURE ACROSS A STRESS GRADIENT The community-level consequences of ecosystem engineering are relatively understudied. We explore how net-spinning caddisfly (Hydropsychidae) retreats differentially facilitate macroinvertebrate communities by identifying traits of the beneficiaries along an environmental gradient. We quantified macroinvertebrates associated with caddisfly retreats versus neighboring rock substrates at five study sites spanning a gradient of hydrologic environmental harshness from headwaters to the mainstream of the Gunnison River, CO. We found that macroinvertebrate density was 5X higher in retreats than on rocks but invertebrate biomass in retreats was 2X lower. Invertebrates using retreats were relatively small in body size regardless of gradient location, whereas body size on the rocks varied. Individuals of the low stress rock communities were relatively large-bodied compared to those of the high stress communities. Taken together, these findings indicate that individuals using retreats in higher stress sites represent a greater proportion of the community size structure compared to lower stress sites. These results suggest that caddisfly engineering could influence a specific body size of the invertebrate community, and size-specific facilitation is mediated by environmental stress. Our findings highlight the complexities between ecosystem engineered facilitation, traits of the surrounding community and abiotic environments.

Benjamin Tumolo (Primary Presenter/Author), Montana State University, bbtumolo@gmail.com;


Lindsey Albertson (Co-Presenter/Co-Author), Montana State University, lalbertson@stroudcenter.org;


Melinda Daniels (Co-Presenter/Co-Author), Stroud Water Research Center, mdaniels@stroudcenter.org;


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11:30 - 11:45: / 251 DE THERE’S NO DIVOT LIKE HOME: BENTHIC FORAGING FISH CREATE NOVEL HABITATS IN SOFT SEDIMENTS

5/23/2019  |   11:30 - 11:45   |  251 DE

THERE’S NO DIVOT LIKE HOME: BENTHIC FORAGING FISH CREATE NOVEL HABITATS IN SOFT SEDIMENTS Ecosystem engineers can control the spatial and temporal distribution of resources and movement by engineers within an ecosystem distribute these engineering effects. Here we present evidence of ecosystem engineering by the Sonora sucker (Catostomus insignis), a dominant fish in streams of the southwestern United States, and show how cryptic movement patterns control heterogeneity in benthic substrates and functionally transform benthic habitats. Sonora suckers exhibit distinct diel movement patterns, spending daylight hours in refuge habitats (typically deep pools) while moving into shallow habitats at night to feed. Feeding by suckers creates substantial disturbance in soft sediments that are patchy in space and time. These disturbances moved up to 2.4 × 104 cm3 of sediment per square meter per week in locations that are up to hundreds of meters away from sucker daytime refuges and created depressional structures in mobile sediments (e.g, sand and silt) that persisted until further bioturbation. Our data indicate that cryptic movement by ecosystem engineers can distribute their effects in space and time generating heterogeneity in resources and suggest that habitat modifications restricting consumer movement may alter the impact of engineering activities.

Nelson Hairston (Co-Presenter/Co-Author), Cornell University, ngh1@cornell.edu;


Alexander Flecker (Co-Presenter/Co-Author), Cornell University, Ithaca, NY, USA, asf3@cornell.edu;


Michael Booth (Primary Presenter/Author), University of Cincinnati, michael.booth@uc.edu;


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11:45 - 12:00: / 251 DE EMERGENT HYDRODYNAMICS, SKIMMING FLOW, AND THE OPTIMAL DENSITIES FOR MUSSEL COVERED BEDS IN LABILE RIVERS

5/23/2019  |   11:45 - 12:00   |  251 DE

EMERGENT HYDRODYNAMICS, SKIMMING FLOW, AND THE OPTIMAL DENSITIES FOR MUSSEL COVERED BEDS IN LABILE RIVERS Freshwater mussels are dominant ecosystem engineers in many streams, yet they are an imperiled fauna and little is known about the interaction between mussels and their hydrodynamic habitat. To explore these interactions, flume experiments were conducted across a range of densities of model mussels and flow rates where two-dimensional particle image velocimetry was employed to quantify the turbulent flow field. The results show that (1) mussels can markedly alter the distributions and magnitudes of time-averaged velocity and Reynolds stress, (2) higher densities of mussels accelerate flow velocity above the mussel canopy, decelerate velocity within the canopy, and shift the maximum Reynolds stress above the canopy, and (3) a hydrodynamic tipping point occurs at a mussel density of 25 mussels m-2, where wall-bounded rough flow is replaced by relatively smoother skimming flow. These results suggest that when mussel density reaches an optimal threshold in rivers, a fundamental shift in the hydraulic flow regime occurs that increases the stability and resiliency of the mussel-covered bed during higher flow stages. Such information is central to understanding the biophysical interactions between mussels and their environment and to advancing efforts to conserve these important organisms.

Brandon Sansom (Primary Presenter/Author), SUNY University at Buffalo, bsansom@buffalo.edu;


Sean Bennett (Co-Presenter/Co-Author), SUNY University at Buffalo, seanb@buffalo.edu;


Joseph Atkinson (Co-Presenter/Co-Author), SUNY University at Buffalo, atkinson@buffalo.edu;


Caryn Vaughn (Co-Presenter/Co-Author), University of Oklahoma, cvaughn@ou.edu;


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12:00 - 12:15: / 251 DE DENSITY-DEPENDENT EFFECTS OF FRESHWATER MUSSELS ON GROWTH OF EMERGENT MACROPHYTES

5/23/2019  |   12:00 - 12:15   |  251 DE

DENSITY-DEPENDENT EFFECTS OF FRESHWATER MUSSELS ON GROWTH OF EMERGENT MACROPHYTES Nutrient cycling hotspots created by dense, multispecies aggregations of unionid freshwater mussels have cascading effects on food webs and ecosystem function. Mussel-derived nutrients can be found throughout mussel-associated food webs, including in emergent macrophytes. Dense macrophyte colonies that form sediment bars at the margins of aquatic ecosystems may be a nutrient-rich food resource for terrestrial animals. Our objective was to determine the effects of mussel density on growth and nutrient content of a common emergent macrophyte. We varied the density of two common mussel species within recirculating mesocosms to investigate the effects of a mussel density gradient on macrophyte (Justicia americana) growth and nutrient content. Justicia growth increased significantly with mussel density, but at the lowest mussel densities Justicia growth was lower than control treatments. Water column NH4-N showed no relationship with mussel biomass, but SRP was higher in high-density treatments. We hypothesize that on small spatial scales, like this experiment or the margins of gravel bars, bioturbation by mussels may disturb macrophyte root systems, inhibiting growth. However, increased P availability at higher densities likely created a fertilization effect, overriding this negative effect and increasing macrophyte growth.

Jonathan Lopez (Primary Presenter/Author), University of Oklahoma, jwlopez@ou.edu;


Thomas Parr (Co-Presenter/Co-Author), University of Oklahoma, Thomas.parr@ou.edu;


Daniel Allen (Co-Presenter/Co-Author), University of Oklahoma, dcallen@ou.edu;


Caryn Vaughn (Co-Presenter/Co-Author), University of Oklahoma, cvaughn@ou.edu;


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12:15 - 12:30: / 251 DE INTERNAL FEEDBACKS BETWEEN VEGETATION AND COASTAL MARSH PERSISTENCE: WHAT HAPPENS WHEN THE SYSTEM IS ALTERED?

5/23/2019  |   12:15 - 12:30   |  251 DE

INTERNAL FEEDBACKS BETWEEN VEGETATION AND COASTAL MARSH PERSISTENCE: WHAT HAPPENS WHEN THE SYSTEM IS ALTERED? The persistence of coastal marshes depends on their ability to keep elevation with sea level rise through vertical and lateral soil building. At small scales, coastal marsh distributions are controlled by internal feedbacks between vegetation, sediment deposition and erosion. Under future climate scenarios and anthropogenic alteration, these feedbacks between sediment deposition and marsh vegetation may change or become asynchronous, affecting marsh soil building. To determine peak vegetation trapping, I track changes to Normalized Difference Vegetation Index (NDVI), a measure of vegetation productivity, in coastal marshes across the Landsat record. In addition, I delineate mosquito ditches and canals along marsh islands to determine degree of anthropogenic alteration to hydrology regionally. Peak NDVI and duration of growing season suggest regional patterns of plant growth and productivity, with more northern marshes having later peaks and longer growing seasons. Anthropogenic modification also depicts regional differences in mosquito ditching and canals, with more northern latitudes across the U.S. having more ditches. These patterns in vegetation change and alteration of hydrology could influence the ecogeomorphic processes and intensity of internal feedbacks that maintain the marsh and determine future persistence in a time of anthropogenic pressure.

Anna Braswell (Primary Presenter/Author), Earth Lab, CIRES, University of Colorado Boulder, anna.braswell@colorado.edu;


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