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Full-Text Articles in Life Sciences
(Non)Parallel Developmental Mechanisms In Vertebrate Appendage Reduction And Loss, Samantha Swank, Thomas Sanger, Yoel E. Stuart
(Non)Parallel Developmental Mechanisms In Vertebrate Appendage Reduction And Loss, Samantha Swank, Thomas Sanger, Yoel E. Stuart
Biology: Faculty Publications and Other Works
Appendages have been reduced or lost hundreds of times during vertebrate evolution. This phenotypic convergence may be underlain by shared or different molecular mechanisms in distantly related vertebrate clades. To investigate, we reviewed the developmental and evolutionary literature of appendage reduction and loss in more than a dozen vertebrate genera from fish to mammals. We found that appendage reduction and loss was nearly always driven by modified gene expression as opposed to changes in coding sequences. Moreover, expression of the same genes was repeatedly modified across vertebrate taxa. However, the specific mechanisms by which expression was modified were rarely shared. …
Anthropogenic Particle (Including Microplastic And Microfiber) Transport And Retention In Streams Under Varied Environmental Conditions, Elizabeth Marjorie Berg
Anthropogenic Particle (Including Microplastic And Microfiber) Transport And Retention In Streams Under Varied Environmental Conditions, Elizabeth Marjorie Berg
Master's Theses
Microplastics (plastic particles <5 mm) and other anthropogenic particles (i.e., synthetic, semi-synthetic and anthropogenically modified cellulose particles < 5mm) are pollutants of concern in aquatic ecosystems worldwide. Anthropogenic particles enter food chains, adsorb harmful chemical pollutants, and are ubiquitous in aquatic ecosystems. Streams are key sites of anthropogenic particle input, retention, and transport, and empirical measurements of particle movement in lotic ecosystems are needed to inform global budgets of anthropogenic particles and microplastics. However, factors that influence anthropogenic particle retention in lotic ecosystems are poorly understood. We demonstrate how environmental characteristics affect plastic transport and retention in streams in experimental and observational studies. In our experimental study, we used particle spiraling metrics to directly measure microplastic retention in outdoor, experimental streams at Notre Dame's Linked Experimental Ecosystem Facility (ND-LEEF). We tested the impact of stream discharge (i.e., high, low), benthic biofilms (i.e., well-established biofilms, reduced biofilms post-scouring), and benthic substrate type (i.e., cobble, pea gravel, sand, mixed substrate) on retention of microplastic fibers using pulsed releases and synchronized water sample collection at 3 sites downstream. We also collected benthic surface samples for biomass and microplastic density. Samples were filtered directly (water samples) or after peroxide digestion (benthic samples), and experimental microplastic fibers were enumerated visually using a dissecting microscope. Microplastic deposition rates were significantly higher with (1) higher discharge, (2) well established benthic biofilm (as opposed to bare substrate), and (3) larger and more homogeneous substrates. The observational study examined anthropogenic particles (including microplastics and microfibers) in the Milwaukee River during storm events. Lotic ecosystems are highly variable (e.g., seasonal changes, storm events), and most research assessing anthropogenic particle pollution extrapolates stream particle loads based on measurements during only one point in time. This limits the accuracy of anthropogenic particle and microplastic dynamics models in rivers, where frequent changes in discharge drives retention and transport of fine particles. In this study, we used automated samplers to collect water from the Milwaukee River during four distinct storm events in the spring and summer of 2018. We quantified anthropogenic particle abundance using standard methods and used nearby USGS gauges to determine discharge. Anthropogenic particle concentrations varied significantly among the four sampling periods, highlighting the temporal variability of anthropogenic particle transport across dates. When data from the sampling periods were pooled, there was a decrease in anthropogenic particle concentration in the water column after storm events, indicating that floods may "flush" microplastics from the river. Unexpectedly, anthropogenic particle concentrations were not correlated with other water quality metrics, including concentrations of total suspended solids, fecal coliform, chloride, nitrate, and sulfate, indicating that these metrics cannot be used to estimate microplastic concentrations and likely have distinct driving factors. These results provide novel insights into the environmental factors controlling anthropogenic particle and microplastic fate and are critical to understanding the role of lotic retention and transport in global plastic budgets.
Anthropogenic Litter In Illinois Streams: Monitoring, Distribution, And Relationship To Biological Indicators Of Stream Health, Lauren Wisbrock
Anthropogenic Litter In Illinois Streams: Monitoring, Distribution, And Relationship To Biological Indicators Of Stream Health, Lauren Wisbrock
Master's Theses
Anthropogenic litter (i.e., trash; AL) is increasing in aquatic ecosystems worldwide. AL shows a patchy, uneven distribution in lotic ecosystems due to heterogeneity in its sources, how it moves, and mechanisms of retention. In addition, the diversity of material types, size, and mobility makes developing techniques to measure AL assemblage in rivers a challenge. In rivers, watershed land-use and riparian features likely impact AL abundance and composition, but this impact is not fully understood. Measuring AL can be time consuming and labor intensive, so rapid assessments are needed for ecosystem managers to quantify the level of AL impairment in a …