MEES Theses and Dissertations

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The Abundance and Distribution of Transparent Exopolymer Particles in the Turbidity Maximum Region of Chesapeake Bay
(2010) Malpezzi, Michael A.; Crump, Byron C; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Transparent exopolymer particle (TEP) concentrations were measured in the turbidity maximum (ETM) region of Chesapeake Bay during eight research cruises over a two-year period. TEP concentrations ranged from <100 to >2500 ug XG eq l^-1 and accounted for an estimated average of 31% ± 14 of POC. Spatially averaged TEP and chl a concentrations were positively correlated over the two year period, although these parameters were rarely correlated within cruises. Peak TEP concentrations were often separated from chl a maxima, suggesting that formation and concentration processes are more responsible for TEP concentrations than the proximity to precursor source material. Significant correlations between TEP and phaeophytin, POC, DOC, TSS and level of stratification were observed during some sampling periods. Settling tube experiments revealed a positive correlation between TEP concentration and the fraction of settling particulate matter. A hypothetical model for TEP formation and concentration in estuaries is proposed.
Acclimation of marine macrophytes (Saccharina latissima and Zostera marina) to water flow
(2008-05-12) Jordan, Terry Lynn; Koch, Evamaria; Davison, Ian; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
I examined the physiological response of two marine macrophytes, the brown alga Saccharina latissima and the angiosperm Zostera marina, to water flow in nature and in controlled experiments. Limitation of photosynthesis of both species by the availability of dissolved inorganic carbon (DIC) was increased under low current velocities. Physiological acclimation to low water flow occurred via upregulation of DIC uptake mechanisms in both S. latissima and Z. marina. Both species increased their ability to generate CO2 in the boundary layer by increasing external carbonic anhydrase and in Z. marina by also increasing proton extrusion and photosynthetic capacity. Changes in the xanthophyll-cycle in low-flow grown S. latissima increased non-photochemical quenching, thus reducing photodamage when photosynthesis was limited by DIC uptake. Water flow also affected root length in Z. marina but root length and below ground biomass were also significantly affected by sediment type, an indirect effect of water flow.
Adaptive Mechanisms of an Estuarine Synechococcus based on Genomics, Transcriptomics, and Proteomics
(2016) Marsan, David Wilfred; Chen, Feng; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Picocyanobacteria are important phytoplankton and primary producers in the ocean. Although extensive work has been conducted for picocyanobacteria (i.e. Synechococcus and Prochlorococcus) in coastal and oceanic waters, little is known about those found in estuaries like the Chesapeake Bay. Synechococcus CB0101, an estuarine isolate, is more tolerant to shifts in temperature, salinity, and metal toxicity than coastal and oceanic Synechococcus strains, WH7803 and WH7805. Further, CB0101 has a greater sensitivity to high light intensity, likely due to its adaptation to low light environments. A complete and annotated genome sequence of CB0101 was completed to explore its genetic capacity and to serve as a basis for further molecular analysis. Comparative genomics between CB0101, WH7803, and WH7805 show that CB0101 contains more genes involved in regulation, sensing, and stress response. At the transcript and protein level, CB0101 regulates its metabolic pathways, transport systems, and sensing mechanisms when nitrate and phosphate are limited. Zinc toxicity led to oxidative stress and a global down regulation of photosystems and the translation machinery. From the stress response studies seven chromosomal toxin-antitoxin (TA) genes, were identified in CB0101, which led to the discovery of TA genes in several marine Synechococcus strains. The activation of the relB2/relE1 TA system allows CB0101 to arrest its growth under stressful conditions, but the growth arrest is reversible, once the stressful environment dissipates. The genome of CB0101 contains a relatively large number of genomic island (GI) genes compared to known marine Synechococcus genomes. Interestingly, a massive shutdown (255 out of 343) of GI genes occurred after CB0101 was infected by a lytic phage. On the other hand, phage-encoded host-like proteins (hli, psbA, ThyX) were highly expressed upon phage infection. This research provides new evidence that estuarine Synechococcus like CB0101 have inherited unique genetic machinery, which allows them to be versatile in the estuarine environment.
Age, growth and recruitment of Hudson River shortnose sturgeon (Acipenser brevirostrum)
(2005-08-10) Woodland, Ryan Jordan; Secor, David H.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Shortnose sturgeon (Acipenser brevirostrum), an Endangered Species, has experienced a several-fold increase in abundance in the Hudson River in recent decades. Age structure and growth were investigated to evaluate the hypothesis that improvements in water quality during the late 1970s stimulated population recovery. Specimens were captured using gill nets bi-monthly 2003 to 2004. Annuli in fin spine sections were determined to form at an annual rate and yielded age estimates of 5-30 years for sizes 49-105cm Total Length (n=554). Hindcast year-class strengths, corrected for gill net mesh selectivity and cumulative mortality indicated high recruitments (28,000-43,000 yearlings) during 1986-1992, which were preceded and succeeded by c. 5 year-periods of lower recruitment (5,000-15,000 yearlings). Results indicated that Hudson River shortnose sturgeon abundance increased due to the formation of several strong year-classes occurring about five years subsequent to improved water quality in important nursery and forage habitats in the upper Hudson River estuary.
ALGAL TOXICITY AND FORMATION OF HALOGENATED ORGANIC COMPOUNDS IN BALLAST WATER AFTER OXIDATIVE TREATMENT
(2019) Ziegler, Gregory; Tamburri, Mario N; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Ballast water plays a vital role in the stabilization and operations of modern ships, and it is estimated that 3 to 5 billion tons of ballast water are transferred around the world each year. However, the discharge of ballast water has led to the release of non-indigenous species, and costly and ecologically damaging biological invasions. To combat this serious problem, ballast water discharge is now regulated and ballast water management systems (BWMS) have been developed to meet required discharge limits for the release of live organisms. The most common BWMS rely on chlorination of ballast water to kill planktonic organisms but also result in the formation of disinfection by-products (DBPs) and the potential for aquatic toxicity. The research in this thesis was conducted to advance the understanding of treated ballast water toxicity, and to document the formation of higher molecular weight DBPs using ultrahigh resolution mass spectrometry. Research was conducted with commercial BWMS that were based on either direct chlorination (Ch. 2 & 3) or in-situ electrochlorination (Ch. 2 & 4). Ballast water treatment was conducted in estuarine waters of the Port of Baltimore (Patapsco River, Maryland). In Chapter 2, I tested the algal toxicity of discharged ballast water from four BWMS at the time of discharge and monthly thereafter, showing the longevity of the toxic effect of treated water on micro algae. In Chapters 3 and 4, I used ultrahigh resolution mass spectrometry to identify the molecular composition of dissolved organic matter (DOM) and halogenated DBPs after oxidative treatment of ballast water. By comparing samples before and after direct chlorination, I was able to document the changes in dissolved organic matter and the formation of numerous halogenated DBPs (Ch. 3). In Chapter 4, I was able to document the change in brominated DBPs after a period of 92 days, showing the relative persistence of dibrominated compounds. This work together demonstrates that use of traditional water treatment to solve one environmental problem may, in fact, cause other unintended consequences to aquatic ecosystems.
Alternate state theory and tidal freshwater mudflat experimental ecology on Anacostia River, Washington, D.C.
(2007-11-13) may, peter; Kangas, Patrick; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The concept that multiple community states may alternately exist for some ecosystems has been the subject of controversy for decades. This theory is tested and applied to the mudflats of the low/middle marsh intertidal zone of two restored freshwater tidal marshes on the Anacostia River. It is believed that experimental exclosures exposed strong species interactions and provided a window with which to view the potential alternate existence of two structurally different systems, intertidal mudflat and emergent marsh. The occurrence, persistence and community composition of the two ecosystem states are examined through experimental exclosures at the two marsh restoration study areas. The power of large grazers to deflect the goals of wetland restoration practitioners is studied in the context of alternate state theory. Initially unvegetated mudflat, native marsh vegetation emerged within exclosure study areas at two restoration sites. Resident Canada geese (Branta canadensis maxima) decimated planted areas of restored marsh left open to grazing, returning marsh to unvegetated mudflats. Data from exclosures are presented on macrophyte community composition, sediment elevation, bird, fish, invertebrate and algae associations from two separate sets of Anacostia River experimental exclosure sites, one covering 588 m2, the other covering 2,700 m2. Results support the hypothesized alternate existence of the two system states in the same space and relative time, each dependant upon the access of a critical mass of large grazers. A description of the mudflat biotic community and its interconnectivity is discussed as an important feature of the Anacostia River system. An emergy analysis of each state and an accounting of fisheries energy flow is conducted. Information collected relating to the pre-restoration (tidal mudflat) and post-restoration (emergent marsh) physical and biological conditions are detailed and analyzed. A determination of the emergy inputs for a large-scale marsh restoration project are calculated and as a final analysis, economic (emdollar) equivalents are developed to compare the yield of fisheries production supplied by mudflats vs. a restored and mature emergent freshwater tidal marsh. Through these studies support is given to valuing mudflats as important system components of Anacostia River.
ALTERNATIVE MIGRATORY PATHWAYS OF JUVENILE STRIPED BASS IN THE PATUXENT RIVER ESTUARY, MARYLAND
(2012) Conroy, Christian William; Secor, David H.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Although highly migratory striped bass Morone saxatilis utilize spatially diverse and dynamic estuarine systems as nurseries, early dispersal behaviors have remained largely unknown. Using otolith chemistry, we identified consistent migratory and residence behaviors in juvenile striped bass year classes. Migrants were further separated by size and age into contingents that shared similar ontogenetic dispersal thresholds. We identified a small group of larval dispersers that moved to mesohaline waters prior to reaching 6 mm. Resident juveniles experienced better early growth that migrants. Small migrants had the lowest growth rates prior to dispersal, but afterward showed enhanced growth rate. Positive growth inflections were also observed for a group of migrants that reinvaded freshwater at larger sizes. Striped bass migration seems to be controlled by individual growth trajectories, where movement is driven by poor growth in the natal habitat.
Ambient sound affects movement and calls of bottlenose dolphins
(2021) Fandel, Amber Desneige; Bailey, Helen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Abundant oceanic shipping and more frequent and intense storms are increasing sound levels in aquatic habitats. Understanding how changing soundscapes affect protected species, especially those that use sound to communicate and navigate, is critical. This study utilizes passive acoustic monitoring to investigate the effects of changing ambient sound levels on bottlenose dolphin (Tursiops truncatus) movements, spatial utilization, and social calls in the Mid-Atlantic Bight, USA. By localizing dolphin whistles, I determined that their habitat use changed under higher ambient sound levels and that these elevated sound levels caused dolphins to alter the acoustic characteristics of their calls. The acoustic characteristics of individually identifiable calls (signature whistles) also varied between the sites and regions in which they were recorded. As changes in the underwater soundscape continue in the future, these findings will help inform resource managers about how protected marine mammals may be affected by anthropogenic activities and sounds.
APPLIED STASIS THEORY AND Q-SORTING FOR ORGANIZING ENVIRONMENTAL SCIENCE COLLABORATION FOR POLICY DELIBERATION: A CASE OF POULTRY HOUSE EMISSIONS—AMMONIA AND PARTICULATE MATTER—ON THE DELMARVA PENINSULA/EASTERN SHORE
(2022) Shea, Mary E; Tjaden, Robert; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
CONTEXT: Poultry farmers respond to national and global demand for low cost, packaged chicken. Raising poultry for market results in ammonia and poultry litter (manure and dust). However, for the Delmarva part of the Chesapeake Bay Watershed and Airsheds, ammonia and poultry litter mean nitrogen pollution, which effects water quality and human health. Therefore, this inquiry looks closely at the values and benefits that shape poultry farmer decisions about managing ammonia from their poultry houses using two technologies: Vegetated Emissions Buffers (VEBs) and Poultry Litter Treatments (PLTs). QUESTION: How can we better understand the values and benefits embodied in ammonia management choices by poultry farmers? METHODS: This dissertation uses three methods to engage with poultry farmers (2012-19) to better understand a range of values—economic and non-economic—about voluntary ammonia management strategies. 1. Stasis theory (Chapter Two), 2. Scaling of conceptual diagrams to three inch by four-inch cards, for designing visual Q-cards (Chapter Three), 3. Q-sorting of cards and findings (Chapter Four). FINDINGS: The Q-sorting events in this November 2019 study (25 value/benefits statements, sorted with 13 poultry producers) did not meet respondent number thresholds for formal Q-method factor analysis. However, results were studied using exploratory data analysis and chi-square testing of Q-sorting data. One important finding is that these eight cards appeared as important in two analysis categories: first, six cards likely MOST IMPORTANT (Photo 1); and second, the next two cards (Photo 2) as perhaps SOMEWHAT IMPORTANT. These pictured two sets of cards are ranked overall as having greater importance to poultry farmers, compared to aggregate card rankings of the other 17 cards in the 25-member card set. Photo 1: In the aggregate, these six cards were sorted most often into the MOST IMPORTANT category. Photo 2: In the aggregate, these two cards were sorted most often into the IMPORTANT category. The six cards in Photo 1 (MOST IMPORTANT) can be understood in several ways. First, these three cards (position noted in bold) represent economic benefits to poultry farmers, important for farm fiscal stability. The three cards on the left all represent health gains for chickens, meaning a better payout when healthy, unblemished, full-weight birds are sold to the poultry company:• Top-left card: This card symbolizes healthy chickens as “happy”—a visual shorthand for healthy—commanding more per pound at payout. • Middle-left card: This card shows reduced in-house ammonia, which means that chicken flesh is less likely to be burned or marred by ammonia, commanding more per pound at payout; generally, lowered in-house ammonia also means healthier birds, which is a specific value noted in just above in the top-left card description. • Bottom-left card: This card shows unblemished chicken “paws” which can command an extra premium for Asian specialty food markets. This portion of the bird represents a newer market for poultry producers. Within this group, two of these cards in Photo 1 (top- and middle-left) also show the value to farmers of using an enhanced schedule of PLTs to reduce ammonia inside the poultry house. The right-hand cards in Photo 1 can be understood thusly as relying on VEB use:• Top-right card: This card shows energy savings from using VEBs to shade poultry houses and provide winter wind cover, thereby reducing energy costs annually, supporting farm fiscal status. • Middle-right card: This card symbolizes reduced ammonia odor by VEB capture, which can help avoid neighbor and nuisance complaints. • Bottom-right card: This card shows the value of VEBs as helping the farmer meet existing nutrient management planning, a state-administered requirement for many poultry farmers. nitrogen and phosphorus are two nutrients associated with poultry production, poultry litter storage/composting, and poultry litter application as field fertilizer. These three VEB-focused cards in Photo 1 share the common context of concerning ammonia management strategies outside the poultry house, relying on the pollution remediation strategies of VEBs, a type of designed hedgerow plant structure._____ The two cards in Photo 2, noted as IMPORTANT but not as MOST IMPORTANT as the six cards in Photo 1 just described, relate to farmer concerns about human health. • Top card: This card show that poultry farmers can use VEBs outside poultry houses to capture ammonia and particle pollution, thereby improving local air quality, especially for farm families who live close to their poultry houses. • Bottom card: This card show that poultry farmers can use enhanced PLTs to reduce in-house ammonia, thereby improving worker conditions inside the poultry house. CONCLUSION: This case study demonstrates the value of Q-sorting used with Delmarva poultry farmers and attitudes about ammonia management. These findings can be also understood as ground-truthing evidence, in that the visual card-sorting data confirm as important the eight cards discussed above. These values/benefits depicted on these cards fit the poultry context of the Chesapeake Bay ecosystem. Additional Q-sorting activities with these cards or revised card sets to meet research needs are worthy undertakings. This dissertation case study also shows the value of humanities within environmental policy deliberation. Stasis theory, from rhetorical studies, helped organize the complexity of this project, as well as made a clear role for valuing activities (including Q-sorting). A second field of humanities inquiry is science visualization studies. This field, closely allied with rhetoric, helped with design values to build clear and environmentally-situated picture cards for Q-sorting the ranked importance of these cards to poultry farmers. Finally, the last chapter reflects on ways that a human dimensions approach supports a re-imagined Delmarva poultry production. One central design criterion about poultry production futures centers the role of poultry farmers, especially young farmers, in planning for resiliency. Among the pressures on poultry production is the well-documented wetter and warmer Delmarva, to climate change. The COVID-19 pandemic due to the 2019 emergence of the SARS-CoV-2 virus, also posed risks to Delmarva poultry resiliency. Scenario analysis and design options are better with humanist and social science knowledge, combined with environmental science.
Archaeal Transcriptional Regulation of Catabolic Carbon Monoxide Dehydrogenase in Methanosarcina species
(2009) Anderson, Kimberly Lynn; Sowers, Kevin R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
In Archaea, the basal transcription machinery is eukaryotic-like, but some components, such as activator and repressor proteins, are bacteria-like. To further gain knowledge into cellular processes of Archaea, the genome of Methanosarcina thermophila was searched for helicase genes. A homolog of yeast RAD25, a gene with helicase and nucleotide excision repair (NER) abilities, was isolated. M. thermophila rad25 has the domains for helicase activity, but the C-terminal end is truncated, indicating that this protein mostly likely does not function in NER. After overexpression, helicase activity assays of Rad25 indicated that it might have helicase activity; however, there appeared to be contaminating proteins in the purification, so it was not possible to assign the activity only to Rad25. Additional work is necessary to characterize this protein. To investigate transcription, catabolic gene regulation was studied, specifically regulation of carbon monoxide dehydrogenase/acetyl CoA synthase (CODH/ACS) from Methanosarcina species. The regions upstream of the transcriptional start site, as well as the 5' leader region of cdhA, were investigated for trans factors and cis elements that might be involved in regulation. Experiments revealed that regulation of cdhABCDE does not appear to involve trans factors upstream of the transcriptional start site. However, deletion analysis indicated that the 5' leader region does have a role in regulation. Comparing the protein levels to the mRNA levels revealed there was no significant difference between the two, indicating that translational regulation was not a factor. Other experiments ruled out differential mRNA stability as a factor in regulation. A region located between +358 and +405 was important in transcriptional regulation, indicating that regulation occurred at the level of transcription elongation. A model for regulation of catabolic CODH/ACS by differential elongation is proposed. Although 5' leader regions identified for other archaeal genes have been postulated to be involved in regulation, this was the first study to demonstrate a regulatory role by an archaeal leader sequence for differential elongation. Identifying regulatory mechanism(s) of catabolic genes such as CODH/ACS is critical for understanding the regulatory strategies employed by the methanoarchaea to efficiently direct carbon and electron flow during biomass conversion to methane.
ARTHROPOD COMMUNITIES IN RIPARIAN GRASS BUFFERS AND ADJACENT CROPS
(2008-05-31) Nelson, Jessica Lynn; Dively, Galen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Riparian buffers composed of either native warm season or non-native cool season grasses are commonly planted alongside crop fields. Although their water quality function is well documented, few studies have examined grass buffers as habitat for arthropod communities. The aerial and epigeal arthropods were surveyed using pitfall traps and sticky cards to assess the effects of both grass types on community structure in the buffer and adjacent crop. I predicted that warm season grasses would provide favorable habitat for more diverse and abundant arthropod populations, particularly natural enemies. The weight of evidence did not support my prediction and suggests that cool season grass buffers provide equivalent, if not better habitat for arthropods than warm season grasses. Coupled with higher food quality, cool season species green-up much earlier than warm season grasses in the spring and provide food resources for many herbivores and natural enemies.
Assessing and Modeling Landscape Change in a Sensitive High-Elevation Region of the Bolivian Andes
(2004-12-06) Brandt, Jodi S; Townsend, Philip; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This study used remotely sensed land cover and topographic data, maximum likelihood classification, and spectral mixing analysis to characterize current landscape patterns and quantify land cover change from 1985 to 2003 in the Southeastern Bolivian Andes. Current land cover was mapped into 9 classes with an overall accuracy of 89%. The change analysis demonstrated significant gains in bare and cultivated land (4.4% and 4.1%, respectively) at the expense of forest and pasture (losses of 4.8% and 3.9%, respectively). Spectral mixture analysis indicated that communal rangeland degradation (as measured by changes in proportions of green vegetation, non-photosynthetic vegetation and bare soil on the landscape) may have occurred, especially where conversion of land to more productive uses is restricted by soil fertility, topography, and climate. The study demonstrated that remotely sensed data and traditional image analysis techniques can be used to characterize land cover and land cover change in remote, mountainous areas.
ASSESSING THE IMPACTS OF NON-POINT SOURCE FRESHWATER AND NUTRIENT INPUTS ON A SHALLOW COASTAL ESTUARY
(2019) Butler, Thomas; Hood, Raleigh R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Academic research models for Chesapeake Bay have, traditionally, been forced with USGS inputs, flows and nutrient loads from 10 major rivers. These tributaries fail to account for 100% of the inputs entering the Bay. In contrast, models used for determining Total Maximum Daily Load for Chesapeake Bay are forced with output from a watershed model at thousands of locations, presumably, accounting for all these inputs. Our aim is to increase understanding of the impacts different forcing schemes have on water quality model simulation. Simulations were completed using three forcing approaches: 1) using “traditional” USGS-derived input from 10 major rivers; 2) using “concentrated” input from 10 major rivers derived from watershed model output; and 3) using “diffuse” input from 1117 rivers derived from watershed model output. Comparisons of these schemes revealed large impacts on simulations in Chesapeake Bay during periods of high flow and extreme weather events under diffuse forcing.
Assessing the influence of abiotic factors and leaf-level properties on the stability of growing-season canopy greenness in a deciduous forest
(2016) Cunningham, Vanessa M.; Nelson, David M; Elmore, Andrew J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Maps depicting spatial pattern in the stability of summer greenness could advance understanding of how forest ecosystems will respond to global changes such as a longer growing season. Declining summer greenness, or “greendown”, is spectrally related to declining near-infrared reflectance and is observed in most remote sensing time series to begin shortly after peak greenness at the end of spring and extend until the beginning of leaf coloration in autumn,. Understanding spatial patterns in the strength of greendown has recently become possible with the advancement of Landsat phenology products, which show that greendown patterns vary at scales appropriate for linking these patterns to proposed environmental forcing factors. This study tested two non-mutually exclusive hypotheses for how leaf measurements and environmental factors correlate with greendown and decreasing NIR reflectance across sites. At the landscape scale, we used linear regression to test the effects of maximum greenness, elevation, slope, aspect, solar irradiance and canopy rugosity on greendown. Secondly, we used leaf chemical traits and reflectance observations to test the effect of nitrogen availability and intrinsic water use efficiency on leaf-level greendown, and landscape-level greendown measured from Landsat. The study was conducted using Quercus alba canopies across 21 sites of an eastern deciduous forest in North America between June and August 2014. Our linear model explained greendown variance with an R2=0.47 with maximum greenness as the greatest model effect. Subsequent models excluding one model effect revealed elevation and aspect were the two topographic factors that explained the greatest amount of greendown variance. Regression results also demonstrated important interactions between all three variables, with the greatest interaction showing that aspect had greater influence on greendown at sites with steeper slopes. Leaf-level reflectance was correlated with foliar δ13C (proxy for intrinsic water use efficiency), but foliar δ13C did not translate into correlations with landscape-level variation in greendown from Landsat. Therefore, we conclude that Landsat greendown is primarily indicative of landscape position, with a small effect of canopy structure, and no measureable effect of leaf reflectance. With this understanding of Landsat greendown we can better explain the effects of landscape factors on vegetation reflectance and perhaps on phenology, which would be very useful for studying phenology in the context of global climate change
Assessing the Potential for Doormats to Reduce Pesticide Residues in the Home
(2006-05-04) Ganser, Leanne Marie; Brown, Amy E; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This study examined the recommended practice of using doormats at entryways into the home to reduce indirect pesticide exposure. Using doormats to reduce track-in of pesticides is commonly recommended to pesticide applicators, but no studies of the usefulness of this recommendation appear in the literature. The effectiveness of doormats was evaluated by determining the soil levels dislodged from doormats and by determining the ability for laundering to remove pesticide residues embedded into the mats. The performance of three doormat types was assessed. High levels of soil were dislodged from all doormat types. Results from laundering mats showed large variability in the level of residues detected. The results from both studies were influenced by the methods used to test the dislodgeability and effectiveness of laundering. The results of the study suggest further studies are needed to determine the effectiveness of doormats to reduce the potential for pesticide contamination inside the home.
Assessing vertebrate biodiversity across the Chesapeake Bay using environmental DNA metabarcoding
(2023) Rodriguez, Lauren Kelly; Bailey, Helen; Woodland, Ryan J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Through the collection and sequencing of trace genomic evidence from environmental samples (e.g., water, air, and soil), environmental DNA (eDNA) metabarcoding can detect a range of vertebrates. Despite the dynamic characteristics of estuarine environments, which often hinder the persistence of genomic material, this project successfully employed metabarcoding to assess the distribution of vertebrates in the Chesapeake Bay. Primarily, the study evaluated the effects of using various eDNA sampling, laboratory, and post-hoc analysis techniques when investigating species presence and biodiversity of an area. This study also identified spatially-explicit fish communities along salinity gradients as described by a Generalized Additive Mixed Model (GAMM) and a Permutational Multivariate Analysis of Variance (PERMANOVA). Community compositions were similar to previous findings by traditional trawling and seining methods. This research supports the usefulness of eDNA metabarcoding to assess species presence across spatiotemporal extents, making it a promising tool for future biomonitoring efforts in the Chesapeake Bay.
Assessment of local abundance, demographics, health and exploitation of Chesapeake Bay American eel
(2009) Fenske, Kari Hammarsten; Wilberg, Michael J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The Chesapeake Bay supports the largest U.S. harvest of American eel Anguilla rostrata, yet little is known about the underlying production rates sustaining harvests. Demographic attributes were compared between six sub-estuaries and with an unexploited population in the Hudson River. A mark-recapture experiment in the Potomac River yielded growth, abundance, and production estimates. Sub-estuaries characterized by lower salinity had a lower proportion of females, and American eels were older, slower growing and showed increased parasitism. Female American eels were larger, older, and had higher growth rates than other gender types. Local abundances were 10-fold higher in the Potomac River estuary in comparison to the Hudson River, but growth rates were similar. Mortality rates were twice as high as those in the Hudson River estuary. The production model indicated American eel recruitment and biomass decreased substantially during the past 20 years.
ASSESSMENT OF MANGROVE AND SALT MARSH MESOCOSM FUNCTIONAL VALUE USING PERIWINKLE SNAILS, LITTORARIA ANGULIFERA AND LITTORARIA IRRORATA, AS AN INDICATOR
(2004-04-01) Swartwood, Stacy Lyn; Kangas, Patrick C; Marine-Estuarine-Environmental Sciences
Although much research has been conducted on restoration techniques, questions about the functional value of restored and constructed ecosystems remain. Gastropods are a particularly useful indicator organism because they play a vital role at the detrital interface. This study addresses the question of whether the age structure, population density, and distribution of Littoraria angulifera in the Smithsonian Institution's Florida Everglades mesocosm in Washington, DC is analogous to that of wild populations. The second phase investigates these same factors, in populations of Littoraria irrorata at a reference site on Slaughter Creek and six mesocosm replicates at Horn Point Laboratory in Cambridge, Maryland. Neither the mangrove nor the salt marsh mesocosms were able to support healthy, reproducing populations of periwinkle snails. Salinity, humidity, territory requirements, habitat complexity, precipitation, photoperiod, and tidal variation were identified as potential causal factors for mortality and the absence of evidence of juvenile recruitment to mesocosm populations.
Assessment of Pesticide Residues In Farmers' House Dust and Educational Intervention to Improve Pesticide Handling Practices
(2004-12-02) Clark, Lisa M; Brown, Amy E; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This study investigated whether pesticide residues occur inside homes of vegetable and small fruit growers, identified pesticide handling practices that could contribute to home contamination, and evaluated the impact of an educational intervention in changing those handling practices. Dust samples were collected from the subjects' homes and analyzed for chlorothalonil. Residues were detected in carpet dust samples (8-277 ng/g), floor wipe samples (0.08-5.1 ug/sq m) and one washing machine sample (1.0 ug/sq m of washing machine). Each subject received an educational intervention consisting of a personalized report noting sites contaminated and providing recommendations of handling practices that would be expected to reduce any residues. Three sequential surveys of Maryland growers provided information regarding handling practices and changes over time. Lessons from this study could be incorporated into pesticide safety education to promote safer pesticide handling.
Assessment of Populations with Spatially Explicit Dynamics and the Consequences for Marine Protected Areas
(2011) Barkman, Jennifer Shari; Wilberg, Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Spatial processes can have important consequences in the population dynamics of fishes and marine invertebrates. Therefore fisheries management should consider space in the techniques used to understand population dynamics. The purpose of this thesis was to investigate spatial dynamics of fish populations in Maryland's coastal bays (Chapter 2) and evaluate effects of spatial management (in the form of marine protected areas (MPAs)) on accuracy of abundance estimates (Chapter 3). In Chapter 2, I examined trawl survey data from Maryland's coastal bays to estimate trends in relative abundance of four commonly caught fish species using a generalized linear model that allowed region specific estimates. Species showed different responses in the two regions, but trends over time were not related to local habitat variables. In chapter 3, I examined the effects of an MPA on the accuracy and bias of estimates from spatially aggregate and explicit surplus production models (SPMs) using a simulation experiment. I found that spatially-explicit SPMs produced more accurate estimates of biomass than spatially-aggregate SPMs, and that larger MPAs produced more accurate estimates than smaller MPAs.