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Impacts And Management Of Foliar Pathogens Of Eastern White Pine (Pinus Strobus) In The Northeastern United States, Cameron Ducayet Mcintire

Doctoral Dissertations

White Pine Needle Damage (WPND) is a complex of foliar fungal pathogens currently impacting forests in the Northeastern US. Since ca. 2009, chlorosis and defoliation caused by WPND has been observed in stands of eastern white pine (Pinus strobus L) throughout the region. A changing climate, notably warmer temperatures and higher than average spring precipitation in the region are thought to be exacerbating the establishment and spread of these native pathogens. The goals of this research are to enhance the understanding of the timing and magnitude of WPND-induced defoliations across infected stands, assess the physiological response of trees affected by …

Microbial Community And Vibrio Parahaemolyticus Population Dynamics In Relayed Oysters, Michael Anthony Taylor

Doctoral Dissertations

The CDC estimates that 45,000 people are sickened each year by foodborne Vibrio parahaemolyticus in the United States. Filter-feeding bivalve shellfish, such as oysters, are routinely inhabited by human pathogenic V. parahaemolyticus and there currently is not a contaminant management process that effectively reduces concentrations of V. parahaemolyticus in oysters. The transplanting of V. parahaemolyticus -laden oysters to an area with low concentrations or no V. parahaemolyticus, called oyster relay, is one reduction strategy that holds promise for treating live oysters. A key consideration for effective strategies to reduce Vibrio spp. in shellfish is the influence of microbiota in natural …

Effects Of Agricultural Practices On Soil Communities And Their Associated Ecosystem Services, Lesley W. Atwood

Doctoral Dissertations

To maximize crop yields, commodity crop production systems typically rely on inputs of fertilizers, pesticides, and irrigation; simplification of crop rotations (e.g., monocultures); and strategic use of soil disturbance (e.g., tillage, cultivation, etc.). While these practices are intended to optimize the soil conditions for crop development and reduce spatial and temporal variability in crop yield, they also impact soil biological diversity and the important agroecosystem services soil communities provide. Identification of management practices that are less prone to causing undesirable changes in the soil food web community are central to improving the sustainability of our agricultural systems. In this dissertation, …

Patterns And Drivers Of Carbon Fluxes In Temperate Forests, Andrew Ouimette

Doctoral Dissertations

Despite decades of carbon cycling research in terrestrial ecosystems, a complex suite of biotic and abiotic interactions make a complete understanding of the natural carbon cycle elusive. This thesis aims to advance our understanding of the carbon cycle, and stems from several ongoing projects aimed at quantifying carbon dynamics in forest ecosystems across a range of scales, with a specific effort to include both above and belowground components of forest ecosystems. I begin with a project using detailed chemical measurements on specific segments of root systems from two different tree species, in order to help refine methods that quantify the …

Nitrogen Dynamics And Retention In The River Network Of A Tropical Forest, Luquillo Mountains, Puerto Rico, Richard Brereton

Doctoral Dissertations

This dissertation identifies gaps in the scientific understanding of nutrient cycling, particularly nitrogen (N) cycling, in streams and riparian zones of tropical montane forests, and addresses several of those gaps with original field-based research using study watersheds in the Luquillo Mountains of Puerto Rico as the model system. The Luquillo Mountains have features typical of mature montane tropical forests, such as high background N concentrations in streams and groundwater relative to streams in other biomes. As a USDA Forest Service Experimental Forest, the Luquillo Mountains are accessible to researchers and have abundant monitoring and experimental datasets from which to build …

Channeled Whelk (Busycotypus Canaliculatus) Ecology In Relation To The Fishery In Vineyard And Nantucket Sounds, Massachusetts, Shelley Ann Edmundson

Doctoral Dissertations

Channeled whelks (Busycotypus canaliculatus) are predatory marine gastropods that support lucrative commercial fisheries along the east coast of the United States, with areas around Massachusetts supplying the largest landings. In the absence of a more thorough and comprehensive understanding of channeled whelk biology, it is unclear how to sustainably manage their fisheries. Within this dissertation, various aspects of whelk ecology were investigated to determine how to protect this species, while effectively managing the local fishery.

Early life history experiments revealed channeled whelk egg strings may incubate for 8 to 9 months in MA water temperatures. Incubation period decreased with increasing …

Hybrid Zone Dynamics Between Saltmarsh (Ammodramus Caudacutus) And Nelson's (Ammodramus Nelsoni) Sparrows, Jennifer Walsh

Doctoral Dissertations

Hybrid zones in nature have long been equated to “windows on the evolutionary process” providing unique environments to understand patterns of gene flow and introgression and the role of these mechanisms in maintaining biodiversity. Ongoing hybridization and introgression can lead to a number of conservation and evolutionary outcomes; as such, identifying the role of introgression in natural populations can provide new insights into species interactions while contributing to our understanding of evolutionary theory.

The research presented below characterizes hybrid zone dynamics between two tidal marsh endemics – the Saltmarsh (Ammodramus caudacutus) and Nelson’s (Ammodramus nelsoni) sparrow. Both species co-inhabit salt …

Causes And Consequences Of Diversity Within Experimental Biofilms Of Pseudomonas Aeruginosa, Kenneth Mark Flynn

Doctoral Dissertations

Currently, we do not understand how much biodiversity may be maintained in any environment, especially not in the structured environments of biofilms, which constitute the dominant mode of microbial life. Although maintenance is associated with the complex spatial structure of biofilm architecture and resulting ecological opportunities, how both the abiotic and biotic environment defines available niches remains poorly understood. Here, we experimentally evolved three replicate populations founded by Pseudomonas aeruginosa strain PA14 for 540 generations under conditions favoring a regular cycle of biofilm formation and dispersal. Utilizing a variety of laboratory and genomic sequencing approaches, we characterize the population genetic …

Full-Waveform And Discrete-Return Lidar In Salt Marsh Environments: An Assessment Of Biophysical Parameters, Vertical Uncertatinty, And Nonparametric Dem Correction, Jeffrey Nickerson Rogers

Doctoral Dissertations

High-resolution and high-accuracy elevation data sets of coastal salt marsh environments are necessary to support restoration and other management initiatives, such as adaptation to sea level rise. Lidar (light detection and ranging) data may serve this need by enabling efficient acquisition of detailed elevation data from an airborne platform. However, previous research has revealed that lidar data tend to have lower vertical accuracy (i.e., greater uncertainty) in salt marshes than in other environments. The increase in vertical uncertainty in lidar data of salt marshes can be attributed primarily to low, dense-growing salt marsh vegetation. Unfortunately, this increased vertical uncertainty often …

Mechanisms Of Nutrient Limitation And Nutrient Acquisition In Managed And Unmanaged Forest Ecosystems, Matthew A. Vadeboncoeur

Doctoral Dissertations

Understanding the interactions between global change, human and natural disturbances, and other factors on biogeochemical processes in forests is necessary to ensure the sustainability of forest management. Here I report the results of several investigations into nutrient acquisition processes in the forests of New Hampshire. I begin with a meta-analysis of fertilization studies showing that phosphorus (P) and calcium (Ca) as well as nitrogen (N) may limit primary production in deciduous forests of the region. Because these limiting nutrients are all removed from the ecosystem when trees are harvested, I compared nutrient budgets under a range of harvesting scenarios with …

The Effects Of Biotic And Abiotic Factors On Byssogenesis, Growth And Movement Patterns Of The Blue Mussel, Mytilus Edulis, Yvette Louise Garner

Doctoral Dissertations

Blue mussels create extensive aggregations on intertidal and low subtidal shores in the Gulf of Maine, in which they modify habitat, trap sediments and create microclimates for many organisms. Mussels are an important aquaculture species worldwide, and play a major part of the economy of New England. Blue mussels produce collagenous byssal threads to anchor themselves to the substrate on wave swept shores. Byssogenesis, growth and movement abilities of mussels are influenced by a host of biotic and abiotic factors. In this dissertation I quantified byssogenesis and growth of the blue mussel, Mytilus edulis, affected by wave exposure, temperature, and …

Ecological Effects Of Ditching And Ditch-Plugging In New England Salt Marshes, Robert E. Vincent

Doctoral Dissertations

Anthropogenic activities in New England salt marshes have altered hydrologic flows in various ways, but unintended consequences from some of these habitat modifications have received little attention. Specifically, ditches have existed on salt marshes for decades, but the effects of these hydrologic alterations are only poorly understood. Ditch-plugging is a more recent methodology used for salt marsh habitat enhancement and mosquito control, but the long-term effects from this management practice are also unclear. I used natural tidal creeks and pools as controls to examine the effects resulting from ditching and plugging, respectively, on hydrology, soil characteristics, marsh surface elevation, plant …

The Role Of Red-Backed Salamanders In Ecosystems, Daniel J. Hocking

Doctoral Dissertations

Ecosystems provide a vast array of services that benefit human societies, which can be divided into provisioning, regulating, cultural, and supporting services. Amphibians provide provisioning services in the form of food and use in medical advances. As one of the major vertebrate groups, amphibians also play an important part in cultures throughout the world. Finally, amphibians can be extremely abundant and play important roles in ecosystem supporting services, including altering both physical structure and ecosystem functions. In aquatic systems, tadpoles can alter sedimentation, water clarity, and filamentous algae growth. Additionally, amphibians affect ecosystem functions, including nutrient cycling, decomposition, and primary …

The Historical Fisheries In The Mediterranean Sea: A Reconstruction Of Trawl Gear, Effort And Trends In Demersal Fish Stocks, Giacomo Chato Osio

Doctoral Dissertations

An extensive search of historical data sources and publications has been carried out in different countries of the Mediterranean. This lead to the construction of the largest compilation of historical fisheries information existing in the Mediterranean region. The goal first here was to quantify historical trawling effort. This shows that Mediterranean demersal communities underwent a much longer and more systematic exploitation than previously thought, very likely the longest known exploitation by means of trawls in Europe and North America. Analysis of the data available for the Catalonian, Italian and French areas showed a clearly emerging pattern: fishing capacity increased in …

The Ecological Role Of Feeding Disturbances Of The Atlantic Horseshoe Crab, Limulus Polyphemus, Wan-Jean Lee

Doctoral Dissertations

This study examined the influence of localized disturbances on the heterogeneity of ecological communities at multiple temporal and spatial scales. Foraging disturbances by the epibenthic predator, Atlantic Horseshoe Crab Limulus polyphemus, on the intertidal mudflats of Great Bay estuary, New Hampshire, USA were used as the study system.

This study overcame methodological hurdles in the study of small localized disturbance over extensive areas of soft-sediments. Using a novel, low-cost technique to monitor Limulus foraging disturbances, Great Bay's tidal flats were found to be critical feeding habitats from late spring till fall. Foraging Limulus disturbed the benthos of Great Bay at …

On The Reproductive Biology Of The Western Atlantic Bluefin Tuna, Thunnus Thynnus, Jessica M. Knapp

Doctoral Dissertations

The Atlantic bluefin tuna, Thunnus thynnus, is a highly migratory species capable of traversing great distances throughout the North Atlantic Ocean, but spawning is known to occur only in the Mediterranean Sea and the Gulf of Mexico/Straits of Florida. The regulatory body charged with managing Atlantic bluefin tuna, the International Commission for the Conservation of Atlantic Tunas (ICCAT), currently recognizes two spawning stocks, eastern and western, separated by a management line at 45° W. The eastern stock spawns from May through July in the Mediterranean Sea with an age at first maturity of 3--4 years. Due in part to a …

Unraveling The Mystery Of Leaf Reddening In Seagrasses, Alyssa B. Novak

Doctoral Dissertations

Seagrass meadows around the world are declining due to natural and anthropogenic stressors, including global climate change. Recently, more attention has been given to identifying responses that offer resistance to stressors so that researchers can better manage seagrasses for resilience to environmental change. Leaf reddening, the expression of red coloration in leaves, is a well-documented response in terrestrial plants that has been shown to increase resilience to stress, but has been poorly understood in seagrasses. To increase our understanding of the prevalence, causes, and function of leaf in seagrasses, surveys were conducted in the world's six seagrass bioregions and a …

Assessing Social-Ecological Resilience And Adaptive Capacity In The Face Of Climate Change: An Examination Of Three Communities In The Crown Of The Continent Ecosystem, Bradley B. Johnson

Doctoral Dissertations

This research examines the social-ecological resilience and adaptive capacity of the Crown of the Continent Ecosystem through a suite of three case study communities and the impacts of climate change on the ecosystem's hydrologic regime. The Crown of the Continent Ecosystem spans the U.S.-Canadian border; case study communities composed of Kalispell and Choteau, Montana and Fernie, British Columbia fall on both sides of the border.

Primary data was gathered through a "bottom-up" qualitative approach utilizing an online survey followed by a semi-structured interview process with stakeholders in natural resource dependant industries and government at the local, state, and federal levels …

Detection Of Mortality In Tropical Forests Using Remote Sensing: From Treefall Gaps To Large Disturbances, Fernando Del Bon Espirito-Santo

Doctoral Dissertations

The frequency, severity, and intensity of natural disturbances in tropical forests continually re-shape forest structure. At small scale, branch or tree-falls gaps and subsequent recovery are important mechanisms for carbon cycling. At landscape scale, large disturbances (blow-downs) may also play a role on the structure and composition of tropical forests. Quantitative studies of natural disturbances across the occurrence spectrum (branch fall-gaps to blow-downs) are rare for the Amazon. Remote sensing coupled with intense field work data collection provides the means to analyze the dynamic of tropical forests at multiple scales. In this dissertation three aspects of natural disturbances were examined: …

Seasonal, Biogeochemical, And Microbial Response Of Soils To Simultaneous Warming And Nitrogen Additions, Alexandra R. Contosta

Doctoral Dissertations

Climate warming and nitrogen deposition are global environmental threats that could alter soil microbial communities and the biogeochemical processes they perform. Few studies have examined interactive effects of elevated temperatures and nitrogen inputs. Many studies have also not considered the role that season plays in mediating the response of soils to warming and nitrogen. Finally, most research has not linked changes in the soil microbial community with ecosystem-scale dynamics. One objective of this dissertation was to examine season-specific microbial and biogeochemical responses to simultaneous warming and nitrogen additions. Another aim was to investigate whether warming and nitrogen can restructure microbial …

Effects Of Physical And Chemical Disturbance On Stream Ecosystem Structure And Function, Elena M. Traister

Doctoral Dissertations

A variety of natural and anthropogenic disturbances influence the structure and function of stream ecosystems. While past investigations have focused on the response of community indicators to stream disturbances, functional indicators may also be helpful for assessing stream ecosystem health. To date, few studies have compared the response of structural and functional indicators to ecosystem-level disturbances. I separately measured the effects of long-term acidification, a large-scale avulsion, and the individual and combined effects of physical streambed disturbance and altered refugia availability on stream structural and functional metrics.

I found that acidification was associated with changes in macroinvertebrate communities including reduced …

The Effects Of Didemnum Vexillum Overgrowth On Mytilus Edulis Biology And Ecology, Linda Ann Auker

Doctoral Dissertations

Didemnum vexillum is an invasive colonial ascidian in the Gulf of Maine that readily colonizes hard substrates. These substrates include hard-shelled organisms, such as the common blue mussel Mytilus edulis. Preliminary observations and short-term studies showed potential effects of epibiosis on M. edulis growth, specifically lip thickness and tissue index. This dissertation study further examined the effects of D. vexillum on growth and reproduction of, and predation on, M. edulis. Shell thickness index, tissue index, shell mass to tissue mass ratio, lip thickness and mussel length were measured throughout a 12-month period in control and overgrown mussels. Additionally, histological preparations …

Trematode Parasites Of The Mudsnail Ilyanassa Obsoleta: An Analysis Of Parasite Communities At Different Scales, Irit Altman

Doctoral Dissertations

This research examines the ecological factors that shape trematode parasite communities of mudsnail Ilyanassa obsoleta at three different spatial scales. Nine species of trematode which obligately infect I. obsoleta during larval stages but use numerous estuarine species as second intermediate and definitive hosts are considered. The work provides the most geographically extensive examination to date of this trematode parasite community.

At the broadest scale, I. obsoleta trematodes were examined across their distributional range (Chapter 2) which includes both native and introduced populations. The results demonstrate that introduced trematode communities are characterized by lower abundance and diversity compared to native communities …

Somatic Condition, Growth And Distribution Of Atlantic Bluefin Tuna (Thunnus Thynnus) In The Gulf Of Maine, Walter J. Golet

Doctoral Dissertations

Atlantic bluefin tuna (Thunnus thynnus), a highly migratory apex predator, utilize temperate feeding grounds to place their tissues into positive lipid balance following reproduction and subsequent migration to northern latitudes. Commercial fishermen target Atlantic bluefin tuna between June and October, but landings have declined 70% from 2004-2009 suggesting adult bluefin tuna may no longer be utilizing the Gulf of Maine as a foraging ground. A series of linear and additive models fitted to multiple fishery dependent datasets identified significant declines in the somatic condition of Atlantic bluefin tuna in the Gulf of Maine. Significant changes in the somatic condition of …

Movement And Behavior Of Ocean Sunfish, Mola Mola, In The Northwest Atlantic, Inga F. Potter

Doctoral Dissertations

The ocean sunfish, Mola mola, has a worldwide distribution and is a common resident of the NW Atlantic Ocean. Notable for its unusual anatomy and large size, the biology of the species is largely unknown. I examined the movement and behavior of M. mola using pop-up satellite archival tags (PSAT's). In addition, analysis of aerial survey data was conducted to determine the distribution of ocean sunfish (Family Molidae) in NW Atlantic shelf waters. Data was analyzed from twenty-five PSAT's deployed on M. mola in the northwest Atlantic between 2005 and 2008. Tags were attached from 7-242 days. Results indicate that …

Survival Strategies Of Eelgrass In Reduced Light, Caroline A. Ochieng

Doctoral Dissertations

Light reduction due to anthropogenic impacts is the most widespread cause of worldwide decline of eelgrass, an ecologically important marine angiosperm whose role in supporting overall coastal ecosystem productivity has been widely recognized. Understanding eelgrass plant and meadow responses to light reduction has therefore received significant research interest over the last 30 years, while managers have sought tools to identify critical thresholds for light availability and predict impacts of human-induced disturbances in order to prevent further eelgrass loss. In the present thesis, a review of some of the literature on light reduction and its effects on eelgrass (i) summarized the …

The Development Of A Modular Integrated Recirculating Aquaculture System Using Porphyra (Nori) For The Bioremediation Of Marine Finfish Effluent, Jennifer Pauline Day

Doctoral Dissertations

It is crucial for the development of the fish aquaculture industry to be managed in a way that provides a reliable, long term source of products without negatively impacting the environment. The simplest form of integrated multi-tropic aquaculture (IMTA) uses a fed component (e.g. finfish) and an extractive component (e.g. seaweed) to remove the inorganic metabolites from finfish aquaculture effluent. In IMTA systems metabolic wastes become nutrients for the other cultured organisms and are incorporated into potentially valuable biomass. A demonstration-scale Modular Integrated Recirculating Aquaculture Systems (MIRAS) was constructed in a greenhouse adjacent to Great Bay Aquaculture, LLC (GBA), Newington, …

Resolving The 150 Year Debate Over The Ecological History Of The Common Periwinkle Snail, Littorina Littorea, In Northeast North America, April M H Blakeslee

Doctoral Dissertations

Littorina littorea (common periwinkle snail) is highly abundant in both Europe and North America. A known native of Europe, its presence in North America has been the subject of a one-hundred year debate. Prior published work attempting to resolve its cryptogenic (=uncertain origin) status with historical, archaeological, ecological and/or genetic data were not successful. I therefore included novel parasite and molecular evidence to definitively resolve L. littorea's North American cryptogenic status.

First, I explored trematode species richness patterns in European versus North American L. littorea and two co-occurring native congeners, L. saxatilis and L. obtusata. Through extensive field and literature …

The Maintenance, Evolution, And Impacts Of Inducible Morphological Defenses In Mytilus Edulis: Responses To Multiple And Invasive Predators, Aaren Scott Freeman

Doctoral Dissertations

The burgeoning field of phenotypic plasticity and inducible defenses has documented a wide variety of predator-induced defenses. I this dissertation I have explored induced defenses in the marine mussel Mytilus edulis as they are affected by (a) shared evolutionary history with invasive crab predators, (b) specificity of responses to multiple predators (singly and combined) with different foraging strategies, and (c) spatial and temporal variation in the expression of predator specific induced defenses in situ.

Mytilus from southern New England expressed induced shell thickening when exposed to waterborne cues from the crab Hemigrapsus , but "naive" northern mussel populations do not …

Interactions Between Two Invasive Crab Predators, Carcinus Maenas And Hemigrapsus Sanguineus, And Consequences For The Native Community, Blaine David Griffen

Doctoral Dissertations

With continued globalization, species are being transported and introduced into novel habitats at an accelerating rate. As invasive species become more common, interactions between invasive species will also increase and may alter the way that these species impact invaded communities. The European green crab Carcinus maenas is an aggressive predator that was introduced to the east coast of North America in the mid 1800s and often has detrimental impacts on prey communities. A newer invasive predator, the Asian shore crab Hemigrapsus sanguineus, was first discovered on the Atlantic coast in the 1980s, and now inhabits many of the same regions …