Life Sciences Commons^™

Spatial And Demographic Variations In Apparent Annual Survival Of Golden-Winged Warblers: A Range-Wide Investigation, Emily Filiberti

Electronic Theses and Dissertations

The Golden-winged Warbler (Vermivora chrysoptera) is a Nearctic-Neotropical migratory songbird that has experienced over 70% population loss since the 1960s. While primary drivers of decline are unclear, habitat loss and hybridization with the genetically similar Blue-winged Warbler (Vermivora cyanoptera) are likely causes. This species breeds in two geographically allopatric regions, the Great Lakes and the Appalachian Mountains. These two populations are experiencing different rates of decline, with the Appalachian Mountain population facing steeper decline than the Great Lakes. Due to pronounced range-wide population decline, Golden-winged Warbler is currently under review for protection under the Endangered Species Act, however information pertaining …

Climate Interactions Drive Tree Physiology And Growth In A Northeastern Forest Ecotone, Alexandra M. Barry

Electronic Theses and Dissertations

Climate change is a threat to global forest ecosystems. In the northeastern United States, forest trees are facing rising temperatures and increasingly inconsistent moisture regimes. In addition to long-term changes in climate conditions, there is concern about the potential for more frequent and intense climate extremes, which can have severe and rapid negative effects on tree physiology and growth. Further, climate extremes may co-occur to produce a greater magnitude of effect than the sum of their parts, with a prominent example being hot droughts, which are increasing in occurrence and severity. The impact of these and other extreme climate interactions …

Effects Of Large Wood Additions On Basal Resources, Macroinvertebrates, And Ecosystem Processes In The Narraguagus River, Maine, Val Watson

Electronic Theses and Dissertations

Ecological restoration is an increasingly common practice across ecosystems, and current practices aim to restore the biological and physical processes underlying ecosystem function, often for the sake of endangered higher-level consumers. Studies of restoration outcomes often report few or inconsistent ecological changes, and monitoring of restoration projects rarely measures ecological processes. Monitoring also usually measures outcomes at a single scale, despite the prevalence of scale- dependent phenomena across ecosystems. My thesis uses measurements of ecological processes to assess restoration response and evaluates responses across multiple scales. I focus here on a long-term large wood addition project on the Narraguagus River …

Genetic Effects Of Anthropogenic Disturbance On Native Charrs, Brad Erdman

Electronic Theses and Dissertations

Artificial propagation has been utilized for over a century to offset anthropogenic declines of abundance for many fishes. Complex and poorly documented histories of habitat degradation and stockings have resulted in considerable uncertainty regarding whether contemporary populations are of native, hatchery, or mixed origins. This uncertainty is problematic as it precludes prioritizing the conservation of native populations that are postulated to possess local adaptations and greater evolutionary potential. Population genetics can assess the relative reproductive contributions of previous stocking events and in this dissertation I apply these methods to four empirical studies of native charr (genus Salvelinus) that have …

Integrating Environmental Dna, Traditional Fisheries Techniques, And Species Distribution Modeling To Assess Bridle Shiner Status In Maine, Lara S. Katz

Electronic Theses and Dissertations

The bridle shiner (Notropis bifrenatus) is a small minnow species native to the eastern United States and southeastern Canada. The species is declining dramatically throughout most of its native range and has legal protection or concern status in thirteen states and two Canadian provinces. In Maine, the bridle shiner is listed as a Species of Special Concern and considered a Species of Greatest Conservation Need, partially because we lack a basic understanding of their status and distribution within the state. Bridle shiners have historically been found in southern and western Maine in densely vegetated, shallow habitats along the …

Cross-Trophic-Level Dynamics In Aquatic Ecosystems And Their Application Across Ecological Contexts, Elliot M. Johnston

Electronic Theses and Dissertations

Cross-trophic-level dynamics represent biotic interactions between organisms in a food web that span two (e.g., predator-prey interactions) or more (e.g., bottom-up or top-down indirect interactions) trophic levels. These dynamics are fundamental to understanding a variety of animal attributes across ecological contexts, including life-history traits, population limitation, and resource management. A classic example illustrates how declines in sea otter (Enhydra lutris) populations had negative indirect effects on giant kelp (Macrocystis pyrifera) populations due to reduced top-down regulation of a primary kelp predator, purple sea urchin (Strongylocentrotus purpuratus). The need for management approaches that incorporate this food-web connectivity is evident in the …

Understanding The Impacts Of Anthropogenic Effects An Habitat Variability Interactions On Maine's Rocky Intertidal Ecosystem, Laura Braun

Electronic Theses and Dissertations

The rocky intertidal ecosystem is an important ecological and cultural aspect of the picturesque Maine coast, playing a vital role in not only Maine’s coastal ecosystem, but also to Maine’s economy. It’s distinct community structure along the sharp elevational gradient and the presence of daily stressors (wave action, heat, and desiccation), make the rocky intertidal ecosystem an important model ecosystem to monitor for effects from anthropogenic impacts. In this thesis, I describe attempts to monitor and understand the impacts of two of these anthropogenic impacts on this system: climate change and industrial harvesting of Ascophyllum nodosum along Maine’s coast. For …

A Sky Island Perspective: New England Alpine Plant Distributions Across The Region, Andrea Tirrell

Electronic Theses and Dissertations

Alpine ecosystems around the globe are at risk due to climate change, human disturbance, and habitat loss. New England alpine zones are small and fragmented, which could make them vulnerable to global change. However, the persistence of tundra relics throughout the Holocene suggests the persistence of these communities in microclimate refugia. Assessing the near-term vulnerability of alpine plant communities is challenged by a lack of standardized, repeat surveys and long-term monitoring data, which presents a challenge for the many agencies monitoring New England’s alpine zones. Island biogeography theory predicts that alpine species richness is a function of area, but this …

Ecological Implications Of Intraspecific Behavioral Variation In A Small Mammal Community, Allison Brehm

Electronic Theses and Dissertations

Variation among individuals is at the root of all evolution by means of natural selection. However, only in recent years has intraspecific behavioral variation been embraced as a potential driver of community and ecosystem processes, rather than considered statistical noise. Animal personalities, or behavioral differences between conspecifics that are consistent across time and contexts, are one such form of variation that has received considerable attention in the last two decades. Investigations of the ecological and ecosystem consequences of personality variation is at the current forefront of the field, but much work on this topic remains conceptual. Here, I apply large-scale …

3d Computer Modeling Offers New Insights Into Diatom Ecology, Joseph Mohan

Electronic Theses and Dissertations

Algae supply over half of the Earth’s global primary production and form the base of almost all aquatic food networks. Thus, changes in algal productivity or composition will induce profound shifts in many ecosystems. This research is guided by two questions. Herein I ask if 3D models of algae can be created accurately enough to use for research applications? If they can be accurately created, then how can these models be used to advance our understanding of functional trait evolution and paleoecology? Herein, I develop 3D computer models for estimating the volume of individual algae and their parts. I also …

The Long-Term Impact Of Dam Removals On Penobscot River Migratory Fishes, Erin Peterson

Electronic Theses and Dissertations

Dams interrupt river connectivity and disrupt fish migrations. We used telemetry to study the migratory movement patterns of adult American shad, sea lamprey, and Atlantic salmon on the Penobscot River, Maine after dam removals and other passage improvements had occurred. We also studied scale formation of marine-stage Atlantic salmon raised in marine net pens, the findings from which could be relevant to captive rearing efforts.

American shad now have access to the majority of their historic spawning habitat, contingent on passage the first main-stem dam (Milford Dam). We found that habitat upstream of dams was infrequently accessed, and first …

Evaluation Of Fish Assemblage Composition And The Expansion Of An Invasive Species Following Dam Removal And Upgraded Fish Passage In The Penobscot River, Maine, Kory A. Whittum

Electronic Theses and Dissertations

The Penobscot River Restoration Project was a large river rehabilitation project, culminating in the removal of the two lowermost dams (Veazie and Great Works) and improvements to fish passage on several remaining dams. Fish assemblages were surveyed for 3 years prior to rehabilitation, 3 years after, and now 8 years post-rehabilitation. Approximately 475 km of shoreline was sampled via boat electrofishing, yielding 133,394 individual fish of 41 species. The greatest shifts in assemblage structure occurred immediately after dam removal in formerly impounded sections, with increased prevalence of riverine and migratory species. Extended sampling documented several additional changes occurring within lower …

Vertical Habitat Gradients: Comparing Phytoplankton Dynamics In Lakes With Low To Moderate Dissolved Organic Carbon Concentration, Matthew J. Farragher

Electronic Theses and Dissertations

Concentrations of dissolved organic carbon (DOC) increased across lakes of Maine for several decades before stabilizing or decreasing in recent years. To investigate the seasonal effects of DOC on phytoplankton habitat structure, I assessed vertical gradients of temperature, oxygen, light, and chlorophyll in four lakes in Acadia National Park from under ice through fall turnover in 2020. Lake DOC concentrations ranged from low (~2 mg L-1) to moderate (~4 mg L-1). Low-DOC lakes were clearer, with greater mean Secchi depths (9-15 m) than moderate-DOC lakes (5-6 m). Moderate-DOC lakes experienced hypolimnetic anoxia in the summer and had more variable concentrations …

Acting Out Of Lyme: Characterizing The Human Dimensions Of Lyme Disease Interventions, Katherine C. Perry

Electronic Theses and Dissertations

Lyme disease (LD), a tick-borne disease caused by the bacterium spirochete Borrelia burgdorferi, is the most commonly occurring tick-borne illness in the United States with the majority of cases concentrated in the Northeast. In Maine, as well as the rest of North America, LD is transmitted to humans via infected black-legged ticks (Ixodes scapularis). As the life cycle of the black-legged tick is tightly coupled with forest ecosystems, prevalence of the disease is common in endemic forest landscapes, and individuals spending time in these areas face an increased risk of exposure to LD as well as other tick-borne diseases. While …

Environmental Dna Monitoring Of Non-Native Mudpuppy (Necturus Maculosus) And Transient Rainbow Smelt (Osmerus Mordax), Vaughn Holmes

Electronic Theses and Dissertations

Whether considering an expanding non-native species or a priority native species with a dwindling local population, the monitoring of low-abundance, sporadically distributed, or otherwise elusive populations, can prove difficult. In separate studies, we tested the viability of environmental DNA (eDNA) for monitoring a species in both of the above circumstances, the common mudpuppy (Necturus maculosus), a spreading non-native species, and rainbow smelt (Osmerus mordax), a declining species of concern. Mudpuppy are fully aquatic salamanders that were introduced to the Belgrade region of central Maine in 1939 and again in 1940. Though they had been present for nearly 80 years when …

Energetic Impacts Of Passage Delays In Migrating Adult Atlantic Salmon, Sarah R. Rubenstein

Electronic Theses and Dissertations

For any migratory organism, habitat connectivity is critical for population stability. Structures that impede movement between necessary habitats can be damaging to population persistence. In riverine systems, dams act as migratory barriers, altering ecosystems and delaying, injuring, or otherwise impairing migratory fish movement into essential habitat. Critically endangered Atlantic salmon (Salmo salar) populations in Maine have been on the decline since the 1800s. Because most Atlantic salmon rivers are now highly dammed systems, hydropower dams have been cited as causal to the decline in returning adult populations. Previous studies have demonstrated that Atlantic salmon experience substantial delays below dams while …

Migration And Winter Movement Ecology Of Red-Throated Loons (Gavia Stellata) In Eastern North America, Carrie E. Gray

Electronic Theses and Dissertations

Migratory animals exploit multiple habitats across the extent of their range and conditions experienced can have considerable effects on individual survival and population size. Understanding where species are exposed to survival risks and evolutionary selection pressures and how connected are different portions of the range requires defining a complete annual movement network with all major seasonal sites—e.g., breeding, migratory stopovers, staging, and wintering—and describing where populations may or may not overlap in space and time. I used movement data collected from satellite-tagged Red-throated Loons (Gavia stellata) to provide new and more accurate information about spatial use during the full annual …

American Eel Behavior And Survival In An Impounded River System, Matthew A. Mensinger

Electronic Theses and Dissertations

After beginning life in the Sargasso Sea, American eel enter river systems as juveniles and swim upstream in pursuit of freshwater habitat. Many encounter dams during this migration which act as barriers to upstream movement and limit eel establishment in headwater systems. Some dams have been retrofitted with fishways to improve watershed connectivity, but the individual selection imposed by these structures remains uncharacterized. We considered whether individual differences in behavior (i.e., personality) may be used to predict the propensity of juveniles to use a passage structure, suggesting that eel personality may predict access to habitat upstream of dams. Migrating, juvenile …

Assessing Predator Risk To Diadromous Fish Conservation In The Penobscot River Estuary, Lauri Leach

Electronic Theses and Dissertations

Successful conservation of pinnipeds in the northwest Atlantic has led to increasing populations of harbor (Phoca vitulina) and gray seals (Halichoerus grypus) in the Gulf of Maine. Seals are often perceived as predators and competitors for fish, and as a result, come into conflict with fisheries and fish conservation. Increasing numbers of seals have become a recent concern in the Penobscot River Estuary in Maine, as habitat restoration and diadromous fish conservation have been top priorities in this region for the past decade.

To understand how pinnipeds are responding to these efforts, as well as the risks they pose to …

Responses Of Juvenile Atlantic Salmon To Competition And Environmental Change: Implications For Performance In Maine Streams, Nicole C. Ramberg-Pihl

Electronic Theses and Dissertations

New England’s climate is changing faster than that of any other region in the continental United States. Over the last century, Maine has experienced an increase in annual temperature of approximately 1.48^oC along with a 15 percent increase in annual precipitation. Temperature and precipitation play vital roles in shaping the ecology of freshwater environments. Therefore, changes in regional climate could undermine the structure and stability of Maine’s freshwater systems as they currently exist.

Maine currently harbors the last wild populations of Atlantic salmon (Salmo salar) in the United States. Atlantic salmon were once abundant in Maine …

Developing A Long-Term Perspective On The Sensitivity Of Lake Trophic State Changes In Maine, Simona Lukasik

Electronic Theses and Dissertations

Even with similar external drivers, lakes can respond differently because of key ecosystem features that determine lake sensitivity. Identifying factors that determine lake sensitivity are important for successful lake management. The purpose of this research was to determine patterns of algal community change over the past 400 years in lakes with watersheds that vary in surficial geology, specifically the glacio-marine clay layer in Maine known as the Presumpscot formation. Responses to two external drivers, major land use changes and climate change, were assessed. Four lakes were chosen based on their surficial geology and land use history: Unity Pond, Webber Pond, …

Sourcing And Evaluating The Use Of Detritus As A Supplementary Diet For Bivalve Aquaculture Using Stable Isotopes And Fatty Acid Biomarkers, Adrianus C. Both

Electronic Theses and Dissertations

Detritus is a ubiquitous component of ecosystems and an important fuel for secondary production. Due to the extractive nature of bivalve aquaculture, detritus is often incorporated into carrying capacity and growth models for cultured bivalves. However, despite the complexity and difficulty in obtaining direct measurements, detritus is often treated as a homogeneous food source in models. Further understanding the role detritus plays in the diet of cultured bivalves could lead to more comprehensive and accurate models as well as more informed site selection for growers. The purpose of this study was to assess the abundance, bioavailability, and contribution of detritus …

Predicting And Managing Risk To Bats At Commercial Wind Farms Using Acoustics, Trevor Peterson

Electronic Theses and Dissertations

Bat populations in North America face novel threats from white-nose syndrome and widespread turbine-related mortality related to the rapidly expanding wind power industry in addition to long-standing pressures from habitat loss and degradation. Bats, unlike most small mammals, are long-lived and slow to reproduce, highlighting the importance of understanding and managing anthropogenic sources of mortality. My dissertation research used acoustic bat detectors to measure bat activity at commercial wind projects, predict patterns in risk, and design strategic measures to reduce fatality rates by curtailing turbine operation during periods when bats are most active. Bats collide with wind turbines only when …

Fish Passage And Hydropower: Investigating Resource Agency Decision-Making During The Ferc Hydropower Relicensing Process, Sarah Vogel

Electronic Theses and Dissertations

Hydropower dams represent a significant challenge for the successful migration of sea-run fish, many species of which are in decline. Most hydropower dams in the United States are regulated by the Federal Energy Regulatory Commission (FERC), an independent federal agency responsible for granting 30 to 50-year licenses to projects for their continued operation. Licenses typically include conditions for the conservation of sea-run fish such as fish passage construction, operational changes, monitoring of effectiveness, and other mitigative conditions. While FERC remains the primary authority in licensing, the current regulatory framework stipulates input from other federal and state resource and regulatory agencies, …

Spatial And Temporal Variation In The Aquatic Invertebrate Community Structure Of Rock Pools Along The Penobscot River, Maine, Chase R. Gagne

Electronic Theses and Dissertations

Pools of water that form in the fissures and depressions of rock outcrops, known as rock pools, are fairly common aquatic habitats that can easily be found along the rocky banks of many of Maine’s major rivers. In general, rock pools and the aquatic invertebrates inhabiting them have received little research attention and, though ubiquitous, have never been studied in Maine. My research addressed this knowledge gap by surveying 40 rock pools at four sites along the Penobscot River in Maine. The rock pools themselves had highly variable environmental characteristics and differed across sites and over time, especially in hydroperiod. …

Landscape Pattern And Wild Bee Communities In Maine, Brianne Du Clos

Electronic Theses and Dissertations

Commercial production of lowbush blueberry (Vaccinium angustifolium Aiton) in Maine relies primarily on managed honeybee hives; however, naturally occurring wild bees are more efficient pollinators of the crop. Wild bees have short foraging distances and must nest near crop fields to provide pollination services. After crop bloom, the surrounding landscape must provide sufficient forage to maintain wild bee populations for the remainder of the growing season. Lowbush blueberries in Maine are produced in a mixed-use landscape with two distinct landscape contexts. Here, we document bee communities and habitat resources (nesting and floral) in power line rights-of-way and eight land …

Assessing The Mechanisms And Implications Of Altered Carbon Cycling In Arctic And Boreal Lakes, Rachel Fowler

Electronic Theses and Dissertations

Dissolved organic carbon (DOC) is an important component of lake ecology, as it contributes to light attenuation and carbon cycling. In recent years, DOC declined in a suite of lakes in Greenland. I performed experiments to test potential mechanisms of DOC loss. The tested mechanisms did not reduce DOC concentration, but DOC composition was affected. I also paired water quality data with meteorological observations to evaluate effects of climate drivers on lake variables. The lake variables were temporally coherent and associated with patterns of mean annual precipitation.

In the northeastern U.S., recovery from acidification and climate change have contributed to …

Response Of Estuarine Fish Biomass To Restoration In The Penobscot River, Maine, Justin R. Stevens

Electronic Theses and Dissertations

Diadromous fish require both freshwater and marine habitat to complete their life cycle. Dams restrict the movement between these habitats and as a result, many populations are historically low across their range. The Penobscot River is the second largest river in Maine and once had large populations of diadromous fish and it has been the focus of mainstem dam removals, dam passage improvements, and stocking with the goal of restoring those populations. Since 2012, NOAA Fisheries has conducted surveys of the Penobscot Estuary using mobile, multi-frequency echosounders (SIMRAD EK60 split-beam 38 and 120 kHz) combined with mid-water trawl surveys to …

Ecological And Economic Implications Of Increased Storm Frequency And Severity For Boreal Lakes, Kathryn Warner

Electronic Theses and Dissertations

In boreal regions, increased precipitation events have been linked to increased concentrations of dissolved organic carbon (DOC), however less is known about the extent and implications of these events on lakes. We assessed the effects of precipitation events on six drinking water lakes in Maine, USA to better understand how DOC concentration and quality change in response to precipitation events. Our results revealed three types of responses: (1) an initial spike in DOC concentrations and quality metrics; (2) a sustained increase in DOC concentrations and quality metrics and; (3) no change during all sampling periods. Lake residence time was a …

Associations Between Avian Spruce-Fir Species, Harvest Treatments, Vegetation, And Edges, Brian W. Rolek

Electronic Theses and Dissertations

Habitat loss is the primary cause of species loss and declines of global biodiversity. Several birds associated with the spruce-fir forest type (hereafter spruce-fir birds) have declining populations across the continent in the Atlantic Northern Forest, and the extent of coniferous forest has declined in some areas. This region is extensively and intensively managed for timber products.

To investigate the influence from harvest treatments on the spruce-fir bird assemblage during the breeding and post-breeding period in lowland conifer and mixed-wood forests, we used avian point count detection data to test for associations between avian assemblages and seven common harvest treatments. …