Digital Commons Network^™

Aspects Of The Reproduction Of An Invasive Crab, Hemigrapsus Sanguineus, In Northern And Southern New England, Emily F. Gamelin

Master's Theses and Capstones

Populations of the invasive shore crab, Hemigrapsus sanguineus , were studied in northern and southern New England to determine if crabs differ in reproductive behavior or characteristics between these regions. Additionally, effects of temperature on reproductive activity were quantified through laboratory experimentation.

Number of broods per season increased with temperature, but the seasonal total was limited to three broods in laboratory experiments. Broods experienced limited success at the lowest temperature, 10°C. The reproductive season was longer at lower latitudes, and females at this site had smaller average ovigerous size. Patterns of ovigery varied between the regions, suggesting the production of …

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 …

An Evaluation Of Habitat Models For The Common Loon (Gavia Immer), Alexis M. Rudko

Master's Theses and Capstones

The Loon Preservation Committee (LPC) has been collecting field data for the common loon (Gavia immer) in New Hampshire for thirty-six years. A habitat model for lakes throughout New Hampshire was created by Dr. Mark Brennan for the time period 1980--2002. This project re-evaluates Brennan's habitat model using new data from 2003--2008. Two additional models, one with all lakes and another with the three largest lakes excluded, were created and compared to Brennan's model to see if the overall accuracy improved. These models show which lakes have high and low potential for loon habitat. The results of the re-evaluation of …

Isotopic Analysis Of Arctic Ground Squirrel Tissues And Potential Food Sources, Julee Shamhart

Master's Theses and Capstones

Given limited knowledge of the food sources of Arctic ground squirrels, an important arctic prey species, it is difficult to predict the implications of changes in food source availability that could result from climate change. I hypothesized that Arctic ground squirrels at two colonies, Atigun and Toolik, would have similar feeding habits and mushrooms would contribute to their diet The Arctic ground squirrels at Toolik had significantly higher del15N (3.7 per mill difference) and del13C values (1.3 per mill difference) than those at Atigun. Mixing models indicated that the signatures observed in the Atigun hair could result from a combination …

Abiotic Immobilization Of Nitrate In Forest Soil: A Double Level Approach, Richard Graham Maclean

Master's Theses and Capstones

Abiotic immobilization of nitrogen may help explain nitrogen retention in soils under chronic nitrogen addition. Methodological limitations have made differentiating between abiotic and biotic immobilization in live soils difficult. This study attempted to make this differentiation with isotopically labeled nitrate, 15N18O3- . My hypothesis was that during biological reduction and assimilation of 15N, 18O would be lost as labeled water, but some 18O would be retained in abiotic reactions with soil chemicals. Lab incubations of soils from a Pinus resinosa stand were treated with 0.140 mg 15N g-1 dry soil of K15N18O3, for 0.25, 1 and 4 hours. Mean mass …

Impacts Of Suburbanization On Food Web Stoichiometry Of Detritus-Based Streams, Nathaniel Burr Morse

Master's Theses and Capstones

Higher non-point source nutrient inputs are one of many impacts associated with the "urban stream syndrome". Research on how non-point source pollution affects the stoichiometry of urban stream food webs has received little attention, however. This study quantified food web stoichiometry in nine headwater, detritus-based streams draining forested or suburban watersheds in northeastern, coastal Massachusetts.

While this study suggests that suburbanization can affect in-stream nutrient recycling by consumers, research that quantifies changes to biomass of different in-stream compartments is needed to calculate the extent of such impacts on suburban stream ecosystems.

A Multi-Scale Evaluation Of Eastern Hognose Snake (Heterodon Platirhinos) Habitat Selection At The Northern Extent Of Its Range, Celine Goulet

Master's Theses and Capstones

A complex interaction of biotic and abiotic variables structure landscapes into a hierarchal assemblage of habitats. Species respond to this environmental hierarchy by selecting habitat based upon a set of ecological variables occurring across a range of organizational levels. However, as the criteria for selection may be scale-dependent, it is vital to quantify the influence these variables have on species distribution at each spatial scale. Two years of telemetry data from 17 individuals were used to examine the multi-scale selection process in the northern population of Heterodon platirhinos on the New Boston Air Force Station in New Boston, New Hampshire. …

Variation In Foliar Nitrogen And Albedo In Response To Nitrogen Fertilization And Elevated Carbon Dioxide, Haley F. Wicklein

Master's Theses and Capstones

It has recently been demonstrated that foliar nitrogen is positively correlated with surface albedo over a broad range of plant functional types. However, the mechanism(s) driving the nitrogen-albedo relationship remain elusive. This study investigated leaf spectral properties from three deciduous species subjected to either nitrogen or CO2 fertilization and compared results to measured chemical and structural properties. We measured reflectance and transmittance, foliar nitrogen, leaf mass per unit area, water content, and d13C values for stacks of 1, 2, 4, and 8 leaves. Nitrogen was the best predictor of leaf-level albedo of the traits that we measured. There were no …