The SELECT model (Frost, 1982) is analyzed, criticized, and extended to embrace new information about the feeding behaviour of copepods and the structure of the planktonic food web in a series of alternative models. Diel variations in photosynthesis, grazing, and predation on copepods (temporal structure) and patchiness of zooplankton and their predators (spatial structure) are modelled in other variants. It is observed that the vertical, temporal, and (horizontal) spatial structure of the planktonic ecosystem are important components of ecosystem models that can not safely be ignored. It is further observed that a convincing mechanism for the termination of diatom blooms is lacking and should be a subject of intensive research, and that the status of chlorophyll-containing microflagellates as phototrophs is questionable and should be reconsidered. / Science, Faculty of / Zoology, Department of / Graduate

Advances in DNA sequencing of microbial communities have revealed a complex relationship between the human microbiome and our health. Community dynamics, host-microbe interactions, and changing environmental pressures create a dynamic ecosystem that is just beginning to be understood. In this work, we develop methods for investigating the dynamics of the microbiome. First, we develop a model for describing community dynamics. We show that the proposed approaches accurately describes community trajectories over time. Next, we develop a method for modeling and eliminating technical noise from longitudinal data. We demonstrate that the method can accurately reconstruct microbial trajectories from noisy data. Finally, we develop a method for estimating bacterial growth rates from metagenomic sequencing. Using a case-control cohort of individuals with irritable bowel disease, we show how growth rates can be associated with disease status, community states, and metabolites. Altogether, these models can be used to help uncover the relationship between microbial dynamics, human health, and disease.

No description available.

No description available.

Studies in modern ecology indicate that most species are distributed independently along environmental gradients according to their individual requirements. Steep gradients often produce species associations separated by discontinuities; gradual gradients produce broadly-overlapping distributions. Approaching the distribution of species populations as a continuum, using gradient analysis, avoids artificial sub-division of totally intergrading distributions, yet permits discontinuities to emerge where present. Faunas of the Martinsburg Formation (Ordovician) in southwestern Virginia offer an excellent opportunity to test the applicability of gradient analysis in a paleoecological setting. A broad spectrum of environments, from nearshore to open-marine, elastic to carbonate-dominated facies, provide both temporal and geographic variation against which to evaluate changes in species distributions. Five classical, Petersen-type communities were recognized in the Martinsburg using cluster analysis: 1) Lingula, 2) bivalve, 3) Rafinesquina, 4) Onniella, and 5) Sowerbyella-dominated associations. Two gradient analysis techniques, ordination and Markov analysis, revealed the same basic associations. However, ordination and Markov analysis permit arrangement of these associations along one or more interpreted environmental gradients. Factors related to water depth and distance from elastic source areas, particularly bottom stability and disturbance frequency, appear to have been the most important of a complex of interrelated physical parameters. The high-stress, nearshore end of the Martinsburg gradient complex was occupied by a Lingula association, followed seaward by an association of bivalves adapted to less stressed environments. Low-stress, open-shelf environments were occupied by Rafinesquina, Onniella, or Sowerbyella-dorninated associations. Broad overlap among these articulate brachiopod communities reflects variations within the open-shelf habitat. / Ph. D.

Classification and mapping of ecological zones on a global scale has been a topic of research for many years. This research looks at the development of a global spatial database of ecological zones for the FRA 2000 Report of the United Nations FAO. Besides evaluating the most appropriate type of classification scheme for this purpose, it explores and demonstrates how existing data, for the United States and Canada, can be reclassified to match the FAO classification scheme. Accuracy of mapping is a synergistic function of error, uncertainty, and quality. An assessment of the draft FAO Level D Ecological Zone map was performed which classifies 10-year average, bi-monthly, smoothed AVHRR-NDVI composites of the conterminous United States by applying linear discriminant and decision tree analyses. The results of the linear discriminant analysis were more significantly correlated to the FAO classes, although both approaches suggest that the classification scheme does maximize between-class variance of the NDVI temporal series.

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: 40-41)

No description available.

Psychology / (M.A.(Clinical Psycholoy)

The predatory sea star, Heliaster kubiniji, has been hypothesized to be a "keystone species" that is instrumental in maintaining diversity in the intertidal zones of the northern Gulf of California (Paine 1966). Four hundred and one Heliaster stomach samples collected in 1974-1976 from Station Beach, Puerto Penasco, Sonora, Mexico indicated that Heliaster consumed a variety of prey but preferred barnacles, Chthamalus anisopoma (93% of all prey items). The catastrophic decline of Heliaster in the Gulf of California in 1978 resulted in mortalities approaching 100% (Dungan et al 1982). Pre-die-off community data from the intertidal reef at Station Beach (Mackie and Boyer 1977) were compared with post-die-off (1981-1984) data to determine effects of the Heliaster disappearance. Community structure data included abundance and intertidal distributions of 20 species of macro-invertebrates including 11 Heliaster prey and 9 non-prey species and consisted of 6 carnivores, 7 herbivores, 5 detritivores and 2 filter feeders. Comparisons were made in two distinct habitats: a basalt boulder habitat (Heliaster's preferred habitat) and a reef flat habitat. In the reef flat zone three prey species increased density while seven were unchanged; two non-prey species decreased while seven were unchanged. In the boulder zone six prey species increased, three decreased and two were unchanged; one non-prey increased, three decreased and five were unchanged. An examination of prey vs. non-prey guild structure indicated an increase in prey guild density in the boulder zone from 1976 to 1981 and a reshuffling of rank order of prey density. Analysis of trophic guild structure revealed an increase in carnivore guild density (but no change in ranks) in the boulder zone only and an increase in herbivore guild boulder density (with change in ranks) between 1976 and 1981. No significant changes in species diversity were observed during the study. Heliaster did not act as a keystone species in this community, but it influenced the abundance and structure of prey species and trophic guilds. A continuum is proposed for the potential effects of predation on community structure.