Life Sciences Commons^™

Marine Fungi Of U.S. Gulf Of Mexico Barrier Island Beaches: Biodiversity And Sampling Strategy, Allison Kathleen Walker

Dissertations

Marine fungi are an important but often overlooked component of marine ecosystems. Primarily saprotrophic, they are vital to coastal nutrient cycling processes and food webs. However, basic marine fungal distribution data are lacking in many parts of the world, as is knowledge of the sampling intensity required to characterize the biodiversity of these communities. The roles of substrate, season and latitude in shaping intertidal ascomycete community structure were examined for the U.S. Gulf of Mexico, and the role of sampling frequency on species richness estimates was also addressed. Best sampling practices were developed and 750 collections of beach detritus, sand …

Survival, Growth And Reproduction Of Non-Native Nile Tilapia Ii: Fundamental Niche Projections And Invasion Potential In The Northern Gulf Of Mexico, Michael R. Lowe, Wei Wu, Mark S. Peterson, Nancy J. Brown-Peterson, William T. Slack, Pamela J. Schofield

Faculty Publications

Understanding the fundamental niche of invasive species facilitates our ability to predict both dispersal patterns and invasion success and therefore provides the basis for better-informed conservation and management policies. Here we focus on Nile tilapia (Oreochromis niloticus Linnaeus, 1758), one of the most widely cultured fish worldwide and a species that has escaped local aquaculture facilities to become established in a coastal-draining river in Mississippi (northern Gulf of Mexico). Using empirical physiological data, logistic regression models were developed to predict the probabilities of Nile tilapia survival, growth, and reproduction at different combinations of temperature (14 and 30°C) and salinity …

Concurrent Effects Of Resource Pulse Amount, Type, And Frequency On Community And Population Properties Of Consumers In Detritus-Based Systems, Donald A. Yee, Steven A. Juliano

Faculty Publications

Episodic resource inputs (i.e., pulses) can affect food web properties and community dynamics, but detailed mechanistic understanding of such effects remain elusive. Natural aquatic microsystems (e.g., tree holes, human-made containers) are colonized by invertebrates that form complex food webs dependent on episodic and sometimes sizeable inputs of allochthonous detritus from adjacent terrestrial environments. We investigated how variation in pulse frequency, amount, and resource type interacted to affect richness, abundance, composition, and population sizes of colonizing invertebrates in water-filled tires and tree hole analogs in a forest habitat. Different container types were used to assess the generality of effects across two …

Genetic Variation In Potentially Virulent Vibrio Parahaemolyticus From The Northern Gulf Of Mexico, Nicholas Felix Noriea Iii

Dissertations

Vibrio parahaemolyticus (V_p) is a gram-negative bacterium found naturally in marine and estuarine environments. V_p is found in oysters including those which are later consumed by the public. Sub-populations of potentially virulent Vp contain specific virulence factors and are relevant human pathogens capable of causing gastroenteritis, wound infection, and death. The tdh and trh genes, both encoding hemolysins, have been correlated with the majority of clinical V_p isolates but have not been shown to be the definitive virulence factors.

A total of 146 V_p isolates from the northern Gulf of Mexico were collected and probed …

Effects Of Hypoxia And 4-Tert-Octylphenol On Gene Expression Profiles Of The Sheepshead Minnow (Cyprinodon Variegatus), Arthur Alan Karels

Dissertations

Hypoxia occurs in estuaries of northern Gulf of Mexico and world-wide, with increasing frequency/severity via eutrophication and anthropogenic influences. Hypoxia inducible factors (HIFs) form transcriptional complex and bind DNA at hypoxia responsive elements (HREs) in promoter regions of genes needed for systemic and cellular adaptation of fish to low dissolved oxygen (hypoxia, DO <2.0 mg/ml). Hypoxia-induced activation of HIF-αs can lead to a cascade of downstream activation, such as erythropoietin (EPO). Return to normal DO levels (normoxia), prolyl hydroxylases (PHDs) are activated to degrade HIF-αs back to baseline. Fish are affected by environmental estrogen mimics, like 4-tert-octylphenol (4tOP), binding estrogen receptor alpha (ERα) at estrogen responsive elements (EREs) and activating genes vitellogenin (VTG). Previous research showed overlap or crosstalk between these two mechanistic pathways. Hypoxia triggers unknown factors regulating ERE-mediated ERα signaling pathway, and stressor combinations could increase/decrease hypoxic or endocrine pathway. Research examined molecular/physiological effects of hypoxia (acute and chronic, moderate and severe) and 4tOP (~60μg/L)on adult male and/or female sheepshead minnow (Cyprinodon variegatus). Three genes identified, cloned, and sequenced (HIF-1α, HIF-2α, and PHD3), plus previously identified genes EPO and VTG, were examined in liver/testes exposed to hypoxia and/or 4tOP for cellular/physiological changes. Endpoints examined included mRNA expression from real-time PCR of HIF-1α, HIF-2α, PHD3, EPO, and VTG using cDNA from total RNA extracts, and microarray analyses of genes expressed during the transition from hypoxia back to normoxia. Phylogenetic analyses confirmed isolation of two HIF-α isofoms (HIF-1α and HIF-2α) and the PHD3 isoform. Significant up-regulation of PHD3 occurred within 10 hrs of chronic hypoxia, and persisted when severe (1.5 mg/L) and declined when moderate (~2.5mg/L). Significant up-regulation of HIF-1α and EPO occurred within 30 minutes to 2 hours of onset of acute severe and very severe (~1.08mg/L) hypoxia. Hypoxia acted similar to an estrogen mimic, with huge up-regulation of VTG gene expression in males, and increased VTG levels (additive effect) when hypoxia was combined with 4tOP. Microarray analyses showed 125 genes with significant transcriptional change, with up- or down-regulation from transitions of: (1) hypoxia (72 hrs) to normoxia (74 hrs) and (2) hypoxia+4tOP (72 hrs) to normoxia+4tOP (74 hrs).