Ecology and Evolutionary Biology Commons^™

Effects Of Freshwater Input On Nutrient Loading, Toxic Cyanobacteria Bloom Development And Cyanotoxin Production In Lake Pontchartrain Estuary, Louisiana, Callie L. Snow

LSU Master's Theses

Estuaries in the northern Gulf of Mexico (GoM) are undergoing profound alterations due to changes in climate and implementation of coastal restoration activities and these may lead to the increasing frequency of harmful algal blooms (HABs). The introduction of large volumes of nutrient-rich, fresh Mississippi River water into nutrient-poor Lake Pontchartrain Estuary is known to substantially change the chemistry and ecology of the estuary, and warm temperatures paired with the persistent nutrient loading into the estuary supports the proliferation of potentially toxic cyanobacteria blooms (CyanoHABs). Throughout 2019, a long-term opening of the Bonnet Carré Spillway (BCS), initially from February to …

Brood Abundance And Invertebrate Availability In Crop-Dominated Landscapes In The Prairie Pothole Region, Catrina V. Terry

LSU Master's Theses

The Prairie Pothole Region (PPR) is the most important region for ducks in North America, producing over half the ducks on the continent, and it is a priority landscape for wetland and grassland conservation. Agricultural expansion has changed the PPR, and the majority of grasslands and potholes have been converted into row-crops. The loss of nesting habitat has directly caused nest success to decline. Most of the remaining wetlands are surrounded by row-crops, and are considered lower quality because they receive runoff of sediment and chemicals, which may decrease primary forage for young ducklings as well as inhibit wetland vegetation. …

Genetic Structuring And Community Assembly In Neotropical Birds, Oscar Johnson

LSU Doctoral Dissertations

The factors that influence how species form is of fundamental interest to biology. Under the framework of the speciation cycle, the process begins by population subdivision creating structured populations that then diverge until two new species form. Following speciation, however, continued divergence is necessary for these new species to be able to coexist without adverse interactions, known as the transition to secondary sympatry. At this point the speciation cycle is complete and the process can begin anew. Many of the factors influencing these processes remain poorly understood. Here, I explore the factors that influence speciation and community assembly in Neotropical …

Blue Carbon In South Florida's Mangroves: The Role Of Large Roots And Necromass, Zoë I. Shribman

LSU Master's Theses

Blue carbon sequestration and storage in mangroves largely result from belowground biomass allocation in response to flooded anaerobic soil conditions and nutrient availability. Biomass allocation to belowground roots is a major driver of mangrove soil formation and organic matter accumulation leading to blue carbon storage potential. Belowground biomass sampling in mangroves is labor intensive, limiting data availability on biomass stocks, particularly for large roots (>20 mm diameter) and necromass (dead roots). The mangrove nutrient model (NUMAN) uses mostly literature values to parameterize a soil cohort approach to simulate depth distribution of root mass and organic carbon concentration. We evaluated …

Phragmites Australis Dieback In The Mississippi River Delta: Chemical Profiles Of Soil Types And Restoration Potential, Herie Lee

LSU Master's Theses

Since 2016, there has been widespread dieback of P. australis in the Lower Mississippi River Delta (hereafter referred to as Lower MRD, which is defined as the Birds Foot Delta) with relatively little to no signs of recovery. The cause of the current dieback is not fully understood. This thesis explores P. australis with emphasis on chemical profile characterization of different soil types and its effects on plant growth and the potential for restoration in the Lower MRD.

In chapter 2, I characterized the chemical profiles of soils collected from healthy and dieback stands of Phragmites, and from newly …

Investigating Local Adaptation To Hypoxia Stress In The Eastern Oyster Through Comparative Transcriptomics, Heather Nichole Smith

LSU Master's Theses

Climate change represents one of the most important challenges to biodiversity, therefore it is important to understand the mechanisms that allow species to respond to rapid environmental change. Here, we compared two populations of eastern oysters, Crassostrea virginica, from the Gulf of Mexico to study the mechanisms underlying hypoxia tolerance. Using a common garden experiment and comparative transcriptomics, we identified sets of genes involved in the hypoxia response and found differences in both the timing and baseline expression of hypoxia-responsive genes between tolerant and sensitive populations, consistent with a scenario of local adaptation. These genes include the signaling transcription factor …

Effects Of Wetland Management And Associated Abiotic Factors On Rare Plant Communities Of Spring-Fed Arid Wetlands, Antonio Cantu De Leija

LSU Master's Theses

Spring-fed arid wetlands support high biological productivity and are hotspots for endemism and distribution of rare plants, making them areas of high conservation value. These systems are driven by complex interactions among groundwater discharge and the geomorphic and climatic features of the setting, which provide gradients of edaphic conditions, particularly soil moisture and salinity that influence the presence and abundance of rare plant communities. However, spring-fed arid wetlands are at particular risk of increases in salinity and drier hydrological regimes due to anthropogenic activities. Such alterations to abiotic conditions may jeopardize the distribution and abundance of rare plants by exceeding …

Seasonal Variation In The Feeding Ecology Of Yellowfin Tuna (Thunnus Albacares) From The Northern Gulf Of Mexico, Mitchell Shay Lovell

LSU Master's Theses

Highly migratory fishes (e.g., tunas, billfishes, and sharks) play a significant role in the structure and function of open-ocean ecosystems and a better understanding of the food web dynamics that support their populations is essential to improve management and conservation. Here, I use complementary approaches (stomach contents, DNA barcoding, & stable isotopes) to examine seasonal variability in the feeding ecology of sub-adult (70 – 100 cm; n = 371) and adult (100 – 160 cm; n = 206) yellowfin tuna (Thunnus albacares) from the northern Gulf of Mexico over a one-year period (April 2019 – March 2020). Stomach …

Leveraging Multiple Data Sources: How Catch Data, Metadata, And Genetic Samples Can Aid The Recovery Of Endangered Smalltooth Sawfish (Pristis Pectinata), Kelcee Smith

LSU Doctoral Dissertations

The small population sizes characteristic of many imperiled species means that they are vulnerable to both demographic and genetic extinction threats. Responses to these threats (e.g., population trends, genetic diversity estimates) are often difficult to obtain, but critical for conservation. Thus, researchers studying imperiled species may have to consult multiple data sources, collaborate with a wide variety of stakeholders, or ask new questions about previously collected data. I used this approach to understand more about the United States (U.S.) population of Pristis pectinata, an endangered elasmobranch that has declined up to 95% due to habitat loss and bycatch in …

Effects Of Salinity On Eastern Oysters: Locating Lower-Salinity Tolerant Populations And Defining Resource Zones Suitable To Restoration, Fisheries, And Aquaculture., Lauren Swam

LSU Master's Theses

Eastern oysters (Crassostrea virginica) provide valuable ecosystem services and support a productive commercial industry in the northern Gulf of Mexico. Declining abundance from water quality changes and other factors drives development of management and restoration strategies focused on a comprehensive, metapopulation approach. Identifying oyster resource zones based on water quality combined with selective breeding of oysters adapted to specific conditions provides strategies to support aquaculture development and ensure resilient oyster populations and high production. Using 2015-2019 satellite-derived continuous salinity and temperature data for coastal Louisiana, this work created maps defining oyster resource zones supportive of (1) broodstock sanctuary …

Penguins Past And Present: Trace Elements, Stable Isotopes, And Population Dynamics In Antarctic And Sub-Antarctic Penguins And Seals, Allyson K. Kristan

LSU Master's Theses

Antarctica and the sub-Antarctic are remote regions where the impacts from climate change and anthropogenic activities are increasingly apparent. Previous studies show that the Antarctic is warming and has been affected by anthropogenic contaminants. Marine predators such as penguins and seals are commonly used in these regions as sentinels of ecosystem health as predator tissues can be used as non-invasive proxies of diet, population trends, and contaminant exposure. This thesis includes two separate studies which investigate the influence of climate change and human activity on Antarctic and sub-Antarctic ecosystems. First, Adelie penguin (Pygoscelis adeliae) eggshell samples were collected …

Examining The Sustainability Of Restored Sub-Tidal Oyster Reefs In Coastal Louisiana, Sarah C. Leblanc

LSU Master's Theses

Climate related alterations and anthropogenic disturbance threaten the ecological integrity and sustainability of coastal estuaries. Many activities seek to restore and sustain these at-risk areas with the goal of restoring systems to historic patterns of succession and community development; however long-term monitoring of restoration projects remains limited. Additionally, restoration efforts aim to achieve certain success thresholds, however, these thresholds are often vague, absent, or inconsistent, and receive little long-term analyses following restoration. A key coastal engineer, the eastern oyster (Crassostrea virginica), provides multiple ecosystem services, but recent population decline has prompted investment in restoration. Restoration activities include cultch …

Henry V. Howe And His Collection Of Foraminifera At Louisiana State University, Lorene E. Smith, Baren K. Sen Gupta

Occasional Papers of the Museum of Natural Science, Louisiana State University

Henry V. Howe, the founder of the current academic program in geology at Louisiana State University (LSU), and a renowned ostracod specialist, was also a distinguished foraminiferal paleontologist. His best work in that field, involving the discovery of many new species, was on the taxonomy of Eocene Foraminifera of Louisiana. The present H.V. Howe Type Collection of Microfossils began with Howe’s gift of slides to LSU. This collection, enriched by contributions from later workers, now includes over 580 slides of foraminiferal primary type specimens, with holotypes and syntypes of 361 species and 15 taxa labeled as “varieties.” Information regarding these …

Micro- And Macroevolution Of Drab Plumage Color In Birds, Rafael Marcondes

LSU Doctoral Dissertations

I address the evolution of drab bird colors at micro- and macroevolutionary scales. I use as a study system the Furnariida, a clade of >600 Neotropical passerine species that, despite tremendous ecological and morphological diversity, are colored almost exclusively in shades of brown and grey produced by melanin pigments.

In chapters two and three, I took a macroevolutionary approach and showed that (1) plumage colors in the Furnariida evolve at similar rates in a monochromatic clade, males of a dichromatic clade, and females of a dichromatic clade; (2) ventral plumage color evolves faster than dorsal; (3) bird species that occupy …

Plant Community Response To The Combined Effects Of Elevation, And Simulated Nutrient And Sediment Loading In Sagittaria Lancifolia-Dominated Wetlands, Donnie Day

LSU Master's Theses

Coastal wetlands are experiencing threats to their long-term sustainability brought about by the combined effects of relative sea-level rise and human modifications to hydrology, sediment delivery and nutrient loading. Restoration and management strategies can include adding sediment to the surface of deteriorating marshes to facilitate positive feedbacks among elevation, plant productivity, sediment trapping, and accretion; however, if delivered using nitrate-enriched river waters, belowground biomass and soil organic matter pools may be negatively affected, resulting in the acceleration of wetland loss. Overall, there is limited information on the combined effects of nutrient loading, sedimentation, and flooding dynamics in regulating feedbacks among …

Free-Floating Invasive Fern Affects Freshwater Marsh Ecosystem Structure: Changes To Water Quality And Chemistry, Aquatic Vegetation, Fish, And Invertebrates, Charles Wahl

LSU Doctoral Dissertations

Aquatic invertebrates are important to the function freshwater marshes. They are vital to the transfer of energy from primary producers and organic matter to higher trophic levels. The structure of macroinvertebrate communities is directly associated with aquatic macrophyte diversity and abundance. Submerged macrophytes produce oxygen, are a food source, and provide physical habitat, which allows numerous aquatic organisms to exist. Introduction of the invasive free-floating aquatic fern giant salvinia, Salvinia molesta Mitchell, poses a risk to freshwater ecosystems through limited light penetration, decreased submerged macrophyte abundance, altered water quality and, changes in macroinvertebrate community structure and energy transfer. The objective …