Marine Biology Commons^™

Evaluating Habitat Use By Nekton In Widgeon Grass (Ruppia Maritima), Shoal Grass (Halodule Wrightii), And Unvegetated Bottom Habitats In The Grand Bay National Estuarine Research Reserve, Jessica Woodall

Master's Theses

Seagrass beds support high biodiversity and animal abundance, serve as feeding grounds for a variety of animals, offer shelter from predation, and act as a nursery habitat for juveniles. The species composition of seagrass beds can impact their use as habitat by animals. Two common species of seagrass in the Gulf of Mexico are Ruppia maritima (widgeon grass) and Halodule wrightii (shoal grass). The shallow coastal waters of the Grand Bay National Estuarine Research Reserve (NERR) support both species, but the use of each seagrass as habitat by nekton is poorly understood, which can limit management decision-making. Nekton communities were …

Effects Of Ph, Eelgrass, And Settlement Substrate On The Growth Of Juvenile Magallana (Crassostrea) Gigas, A Commercially Important Oyster Species, Johnny S. Roche

Cal Poly Humboldt theses and projects

Worsening ocean acidification (OA), resulting from ongoing absorption of atmospheric carbon dioxide (CO₂) by the oceans, threatens marine life globally. Calcifying organisms, especially their early life stages, are particularly vulnerable; this includes the economically important Pacific oyster, Magallana (Crassostrea) gigas. Uptake of dissolved CO₂ through photosynthesis by seagrasses, like eelgrass (Zostera marina), may benefit calcifying organisms by increasing pH and carbonate availability. I conducted laboratory and field experiments to quantify carbonate chemistry modification by eelgrass and potential mitigation of OA impacts on growth in juvenile Pacific oysters. In the laboratory experiment, daytime …

A Spatial Assessment Of Impacts To The Flats Fishery By Recreational Boating In The Florida Keys National Marine Sanctuary, Kristin Anderson

All HCAS Student Capstones, Theses, and Dissertations

The recreational flats fishery in the Florida Keys is a significant component of the marine resource-based economy, exceeding $465 million (USD) in annual economic impact. Permit (Trachinotus falcatus), bonefish (Albula vulpes), and tarpon (Megalops atlanticus) are the three main species targeted by flat fishers. Those participating in this fishery generally practice catch-and-release angling therefore, the fishery is considered a more sustainable marine use compared to more traditional commercial fisheries. However, with population and tourism rising in South Florida, the fishery is increasingly threatened by habitat degradation and user conflicts. Ongoing revisions to the Florida …

Patterns Of Habitat Use And Trophic Structure In Turtle Grass (Thalassia Testudinum)-Dominated Systems Across The Northern Gulf Of Mexico, Christian Hayes

Dissertations

Seagrass structural complexity is a primary driver of nekton recruitment and faunal community structure. Few studies, however, have quantified the role of seagrass complexity on habitat use and trophic structures over large spatial scales. A large-scale simultaneous survey was conducted to assess relationships of multiple seagrass morphological complexity metrics to nekton habitat use, trophic dynamics, and blue crab (Callinectes sapidus) growth and mortality across the Northern Gulf of Mexico. Seagrass morphological and nekton community characteristics depended on site and season, and regional variation in seagrass morphology was an important driver of juvenile nekton abundance, species richness, beta diversity, …

Developing Multispectral Imaging Techniques To Determine Canopy Coverage And Carbon Storage Of Seagrasses In The Gulf Of Mexico, Ivy Michelle Hinson

Theses and Dissertations

Although seagrass beds provide global ecosystem services, coverage is in rapid decline, with the capacity of seagrasses to sequester carbon of special concern. Current seagrass monitoring methods are labor intensive and may not offer a complete picture of coverage. Remote sensing offers the ability to oversee landscapes but water in coastal environments presents challenges, as the commonly used near-infrared wavelength dissipates in water.

This project aimed to provide reliable methodology to assess seagrass coverage using multispectral imagery taken from an unmanned aerial vehicle and to provide evidence for the link between seagrass coverage and stored belowground carbon for common seagrasses …

Effects Of Drift Macroalgae On Sediment Nitrogen Cycling In Thalassia Testudinum Beds Of St. Joseph Bay, Fl, Erica Strope

Master of Science in Integrative Biology Theses

Anthropogenic nitrogen (N) loading and eutrophication can affect valuable ecosystem services and seagrass habitats by modifying structural and functional aspects of estuarine communities including increasing and prolonging macroalgae blooms. In some contexts, macroalgae may play a key role in N cycling pathways because they can alter sediment chemistry. Previous research has associated drift macroalgae blooms with elevated dissolved inorganic N concentrations in sediments as a result of increased remineralization of organic matter, but drift macroalgae effects on microbial N transformation pathways are not well understood. This study quantified the effects of macroalgae on estuarine N cycling in Thalassia testudinum seagrass …

Evaluating In Situ Grazing Patterns Of Lytechinus Variegatus And Their Effects On Seagrass Beds Of Thalassia Testudinum, Adrianna Parson

Master of Science in Integrative Biology Theses

The sea urchin Lytechinus variegatus is a known grazer of the seagrass Thalassia testudinum, and has been known to denude vast stands of seagrass beds at high densities. Outside of these denudation events, the effects of sea urchins on seagrass are poorly understood. This study examines the effects of L. variegatus on T. testudinum in situ, to understand how sea urchins are affecting seagrasses in situ. Results indicate that urchins were found in the offshore portion of the seagrass bed at densities up to 4 urchins/m². Changes in temperature and sediment size in the bay indicate …

Historical Change Of Seagrasses In The Mississippi And Chandeleur Sounds, Linh Thuy Pham

Dissertations

Seagrasses are important coastal resources facing numerous stressors, and losses have been documented from local to global assessments. Under the broad theme of habitat loss and fragmentation, a study of historical change in total area and landscape configuration of seagrasses in the Mississippi and Chandeleur Sounds was conducted. Mapping data was collated from a multitude of previous projects from 1940 to 2011.

Comparisons of seagrass area among various studies that used different mapping methods can result in overestimation of area change and misleading conclusions of change over time. The vegetated seagrass area (VSA) data were generalized to a common resolution …

The Population Genetics Of Morro Bay Eelgrass (Zostera Marina), Julia Gardner Harencar

Master's Theses

Seagrass populations are in decline worldwide. Zostera marina (eelgrass), one of California’s native seagrasses, is no exception to this trend. In the last 8 years, Morro Bay, California has lost 95% of its eelgrass. Eelgrass is an ecosystem engineer, providing important ecosystem services such as sediment stabilization, nutrient cycling, and nursery habitats for fish. The failure of recent restoration efforts necessitates a better understanding of the causes of eelgrass decline in this estuary. Previous research on eelgrass in California has demonstrated a link between population genetic diversity and eelgrass bed health, ecosystem functioning, and resilience to disturbance and extreme climatic …

Investigating The Effects Of Changes In Light Quality On Different Life History Stages Of Seagrasses, Simone Strydom

Theses: Doctorates and Masters

Seagrass meadows provide crucial ecosystem services to the coastal zone but globally are threatened. Seagrass loss to date has mainly been attributed to anthropogenic activities that reduce light quantity, such as dredging, declining water quality from urban and agricultural run-off and eutrophication. However, light quality (wavelengths of light) is also altered by these anthropogenic stressors as well as natural events. This study consisted of three main components: (1) characterising light quality to which seagrasses are exposed across a local natural estuarine-ocean gradient and with a human impact pressure; (2) the influence of monochromatic light quality (blue λ=451 nm; green λ=522 …

Gene Flow And Genetic Structure Of The Seagrass Thalassia Hemprichii In The Indo-Australian Archipelago, Udhi Eko Hernawan

Theses: Doctorates and Masters

How genetic variation is distributed across space (genetic structure) and what factors influence the spatial genetic structuring is one of the primary questions in population genetics. The interaction between species biology (e.g. life-history traits) and physical processes operating in the seascape over time, including palaeo-historical events (e.g. sea level fluctuations) and contemporary processes (e.g. ocean currents), have been predicted to influence the extent of gene flow and the spatial genetic structuring in marine organisms. However, the relative contribution of each factor in governing the genetic pattern remains unclear. This study examined the pattern of genetic structure and the factors influencing …

Rare Occurrences Of Free-Living Bacteria Belonging To Sedimenticola From Subtidal Seagrass Beds Associated With The Lucinid Clam, Stewartia Floridana, Aaron M. Goemann

Masters Theses

Lucinid clams and their sulfur-oxidizing endosymbionts comprise two compartments of a three-stage, biogeochemical relationship among the clams, seagrasses, and microbial communities in marine sediments. A population of the lucinid clam, Stewartia floridana, was sampled from a subtidal seagrass bed at Bokeelia Island Seaport in Florida to test the hypotheses: (1) S. floridana, like other lucinids, are more abundant in seagrass beds than bare sediments; (2) S. floridana gill microbiomes are dominated by one bacterial operational taxonomic unit (OTU) at a sequence similarity threshold level of 97% (a common cutoff for species level taxonomy) from 16S rRNA genes; …

Changes In A Tropical Seagrass Environment After Installation Of Small Artificial Reefs, Joseph M. Penta

HCNSO Student Theses and Dissertations

The 3-dimensional structural complexity of coral reef environments is positively correlated with measurements of biodiversity and biomass. EcoReefs are a type of artificial reef that resemble branching corals, such as Acropora cervicornis, which provide an environment of high structural diversity, and that are effective at recruiting and sustaining fish populations. Little is known, however, about the effects of EcoReefs on the surrounding environments in which they are deployed, so this study examined the results after installing Ecoreef modules in a seagrass environment. The installation occurred in March 2009 at Coco Cay in the Berry Island chain in the Bahamas …

Density And Diversity Of Penaeid Shrimp And Fish Species In Near-Shore Seagrass Beds Of Northern Biscayne Bay, Florida (Usa), Robin Cascioli

HCNSO Student Theses and Dissertations

Seagrass beds serve critical functions in coastal Florida ecosystems. The beds serve as nursery habitat for many juvenile reef fish species and provide protection for many types of benthic organisms found in Biscayne Bay. They help stabilize sediment that would otherwise increase turbidity around coral reefs, filter the water of contaminants, and help support an entire food web. Three species of seagrass were found at the study sites in northern Biscayne Bay: Thalassia testudinum, Halodule wrightii, and Syringodium filiforme. This study focused on understanding the organism habitat interaction by determining the species diversity, seasonal densities, and the …

Relating Water And Otolith Chemistry In Chesapeake Bay, And Their Potential To Identify Essential Seagrass Habitats For Juveniles Of An Estuarine-Dependent Fish, Spotted Seatrout (Cynoscion Nebulosus), Emmanis Dorval

Biological Sciences Theses & Dissertations

A quantitative understanding of habitat use of estuarine-dependent fishes is critical to the conservation of their most essential habitats. Because recruitment and fitness may be influenced by the quality of juvenile habitats, developing methods to quantify habitat-specific survivorship is pivotal to such understanding. An initial step to quantify survivorship is to validate the habitat-specific natural tags contained in otoliths. To this aim I investigated the variability in the chemistry of surface waters and otoliths of juvenile spotted seatrout, Cynoscion nebulosus, in five seagrass habitats of Chesapeake Bay, namely: Potomac, Rappahannock, York, Island, and Eastern Shore. I measured Mg, Ca, …