Ph.D. - Zoology (Marine Biology)

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    Investigating Social And Cultural Drivers Of Pacific Coral Reef Resilience
    ( 2018-05) Dacks, Rachel ; ZOOLOGY (MARINE BIOLOGY)
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    Influences of Spatial and Temporal Variability of Sound Scattering Layers on Deep Diving Odontocete Behavior
    ([Honolulu] : [University of Hawaii at Manoa], [August 2016], 2016-08) Copeland, Adrienne
    Patchiness of prey can influence the behavior of a predator, as predicted by the optimal foraging theory which states that an animal will maximize the energy gain while minimizing energy loss. While this relationship has been studied and is relatively well understood in some terrestrial systems, the same is far from true in marine systems. It is as important to investigate this in the marine realm in order to better understand predator distribution and behavior. Micronekton, organisms from 2 – 20 cm, might be a key component in understanding this as it is potentially an essential link in the food web between primary producers and higher trophic levels, including cephalopods which are primary prey items of deep diving odontocetes (toothed whales). My dissertation assesses the spatial and temporal variability of micronekton in the Northwestern Hawaiian Islands (NWHI), the Main Hawaiian Islands’ (MHI) Island of Hawaii, and the Gulf of Mexico (GOM). Additionally it focuses on understanding the relationship between the spatial distribution of micronekton and environmental and geographic factors, and how the spatial and temporal variability of this micronekton relates to deep diving odontocete foraging. I used both an active Simrad EK60 echosounder system to collect water column micronekton backscatter and a passive acoustic system to detect the presence of echolocation clicks from deep diving beaked, sperm, and short-finned pilot whales. My results provide insight into what might be contributing to hotspots of micronekton which formed discrete layers in all locations, a shallow scattering layer (SSL) from the surface to about 200 m and a deep scattering layer (DSL) starting at about 350 m. In both the GOM and the NWHI, the bathymetry and proximity to shore influenced the amount of micronekton backscatter with locations closer to shore and at shallower depths having higher backscatter. We found in all three locations that some species of deep diving odontocetes were searching for prey in these areas with higher micronekton backscatter. Beaked whales in the NWHI, short-finned pilot whales in the NWHI and MHI, and sperm whales in the GOM where present in areas of higher micronekton backscatter. These hotspots of backscatter may be good predictors of the distribution of some deep-diving toothed whale foragers since the hotspots potentially indicate a food web supporting the prey of the cetaceans.
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    New Insights into the Biology and Ecology of Hawaiian Corals Enabled by 3D Reconstruction Technology
    ([Honolulu] : [University of Hawaii at Manoa], [August 2016], 2016-08) Burns, John
    Nearshore coral reef ecosystems have provided a source of sustenance and cultural importance to Hawaiian communities for hundreds of years. Recent research has provided evidence that Hawaiian corals are exhibiting signs of reduced coral health and disease, a scenario likely related to rapid development occurring throughout this region. Marine diseases that affect ecosystem engineers, such as corals, are of particular concern as declines in these organisms can result in dramatic shifts in community structure. Coral health surveys were conducted throughout the Hawaiian archipelago, and multivariate modeling was used to identify demographic parameters associated with the severity of diseases and conditions of reduced health. Population demographics of the host plays an important role in coral health, as the density, diversity, age-, and size structure of a population can affect the severity, extent, and timing of diseases by altering transmission patterns and susceptibility to infection. In order to bridge the gap between disease ecology and large-scale reef processes, I developed innovative techniques to create high- resolution 3D reconstructions of coral reef habitats. The structural complexity of reefs plays a major role in the biodiversity, productivity, and functionality of coral reef ecosystems. The 3D structural properties of the reconstructed reefs were analyzed using geospatial software to determine how each coral species and abiotic feature contributes to the structural complexity of the benthic environment. Temporal analyses were also performed to assess the impacts of acute disturbances and disease on the volume and 3D architectural complexity of coral communities. Loss of live coral cover was found to directly correlate with reductions in both habitat complexity and volume. Furthermore, these techniques were used to map disease lesions on affected coral colonies in a 3D framework. The lesions exhibited statistically distinct clustering across the surface of the affected colonies, thus providing useful information for characterizing disease epizootiology. These cutting-edge techniques can be utilized for an array of research purposes to improve our understanding of how changes in coral composition and habitat structure affect ecosystem processes.
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    Building Island Resilience against Climate Change: Integrating Science into a Community-Based Initiative Reviving Watersheds, Coral Reefs, and Fisheries in Guam
    ([Honolulu] : [University of Hawaii at Manoa], [December 2015], 2015-12) Shelton, Austin
    Climate change is a clear and present threat in small tropical islands, requiring solutions at both global and local levels. The goal of this research was to take a community-based approach to building island resilience against climate change. The removal of local environmental stressors helps to restore natural ecosystem functions, promoting resistance to and more rapid recovery from global climate change impacts. The Humåtak Project was developed as a community-based initiative directed at reviving coastal watersheds, downstream coral reefs, and nearshore fisheries in Guam, Micronesia. A sixpart community engagement strategy was created and serves as a model for other communities. The Humåtak Project addresses accelerated erosion, a major local environmental stressor caused by poor land-use practices. Erosion results in terrigenous sedimentation on coral reefs, which smothers and kills corals, interferes with coral reproduction and recruitment, and destroys essential fish habitat. Nearly 2,000 volunteer hours were contributed to reducing erosion in the La Sa Fu’a Watershed. Tree seedlings and sediment filter socks were tested as watershed restoration tools over a 21-month period. These tools were effective in trapping 112 tons of sediment on land. Previous studies indicate a 75% reduction in sedimentation rate is required to bring Fouha Bay below severe-catastrophic sedimentation stress (>50 mg cm-2 day-1). Based on the observed sediment trapping efficiency of restoration tools in this study, an estimated 0.05 km2 of severely eroding hillsides must be treated with 19 km of socks and 11,000 trees to trap 2,121 tons of sediment to achieve the necessary reduction. To inform future monitoring efforts as restoration of the watershed continues, deposited sediment in Fouha Bay was analyzed to determine grain size fractions and composition. If sediment input into the bay is controlled, existing sediment will clear out with storm-driven swells. As shown in other high islands, coral reefs are resilient and can recover after sedimentation stress is reduced, provided recruitment and survivorship remain viable. The community engagement strategy and data generated on the effectiveness of watershed restoration tools can be used in management plans to build resilience against climate change in other tropical islands.
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    Reef and Shore Polychaetes of Hawaii and the Western Pacific Islands
    ([Honolulu] : [University of Hawaii at Manoa], [December 2015], 2015-12) Magalhaes, Wagner
    Polychaete worms are one of the most successful groups of marine benthic invertebrates in terms of diversity of species, life styles, feeding modes and reproductive strategies. The polychaetes from the western Pacific Islands are scarcely known and the literature available for identification is outdated. A revision of the literature on Hawaii polychaete worms is presented in Chapter 1, together with a list of described species. In Chapter 2, an ecological study was performed in 16 sampling stations in the south shore of Oahu, ten stations were distributed in areas where an invasive alga occurred abundantly and six stations were placed on bare sand patches. Based on the comparison between Avrainvillea amadelpha-dominated bottoms and the surrounding bare sediment patches, our study demonstrates that these habitats support a diverse and abundant polychaete assemblage, with 2,621 individuals and 84 species collected. The possible effects of the presence of this invasive alga on the structure of the polychaete assemblages are discussed. A thorough taxonomic revision of six polychaete families occurring in Hawaii is presented in Chapter 3. The families Acrocirridae, Fauveliopsidae, Lacydoniidae, Poecilochaetidae, and Sphaerodoridae are new records to the Hawaiian marine fauna. A total of 24 species (7 of them new) are described in several papers organized by family. Chapter 4 aimed to review the Cirratulidae (including Ctenodrilidae) from the western Pacific (Hawaiian, Marshall, and Mariana Islands) and Eastern Atlantic oceans. Thirty species are fully described and illustrated, 17 of them are new. Chapter 5 includes a study on the feeding behavior and particle selection of a bitentaculate and a multitentaculate cirratulid species. The multitentaculate species studied was more successful in collecting particles from a greater area and at a faster rate than the bitentaculate species. This satisfied our expectations that feeding activities in multitentaculate species are more efficient than in bitentaculate species but a better understanding of the phylogenetic relationships between the bitentaculate and multitentaculate cirratulids was needed. In Chapter 6, a preliminary phylogeny was performed using morphological, anatomical and reproductive data of 11 cirratulid genera, four ctenodrilid genera and three outgroup genera. The dataset was analysed using Maximum Parsimony and Bayesian Inference. The family Cirratulidae is recovered in all analyses as monophyletic if all ctenodrilid genera are included within it. Three main clades are observed: i) the multitentaculate genera, ii) the bitentaculate genera and iii) the atentaculate genera. This new phylogenetic hypothesis and a better understanding of character evolution will provide information for several taxonomic improvements such as synonymization of Ctenodrilidae to Cirratulidae and revision of all generic diagnosis.
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    Olfactory Morphology of Juvenile Scalloped Hammerhead and Sandbar Sharks and the Effects of Acute Copper Exposure on the Hammerhead Olfactory System
    ([Honolulu] : [University of Hawaii at Manoa], [December 2015], 2015-12) Boswell, Leigh
    Olfaction plays a large role in the excitation and orientation behaviors elasmobranchs display when hunting. These behaviors are dependent on an intact olfactory system, composed of olfactory receptor neurons (ORNs) which detect odorants and send these signals toward the brain. The impact of heavy metal toxicants on the olfactory system in teleosts is well-characterized, with damaged ORNs and decreased or eliminated olfactory-mediated behaviors. The current research is the first examination of the impact of an environmental toxicant on the olfactory system of an elasmobranch, the juvenile scalloped hammerhead shark Sphyrna lewini. The olfactory epithelium of S. lewini was first examined to identify the types of ORNs present and determine a baseline density and total number of ORNs. Microvillar ORNs (mORNs) and crypt neurons (CNs) were identified, with an average of 230 million ORNs for an average 60 cm shark. In comparison, Carcharhinus plumbeus, the sandbar shark, possessed only mORNs, which may indicate that CNs have independently evolved within the Sphyrnidae family. Sphyrna lewini were then exposed to one of three copper (Cu) concentrations for 60 minutes: unfiltered seawater + 0 μg L-1 (0M) Cu, seawater + 29 μg L-1 (0.5 μM) Cu, or seawater + 286 μg L-1 (5 μM) Cu. Electro-olfactogram measurements showed a decrease in olfactory sensitivity after exposure to the elevated Cu concentrations, followed by a complete recovery to baseline sensitivity after a recovery period. The label for olfactory marker protein (OMP) showed no difference in ORN density between the treatment and non-treatment rosettes, regardless of Cu exposure level. Though Cu did impact the olfactory sensitivity of juvenile S. lewini, the lack of damage to OMP and the recovery of sensitivity indicates that the impact was small and reversible. Unrealistically high Cu concentrations did not cause lasting damage to the olfactory sensitivity of an elasmobranch. As coastal pollution increases, olfactory damage from toxicants could lead to the functional removal of elasmobranchs as top predators, resulting in less predation control and subsequent ecosystem shifts. The impact of heavy metal toxicants on elasmobranch olfaction, including the possible permanent effects of Cu on physiology and morphology, warrants further investigation.
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    Environmental Drivers of the Coral Reef Accretion-Erosion Balance in Present and Future Ocean Conditions
    ([Honolulu] : [University of Hawaii at Manoa], [August 2015], 2015-08) Silbiger, Nyssa
    Worldwide, declines in coral cover and shifts in coral reef community composition have raised concerns about whether reef accretion will continue to exceed reef erosion. Reef persistence is influenced by global and local anthropogenic factors, such as ocean warming, acidification, eutrophication, and overfishing, as well as natural environmental variability. Predicting reef response to environmental stress requires an understanding of both natural and anthropogenic environmental drivers of reef accretion and erosion, and how these drivers interact at different spatiotemporal scales. In Chapters 2 and 3, I measured the variation in accretion, erosion, and net change rates along a natural gradient to determine the dominant environmental drivers of accretion-erosion rates at small spatial scales (tens of meters). In Chapter 4, I expanded the geographic range to 1000s of kilometers, measuring variation in accretion and erosion rates, as well as bioeroder community composition, across the Hawaiian Archipelago. In Chapter 5, I used a controlled mesocosm experiment to directly examine the effects of global anthropogenic drivers (i.e., temperature and ocean acidification) on the coral reef accretion-erosion balance. The results of my dissertation research highlight the significance of spatial scale in understanding reef dynamics and the differential responses of reef accretion and erosion to environmental drivers, which will change our predictions of net coral reef response to future environmental change. Further, my results suggest that increases in reef erosion, combined with expected decreases in calcification, could accelerate the shift of coral reefs to an erosiondominated system in a high CO2 world.
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    The Effects of Ultraviolet Radiation on Reef Corals and the Sun-Screening Role of Mycosporine-like Amino Acids
    (University of Hawai'i, Honolulu, 1999-12-01) Kuffner, Ilsa Boysen
    Shallow-dwelling scleractinian corals live in high irradiance environments where they are exposed to large fluxes of ultraviolet radiation (UVR, 280 - 400 nm). A suite of UV-aborbing compounds, know as mycosporine-like amino acids, is found within the tissues of coral-algal symbioses and may perform a sun-screening role. The seasonal variation in MAA concentration was investigated for two corals in Kaneohe Bay, Hawai'i, Porites compressa and Montipora verrucosa. Regressions of MAA concentration and the amount of UVR measured prior to collection date were not significant for total MAA concentration of either species. However, individual MAAs, shinorine in P. compressa and palythene in M. verrucosa, did show significant correlation with UVR. The effects of UVR and water motion on Porites compressa were investigated in a flume and in the field. Exposure to ambient UVR was the most important factor tested in determining the concentration of MAAs in the tissues of P. compressa. Water motion also positively affected the concentration of MAAs, but only in the presence of UVR. When UVR was screened from the corals' environment, the tissue concentration of MAAs slowly decreased over time (approximately 2.5 to 5% per week) regardless of water motion. The effect of UVR on coral planulae was investigated in field experiments with Pocillopora damicornis. Larvae were taken from four different source adults: those from <0.5 m, those from 3 m, those incubated in the absence of UVR for two months, and those incubated in ambient UVR for two months. Deep larvae and larvae from adults incubated in the absence of UVR had roughly half the amount ofMAAs found in the shallow larvae and the larvae from adults in ambient UVR. Origin of larvae was not a significant factor in determining larval survival or recruitment success. UVR, however, was important in determining recruitment rate. Larvae were less likely to recruit to the settlement tile in the presence of ambient UVR than in treatments where the UVR was screened out.
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