Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Appendixes: p. 56-71. Includes bibliographical references (leaves 52-55).

Thesis (M.S.) in Oceanography--University of Maine, 2002. / Includes vita. Bibliography: leaves 72-78.

Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2010. / Committee Chair: Ellery Ingall; Committee Member: Irina Sokolik; Committee Member: Josef Dufek. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Although the deep seafloor represents the largest biome on the planet, its benthos has remained understudied because of logistical difficulties and the cost of access. Long-term, time-series information is needed to understand the small-scale and inter-annual variations required to build predictive models of ecological processes. In this thesis, we employed three newly developed observatory systems, which coupled in situ imagery with environmental data to examine ecological processes in three deep-sea benthic habitats: 1) Megabenthic surface bioturbation on the upper continental slope (400m depth) near Barkley Canyon, off Vancouver Island, 2) Thermal response in polynoid taxa at Main Endeavour Hydrothermal Vent Field (2,100m depth) on the Juan de Fuca Ridge and 3) Behavioural rhythms and bacterial mat growth in Saanich Inlet (100m), a fjord in southern Vancouver Island. To ensure that the imagery collected was useful for quantitative hypothesis testing by a single observer, we employed a step-wise methodological approach, taking advantage of previously acquired knowledge and, in two cases, the interactive nature of cabled observatories, to tailor the sampling frequency to the variables of interest. The application of a diverse array of image analysis techniques and statistical models, easily extendable to other systems, was also demonstrated. The results obtained while conducting the protocol optimization phase described organism and community level responses to environmental variations. Using a remotely operated camera connected to the NEPTUNE Canada cabled observatory, we estimated that total surface sediment turnover by sea urchins and flatfish, the two most important megafaunal contributors, within the field of view required 93 to 125 days in the absence of phytodetrital accumulations. When employing a camera-temperature array system, the most frequently observed mobile megafaunal species, two polynoid taxa, were not found to exploit the recorded temperature gradients suggesting that they employed a thermoconforming strategy to cope with thermal variability. In the aphotic, mostly hypoxic benthos of Saanich Inlet, strong behavioural entrainment, neither diel nor tidal, was not observed. However, significant changes in species composition and bacterial mat substratum coverage were observed following intrusion of oxygenated waters, a yearly event resulting from specific bathymetric features and oceanographic dynamics of this fjord. A Bayesian approach to data modeling was found to be particularly well suited to protocol optimization purposes as complex models could be more easily and intuitively implemented. The further application of our multi-disciplinary step-wise approach will reduce the time required to approach new ecological questions and improve integration of studies carried in different locations. By carefully choosing ecosystem functions which can be used as indicators of change, the current baseline state of the system can be described. Informed long-term monitoring initiatives can then be implemented in order to quantify global ocean responses to anthropogenic factors such as climate change, resource extraction or eutrophication. / Graduate

While the impact of top-down and bottom-up drivers of ecosystem functions has been given considerable argument, here the mid-trophic level is given focus. In marine systems the influence of mid-trophic level species operates in a ‘wasp-waisted’ structure, where they exert regulatory control by acting as a valve to energy flow between large seasonal pulses of primary production and upper level species. In this study I examine the impact of foraging eastern Pacific gray whales (Eschrichtius robustus) on mysid species at the ‘wasp-waist’ (Order Mysidacea), and vice versa, at feeding sites in Clayoquot Sound off the west coast of Vancouver Island. I appraise previously unknown aspects of the ‘prey-scape’, and further explore life-history traits that allow prey populations to persist in a given species array. The set of problems that I examine are all based on the whales’ top-down forcing in a localized area, and the prey response. I use several scales of observation as dictated by the nature of each question. I examine top down forcing and subsequent prey switching over a 25-year period, the variation in foraging intensity over a 15 year period, the differential prey species’ response to persistent predatory pulses that creates dominance and diversity among the mysid species flock, and whales’ within-season response to possible satiation. Each of these studies is linked by the common goal of illuminating the intimate relationship between predator and prey. Gray whale foraging has decimated amphipod prey resources in the study area past the point of recovery over the last 25 years, and the prey resource is no longer a viable energy source. This has led to the abandonment of benthic-feeding by gray whales in the area, and a switch to mysids as a primary prey source. It is in investigating these mysid species’ ability to rebound following severe foraging pressure that I uncovered two principal life history strategies, one held by the single dominant mysid species, and another used by 9 or 10 others consistently sampled. The capacity for renewal of mysid swarms is imperative if Clayoquot Sound is to persist as a productive foraging area for gray whales. The pattern of this relationship that I present, based on a 15 year span, was previously unknown. Intense foraging of mysids by gray whales during a summer affects the reserves for the following season, leading to a biennial fluctuation in the number of whales the area can sustain, although some of the heaviest foraging seasons require several years to show mysid recovery. I state 9 or 10 other species, as through the intense examination of mysids here, there may be a new species designated. The data gathered by myself and colleagues over the past 25 years that whales have been studied in Clayoquot Sound, clearly shows that predation by baleen whales can affect the future quality of their foraging areas, as well as influencing the population, life-stage and diversity of prey species. My work furthers knowledge in life history characteristics of the mysid species present in the study area, particularly growth and reproduction, and ability to capitalize on a release of predation pressure over winter to recover. That, in turn creates a series of following questions about how different life history strategies make use of a variety of possible energy pathways to stabilize ecosystems at least at discrete spatial scales. / Graduate

Macroalgae are abundant on shallow temperate reef environments, often forming complex communities that comprise several strata. In southern Australia, these assemblages are dominated by large canopy forming taxa from the Orders Laminariales and Fucales. The presence of subtidal fucoid macroalgae differentiates these communities from that elsewhere, and emphasises the need for local studies rather than relying on generalisations made elsewhere. Like most natural systems, temperate reefs are often threatened by human activity with degradation reported from many locations in close proximity to urban settlements. The work presented in this thesis involves an examination of the temporal and spatial variability in the structure of macroalgal communities from reefs along the Adelaide (South Australia) metropolitan coast. The work looked specifically at the effects of a dispersed sediment plume, resulting from the 1997 beach sand-replenishment dredging program, on shallow sub-tidal reef systems. An examination of the structure of canopy forming phaeophycean macroalgae in Gulf St Vincent (South Australia), noted large amounts of both spatial and temporal heterogeneity. Notwithstanding, this variation was not random, but demonstrated considerable structure that could be linked to a number of important underlying processes. In particular, macroalgal assemblages appeared as a mosaic of patches, each of which comprised a high-density state clearly dominated by a single genus (Cystophora, Sargassum, or Ecklonia), or alternatively a lower density mixed assemblage (Variable Low Abundance, VLA). Macroalgal community structure appeared to be driven by biotic interactions at small scales (metres), such that patches comprised of different species of algae in high density states rarely abutted one another. Instead, VLA assemblages frequently formed a buffer being situated between these mono generic patches. In terms of successional processes, the high-density states appeared to be relatively stable whereas the VLA state, at least in some systems, was transitory. This finding was supported by the absence of intermediary high- density states (e.g. a mix of Cystophora and Ecklonia) implying that state changes must occur via the VLA state following some form of disturbance. Larger scale patterns appeared to be driven by environmental variation, with factors such as wave exposure influencing habitat suitability for individual species and thereby affecting community composition. These phenomena were examined in terms of life history strategies that tend to promote stability, and which are common in late successional taxa. The importance of properties enhancing stability and the role of disturbance was investigated experimentally using a dispersed sediment plume, which entirely engulfed two reefs, as a pulse impact. This disturbance was of particular relevance given that degradation of macroalgal communities in close proximity to the City of Adelaide has been, at least in part, attributed to the effects of elevated levels of sediment. Follow up surveys revealed that the sedimentation from the plume had primarily affected newly recruiting individuals, with few juveniles surviving to one year of age. Over the following few years, the effect of this recruitment failure cascaded into the adult stand. In broader terms, unfavourable climatic conditions prior to the start of the study, including a particularly severe El Nino event, had a widespread effect on local assemblages, causing high levels of both adult and juvenile mortality. As such, at the commencement of the study, macroalgal communities across the study area were in the process of recovery. This was observed at control sites over the duration of the study. In contrast, recruitment failure at the sediment-affected sites retarded the recovery process, exacerbating the problems associated with prior unfavourable climatic events and leaving them in a degraded state. This study demonstrated that macroalgal assemblages are equipped (under natural conditions) to handle 'normal' environmental fluctuations (such as inter-annual variability). However, the additional stress associated with certain anthropogenic impacts has the potential to push them over the limit, causing degradation. The loss of canopy macroalgae reduces the structural complexity of the system, leading to a concomitant reduction in their ability to recover. As such, these findings are of particular relevance to those charged with the responsibility for managing near-shore marine environments. The plume was created accidentally during a dredging operation for beach sand replenishment of Adelaide's eroding shoreline. / Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.

This body of work examines the influence of land use on nearshore water quality, and how this can drive changes to algal and invertebrate communities along Australia's southern coastline. The overall aim of the thesis was to investigate links between increasing coastal water-column nitrogen concentrations (derived from terrestrial inputs) and the expansion of turf-forming habitats that can alter the structure and function of subtidal ecosystems. I initially tested whether human activities in coastal catchments can increase subsidies of nitrogen to open rocky coasts. I identified landscape-scale variation in the supply of Dissolved Inorganic Nitrogen (DIN) to coastal waters adjacent to natural, agricultural and urban catchments. Compared to natural catchments, subsidies of DIN were 8 - 407 times greater in urban catchments, and 1 - 63 times greater in agricultural catchments. Subsidies of nitrogen from urban catchments were attributed to the release of sewage effluent, as delineated by δ¹ ⁵N isotopic values of transplanted algae. Having made this link, I then assessed whether catchment-scale variation in nitrogen subsidies may predict patterns of subtidal habitat structure, particularly as related to theories of regime shifts from forested landscapes to structurally depauperate turf-forming habitats. I validated this hypothesis, demonstrating that both relative covers and patch-sizes of turfed habitat were greater where the ratio of terrestrial nitrogen inputs to ambient coastal resources was large. An important realisation was that loss of forests may be more strongly related to the size of subsidy (i.e. the relative increases in water column nitrogen concentrations along urban coasts) rather than the size of coastal populations. Together, these data link coastal development with modified land-to-sea subsidies, and indirectly support the model that ecological effects may be proportional to the disparity between donor and recipient resources. Having demonstrated a link between nitrogen subsidies and subtidal habitat change, I then investigated factors likely to initiate and maintain such shifts. My results demonstrate that nutrient elevation can alter the natural phenology of turfs, sustaining dense covers throughout periods of natural senescence (winter). Perennial turf covers are able to accumulate large volumes of sediment; a synergy can impede the winter recruitment of canopy-forming species (kelps and fucoid algae). My observations of reduced forest recovery along urban coasts serve to highlight the complex interaction between elevated nutrients, persistent turf covers and increased sediment accumulation, which can reduce the resilience of coastal ecosystems to disturbance. In recognition that regime shifts are likely to have consequences for higher trophic levels, I compared the diet of invertebrate herbivores from healthy and degraded coastlines using stable isotope analysis (δ¹³C and δ¹⁵N). Dietary modelling showed that turfs contributed more to the diet of consumers along degraded coastlines where turfed landscapes have replaced extensive covers of macroalgal forest. Additionally, there were strong correlations between covers of turfed habitat, herbivore diet and relative densities. Changes to ambient food quality associated with regime shift may be an important aspect of nutrient-driven change along human-dominated coastlines. The final component of my thesis redressed some of the uncertainty about restoration initiatives for urban coasts by demonstrating that regime shifts are not necessarily permanent. I showed that turf removal can facilitate the recovery of degraded forests. Future restoration, therefore, is a possible outcome of polices that aim to decouple the link between nutrient inputs and recalcitrant turfed habitats that prevent forest recovery. Initiatives that reduce nutrient discharge to coastal waters (e.g., wastewater recycling) are likely to restore the resilience of nearshore marine ecosystems and promote their rehabilitation. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1473469 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009

This body of work examines the influence of land use on nearshore water quality, and how this can drive changes to algal and invertebrate communities along Australia's southern coastline. The overall aim of the thesis was to investigate links between increasing coastal water-column nitrogen concentrations (derived from terrestrial inputs) and the expansion of turf-forming habitats that can alter the structure and function of subtidal ecosystems. I initially tested whether human activities in coastal catchments can increase subsidies of nitrogen to open rocky coasts. I identified landscape-scale variation in the supply of Dissolved Inorganic Nitrogen (DIN) to coastal waters adjacent to natural, agricultural and urban catchments. Compared to natural catchments, subsidies of DIN were 8 - 407 times greater in urban catchments, and 1 - 63 times greater in agricultural catchments. Subsidies of nitrogen from urban catchments were attributed to the release of sewage effluent, as delineated by δ¹ ⁵N isotopic values of transplanted algae. Having made this link, I then assessed whether catchment-scale variation in nitrogen subsidies may predict patterns of subtidal habitat structure, particularly as related to theories of regime shifts from forested landscapes to structurally depauperate turf-forming habitats. I validated this hypothesis, demonstrating that both relative covers and patch-sizes of turfed habitat were greater where the ratio of terrestrial nitrogen inputs to ambient coastal resources was large. An important realisation was that loss of forests may be more strongly related to the size of subsidy (i.e. the relative increases in water column nitrogen concentrations along urban coasts) rather than the size of coastal populations. Together, these data link coastal development with modified land-to-sea subsidies, and indirectly support the model that ecological effects may be proportional to the disparity between donor and recipient resources. Having demonstrated a link between nitrogen subsidies and subtidal habitat change, I then investigated factors likely to initiate and maintain such shifts. My results demonstrate that nutrient elevation can alter the natural phenology of turfs, sustaining dense covers throughout periods of natural senescence (winter). Perennial turf covers are able to accumulate large volumes of sediment; a synergy can impede the winter recruitment of canopy-forming species (kelps and fucoid algae). My observations of reduced forest recovery along urban coasts serve to highlight the complex interaction between elevated nutrients, persistent turf covers and increased sediment accumulation, which can reduce the resilience of coastal ecosystems to disturbance. In recognition that regime shifts are likely to have consequences for higher trophic levels, I compared the diet of invertebrate herbivores from healthy and degraded coastlines using stable isotope analysis (δ¹³C and δ¹⁵N). Dietary modelling showed that turfs contributed more to the diet of consumers along degraded coastlines where turfed landscapes have replaced extensive covers of macroalgal forest. Additionally, there were strong correlations between covers of turfed habitat, herbivore diet and relative densities. Changes to ambient food quality associated with regime shift may be an important aspect of nutrient-driven change along human-dominated coastlines. The final component of my thesis redressed some of the uncertainty about restoration initiatives for urban coasts by demonstrating that regime shifts are not necessarily permanent. I showed that turf removal can facilitate the recovery of degraded forests. Future restoration, therefore, is a possible outcome of polices that aim to decouple the link between nutrient inputs and recalcitrant turfed habitats that prevent forest recovery. Initiatives that reduce nutrient discharge to coastal waters (e.g., wastewater recycling) are likely to restore the resilience of nearshore marine ecosystems and promote their rehabilitation. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1473469 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009

This body of work examines the influence of land use on nearshore water quality, and how this can drive changes to algal and invertebrate communities along Australia's southern coastline. The overall aim of the thesis was to investigate links between increasing coastal water-column nitrogen concentrations (derived from terrestrial inputs) and the expansion of turf-forming habitats that can alter the structure and function of subtidal ecosystems. I initially tested whether human activities in coastal catchments can increase subsidies of nitrogen to open rocky coasts. I identified landscape-scale variation in the supply of Dissolved Inorganic Nitrogen (DIN) to coastal waters adjacent to natural, agricultural and urban catchments. Compared to natural catchments, subsidies of DIN were 8 - 407 times greater in urban catchments, and 1 - 63 times greater in agricultural catchments. Subsidies of nitrogen from urban catchments were attributed to the release of sewage effluent, as delineated by δ¹ ⁵N isotopic values of transplanted algae. Having made this link, I then assessed whether catchment-scale variation in nitrogen subsidies may predict patterns of subtidal habitat structure, particularly as related to theories of regime shifts from forested landscapes to structurally depauperate turf-forming habitats. I validated this hypothesis, demonstrating that both relative covers and patch-sizes of turfed habitat were greater where the ratio of terrestrial nitrogen inputs to ambient coastal resources was large. An important realisation was that loss of forests may be more strongly related to the size of subsidy (i.e. the relative increases in water column nitrogen concentrations along urban coasts) rather than the size of coastal populations. Together, these data link coastal development with modified land-to-sea subsidies, and indirectly support the model that ecological effects may be proportional to the disparity between donor and recipient resources. Having demonstrated a link between nitrogen subsidies and subtidal habitat change, I then investigated factors likely to initiate and maintain such shifts. My results demonstrate that nutrient elevation can alter the natural phenology of turfs, sustaining dense covers throughout periods of natural senescence (winter). Perennial turf covers are able to accumulate large volumes of sediment; a synergy can impede the winter recruitment of canopy-forming species (kelps and fucoid algae). My observations of reduced forest recovery along urban coasts serve to highlight the complex interaction between elevated nutrients, persistent turf covers and increased sediment accumulation, which can reduce the resilience of coastal ecosystems to disturbance. In recognition that regime shifts are likely to have consequences for higher trophic levels, I compared the diet of invertebrate herbivores from healthy and degraded coastlines using stable isotope analysis (δ¹³C and δ¹⁵N). Dietary modelling showed that turfs contributed more to the diet of consumers along degraded coastlines where turfed landscapes have replaced extensive covers of macroalgal forest. Additionally, there were strong correlations between covers of turfed habitat, herbivore diet and relative densities. Changes to ambient food quality associated with regime shift may be an important aspect of nutrient-driven change along human-dominated coastlines. The final component of my thesis redressed some of the uncertainty about restoration initiatives for urban coasts by demonstrating that regime shifts are not necessarily permanent. I showed that turf removal can facilitate the recovery of degraded forests. Future restoration, therefore, is a possible outcome of polices that aim to decouple the link between nutrient inputs and recalcitrant turfed habitats that prevent forest recovery. Initiatives that reduce nutrient discharge to coastal waters (e.g., wastewater recycling) are likely to restore the resilience of nearshore marine ecosystems and promote their rehabilitation. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1473469 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009

Water motion has been shown to influence almost every aspect of the ecology of seagrass communities; seagrass communities have likewise been shown to significantly influence water movement around them. This thesis examines the important role of water motion on seagrass ecosystems by integrating field and laboratory studies of several aspects of seagrass ecology influenced by water motion. To facilitate the study of hydrodynamics of seagrass ecosystems, a solid state electronic current meter was designed and developed, using thermistors as flow sensing devices. Important characteristics of the meters include: no moving parts, compact size, high sensitivity (resolution better than ± 0.5 cm s-1), and high sampling rate (greater than 0.2 Hz). Deployment of the meters in field measurements provided reliable and meaningful results of flow conditions through seagrass canopies, and they show great potential for use in many studies of marine ecology. Field studies of water velocity profiles revealed significant differences between the shapes of profiles of different seagrass species, particularly between species of Posidonia and Amphibolis. Of particular note is the observation of a region of high water velocity beneath the leafy canopy of Amphibolis, which was not present in the Posidonia plants. Water velocity profile measurements, sediment grain size analyses and standing stock measurements were conducted across an exposure gradient in a Posidonia sinuosa meadow. These studies revealed that, while the exposed location experienced a higher ambient water velocity than the sheltered site, the baffling influence of the seagrass canopy reduced the water velocity to approximately the same at both sites, within the meadow, although the effects varied seasonally. It was also observed that the seagrass meadow produced apparent skimming flow under the low flow conditions measured at the sheltered location; this phenomenon reflects the capacity for flow redirection over the canopy, and has important implications for the sub-canopy ecosystem and the protective role of seagrasses on the seabed. Field and laboratory studies on the role of seagrass density on the hydrodynamic nature of seagrass ecosystems revealed that water velocity profiles through meadows of reduced densities, and different shoot arrangements, were markedly different to “natural” profiles, implying the existence of a “critical density” (approximately 25 % of natural meadow density) with regard to canopy hydraulics. The role of water motion at an individual leaf scale was investigated with a series of laboratory flume studies of photosynthetic rates of seagrass and algae. The results show that the response of photosynthetic rate to water velocity depends very much on the plant species, with the algae markedly more productive (on a unit chlorophyll basis) than the seagrasses tested. Increases in photosynthetic rate were observed at water velocities above approximately 2.5 cm s-1; negligible photosynthetic activity was observed below this velocity. Calculation of P v. I curves indicated that the Posidonia species had high Ik values at low velocities (1360 :mol quanta m-2 s-1 for P. australis and 250.8 :mol quanta m-2 s-1 for P. sinuosa at 1.58 cm s-1), which decreased with increasing water velocity (to 138.9 and 24.77 :mol quanta m-2 s-1 for P. australis and P. sinuosa respectively), while the algal species had relatively constant values of Ik across all water velocities (85.42 to 312.7 :mol quanta m-2 s-1 for Ulva lactuca and 169.7 to 573.9 :mol quanta m-2 s-1 for Laurencia cruciata). Dye visualization studies showed that the algae remained quite rigid at all the velocities tested, while the seagrass leaves compressed as velocity increased. This resulted in an increased rate of turbulence creation by the algae, which is believed to enhance photosynthetic rates, through improved nutrient exchange rates across the boundary layer adjacent to the thallus. Further dye visualization studies revealed the significance of blade morphology on the creation of microscale turbulence at the surface of seagrass leaves. Epiphytic growth on seagrass leaves was observed to play an important role in breaking up water flow across the leaf surface, thereby enhancing the creation of microscale turbulence. From these studies, it is clear that water motion influences all aspects of the functioning of all components of seagrass communities, playing a role in nutrient supply, reproduction, physical stability, temperature and metabolic functions. The influence of seagrass meadows on coastal hydrodynamics is also apparent, with potential impacts on sediment stability, recruitment of benthic species and coastal erosion. This thesis has clearly demonstrated that water motion is an important parameter in seagrass ecology, and requires serious consideration in seagrass research, conservation and rehabilitation programmes.