Graduation date: 1999

Thesis (Ph. D.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references (leaves 234-248) / Microfiche. / xv, 248 leaves, bound ill. 29 cm

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.

Agricultural runoff is a major non-point source of phosphorus (P) and nitrogen (N) in aquatic environments and often contributes to coastal eutrophication. Chemical extraction techniques that measure P and N in runoff and sediments have provided little information on biologically available P and N, particularly when soils/sediments move from an agricultural setting to freshwater, estuarine and marine systems. The aims of this thesis were to a) develop algal bioassay techniques for assessing bioavailability of P in marine and freshwater sediments, b) apply algal bioassays to determine the role of suspended sediments as P and N sources c) examine how sediment type and sediment load affect P bioavailability and identify the chemical analysis of soil P that best reflects bioavailable P, and d) determine nutrient bioavailability of agricultural soil runoff in estuarine and coastal marine ecosystems. An accurate and repeatable sediment bioassay was developed using non-axenic uni-algal cultures of the euryhaline diatom Skeletonema costatum and freshwater chlorophyte Selenastrum capricornutum. Bioassays were conducted in 250 mL Erlenmeyer flasks, with 100 mg L-1 of simulated sediment and 100 mL of modified growth media, which were continuously shaken. Suspended sediments were simulated from 7 major soil types of the Maroochy River catchment in Australia, a coastal catchment influenced by agriculture. Simulated sediments were used as the sole P source in replicate batch 7-14 d bioassays in which changes in in vivo Chl a fluorescence were measured. Maximum algal biomass in bioassays was significantly correlated to total sediment P content of the added sediment in marine and freshwater. Bioassay methodology was adapted to assess N as well as P bioavailability in simulated suspended sediments using Skeletonema costatum. S. costatum biomass was significantly influenced by sediment type and correlated with the Total P content of the sediment. Conversely, S. costatum response did not correlate to total nitrogen (TN), ammonium (NH4+), nitrate (NO3-) and easily mineralisable N content of the sediment. Sediment type did significantly influence response, suggesting that sorption/desorption properties of the sediment influenced N bioavailability. Suspended sediments appear to be a significant source of bioavailable P as S. costatum biomass was enhanced by their addition. Conversely, the lack of stimulation by sediments when used as a N source implies that suspended sediments are not an immediate source of bioavailable N, although they do contribute to the sediment nutrient pool once deposited. The influence of sediment type and sediment load on phosphorus (P) bioavailability was compared using Skeletonema costatum bioassays. The amount of sediment and associated P load influenced the maximum algal biomass reached, with low sediment loads (&lt 100 mg L-1) capable of stimulating high algal biomass. Maximum algal biomass correlated with sediment iron-oxide extractable inorganic P (FeO-P) and inorganic P (Pi) extracted by sodium bicarbonate for all sediment types. Total P (TP) did not discriminate at low TP concentrations and organic P (Po) extracted by sodium bicarbonate only correlated with algal biomass when bioavailable P was low. Thus FeO-P and Pi are the most representative analyses of bioavailable P. FeO-P can also be used to accurately measure rate of sediment P desorption, which significantly influences algal growth rate. Nutrient bioavailability of agricultural soil runoff was investigated in the Maroochy River catchment in southeast Queensland Australia, a coastal catchment influenced by agriculture. Suspended sediments, river and estuarine sediments and deposited sediment in the near-shore coastal zone were collected and analysed for nutrient bioavailability using chemical analyses and S. costatum bioassays. Suspended sediments in the Maroochy River, which consisted of silt and clay sized particles, had elevated FeO-P and TP concentrations comparable to fertilised soil. Similarly the deposited sediment sampled offshore to the river mouth had elevated total P, FeO-P and total N concentrations which were much greater than the underlying marine sediment. The deposited offshore sediment contained mainly silt sized particles and appeared to be terrigenous in origin as it was more similar in composition (TP, FeO-P, TN, total carbon, total aluminium, total iron, total silica) to estuarine suspended sediments and terrestrial soils, than the underlying marine sediment. This study demonstrated that fine silt sized particles, rich in bioavailable P and N, are being transported and deposited offshore during erosion events. These findings highlight the importance of effective land management and erosion control measures that reduce the suspended sediment load. Although agricultural practices are continually improving to reduce soil erosion, practices need to encompass a broader approach that emphasizes the link between land and sea. Effective management must consider agricultural productivity as well as the environmental impact or ‘algal bloom potential’ that a soil may have when eroded into a waterway. Soils high in bioavailable nutrients must be targeted and managed effectively, particularly in areas prone to erosion.

Thesis (M.S. - Renewable Natural Resources)--University of Arizona, 1983. / Includes bibliographical references (leaves 65-67).

Thesis (M.S. - Renewable Natural Resources)--University of Arizona, 1986. / Includes bibliographical references (leaves 79-83).

Thesis (M.S.)--Northwest Missouri State University, 2005. / The full text of the thesis is included in the pdf file. Title from title screen of full text.pdf file (viewed on January 25, 2008) Includes bibliographical references.

Thesis (M.S.)--Baylor University, 2007. / Includes bibliographical references (p. 90-92).

Thesis (M.S.) in Biochemistry--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 66-75).

Thesis (Ph.D.)--University of Rhode Island, 2006. / Includes bibliographical references (leaves 172-197).