Graduation date: 1994

Pteroceramium, a descriptive name given to an undescribed winged species closely related to Ceramium, has uniaxial filamentous thallus construction with pseudodichotomous branching. Alternate branches become dominant. This pattern of growth is referred to as cellulosympodial growth. All growth is from an apical cell which cuts off subapical cells. The subapical cells develop into axial cells. Each axial cell cuts off six pericentral cells in a ring around its apical pole. The pericentral cells divide further to form the cortical band. Pc1 always forms on the outer face of the thallus as determined by the preceding pseudodichotomy and gives rise to the larger outer wing which is a lateral expansion of the cortical band. The smaller inner wing forms from Pc6 on the inner face. The other pericentral cells give rise apically to uniseriate spines. The pericentral cells also give rise to rhizoids and adventitious lateral branches. Each axial cell has a large central vacuole with a few peripheral chloroplasts, mitochondria and floridean starch granules. The smaller wing cells have a much denser cytoplasm with fewer small vacuoles, many chloroplasts which are more closely packed together and more floridean starch granules than axial cells. Chloroplasts have a typical Rhodophyta ultrastructure with single, evenly spaced thylakoids with phycobilisomes. Pit connections have a plug core but no plug cap. Pteroceramium has a typical Polysiphonia-type triphasic life history. The carposporophyte is naked and tetraspores are produced in a characteristic decussate cruciate arrangement. The effect of a number of physical and chemical factors on growth and morphogenesis was investigated. Pteroceramium grew best at irradiance levels between 79 μmol m⁻² S¯¹ and 129 μmol m⁻² S¯¹ with growth being limited at 30 μmol m⁻² S-I. The largest axial cells and wings were obtained from the material grown at 79 μmol m⁻² S¯¹ and the smallest measurements for material grown at 129 μmol m⁻² S¯¹. Monochromatic light fields of red, green and blue caused reduced growth rates compared to the control replicates grown in a white light from both incandescent and fluorescent lights. Light quality had no effect on morphogenesis. The critical daylength for maximum rates of cell elongation was 10 hours or longer, although 16 hours light caused a decrease in final axial cell volume. Optimum temperatures for growth of Pteroceramium were between 20°C and 25°C with growth decreasing at 15°C and 30°C. Axial cell volume was reduced and wing size was stunted at these two extreme temperatures tested. Scouring by sand caused axial cells to decrease in volume although the wings were unaffected. Smothering by sand did not prevent growth although axial cells and wings were greatly decreased in size, with the wings consisting of only one or two other cells. Tumbling to disrupt gravity did not affect the angle of each pseudodichotomy. Decreased levels of nitrogen and phosphorus limited growth but had little effect on axial cell volume and wing development. Pteroceramium was stenohaline with maximum growth at 34°/[00] and reduced growth at 300/[00] and 40°/[00]. Pteroceramium grew best at pH 7.5 and pH 8.5 with decreased growth at pH 6.5 and pH 5.5. The various pHs tested had little effect on morphogenesis. The best photosynthetic responses were obtained from material preconditioned at 80 μmol m⁻² S¯¹ compared with that at 30 μmol m⁻² S¯¹ and 150 μmol m⁻² S¯¹. There was a decrease in pigment content with increasing irradiance at which the alga was grown. Phycoerythrin was the dominant pigment. Exposure to a high irradiance (3000 μmol m⁻² S¯¹) for 30 minutes or longer inhibited photosynthesis. Plants did not fully recover even 24 hours later, indicating that this damage was permanent. Pteroceramium was able to acclimatize slowly over a week to temperature changes within the range of 15°C to 25°C. Rapid increases of 5°C within this temperature range increased photosynthetic performance and a rapid drop of 5°C decreased photosynthetic performance. However, a 10°C increase or drop reduced Pteroceramium's photosynthetic performance. Photosynthetic rates were decreased in alkaline conditions and increased in acidic conditions. Pteroceramium has well defined developmental patterns with basal band growth of axial cells and tip growth in the rhizoids. The pericentral cells are formed in a set sequence similar to Ceramium species with Pcl forming on the outer face, Pc2 and Pc3 forming on the lower and upper surface nearest to Pel respectively, Pc4 and PcS forming on the lower and upper surface respectively farthest from Pel, and Pc6 forming on the inner face. This sequence is unaffected by the direction of illumination or gravity. Exogenous application of plant hormones (IAA, GA3 and kinetin) in the concentration range of 10[-9] M to 10[-5] M had no effect on growth and morphogenesis in Pteroceramium. Application of polyamines and their precursors caused a decrease in growth and a reduction in cell size at concentrations higher than 10[-4] M. Polyamine inhibitors caused a reduction in growth and cell size at concentrations higher than 10[-5] M. Arginine increased growth at concentrations 10[-5] M and 10[-6] M. High power liquid chromatography (HPLC) separation of Pteroceramium extracts indicated that spermidine was present in Pteroceramium at approximately 38 μg spermidine g¯¹ fresh weight. The apical tip exerts an apical dominance effect on the subordinate branches, suppressing their elongation. Removal of the dominant apical tip increased adventitious branch formation. This effect was not reversed by application of exogenous IAA at concentrations of 10[-9] M to 10[-4] M. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1993.

No description available.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1996. / Includes bibliographical references. / Microfiche. / xxi, 302 leaves, bound ill 29 cm

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. / Includes bibliographical references. / Microfiche. / xvii, 206 leaves, bound ill. 29 cm

Seaweeds that occupy the intertidal zone grow in distinct vertical bands. Elucidating the causes of zonation of intertidal seaweeds has been a key question for over a century, and the prevailing paradigm is that species occupying the higher shore position are limited by abiotic factors associated with exposure to atmospheric conditions, whereas for the lower-shore species competition is considered to limit a macroalga�s distribution. The main objective of this study was to assess the effect of desiccation, and to a lesser extent nutrient limitation, on the distribution of Stictosiphonia arbuscula, a red intertidal seaweed that grows in a wide vertical band in the mid - high shore region. A multi-disciplinary approach was used to investigate the effect of desiccation at different functional levels, from individual cells to the whole organism. Ecophysiological comparisons were made on high-shore and low-shore populations to determine whether the upper and lower shore distributions have different abilities to tolerate and recover from desiccation stress during summer and winter. The effect of desiccation was visually assessed, using electron microscopy, at the cellular and whole organism level. Carbohydrate and pigment concentrations were determined to provide information on how S. arbuscula allocates its resources between winter and summer. Investigations into the ability of Stictosiphonia arbuscula to tolerate and recover photosynthetic capacity after desiccation events (relative humidity (R.H.) 5% and 40%; ranging from 30 minutes - 24 hours) unexpectedly revealed no differences between high- and low-shore specimens. However, there were seasonal differences, with summer specimens better able to recover both tissue water content and photosynthetic capacity after desiccation compared to winter specimens, especially after desiccation for 24 hours. In contrast high-shore specimens had increased rates of nitrogen uptake after mild desiccation treatments, compared to low-shore specimens during summer, and specimens from the low-shore had increased variability in their uptake rates, indicating disruption to the uptake mechanisms, compared to the high-shore specimens. S. arbuscula was able to recover photosynthetic capacity faster than nitrogen and phosphorus uptake during re-immersion after desiccation, which indicates that the ability to regain photosynthetic function may be more important for this species than regaining the ability to take up nitrogen and phosphorus. As S. arbuscula can photosynthesise in air (providing there is sufficient tissue water content) and water, the �window of opportunity� to assimilate carbon is greater than for nitrogen and phosphorus uptake, which is only available to S. arbuscula during immersion at high tides. Despite this, no evidence was found of severe nutrient limitation in either high- or low-shore specimens. The disruption and recovery of cellular organisation during rehydration, assessed visually using electron microscopy, showed that the rate and duration of desiccation also affected the extent of recovery. Extremely desiccating conditions (R.H. 5%) damaged the cells and no recovery was observed during rehydration, compared to moderate desiccation treatments (R.H. 40%) where the time taken to recover during rehydration increased with increasing desiccation periods. The disruption of cellular organisation observed in Stictosiphonia arbuscula cells, was found to match the reduction and / or disruption to photosynthesis and the uptake of nitrogen and phosphorus under similar desiccation regimes. The formation of ridges and depressions on the surface of the tissue was also observed during desiccation, which is thought to help reduce the rate of evaporation by trapping �pockets� of air. Finally, Stictosiphonia arbuscula is extremely well suited to the mid - high region in the intertidal zone and it can maximise its competitive ability within this niche during immersion by fully rehydrating within 10 minutes, regaining maximum photosynthetic capacity within 20 minutes, and stability of nutrient uptake rates within 90 minutes. Further, S. arbuscula has higher rates of photosynthesis in winter, associated with increased photosynthetic pigment concentrations at this time. In contrast, during summer, the photosynthetic rates, chlorophyll a and phycobiliprotein concentrations are reduced and S. arbuscula increases its allocation of resources into protective mechanisms such as UV-absorbing compounds.

Typewritten copy / Includes bibliographical references (leaves 269-271) / Pts. 1-3 are reprinted from: Transactions, Royal Society of South Australia v. 71 (2), 1 December 1947; v. 72 (1), 23 August 1948; and, v. 73 (2), December 1950 / 271 leaves : ill., maps (some folded), plates ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1952

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.

The thesis investigates members of the crustose and largely calcified red algal family Peyssonneliaceae through molecular analyses and anatomical and ultrastructural observations. Mitochondrial CO1 DNA barcoding was implemented, in combination with fine-scale anatomy, to recognise species boundaries and identify complexes of cryptic species. Nuclear and organellar DNA markers were employed to construct a multigene phylogeny for Vanuatu and southern Australian members of the family facilitating the recognition of two undescribed genera Annea and Incendia.

Seaweeds that occupy the intertidal zone grow in distinct vertical bands. Elucidating the causes of zonation of intertidal seaweeds has been a key question for over a century, and the prevailing paradigm is that species occupying the higher shore position are limited by abiotic factors associated with exposure to atmospheric conditions, whereas for the lower-shore species competition is considered to limit a macroalga�s distribution. The main objective of this study was to assess the effect of desiccation, and to a lesser extent nutrient limitation, on the distribution of Stictosiphonia arbuscula, a red intertidal seaweed that grows in a wide vertical band in the mid - high shore region. A multi-disciplinary approach was used to investigate the effect of desiccation at different functional levels, from individual cells to the whole organism. Ecophysiological comparisons were made on high-shore and low-shore populations to determine whether the upper and lower shore distributions have different abilities to tolerate and recover from desiccation stress during summer and winter. The effect of desiccation was visually assessed, using electron microscopy, at the cellular and whole organism level. Carbohydrate and pigment concentrations were determined to provide information on how S. arbuscula allocates its resources between winter and summer. Investigations into the ability of Stictosiphonia arbuscula to tolerate and recover photosynthetic capacity after desiccation events (relative humidity (R.H.) 5% and 40%; ranging from 30 minutes - 24 hours) unexpectedly revealed no differences between high- and low-shore specimens. However, there were seasonal differences, with summer specimens better able to recover both tissue water content and photosynthetic capacity after desiccation compared to winter specimens, especially after desiccation for 24 hours. In contrast high-shore specimens had increased rates of nitrogen uptake after mild desiccation treatments, compared to low-shore specimens during summer, and specimens from the low-shore had increased variability in their uptake rates, indicating disruption to the uptake mechanisms, compared to the high-shore specimens. S. arbuscula was able to recover photosynthetic capacity faster than nitrogen and phosphorus uptake during re-immersion after desiccation, which indicates that the ability to regain photosynthetic function may be more important for this species than regaining the ability to take up nitrogen and phosphorus. As S. arbuscula can photosynthesise in air (providing there is sufficient tissue water content) and water, the �window of opportunity� to assimilate carbon is greater than for nitrogen and phosphorus uptake, which is only available to S. arbuscula during immersion at high tides. Despite this, no evidence was found of severe nutrient limitation in either high- or low-shore specimens. The disruption and recovery of cellular organisation during rehydration, assessed visually using electron microscopy, showed that the rate and duration of desiccation also affected the extent of recovery. Extremely desiccating conditions (R.H. 5%) damaged the cells and no recovery was observed during rehydration, compared to moderate desiccation treatments (R.H. 40%) where the time taken to recover during rehydration increased with increasing desiccation periods. The disruption of cellular organisation observed in Stictosiphonia arbuscula cells, was found to match the reduction and / or disruption to photosynthesis and the uptake of nitrogen and phosphorus under similar desiccation regimes. The formation of ridges and depressions on the surface of the tissue was also observed during desiccation, which is thought to help reduce the rate of evaporation by trapping �pockets� of air. Finally, Stictosiphonia arbuscula is extremely well suited to the mid - high region in the intertidal zone and it can maximise its competitive ability within this niche during immersion by fully rehydrating within 10 minutes, regaining maximum photosynthetic capacity within 20 minutes, and stability of nutrient uptake rates within 90 minutes. Further, S. arbuscula has higher rates of photosynthesis in winter, associated with increased photosynthetic pigment concentrations at this time. In contrast, during summer, the photosynthetic rates, chlorophyll a and phycobiliprotein concentrations are reduced and S. arbuscula increases its allocation of resources into protective mechanisms such as UV-absorbing compounds.