Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 123-129)

Cell wall structure was investigated in 20 different red algae. Representatives from all 4- families of the order Ceramiales and one family of the order Gigartinales were investigated. Of these, 3 genera, Polysiphonia, Pterosiphonia and Antithamnion were investigated with regards to both the cellulosic and mucilaginous portions of the cell wall. A new staining technique utilizing a combination of ruthenium red and osmium tetroxide as a postfixation was used in the latter portion of the study. The ultrastructure of pit connections was examined in all algae. The inner cellulosic portion of the cell wall consists of a reticulate pattern of microfibrils which appear densely stained, In Pterosiphonia this cellulosic portion was found to consist of 2 layers; an inner layer of microfibrils which ensheathed individual cells and an outer layer of microfibrils which ensheathed the entire thallus and was in contact with the mucilaginous coat. The microfibrils in the inner layer appear nearly cross-sectioned, while those in the outer layer appear more longitudinally oriented to the plane of sectioning. The outer mucilaginous coat covers the entire thallus. It consists of 4 layers. The first or outermost layer consists of loose bunches of microfibrils extending out from the second layer. The second layer consists of a zone of medium electron density approximately 750 A in thickness. The third layer is wholly contained within the second layer. It is composed of a densely staining band of microfibrils extending from a similarly staining membrane-like structure. The fourth layer is a densely stained membrane-like structure in contact with the cellulosic portion of the cell wall. An additional layer, the D layer, is sometimes found in the cell wall. When present it is found in the outermost portion of the cellulosic wall and obscures the fourth layer of the mucilaginous coat. It consists of a densely staining amorphous material. Investigation of the pit connection showed the occurrence of 2 stages of one basic pit structure. One stage, the single disc stage-pit structure, has been found in all algae investigated. It consists of a solid, lenticular, membrane-bound plug situated within an aperture in the cell wall. The plug consists of a granular material surrounded by a zone of densely staining amorphous material. The other stage, the double disc stage pit structure, is a modification of the single disc stage. It is not found in young cells near the apex of the thallus, but only in cells which have, or are undergoing, rapid elongation and vacuolation. This pit structure has only been observed in axial cells of the family Ceramiaceae in the order Ceramiales. The double disc stage pit structure differs from the single disc stage in that the granular material of the plug is segregated into 2 regions or plates, one on either side of the plug. The central region of the plug at first appears clear but later appears to be partially occupied by a granular to fibrillar material. The differentiation of the double disc stage pit structure from the single disc stage has been described. These observations are thought to support and confirm the earlier work of Jungers (25). However, his observations have been extended through the use of electron microscopy in this study. It has been proposed that the terms used in this study, single disc stage- and double disc stage pit structures, replace the terms Polysiphonia and Griffithsia pits used by Jungers. / Science, Faculty of / Botany, Department of / Graduate

Thesis (master's)--Göteborg University, 1999. / Title from PDF t.p. (viewed on Sept. 25, 2007). At head of title: Tjärno Marine Biological Laboratory. Includes bibliographical references (p. 13-14).

Thesis (master's)--Göteborg University, 1999. / Title from PDF t.p. (viewed on Sept. 25, 2007). At head of title: Tjärno Marine Biological Laboratory. Includes bibliographical references (p. 13-14).

A comparative study was made between two similar red algal endophytes, Audouinella porphyrae (Drew) Garbary and Audouinella vaga (Drew) Garbary, Hansen et Scagel, (Acrochaetiaceae, Acrochaetiales) and their red algal hosts Porphyra spp. and Pterosiphonia bipinnata, respectively. Both endophytes have axial, stellate chloroplasts with a central pyrenoid and reside in their host's cell walls, producing erect portions outside the host that may bear monosporangia. The endophytes were cultured "free" from their hosts and morphological and cytological features of the free-living forms were compared with field material. Although the two endophytes differ significantly in cell dimensions and branching patterns, the free-living forms do not retain these differences. Cell dimensions, branching patterns and developmental patterns are identical in the two free-living forms. Asexual reproduction with regeneration by monospores was observed. Sexual reproduction was not observed in either endophytic or free-living forms of the endophytes. Free-living forms were used for re-infection and cross-infection experiments. Under all experimental conditions, the endophytes showed only epiphytic growth. The hosts seem to have some effect on both of the endophytes. Epiphytes, Audouinella porphyrae and A. vaga were not selective and grew on both hosts, Porphyra torta and Pterosiphonia bipinnata. Both epiphtyes growing on blades of Porphyra tended to branch and have more extensive prostrate portions (3-5 cells) whereas both epiphytes on Pterosiphoni a bipinnata tend not to branch and have only 1-2 cells in the prostrate portions. Ultrastructural studies of both endophytes showed typical florideophycean features. Ultrastructural features of field material of the two endophytes were similar and free-living, cultured endophytes were similar to field material. A large vacuole was observed in sections of the field material of both prostrate and erect portions whereas this was not observed in cultured material. Based on the results of this study it is proposed that the two endophytes are conspecific. Audouinella vaga is referred to synonymy in Audouinella porphyrae (Drew) Garbary, Hansen et Scagel. / Science, Faculty of / Botany, Department of / Graduate

The purpose of this thesis was to provide a revision and characterization of the species of nongeniculate coralline algae previously ascribed to the now defunct genus Porolithon / to provide a modern account of selected taxa from the genus Hydrolithon and descriptions of taxa found to conform the generic delimitation of Hydrolithon and to use a phenetic cluster analysis to determine the taxonomic relationships between the various taxa ascribed to the genera Polorithon and Hydrolithon.

I investigated the ecological functions of halogenated secondary metabolites from the red alga Asparagopsis armata, their localisation in specialised cells and also their cost of production. A. armata produces large amounts of halogenated metabolites ( &lt 20 ??g / mg dry weight) that are sequestered in gland cells, as was demonstrated with light, epifluorescence and transmission electron microscopy. Cellular structures were identified that likely assist the release of metabolites from the gland cells to the algal surface. The halogenated metabolites of A. armata have multiple ecological roles, functioning as both inhibitors of bacterial fouling and as herbivore deterrents. Their activity against bacteria and herbivores was measured by a novel test in which the metabolites were manipulated in A. armata by omitting bromide ions from the culture media. This technique prevented the production of halogenated metabolites, but did not impact on other aspects of algal biology. Algae lacking halogenated metabolites (bromide [-] algae) had higher densities of epiphytic bacteria than those that continued to produce metabolites (bromide [+] algae). Bioassays with pure compounds against individual bacterial isolates further supported an inhibitory role for the halogenated metabolites against epiphytic bacteria, and also indicated an affect on bacterial community structure as well as abundance. Bromide (+) A. armata produced halogenated metabolites that also deterred feeding by two herbivores (an amphipod and an abalone), but not a third (an opisthobranch mollusc). A novel outcome from these feeding assays was the demonstration of a relationship between herbivore size and consumption of the chemically defended A. armata by the abalone Haliotis rubra. In addition to the fitness benefits gained from chemical defence, there were also costs for allocating resources to secondary metabolites. These costs were only detected under limiting light resources, consistent with predictions of the plant defence models. The integration of chemical analyses and cellular measures of chemical defence proved essential in elucidating resource allocation to chemical defence in the filamentous stage of A. armata. This thesis highlights that the simple relationships between growth and defence in filamentous algae can provide an excellent model for studies of the ecology and evolution of chemical defences in marine algae.

A prevailing view exists in the literature which suggests that macroalgae growing in slow-flow environments (<4 cm s⁻�) are less productive because of "mass-transfer" limitation compared to fast-flow environments. Macroalgae in slow-flow environments are thought to have thicker diffusion boundary-layers which limit the flux of essential molecules to and from the algal thallus. However nutrient demand of a macroalga can also influence nutrient flux. The main objective of this research was to determine the relative importance of physical (mainstream velocity) and physiological (nutrient demand) factors influencing the growth rate of Adamsiella chauvinii, a small (<20 cm) red algal species, that grows within the benthic boundary-layer in a soft sediment habitat. To establish the influence of water velocity, the growth rate of A. chauvinii was measured in situ each month (March 2003 to March 2004) at three sites with varying degrees of water velocity (slow, intermediate and fast) at which all other environmental parameters (photon flux density, seawater temperature and nutrients) were similar. To determine the metabolic demand and nutrient uptake rate of A. chauvinii, the internal nutrient status (C:N, soluble tissue nitrate, ammonium and phosphate), uptake kinetics (V[max] and K[s]) and nutrient uptake rate at a range of mainstream velocities were also determined on a seasonal basis. The hydrodynamic environment around A. chauvinii canopies was characterised in situ and compared with controlled laboratory experiments. Growth rates of Adamsiella chauvinii thalli at the slow-flow site were significantly lower in winter (June) to summer (February) than the intermediate- and fast-flow sites, while in autumn growth rates were similar between sites. However, A. chauvinii at the slow-flow site had similar or higher tissue N content compared to thalli at the other two sites during winter, spring and summer suggesting that growth rates of A. chauvinii were not mass-transfer limited. Nitrogen uptake rates of A. chauvinii were similar between sites in summer and winter, however uptake rates were lower in summer compared to winter even though thalli were nitrogen limited in summer. Water velocity had no effect on nitrate uptake in either summer or winter and uptake of ammonium increased with increasing water velocity during summer only. Two hydrodynamically different environments were distinguished over a canopy of A. chauvinii, with both the laboratory and field velocity profiles in good agreement with each other. In the top half of the canopy, the Turbulent Kinetic Energy (TKE) and Reynolds stresses were greatest while in the bottom half of the canopy flow rates were less than 90 % of mainstream velocity (< 1 cm s⁻�). When considered together, the influence of water velocity on the growth rates of A. chauvinii was not completely clear. Results suggest that mainstream velocity had little influence on nutrient availability to A. chauvinii because of the unique hydrodynamic environment created by the canopy. Nutrients, especially ammonium and phosphate, derived from the sediment and invertebrates, may provide enough nitrogen and phosphate to saturate the metabolic demand of Adamsiella chauvinii, consequently, A. chauvinii is well adapted to this soft-sediment environment.

Graduation date: 1998

The purpose of this thesis was to provide a revision and characterization of the species of nongeniculate coralline algae previously ascribed to the now defunct genus Porolithon / to provide a modern account of selected taxa from the genus Hydrolithon and descriptions of taxa found to conform the generic delimitation of Hydrolithon and to use a phenetic cluster analysis to determine the taxonomic relationships between the various taxa ascribed to the genera Polorithon and Hydrolithon.