Abstract:
Metadata record for data from ASAC Project 102 See the link below for public details on this project.
From the abstracts of some of the referenced papers:
Six species of marine microalgae, namely Phaeodactylum tricornutum Bohlin, Dunaliella tertiolecta Butcher, Isochrysis galbana Parke, Porphyridium purpureum (Bory) Ross, Chroomonas sp., and Oscillatoria ... woronichinii Anis., have been examined with respect to their gas exchange characteristics and the inorganic carbon species taken up by the cells from the bulk medium. All species showed a high affinity, in photosynthesis, for inorganic carbon and low CO2 compensation concentations. Such data are suggestive of operation of a 'CO2-concentrating mechanism' in these microalgae. Direct measurements of internal organic carbon pools in four of the species studied confirm this (O. woronichinii and Chroomonas were not tested). By comparison of achieved photosynthetic rates with calculated rates of CO2 supply from the dehydration of bicarbonate, it was shown that Phaeodactylum, Porphyridium and Dunaliella could utilise the bicarbonate present in the medium. Data for the other species were inconclusive although the pH dependence of K 1/2CO2 for photosynthesis by Oscillatoria indicated that this species too could utilise bicarbonate. Such observations could, however, not be used as evidence that, at least in the eucaryotic algae examined, bicarbonate was the inorganic carbon species crossing the plasmalemma as Phaeodactylum, Porphyridium and Dunaliella, and Isochrysis all showed the presence of carbonic anhydrase activity in intact cells as well as in crude extracts. 'External' carbonic anhydrase activity represented from 1/4 to 1/2 of the total activity in the cells of these algae. It is concluded that, as a consequence of a CO2-concentrating mechanism, photorespiration was suppressed in the marine microalgae examined although the data obtained did not allow any firm conlusions to be drawn regarding the species of inorganic carbon transported into the cell.
Analysis of the age composition of a given species within a community is fundamental to any study of population dynamics and to the subsequent analyses of community interactions such as competition, succession and productivity. A problem exists in that calendar age often provides little information on the role played by any given individual plant within a population. For many populations the most useful definition of population structure is obtained from an analysis of both the functional age and the vitality of the component plants. Data from such studies on populations of marine macroalgae are lacking mainly because of the lack of suitable methods. This paper provides a review of the methods which have ben applied to such analyses in both terrestrial and marine communities, discusses these methods in the context of marine algae and presents the results of a case study on the analysis of population structure in the large brown alga Durvillaea potatorum.
Evidence is presented for the occurrence of sexual reproduction including plasmogamy and meiosis, events previously undescribed in the life history of Ascoseira mirabilis. Ascoseira is monoecious. Gametangia are formed in chains within conceptacles. Synaptonemal complexes, structures concerned with chromosome pairing in meiosis, have been observed in the nucleus of gametangial initials. Mature male and female gametes have the same size and appearance, and resemble typical brown algal zoids. Sexual interaction begins after the female gamete settles down, and both zygotes and unfused gametes develop into sporophytes. It is concluded that Ascoseira has the same basic pattern of life history that characterises the order Fucales, and it is argued that this is probably the result of convergent evolution rather than being indicative of close phylogenetic relationship.
Life histories are of central importance in understanding evolution and phylogeny of brown algae. Like other hereditary traits, life history characteristics evolve by processes of natural selection, but because they are important determinants of biological fitness they have special evolutionary significance. Concepts of life history, as traditionally applied to brown algae, do not adequately reflect this, and they need to be broadened to include consideration of additional characteristics such as longevity and reproductive span. Life histories can be interpreted as adaptive strategies. Experimental evidence indicates that heteromorphic life histories probably evolved in response to seasonal change. Isomorphic life histories are possible adapted to stale environments, although some may also possess certain features which are adaptations to seasonal change. Life histories that lack an independent gametophyte generation may have evolved through reduction of heteromorphic life histories. It is argued that a significant increase in the longevity of sporophytes may have ben critical for the evolution of life histories lacking a free-living gametophyte, and also for the evolution of oogamy, phenomena which have occurred in several brown algal evolutionary lines. The common absence of asexual reproduction in advanced taxa probably indicates that its accessory ecological role in maintaining population size has become redundant, as well as reflecting the advantage of sexual over asexual reproduction. However, there is good evidence that sexual reproduction has been lost in a few species of brown algae, and the possible mechanisms and adaptive significance of this are discussed.
Studies on Durvillaea antarctica on Macquarie Island, in the subantarctic, were conducted throughout the 1984 and in the summers of 1983 and 1985. Thereafter the annual sequence of conceptacle initiation, development, maturation and senescence was examined, using light and electron microscopy. Durvillaea antarctica on Macquarie Island releases mature ova and spermatozooids from February to Ausgust, with early stages of conceptacle development being observed during November, December and January, and senescent conceptacles from September to December. Both intertidal and subtidal forms of Durvillaea antarctica are found on Macquarie Island, the subtidal form lacking air cavities. In the light of mating experiments which resulted in successful cross-fertilisation, the two forms are considered to be conspecific.
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This
"Biology of Antarctic Algae" is licensed under a Creative Commons Attribution 3.0 Unported License.
Dept Biological Sciences
Wellington Road
Monash University
City:
CLAYTON
Province or State:
Victoria
Postal Code:
3168
Country:
Australia
Publications/References
Beardall J. (1989) Photosynthesis in marine phytoplankton. Aquatic Botany 34 105
Gibson G., Clayton M. (1987) Sexual reproduction, early development and branching in Notheia anomala (Phaeophyta) and its classification in the order Fucales. Phycologia 26. 363
Clayton M. (1987) Observations on isogamy and a fucalean type of life history in the Antarctic brown alga Acoseira ... mirabilis (Ascoseirales, haeophyta). Botanica Marina 30. 447
Clayton M. (1988) Evolution and life histories in the Phaeophyta. Botanica Marina 31. 379
Burns D.B., Beardall J. (1987) Inorganic carbon utilization by marine microalgae. Journal of Experimental Marine Biology and Ecology 107. 75
Clayton M., Hallam N., Shankly C. (1987) The seasonal pattern of conceptacle development and gamete maturation in Durvillaea potatorum (Durvillaeales, Phaeophyta). Phycologia 26(1). 35
Klemm M., Hallam N. (1987) Branching pattern and growth in Cystophora (Fucales ,Phaeophyta). Phycologia 26. 252
Klemm M., Hallam N. (1988) Conceptacle development, gamete maturation and embryology of Durvillaea antarctica from Macquarie Island. Papers and Proceedings of the Royal Society of Tasmania 122(1). 199
Klemm M., Hallam N. (1988) Standing crop of Durvillaea antarctica (Chamisso) Hariot (Phaeophyta) on the Australian sub-antarctic Macquarie and Heard Islands. Phycologia 27. 505
Cheshire T., Hallam N. (1989) Methods of assessing the age composition of native stands of subtidal macro algae. A case study on Durvillaea potatorum. Botanica Marina 32. 199
Hallam N., Luff S.E. (1988) The fixation and infiltration of the larger brown algae (Phaeophyta) for electron microscopy. British Journal of Phycology 23. 337
Hallam N., Klemm M. (1991) Detachment and biomass of Durvillaea antarctica on sub-Antarctic islands. Proceedings of the 1V International Phycological Congress 28
Xu X., Beardall J. (1992) Effects of salinity on growth and photosynthesis of Antarctic microalgae. Proceedings of the Tenth Conference, Australian Society for Phycology and Aquatic Botany
Wood M.D., Beardall J. (1992) Effects of growth temperature on the kinetic characteristics of malate dehydrogenase in Antarctic and temperate microalgae. Proceedings of the Tenth Conference, Australian Society for Phycology and Aquatic Biology
Wood M.D., Beardall J. (1992) Effects of growth temperature on the kinetic characteristics of malate dehydrogenase in Antarctic and temperate microalgae. Proceedings of the 32nd Annual Meeting of the Australian Society of Plant Physiologists
Xin Qing Xu and John Beardall (1997) Effect of salinity on fatty acid composition of a green microalga from an Antarctic hypersaline lake. Phytochemistry. 45, 655-658.
Xu, X.Q. Beardall, J. and Hallam, N.D. (1998) Modification of fatty acid composition in halophilic Antarctic microalgae. Phytochemistry. 49: 1249-1252
Xinqing Xu (1994)Studies on the physiology and biochemistry of microalgae from Antarctic hypersaline lakes. PhD Thesis, Monash University
