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 concentrations. 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 conclusions 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