Hatcher, BG & Larkum, AWD 1983, 'An experimental analysis of factors controlling the standing crop of the epilithic algal community on a coral reef', Journal of Experimental Marine Biology and Ecology, vol. 69, no. 1, pp. 61-84.
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The hypotheses that grazing losses and/or ambient inorganic nitrogen concentrations control the standing crop of the epilithic algal community were tested in two habitats at One Tree Reef (Great Barrier Reef, Australia). Short (12-15 days) and long (167-306 days) multifactorial experiments using grazer exclusion and nitrogen fertilization treatments were used to partition variance in algal community biomass on portable segments of natural reef substratum during 1980. On outer reef slopes, inorganic nitrogen limited algal community growth, but the standing crop was determined by grazing losses. In the subtidal lagoon inorganic nitrogen and grazing alternated seasonally in controlling standing crop. The recolonization of cleared natural substratum was followed at two additional sites. The algal standing crop in subtidal habitats reached control levels within 4 months, while that in an intertidal reef habitat took up to 14 months. The standing crop of benthic algae on natural reef substrata was monitored in all habitats over 2 yr. In shallow and intertidal habitats, the standing crop was three to five times higher than in deeper areas, and showed a spatial and seasonal variation apparently controlled by factors other than grazing intensity, despite high levels of yield to grazers. Seasonal variation was much less in subtidal habitats. It is concluded that only within limited temporal and spatial scales is grazing intensity alone an adequate predictor of benthic algal standing crop. © 1983.
Larkum, AWD & Barrett, J 1983, 'Light-harvesting Processes in Algae', Advances in Botanical Research, vol. 10, no. C, pp. 1-219.
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The importance of algae, both as a contribution to the understanding of living things and in practical terms, hardly needs stressing today. Despite the previous emphasis on photosynthesis research in land plants there is now a large corpus of work on algae. This chapter intends to bring much of the dispersed literature together, so as to achieve an integrated framework from which conclusions can be drawn to further stimulate research. Organisms from the borderline of groups loosely called prokaryotes, plants, and animals have been discussed along with how the majority of algae are influenced by the light climate properties. The structure and function of the photosynthetic membrane have been described. Various kinds and levels of light harvesting available to algae are reviewed briefly. A more detailed analysis of some biochemical and biophysical aspects of light harvesting are also given. Light is essential to all photosynthetic autotrophs. But it is only to the extent that light is limiting to growth that light-harvesting strategies become important. It is therefore necessary to consider under what conditions light does become limiting for algal growth. Strategies of light harvesting are discussed in terms of general ecological, taxonomic, morphological, and cytological aspects. The chapter looks into photosynthetic pigments, reaction centre complexes, and pigment protein (light-harvesting) complexes with details of the principles of light harvesting in light of quantum chemistry and transfer of excitation energy, structure and function, distribution of excitation energy between the photosystems, and interaction of the light-harvesting apparatus with other photosynthetic processes. © 1983, Academic Press Inc. (London) Ltd.
Stewart, AC & Larkum, AWD 1983, 'Photosynthetic electron transport in thylakoid preparations from two marine red algae (Rhodophyta)', Biochemical Journal, vol. 210, no. 2, pp. 583-589.
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Thylakoid membrane preparations active in photosynthetic electron transport have been obtained from two marine red algae, Griffithsia monilis and Anotrichium tenue. High concentrations (0.5-1.0 M) of salts such as phosphate, citrate, succinate and tartrate stabilized functional binding of phycobilisomes to the membrane and also stabilized Photosystem II-catalysed electron-transport activity. High concentrations (1.0 M) of chloride and nitrate, or 30 mM-Tricine/NaOH buffer (pH 7.2) in the absence of salts, detached phycobilisomes and inhibited electron transport through Photosystem II. The O2-evolving system was identified as the electron-transport chain component that was inhibited under these conditions. Washing membranes with buffers containing 1.0-1.5 M-sorbitol and 5-50 mM concentrations of various salts removed the outer part of the phycobilisome but retained 30-70% of the allophycocyanin ‘core’ of the phycobilisome. These preparations were 30-70% active in O2 evolution compared with unwashed membranes. In the sensitivity of their O2-evolving apparatus to the composition of the medium in vitro, the red algae resembled blue-green algae and differed from other eukaryotic algae and higher plants. It is suggested that an environment of structured water may be essential for the functional integrity of Photosystem II in biliprotein-containing algae.
