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doi: 10.1111/j.1095-8312.1974.tb00711.xpmid: N/A
Various methods of sampling sedentary organisms on Australian coral reefs have been examined and a standardized photographic procedure has been suggested to suit the needs of an ecological study of Acanthaster planci and Linckia laevigata. To obtain reliable estimates of percentage cover of sedentary organisms and their spatial distribution metre square quadrats should be taken every fourth metre along transects orientated at right angles to the reef perimeter.
doi: 10.1111/j.1095-8312.1974.tb00712.xpmid: N/A
In the central region of the Great Barrier Reef, Acanthaster planci eats its own disk area of coral each day. At the southern end of the reef lagoon populations of A. planci eat substantially less than this amount of coral per day. Branching and plate corals are preferred food species and massive and encrusting forms are rejected while the preferred food species are available. Only when branching and plate forms on a reef have been consumed will A. planci attack massive and encrusting species. On Australian reefs preferred food species form between 70–99% of the coral cover. On the Great Barrier Reef A. planci spawns in January and juveniles settle in the top 3 m of water on the windward edge of reefs or on isolated patch reefs behind the main reef. Intolerance of wave attack forces the growing starfish to migrate into deeper water. Lateral movements, probably induced by shortage of living coral in deep water, bring the starfish around the ends of the reef to the leeward side. Here they destroy most of the living coral. It is suggested that the visual impact of A. planci on reefs of the Indo‐Pacific region is related to the composition of the coral fauna. Reefs with a high proportion of preferred food species will be severely damaged while those with faunas composed mainly of massive and encrusting forms will not be altered greatly by starfish predation. Work on larval development of A. planci carried out by Henderson & Lucas, 1971 showed that metamorphosis took place only at water temperatures of 28o ‐29o C. This suggests that the A. planci plague on the Great Barrier Reef will not spread south of latitude 20o S (29o C isotherm in January).
doi: 10.1111/j.1095-8312.1974.tb00713.xpmid: N/A
The blue starfish Linckia laevigata grazes coralline algae. The starfish populations studied were composed entirely of adults. Spawning takes place in October at the southern end of the Great Barrier Reef. On reefs which were unaffected by Acanthaster planci, L. laevigata was confined to algae covered reef tops and rubble banks. On reefs affected by A. planci, L. laevigata had extended its range and was feeding on and among the coralline algae covered dead hard coral skeletons on the reef perimeter. Coral regrowth, followingattack by A. planci, was found to be slower on reefs with populations of L. laevigata living on the reef perimeter than on reefs where they were absent from this region. It is suggested that grazing by L. laevigata destroys small coral colonies and newly settled larvae thus slowing down the rate of coral regeneration. The consequences of this reduced rate of recolonisation is also discussed.
doi: 10.1111/j.1095-8312.1974.tb00714.xpmid: 11631652
Research on xeromorphic and sclerophyllous (the literal meanings of which are “dry‐form” and “hard‐leaved”) plants offers a case‐history illustrating the nature of “progress” in one branch of science. The story runs from about 1890–1970, beginning with the birth of ecological concepts, including Warming's 1895 classification of plants into hydrophytes, xerophytes and meso‐phytes, Schimper's pioneer work on the sclerophylls, and with the conceptions that lay behind this work; and so on through the main lines of research, concluding with an account of work on the “anomalous” distribution of the sclerophylls in Australia. This case‐history shows how the problems of classification and categorization may be linked to conceptual and empirical problems of substance, and hence are not “merely” classificatory. Indeed, the hypotheses under test are not formulated explicitly, but are encapsulated in the terminology, as is so often the case in the biological sciences.
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